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The pterygoid canal (Fig. 8.154A) is a bony canal running horizontally through the root of the pterygoid process of the sphenoid bone. It opens anteriorly into the pterygopalatine fossa. Posteriorly it continues through the cartilage filling the foramen lacerum and opens into the middle cranial fossa just anteroinferior to the internal carotid artery as the vessel enters the cranial cavity through the carotid canal (Fig. 8.154B).
Seven foramina and fissures provide apertures through which structures enter and leave the pterygopalatine fossa (Fig. 8.155):
The foramen rotundum and pterygoid canal communicate with the middle cranial fossa and open onto the posterior wall.
A small palatovaginal canal opens onto the posterior wall and leads to the nasopharynx.
The palatine canal leads to the roof of the oral cavity (hard palate) and opens inferiorly.
The sphenopalatine foramen opens onto the lateral wall of the nasal cavity and is in the medial wall.
The lateral aspect of the pterygopalatine fossa is continuous with the infratemporal fossa via a large gap (the pterygomaxillary fissure) between the posterior surface of the maxilla and pterygoid process of the sphenoid bone.
The superior aspect of the anterior wall of the fossa opens into the floor of the orbit via the inferior orbital fissure.
The maxillary nerve [V2] and terminal part of the maxillary artery enter and branch within the pterygopalatine fossa. In addition, the nerve of the pterygoid canal enters the fossa carrying: preganglionic parasympathetic fibers from the greater petrosal branch of the facial nerve [VII], and postganglionic sympathetic fibers from the deep petrosal branch of the carotid plexus.
The preganglionic parasympathetic fibers synapse in the pterygopalatine ganglion and both the sympathetic and postganglionic parasympathetic fibers pass with branches of the maxillary nerve [V2] out of the fossa and into adjacent regions.
In addition to nerves and arteries, veins and lymphatics also pass through the pterygopalatine fossa.
The maxillary nerve [V2] is purely sensory. It originates from the trigeminal ganglion in the cranial cavity, exits the middle cranial fossa, and enters the pterygopalatine fossa through the foramen rotundum (Fig. 8.156). It passes anteriorly through the fossa and exits as the infra-orbital nerve through the inferior orbital fissure.
While passing through the pterygopalatine fossa, the maxillary nerve [V2] gives rise to the zygomatic nerve, the posterior superior alveolar nerve, and two ganglionic branches (Fig. 8.156). The two ganglionic branches originate from its inferior surface and pass through the pterygopalatine ganglion.
Postganglionic parasympathetic fibers, arising in the pterygopalatine ganglion, join the general sensory branches of the maxillary nerve [V2] in the pterygopalatine ganglion, as do postganglionic sympathetic fibers from the carotid plexus. The three types of fibers leave the ganglion as orbital, palatine, nasal, and pharyngeal branches.
Orbital branches. The orbital branches are small and pass through the inferior orbital fissure to contribute to the supply of the orbital wall and of the sphenoidal and ethmoidal sinuses.
Greater and lesser palatine nerves. The greater and lesser palatine nerves (Fig. 8.156) pass inferiorly from the pterygopalatine ganglion, enter and pass through the palatine canal, and enter the oral surface of the palate through the greater and lesser palatine foramina. |
The greater palatine nerve passes forward on the roof of the oral cavity to innervate mucosa and glands of the hard palate and the adjacent gingiva, almost as far forward as the incisor teeth.
In the palatine canal, the greater palatine nerve gives origin to posterior inferior nasal nerves, which pass medially through small foramina in the perpendicular plate of the palatine bone and contribute to the innervation of the lateral nasal wall.
After passing through the lesser palatine foramen, the lesser palatine nerve passes posteriorly to supply the soft palate.
Nasal nerves. The nasal nerves (Fig. 8.156), approximately seven in number, pass medially through the sphenopalatine foramen to enter the nasal cavity. Most pass anteriorly to supply the lateral wall of the nasal cavity, while others pass across the roof to supply the medial wall.
One of the nerves passing across the roof to supply the medial wall of the nasal cavity (the nasopalatine nerve) is the largest of the nasal nerves and passes anteriorly down the nasal septum, through the incisive canal and fossa in the hard palate to enter the roof of the oral cavity and supply mucosa, gingiva, and glands adjacent to the incisor teeth.
Pharyngeal nerve. The pharyngeal nerve (Fig. 8.156) passes posteriorly from the pterygopalatine ganglion, and leaves the fossa through the palatovaginal canal, which it then exits to supply the mucosa and glands of the nasopharynx.
Zygomatic nerve. The zygomatic nerve (Fig. 8.156) originates directly from the maxillary nerve [V2] in the pterygopalatine fossa, which it leaves to enter the orbit through the inferior orbital fissure. It passes forward on the lateral orbital wall and divides into zygomaticotemporal and zygomaticofacial branches:
The zygomaticotemporal branch continues forward at the base of the lateral orbital wall, passes through a small bony canal in the zygomatic bone to enter the temporal fossa through a small foramen in the lateral orbital margin on the posterior surface of the frontal process of the zygomatic bone, and passes superficially to supply skin over the temple.
The zygomaticofacial branch also passes forward at the base of the lateral orbital wall and leaves through a small bony canal, in the orbital margin, which opens via multiple small foramina on the anterolateral surface of the zygomatic bone, and its branches supply the adjacent skin.
Posterior superior alveolar nerve. The posterior superior alveolar nerve (Fig. 8.156) originates from the maxillary nerve [V2] in the pterygopalatine fossa and passes laterally out of the fossa through the pterygomaxillary fissure to enter the infratemporal fossa. It continues laterally and inferiorly to enter the posterior surface of the maxilla through a small alveolar foramen approximately midway between the last molar tooth and the inferior orbital fissure. It then passes inferiorly just deep to the mucosa of the maxillary sinus to join the superior dental plexus.
The posterior superior alveolar nerve supplies the molar teeth and adjacent buccal gingivae, and contributes to the supply of the maxillary sinus.
Infra-orbital nerve. The infra-orbital nerve (Fig. 8.156) is the anterior continuation of the maxillary nerve [V2] that leaves the pterygopalatine fossa through the inferior orbital fissure. It lies first in the infra-orbital groove in the floor of the orbit and then continues forward in the infra-orbital canal.
While in the infra-orbital groove and canal, the infra-orbital nerve gives origin to middle and anterior superior alveolar nerves, respectively, which ultimately join the superior alveolar plexus to supply the upper teeth:
The middle superior alveolar nerve also supplies the maxillary sinus. |
The anterior superior alveolar nerve also gives origin to a small nasal branch, which passes medially through the lateral wall of the nasal cavity to supply parts of the areas of the nasal floor and walls.
The infra-orbital nerve exits the infra-orbital canal through the infra-orbital foramen inferior to the orbital margin and divides into nasal, palpebral, and superior labial branches:
Nasal branches supply skin over the lateral aspect of the external nose and part of the nasal septum.
Palpebral branches supply skin of the lower eyelid.
Superior labial branches supply skin over the cheek and upper lip, and the related oral mucosa.
Nerve of the pterygoid canal and the pterygopalatine ganglion
The nerve of the pterygoid canal (Fig. 8.157) is formed in the middle cranial fossa by the union of: the greater petrosal nerve (a branch of the facial nerve [VII]), and the deep petrosal nerve (a branch of the internal carotid plexus).
The nerve of the pterygoid canal passes into the pterygopalatine fossa and joins the pterygopalatine ganglion. It carries mainly preganglionic parasympathetic and postganglionic sympathetic fibers.
The greater petrosal nerve, which originates from the geniculate ganglion of the facial nerve [VII] in the temporal bone, exits the temporal bone through a small canal that opens via a fissure onto the anterior surface of the petrous part of the temporal bone. It passes anteromedially along the posterior margin of the middle cranial fossa and then under the internal carotid artery to reach the superior surface of the cartilage filling the foramen lacerum.
As the greater petrosal nerve passes under the internal carotid artery, it is joined by the deep petrosal nerve to form the nerve of the pterygoid canal.
The greater petrosal nerve carries parasympathetic innervation to all glands above the oral fissure, including: mucous glands in the nasal cavity, salivary glands in the upper half of the oral cavity, and the lacrimal gland in the orbit.
The greater petrosal nerve also carries some taste (SA) fibers from the soft palate in the lesser palatine nerve.
The deep petrosal nerve is formed by postganglionic sympathetic fibers that originate in the superior cervical sympathetic ganglion in the neck and leave the ganglion as the internal carotid nerve.
Preganglionic fibers that synapse in the ganglion are from the T1 spinal nerve.
The internal carotid nerve forms the internal carotid plexus around the internal carotid artery as the internal carotid artery passes through the skull and into the cranial cavity. Some of the fibers from the internal carotid plexus converge to form the deep petrosal nerve, which leaves the internal carotid plexus in the middle cranial fossa and joins the greater petrosal branch of the facial nerve [VII].
The deep petrosal nerve carries postganglionic sympathetic fibers destined mainly for blood vessels.
The nerve of the pterygoid canal enters the superior surface of the cartilage that fills the foramen lacerum and passes anteriorly through the cartilage to enter the pterygoid canal in the root of the pterygoid process of the sphenoid bone. It passes through the canal and into the pterygopalatine fossa where it joins the pterygopalatine ganglion formed around the branches of the maxillary nerve [V2] (Fig. 8.157).
The pterygopalatine ganglion is the largest of the four parasympathetic ganglia in the head and is formed by the cell bodies of the postganglionic neurons associated with preganglionic parasympathetic fibers of the facial nerve [VII] carried by the greater petrosal nerve and the nerve of the pterygoid canal. |
The postganglionic parasympathetic fibers that originate in the pterygopalatine ganglion, together with postganglionic sympathetic fibers passing through the ganglion, join fibers from the ganglionic branches of the maxillary nerve [V2] to form orbital, palatine, nasal, and pharyngeal branches, which leave the ganglion.
Other postganglionic parasympathetic and sympathetic fibers pass superiorly through the ganglionic branches of the maxillary nerve [V2] to enter the main trunk of the maxillary nerve and be distributed with the zygomatic, posterior superior alveolar, and infra-orbital nerves. Of these, the postganglionic parasympathetic and sympathetic fibers that pass into the orbit with the zygomatic nerve are particularly important because they ultimately innervate the lacrimal gland.
Innervation of the lacrimal gland
Approximately midway along the orbital wall, the postganglionic parasympathetic and sympathetic fibers leave the zygomaticotemporal branch of the zygomatic nerve and form a special autonomic nerve, which travels up the lateral orbital wall to join the lacrimal nerve (Fig. 8.157; also see Fig. 8.87).
The lacrimal nerve is a major general sensory branch of the ophthalmic nerve [V1], which passes forward in the orbit at the margin between the lateral wall and roof.
The postganglionic parasympathetic and sympathetic fibers pass with the lacrimal nerve to the lacrimal gland.
A lesion anywhere along the course of parasympathetic fibers that leave the brain as part of the facial nerve [VII] and are ultimately carried to the lacrimal gland along branches of the ophthalmic nerve [V1] results in “dry eye” and can eventually lead to loss of vision in the affected eye.
The maxillary artery is a major branch of the external carotid artery in the neck. It originates adjacent to the neck of the mandible, passes forward through the infratemporal fossa, and then enters the pterygopalatine fossa through the pterygomaxillary fissure (Fig. 8.158).
The part of the maxillary artery in the pterygopalatine fossa (the third part) is anterior to the pterygopalatine ganglion and gives origin to branches that accompany branches of the maxillary nerve [V2] and the pterygopalatine ganglion.
Branches of the maxillary artery include the posterior superior alveolar, infra-orbital, greater palatine, pharyngeal, and sphenopalatine arteries, and the artery of the pterygoid canal (Fig. 8.158). Collectively, these branches supply much of the nasal cavity, the roof of the oral cavity, and all upper teeth. In addition, they contribute to the blood supply of the sinuses, oropharynx, and floor of the orbit.
Posterior superior alveolar artery. The posterior superior alveolar artery (Fig. 8.158) originates from the maxillary artery as it passes through the pterygomaxillary fissure. It meets the posterior superior alveolar nerve, accompanies it through the alveolar foramen on the infratemporal surface of the maxilla, and supplies the molar and premolar teeth, adjacent gingiva, and the maxillary sinus.
Infra-orbital artery. The infra-orbital artery (Fig. 8.158) passes forward with the infra-orbital nerve and leaves the pterygopalatine fossa through the inferior orbital fissure. With the infra-orbital nerve, it lies in the infra-orbital groove and infra-orbital canal, and emerges through the infra-orbital foramen to supply parts of the face. |
Within the infra-orbital canal, the infra-orbital artery gives origin to: branches that contribute to the blood supply of structures near the floor of the orbit—the inferior rectus and inferior oblique muscles, and the lacrimal sac; and anterior superior alveolar arteries (Fig. 8.158), which supply the incisor and canine teeth and the maxillary sinus.
Greater palatine artery. The greater palatine artery (Fig. 8.158) passes inferiorly with the palatine nerves into the palatine canal. It gives origin to a lesser palatine branch (Fig. 8.158), which passes through the lesser palatine foramen to supply the soft palate, and then continues through the greater palatine foramen to supply the hard palate. The latter vessel passes forward on the inferior surface of the palate to enter the incisive fossa and pass superiorly through the incisive canal to supply the anterior aspect of the septal wall of the nasal cavity.
Pharyngeal branch. The pharyngeal branch (Fig. 8.158) of the maxillary artery travels posteriorly and leaves the pterygopalatine fossa through the palatovaginal canal with the pharyngeal nerve. It supplies the posterior aspect of the roof of the nasal cavity, the sphenoidal sinus, and the pharyngotympanic tube.
Sphenopalatine artery. The sphenopalatine artery (Fig. 8.158) is the terminal branch of the maxillary artery. It leaves the pterygopalatine fossa medially through the sphenopalatine foramen and accompanies the nasal nerves, giving off: posterior lateral nasal arteries, which supply the lateral wall of the nasal cavity and contribute to the supply of the paranasal sinuses; and posterior septal branches, which travel medially across the roof to supply the nasal septum—the largest of these branches passes anteriorly down the septum to anastomose with the end of the greater palatine artery.
Artery of pterygoid canal. The artery of the pterygoid canal passes posteriorly into the pterygoid canal. It supplies surrounding tissues and terminates, after passing inferiorly through cartilage filling the foramen lacerum, in the mucosa of the nasopharynx.
Veins that drain areas supplied by branches of the terminal part of the maxillary artery generally travel with these branches back into the pterygopalatine fossa.
The veins coalesce in the pterygopalatine fossa and then pass laterally through the pterygomaxillary fissure to join the pterygoid plexus of veins in the infratemporal fossa (Fig. 8.159).
The infra-orbital vein, which drains the inferior aspect of the orbit, may pass directly into the infratemporal fossa through the lateral aspect of the inferior orbital fissure, so bypassing the pterygopalatine fossa.
The neck is a tube providing continuity from the head to the trunk. It extends anteriorly from the lower border of the mandible to the upper surface of the manubrium of the sternum, and posteriorly from the superior nuchal line on the occipital bone of the skull to the intervertebral disc between the CVII and TI vertebrae. Within the tube, four compartments provide longitudinal organization (Fig. 8.160):
The visceral compartment is anterior and contains parts of the digestive and respiratory systems, and several endocrine glands.
The vertebral compartment is posterior and contains the cervical vertebrae, spinal cord, cervical nerves, and muscles associated with the vertebral column.
The two vascular compartments, one on each side, are lateral and contain the major blood vessels and the vagus nerve [X].
All these compartments are contained within unique layers of cervical fascia.
For descriptive purposes the neck is divided into anterior and posterior triangles (Fig. 8.161): |
The boundaries of the anterior triangle are the anterior border of the sternocleidomastoid muscle, the inferior border of the mandible, and the midline of the neck.
The boundaries of the posterior triangle are the posterior border of the sternocleidomastoid muscle, the anterior border of the trapezius muscle, and the middle one-third of the clavicle.
The fascia of the neck has a number of unique features.
The superficial fascia in the neck contains a thin sheet of muscle (the platysma), which begins in the superficial fascia of the thorax, runs upward to attach to the mandible and blend with the muscles on the face, is innervated by the cervical branch of the facial nerve [VII], and is only found in this location.
Deep to the superficial fascia, the deep cervical fascia is organized into several distinct layers (Fig. 8.160). These include: an investing layer, which surrounds all structures in the neck; the prevertebral layer, which surrounds the vertebral column and the deep muscles associated with the back; the pretracheal layer, which encloses the viscera of the neck; and the carotid sheaths, which receive a contribution from the other three fascial layers and surround the two major neurovascular bundles on either side of the neck.
The investing layer completely surrounds the neck and encloses the trapezius and sternocleidomastoid muscles (Fig. 8.162).
Attaching posteriorly to the ligamentum nuchae and the spinous process of the CVII vertebra, this fascial layer splits as it passes forward to enclose the trapezius muscle, reunites into a single layer as it forms the roof of the posterior triangle, splits again to surround the sternocleidomastoid muscle, and reunites again to join its twin from the other side.
Anteriorly, the investing fascia merges with fascia surrounding the infrahyoid muscles.
The investing fascia is attached: superiorly to the external occipital protuberance and the superior nuchal line, laterally to the mastoid process and zygomatic arch, and inferiorly to the spine of the scapula, the acromion, the clavicle, and the manubrium of the sternum.
The external and anterior jugular veins, and the lesser occipital, great auricular, transverse cervical, and supraclavicular nerves, all branches of the cervical plexus, pierce the investing fascia.
The prevertebral layer is a cylindrical layer of fascia that surrounds the vertebral column and the muscles associated with it (Fig. 8.162). Muscles in this group include the prevertebral muscles, the anterior, middle, and posterior scalene muscles, and the deep muscles of the back.
The prevertebral fascia is attached posteriorly along the length of the ligamentum nuchae, and superiorly forms a continuous circular line attaching to the base of the skull. This circle begins: anteriorly as the fascia attaches to the basilar part of the occipital bone, the area of the jugular foramen, and the carotid canal; continues laterally, attaching to the mastoid process; and continues posteriorly along the superior nuchal line ending at the external occipital protuberance, where it associates with its partner from the opposite side.
Anteriorly, the prevertebral fascia is attached to the anterior surfaces of the transverse processes and bodies of vertebrae CI to CVII.
The prevertebral fascia passing between the attachment points on the transverse processes is unique. In this location, it splits into two layers, creating a longitudinal fascial space containing loose connective tissue that extends from the base of the skull through the thorax (Figs. 8.162 and 8.163).
There is one additional specialization of the prevertebral fascia in the lower region of the neck. The prevertebral fascia in an anterolateral position extends from the anterior and middle scalene muscles to surround the brachial plexus and subclavian artery as these structures pass into the axilla. This fascial extension is the axillary sheath. |
The pretracheal layer consists of a collection of fascias that surround the trachea, esophagus, and thyroid gland (Fig. 8.162). Anteriorly, it consists of a pretracheal fascia that crosses the neck and encloses the infrahyoid muscles, and covers the trachea and the thyroid gland. The pretracheal fascia begins superiorly at the hyoid bone and ends inferiorly in the upper thoracic cavity. Laterally, this fascia encloses the thyroid gland and more posteriorly is continuous with fascia that surrounds the esophagus.
Posterior to the pharynx, the pretracheal layer is referred to as the buccopharyngeal fascia and separates the pharynx from the prevertebral layer (Fig. 8.163).
The buccopharyngeal fascia begins superiorly at the base of the skull and merges with fascia covering the esophagus that then continues inferiorly into the thoracic cavity.
Each carotid sheath is a column of fascia that surrounds the common carotid artery, the internal carotid artery, the internal jugular vein, and the vagus nerve as these structures pass through the neck (Fig. 8.162).
It receives contributions from the investing, prevertebral, and pretracheal layers, though the extent of each component’s contribution varies.
The arrangement of the various layers of cervical fascia organizes the neck into four longitudinal compartments (Fig. 8.160):
The first compartment is the largest, includes the other three, and consists of the area surrounded by the investing layer.
The second compartment consists of the vertebral column and the deep muscles associated with this structure, and is the area contained within the prevertebral layer.
The third compartment (the visceral compartment) contains the pharynx, the trachea, the esophagus, and the thyroid gland, which are surrounded by the pretracheal layer.
Finally, there is a compartment (the carotid sheath) consisting of the neurovascular structures that pass from the base of the skull to the thoracic cavity, and the sheath enclosing these structures receives contributions from the other cervical fascias.
Between the fascial layers in the neck are spaces that may provide a conduit for the spread of infections from the neck to the mediastinum.
(Fig. 8.163):
The first is the pretracheal space between the investing layer of cervical fascia covering the posterior surface of the infrahyoid muscles and the pretracheal fascia (covering the anterior surface of the trachea and the thyroid gland), which passes between the neck and the anterior part of the superior mediastinum.
The second is the retropharyngeal space between the buccopharyngeal fascia (on the posterior surface of the pharynx and esophagus) and the prevertebral fascia (on the anterior surface of the transverse processes and bodies of the cervical vertebrae), which extends from the base of the skull to the upper part of the posterior mediastinum.
The third space is within the prevertebral layer covering the anterior surface of the transverse processes and bodies of the cervical vertebrae. This layer splits into two laminae to create a fascial space that begins at the base of the skull and extends through the posterior mediastinum to the diaphragm.
The external jugular and anterior jugular veins are the primary venous channels for superficial venous drainage of the neck (Fig. 8.164).
The external jugular vein is formed posterior to the angle of the mandible as the posterior auricular vein and the retromandibular vein join:
The posterior auricular vein drains the scalp behind and above the ear. |
The retromandibular vein is formed when the superficial temporal and maxillary veins join in the substance of the parotid gland and it descends to the angle of mandible, where it divides into an anterior and a posterior division (Fig. 8.164)—the posterior division joins the posterior auricular vein to form the external jugular vein, and the anterior division joins the facial vein to form the common facial vein, which passes deep and becomes a tributary to the internal jugular vein.
Once formed, the external jugular vein passes straight down the neck in the superficial fascia and is superficial to the sternocleidomastoid muscle throughout its course, crossing it diagonally as it descends.
Reaching the lower part of the neck, just superior to the clavicle and immediately posterior to the sternocleidomastoid muscle, the external jugular vein pierces the investing layer of cervical fascia, passes deep to the clavicle, and enters the subclavian vein.
Tributaries received by the external jugular vein along its course include the posterior external jugular vein (draining superficial areas of the back of the neck) and the transverse cervical and suprascapular veins (draining the posterior scapular region).
The anterior jugular veins, although variable and inconsistent, are usually described as draining the anterior aspect of the neck (Fig. 8.164). These paired venous channels, which begin as small veins, come together at or just superior to the hyoid bone. Once formed, each anterior jugular vein descends on either side of the midline of the neck.
Inferiorly, near the medial attachment of the sternocleidomastoid muscle, each anterior jugular vein pierces the investing layer of cervical fascia to enter the subclavian vein. Occasionally, the anterior jugular vein may enter the external jugular vein immediately before the external jugular vein enters the subclavian vein.
Often, the right and left anterior jugular veins communicate with each other, being connected by a jugular venous arch in the area of the suprasternal notch.
Anterior triangle of the neck
The anterior triangle of the neck is outlined by the anterior border of the sternocleidomastoid muscle laterally, the inferior border of the mandible superiorly, and the midline of the neck medially (Fig. 8.166). It is further subdivided into several smaller triangles as follows:
The submandibular triangle is outlined by the inferior border of the mandible superiorly and the anterior and posterior bellies of the digastric muscle inferiorly.
The submental triangle is outlined by the hyoid bone inferiorly, the anterior belly of the digastric muscle laterally, and the midline.
The muscular triangle is outlined by the hyoid bone superiorly, the superior belly of the omohyoid muscle, and the anterior border of the sternocleidomastoid muscle laterally, and the midline.
The carotid triangle is outlined by the superior belly of the omohyoid muscle anteroinferiorly, the stylohyoid muscle and posterior belly of the digastric superiorly, and the anterior border of the sternocleidomastoid muscle posteriorly.
Each of these triangles contains numerous structures that can be identified as being within a specific triangle, passing into a specific triangle from outside the area, originating in one triangle and passing to another triangle, or passing through several triangles while passing through the region.
A discussion of the anterior triangle of the neck must therefore combine a systemic approach, describing the muscles, vessels, and nerves in the area, with a regional approach, describing the contents of each triangle.
The muscles in the anterior triangle of the neck (Table 8.12) can be grouped according to their location relative to the hyoid bone:
Muscles superior to the hyoid are classified as suprahyoid muscles and include the stylohyoid, digastric, mylohyoid, and geniohyoid.
Muscles inferior to the hyoid are infrahyoid muscles and include the omohyoid, sternohyoid, thyrohyoid, and sternothyroid. |
The four pairs of suprahyoid muscles are related to the submental and submandibular triangles (Fig. 8.166). They pass in a superior direction from the hyoid bone to the skull or mandible and raise the hyoid, as occurs during swallowing.
The stylohyoid muscle arises from the base of the styloid process and passes anteroinferiorly to attach to the lateral area of the body of the hyoid bone (Fig. 8.167). During swallowing it pulls the hyoid bone posterosuperiorly and it is innervated by the facial nerve [VII].
The digastric muscle has two bellies connected by a tendon, which attaches to the body of the hyoid bone (Fig. 8.167):
The posterior belly arises from the mastoid notch on the medial side of the mastoid process of the temporal bone.
The anterior belly arises from the digastric fossa on the lower inside of the mandible.
The tendon between the two bellies, which is attached to the body of the hyoid bone, is the point of insertion of both bellies. Because of this arrangement, the muscle has multiple actions depending on which bone is fixed:
When the mandible is fixed, the digastric muscle raises the hyoid bone.
When the hyoid bone is fixed, the digastric muscle opens the mouth by lowering the mandible.
Innervation of the digastric muscle is from two different cranial nerves.
The innervation of the posterior belly of the digastric muscle is by the facial nerve [VII], whereas the anterior belly of the muscle is innervated by the mandibular division [V3] of the trigeminal nerve [V].
The mylohyoid muscle is superior to the anterior belly of the digastric and, with its partner from the opposite side, forms the floor of the mouth (Fig. 8.167). It originates from the mylohyoid line on the medial surface of the body of the mandible and inserts into the hyoid bone and also blends with the mylohyoid muscle from the opposite side.
This mylohyoid muscle supports and elevates the floor of the mouth and elevates the hyoid bone. It is innervated by the mandibular division [V3] of the trigeminal nerve [V].
The geniohyoid muscle is superior to the floor of the oral cavity and is not generally considered a muscle of the anterior triangle of the neck; however, it can be regarded as a suprahyoid muscle. It is the final muscle in the suprahyoid group (Fig. 8.167). A narrow muscle, it is superior to the medial part of each mylohyoid muscle. The muscles from each side are next to each other in the midline.
The geniohyoid arises from the inferior mental spine of the mandible and passes backward and downward to insert on the body of the hyoid bone.
It has two functions depending on which bone is fixed:
Fixation of the mandible elevates and pulls the hyoid bone forward.
Fixation of the hyoid bone pulls the mandible downward and inward.
The geniohyoid is innervated by a branch from the anterior ramus of C1 carried along the hypoglossal nerve [XII].
The four infrahyoid muscles are related to the muscular triangle (Fig. 8.166). They attach the hyoid bone to inferior structures and depress the hyoid bone. They also provide a stable point of attachment for the suprahyoid muscles. Because of their appearance, they are sometimes referred to as the “strap muscles.”
The sternohyoid muscle is a long, thin muscle originating from the posterior aspect of the sternoclavicular joint and adjacent manubrium of the sternum (Fig. 8.168). It ascends to insert onto the body of the hyoid bone. It depresses the hyoid bone and is innervated by the anterior rami of C1 to C3 through the ansa cervicalis. |
Lateral to the sternohyoid muscle is the omohyoid muscle (Fig. 8.168). This muscle consists of two bellies with an intermediate tendon in both the posterior and anterior triangles of the neck:
The inferior belly begins on the superior border of the scapula, medial to the suprascapular notch, and passes forward and upward across the posterior triangle ending at the intermediate tendon.
The superior belly begins at the intermediate tendon and ascends to attach to the body of the hyoid bone just lateral to the attachment of the sternohyoid.
The intermediate tendon is attached to the clavicle, near its medial end, by a fascial sling.
The omohyoid depresses and fixes the hyoid bone. It is innervated by the anterior rami of C1 to C3 through the ansa cervicalis.
The thyrohyoid muscle is deep to the superior parts of the omohyoid and sternohyoid (Fig. 8.168). Originating at the oblique line on the lamina of the thyroid cartilage it passes upward to insert into the greater horn and adjacent aspect of the body of the hyoid bone.
The thyrohyoid muscle has variable functions depending on which bone is fixed. Generally, it depresses the hyoid, but when the hyoid is fixed it raises the larynx (e.g., when high notes are sung). It is innervated by fibers from the anterior ramus of C1 that travel with the hypoglossal nerve [XII].
Lying beneath the sternohyoid and in continuity with the thyrohyoid, the sternothyroid is the last muscle in the infrahyoid group (Fig. 8.168). It arises from the posterior surface of the manubrium of the sternum and passes upward to attach to the oblique line on the lamina of the thyroid cartilage.
The sternothyroid muscle draws the larynx (thyroid cartilage) downward and is innervated by the anterior rami of C1 to C3 through the ansa cervicalis.
Passing through the anterior triangle of the neck are the common carotid arteries and their branches, the external and internal carotid arteries. These vessels supply all structures of the head and neck.
Associated with this arterial system are the internal jugular vein and its tributaries. These vessels receive blood from all structures of the head and neck.
The common carotid arteries are the beginning of the carotid system (Fig. 8.169):
The right common carotid artery originates from the brachiocephalic trunk immediately posterior to the right sternoclavicular joint and is entirely in the neck throughout its course.
The left common carotid artery begins in the thorax as a direct branch of the arch of the aorta and passes superiorly to enter the neck near the left sternoclavicular joint.
Both right and left common carotid arteries ascend through the neck, just lateral to the trachea and esophagus, within a fascial compartment (the carotid sheath). They give off no branches as they pass through the neck.
Near the superior edge of the thyroid cartilage each common carotid artery divides into its two terminal branches—the external and internal carotid arteries (Fig. 8.170).
The superior part of each common carotid artery and its division into external and internal carotid arteries occurs in the carotid triangle (Fig. 8.170), which is a subdivision of the anterior triangle of the neck (see Fig. 8.166).
At the bifurcation, the common carotid artery and the beginning of the internal carotid artery are dilated. This dilation is the carotid sinus (Fig. 8.171) and contains receptors that monitor changes in blood pressure and are innervated by a branch of the glossopharyngeal nerve [IX].
Another accumulation of receptors in the area of the bifurcation is responsible for detecting changes in blood chemistry, primarily oxygen content. This is the carotid body and is innervated by branches from both the glossopharyngeal [IX] and vagus [X] nerves. |
After its origin, the internal carotid artery ascends toward the base of the skull (Fig. 8.171). It gives off no branches in the neck and enters the cranial cavity through the carotid canal in the petrous part of the temporal bone.
The internal carotid arteries supply the cerebral hemispheres, the eyes and the contents of the orbits, and the forehead.
The external carotid arteries begin giving off branches immediately after the bifurcation of the common carotid arteries (Fig. 8.171 and Table 8.13) as follows:
The superior thyroid artery is the first branch—it arises from the anterior surface near or at the bifurcation and passes in a downward and forward direction to reach the superior pole of the thyroid gland.
The ascending pharyngeal artery is the second and smallest branch—it arises from the posterior aspect of the external carotid artery and ascends between the internal carotid artery and the pharynx.
The lingual artery arises from the anterior surface of the external carotid artery just above the superior thyroid artery at the level of the hyoid bone, passes deep to the hypoglossal nerve [XII], and passes between the middle constrictor of the pharynx and hyoglossus muscles.
The facial artery is the third anterior branch of the external carotid artery—it arises just above the lingual artery, passes deep to the stylohyoid and posterior belly of the digastric muscles, continues deep between the submandibular gland and mandible, and emerges over the edge of the mandible just anterior to the masseter muscle, to enter the face.
The occipital artery arises from the posterior surface of the external carotid artery, near the level of origin of the facial artery, passes upward and posteriorly deep to the posterior belly of the digastric muscle, and emerges on the posterior aspect of the scalp.
The posterior auricular artery is a small branch arising from the posterior surface of the external carotid artery and passes upward and posteriorly.
The superficial temporal artery is one of the terminal branches and appears as an upward continuation of the external carotid artery—beginning posterior to the neck of the mandible, it passes anterior to the ear, crosses the zygomatic process of the temporal bone, and above this point divides into anterior and posterior branches.
The maxillary artery is the larger of the two terminal branches of the external carotid artery—arising posterior to the neck of the mandible, it passes through the parotid gland, continues medial to the neck of the mandible and into the infratemporal fossa, and continues through this area into the pterygopalatine fossa.
Collecting blood from the skull, brain, superficial face, and parts of the neck, the internal jugular vein begins as a dilated continuation of the sigmoid sinus, which is a dural venous sinus. This initial dilated part is referred to as the superior bulb of jugular vein and receives another dural venous sinus (the inferior petrosal sinus) soon after it is formed. It exits the skull through the jugular foramen associated with the glossopharyngeal [IX], vagus [X], and accessory [XI] nerves, and enters the carotid sheath.
The internal jugular vein traverses the neck within the carotid sheath, initially posterior to the internal carotid artery, but passes to a more lateral position farther down. It remains lateral to the common carotid artery through the rest of the neck with the vagus nerve [X] posterior and partially between the two vessels.
The paired internal jugular veins join with the subclavian veins posterior to the sternal end of the clavicle to form the right and left brachiocephalic veins (Fig. 8.169).
Tributaries to each internal jugular vein include the inferior petrosal sinus, and the facial, lingual, pharyngeal, occipital, superior thyroid, and middle thyroid veins. |
Numerous cranial and peripheral nerves: pass through the anterior triangle of the neck as they continue to their final destination, send branches to structures in or forming boundaries of the anterior triangle of the neck, and while in the anterior triangle of the neck, send branches to nearby structures.
The cranial nerves in these categories include the facial [VII], glossopharyngeal [IX], vagus [X], accessory [XI], and hypoglossal [XII].
Branches of spinal nerves in these categories include the transverse cervical nerve from the cervical plexus and the upper and lower roots of the ansa cervicalis.
After emerging from the stylomastoid foramen, the facial nerve [VII] gives off branches that innervate two muscles associated with the anterior triangle of the neck: the posterior belly of the digastric, and the stylohyoid.
The facial nerve [VII] also innervates the platysma muscle that overlies the anterior triangle and part of the posterior triangle of the neck.
The glossopharyngeal nerve [IX] leaves the cranial cavity through the jugular foramen. It begins its descent between the internal carotid artery and the internal jugular vein, lying deep to the styloid process and the muscles associated with the styloid process. As the glossopharyngeal nerve [IX] completes its descent, it passes forward between the internal and external carotid arteries, and curves around the lateral border of the stylopharyngeus muscle (Fig. 8.172). At this point, it continues in an anterior direction, deep to the hyoglossus muscle, to reach the base of the tongue and the area of the palatine tonsil.
As the glossopharyngeal nerve [IX] passes through the area of the anterior triangle of the neck it innervates the stylopharyngeus muscle, sends a branch to the carotid sinus, and supplies sensory branches to the pharynx.
The vagus nerve [X] exits the cranial cavity through the jugular foramen between the glossopharyngeal [IX] and accessory [XI] nerves.
Outside the skull the vagus nerve [X] enters the carotid sheath and descends through the neck enclosed in this structure medial to the internal jugular vein and posterior to the internal carotid and common carotid arteries (Fig. 8.173).
Branches of the vagus nerve [X] as it passes through the anterior triangle of the neck include a motor branch to the pharynx, a branch to the carotid body, the superior laryngeal nerve (which divides into external and internal laryngeal branches), and possibly a cardiac branch.
The accessory nerve [XI] is the most posterior of the three cranial nerves exiting the cranial cavity through the jugular foramen. It begins its descent medial to the internal jugular vein, emerging from between the internal jugular vein and internal carotid artery to cross the lateral surface of the internal jugular vein as it passes downward and backward to disappear either into or beneath the anterior border of the sternocleidomastoid muscle (Fig. 8.174).
The accessory nerve gives off no branches as it passes through the anterior triangle of the neck.
The hypoglossal nerve [XII] leaves the cranial cavity through the hypoglossal canal and is medial to the internal jugular vein and internal carotid artery immediately outside the skull. As it descends, it passes outward between the internal jugular vein and internal carotid artery (Fig. 8.175). At this point it passes forward, hooking around the occipital artery, across the lateral surfaces of the internal and external carotid arteries and the lingual artery, and then continues deep to the posterior belly of the digastric and stylohyoid muscles. It passes over the surface of the hyoglossus muscle and disappears deep to the mylohyoid muscle.
The hypoglossal nerve [XII], which supplies the tongue, does not give off any branches as it passes through the anterior triangle of the neck. |
The transverse cervical nerve is a branch of the cervical plexus arising from the anterior rami of cervical nerves C2 and C3. It emerges from beneath the posterior border of the sternocleidomastoid muscle, near the middle of the muscle, and loops around the sternocleidomastoid to cross its anterior surface in a transverse direction (Fig. 8.176). It continues across the neck and provides cutaneous innervation to this area.
The ansa cervicalis is a loop of nerve fibers from cervical nerves C1 to C3 that innervate the “strap muscles” in the anterior triangle of the neck (Fig. 8.177). It begins as branches from the cervical nerve C1 join the hypoglossal nerve [XII] soon after it leaves the skull.
As the hypoglossal nerve [XII] completes its descent and begins to pass forward across the internal and external carotid arteries, some of the cervical nerve fibers leave it and descend between the internal jugular vein and the internal, and then common, carotid arteries. These nerve fibers are the superior root of the ansa cervicalis and innervate the superior belly of the omohyoid muscle, and the upper parts of the sternohyoid and sternothyroid muscles.
Completing the loop is a direct branch from the cervical plexus containing nerve fibers from the second and third cervical nerves C2 and C3 (Fig. 8.177). This is the inferior root of the ansa cervicalis. It descends either medial or lateral to the internal jugular vein before turning medially to join the superior root. At this location, the ansa cervicalis gives off branches that innervate the inferior belly of the omohyoid, and the lower parts of the sternohyoid and sternothyroid muscles.
Elements of the gastrointestinal
The esophagus, trachea, pharynx, and larynx lie in the neck and are related to the anterior triangles.
The esophagus is part of the gastrointestinal system and has only a short course in the lower neck. It begins at vertebral level CVI, where it is continuous with the pharynx above and courses inferiorly to pass through the thoracic inlet. It lies directly anterior to the vertebral column (Fig. 8.178B).
The trachea is part of the lower airway and, like the esophagus, begins at vertebral level CVI, where it is continuous with the larynx above (Fig. 8.178B). The trachea lies directly anterior to the esophagus and passes inferiorly in the midline to enter the thorax.
The pharynx is a common pathway for air and food, and the head with similar compartments in the lower neck (see pp. 1029–1041).
The larynx is the upper end of the lower airway. It is continuous with the trachea below and the pharynx posterosuperiorly (see pp. 1041–1058).
The thyroid and parathyroid glands are endocrine glands positioned anteriorly in the neck.
Both glands begin as pharyngeal outgrowths that migrate caudally to their final positions as development continues.
The thyroid gland is a large, unpaired gland, while the parathyroid glands, usually four in number, are small and are on the posterior surface of the thyroid gland.
The thyroid gland is anterior in the neck below and lateral to the thyroid cartilage (Fig. 8.178). It consists of two lateral lobes (which cover the anterolateral surfaces of the trachea, the cricoid cartilage, and the lower part of the thyroid cartilage) with an isthmus that connects the lateral lobes and crosses the anterior surfaces of the second and third tracheal cartilages. |
Lying deep to the sternohyoid, sternothyroid, and omohyoid muscles, the thyroid gland is in the visceral compartment of the neck. This compartment also includes the pharynx, trachea, and esophagus and is surrounded by the pretracheal layers of fascia.
The thyroid gland arises as a median outgrowth from the floor of the pharynx near the base of the tongue. The foramen cecum of the tongue indicates the site of origin and the thyroglossal duct marks the path of migration of the thyroid gland to its final adult location. The thyroglossal duct usually disappears early in development, but remnants may persist as a cyst or as a connection to the foramen cecum (i.e., a fistula).
There may also be functional thyroid gland: associated with the tongue (a lingual thyroid), anywhere along the path of migration of the thyroid gland, or extending upward from the gland along the path of the thyroglossal duct (a pyramidal lobe).
Two major arteries supply the thyroid gland.
Superior thyroid artery. The superior thyroid artery is the first branch of the external carotid artery (Fig. 8.179). It descends, passing along the lateral margin of the thyrohyoid muscle, to reach the superior pole of the lateral lobe of the gland where it divides into anterior and posterior glandular branches:
The anterior glandular branch passes along the superior border of the thyroid gland and anastomoses with its twin from the opposite side across the isthmus (Fig. 8.179).
The posterior glandular branch passes to the posterior side of the gland and may anastomose with the inferior thyroid artery (Fig. 8.180).
Inferior thyroid artery. The inferior thyroid artery is a branch of the thyrocervical trunk, which arises from the first part of the subclavian artery (Figs. 8.179 and 8.180). It ascends along the medial edge of the anterior scalene muscle, passes posteriorly to the carotid sheath, and reaches the inferior pole of the lateral lobe of the thyroid gland.
At the thyroid gland the inferior thyroid artery divides into an: inferior branch, which supplies the lower part of the thyroid gland and anastomoses with the posterior branch of the superior thyroid artery, and an ascending branch, which supplies the parathyroid glands.
Occasionally, a small thyroid ima artery arises from the brachiocephalic trunk or the arch of the aorta and ascends on the anterior surface of the trachea to supply the thyroid gland.
Three veins drain the thyroid gland (Fig. 8.179):
The superior thyroid vein primarily drains the area supplied by the superior thyroid artery.
The middle and inferior thyroid veins drain the rest of the thyroid gland.
The superior and middle thyroid veins drain into the internal jugular vein, and the inferior thyroid veins empty into the right and left brachiocephalic veins, respectively.
Lymphatic drainage of the thyroid gland is to nodes beside the trachea (paratracheal nodes) and to deep cervical nodes inferior to the omohyoid muscle along the internal jugular vein.
The thyroid gland is closely related to the recurrent laryngeal nerves. After branching from the vagus nerve [X] and looping around the subclavian artery on the right and the arch of the aorta on the left, the recurrent laryngeal nerves ascend in a groove between the trachea and esophagus (Fig. 8.180). They pass deep to the posteromedial surface of the lateral lobes of the thyroid gland and enter the larynx by passing deep to the lower margin of the inferior constrictor of the pharynx. |
Together with branches of the inferior thyroid arteries, the recurrent laryngeal nerves are clearly related to, and may pass through ligaments, one on each side, that bind the thyroid gland to the trachea and to the cricoid cartilage of the larynx. These relationships need to be considered when surgically removing or manipulating the thyroid gland.
The parathyroid glands are two pairs of small, ovoid, yellowish structures on the deep surface of the lateral lobes of the thyroid gland. They are designated as the superior and inferior parathyroid glands (Fig. 8.180). However, their position is quite variable and they may be anywhere from the carotid bifurcation superiorly to the mediastinum inferiorly.
Derived from the third (the inferior parathyroid glands) and fourth (the superior parathyroid glands) pharyngeal pouches, these paired structures migrate to their final adult positions and are named accordingly.
The arteries supplying the parathyroid glands are the inferior thyroid arteries, and venous and lymphatic drainage follows that described for the thyroid gland.
Location of structures in different regions of the anterior triangle of the neck
The regional location of major structures in the anterior triangle of the neck is summarized in Table 8.14. Structures can be identified as being within a specific subdivision, passing into a specific subdivision from outside the area, originating in one subdivision and passing to another subdivision, or passing through several subdivisions while traversing the region.
Posterior triangle of the neck
The posterior triangle of the neck is on the lateral aspect of the neck in direct continuity with the upper limb (Fig. 8.183). It is bordered: anteriorly by the posterior edge of the sternocleidomastoid muscle, posteriorly by the anterior edge of the trapezius muscle, basally by the middle one-third of the clavicle, and apically by the occipital bone just posterior to the mastoid process where the attachments of the trapezius and sternocleidomastoid come together.
The roof of the posterior triangle consists of an investing layer of cervical fascia that surrounds the sternocleidomastoid and trapezius muscles as it passes through the region.
The muscular floor of the posterior triangle is covered by the prevertebral layer of cervical fascia; and from superior to inferior consists of the splenius capitis, levator scapulae, and the posterior, middle, and anterior scalene muscles.
Numerous muscles participate in forming the borders and floor of the posterior triangle of the neck (Table 8.15).
In addition, the omohyoid muscle passes across the inferior part of the posterior triangle before disappearing under the sternocleidomastoid muscle and emerging in the anterior triangle (Fig. 8.184). It is enclosed in the investing layer of cervical fascia and crosses the posterior triangle from lateral to medial as it continues in a superior direction. It originates on the superior border of the scapula, just medial to the scapular notch and eventually inserts into the inferior border of the body of the hyoid bone. It has two bellies connected by a tendon, which is anchored by a fascial sling to the clavicle:
The superior belly is in the anterior triangle.
The inferior belly crosses the posterior triangle, subdividing it into a small, omoclavicular or subclavian triangle inferiorly and a much larger occipital triangle superiorly.
The omohyoid is innervated by branches of the ansa cervicalis (anterior rami from C1 to C3) and it depresses the hyoid bone.
One of the most superficial structures passing through the posterior triangle of the neck is the external jugular vein (Fig. 8.185). This large vein forms near the angle of the mandible, when the posterior branch of the retromandibular and posterior auricular veins join, and descends through the neck in the superficial fascia.
After crossing the sternocleidomastoid muscle, the external jugular vein enters the posterior triangle and continues its vertical descent. |
In the lower part of the posterior triangle, the external jugular vein pierces the investing layer of cervical fascia and ends in the subclavian vein.
Tributaries to the external jugular vein while it traverses the posterior triangle of the neck include the transverse cervical, suprascapular, and anterior jugular veins.
Several arteries are found within the boundaries of the posterior triangle of the neck. The largest is the third part of the subclavian artery as it crosses the base of the posterior triangle (Fig. 8.186).
The first part of the subclavian artery ascends to the medial border of the anterior scalene muscle from either the brachiocephalic trunk on the right side or directly from the arch of the aorta on the left side. It has numerous branches.
The second part of the subclavian artery passes laterally between the anterior and middle scalene muscles, and one branch may arise from it.
The third part of the subclavian artery emerges from between the anterior and middle scalene muscles to cross the base of the posterior triangle (Fig. 8.186). It extends from the lateral border of the anterior scalene muscle to the lateral border of rib I where it becomes the axillary artery and continues into the upper limb.
A single branch (the dorsal scapular artery) may arise from the third part of the subclavian artery. This branch passes posterolaterally to reach the superior angle of the scapula where it descends along the medial border of the scapula posterior to the rhomboid muscles.
Two other small arteries also cross the base of the posterior triangle. These are the transverse cervical and the suprascapular arteries (Fig. 8.186). They are both branches of the thyrocervical trunk, which arises from the first part of the subclavian artery.
After branching from the thyrocervical trunk, the transverse cervical artery passes laterally and slightly posteriorly across the base of the posterior triangle anterior to the anterior scalene muscle and the brachial plexus. Reaching the deep surface of the trapezius muscle, it divides into superficial and deep branches:
The superficial branch continues on the deep surface of the trapezius muscle.
The deep branch continues on the deep surface of the rhomboid muscles near the medial border of the scapula.
The suprascapular artery, also a branch of the thyrocervical trunk, passes laterally, in a slightly downward direction across the lowest part of the posterior triangle, and ends up posterior to the clavicle (Fig. 8.186). Approaching the scapula, it passes over the superior transverse scapular ligament and distributes branches to muscles on the posterior surface of the scapula.
Veins accompany all the arteries described previously.
The subclavian vein is a continuation of the axillary vein and begins at the lateral border of rib I. As it crosses the base of the posterior triangle, the external jugular, and, possibly, the suprascapular and transverse cervical veins enter it (Fig. 8.185). It ends by joining with the internal jugular vein to form the brachiocephalic vein near the sternoclavicular joint. In the posterior triangle it is anterior to, and slightly lower than, the subclavian artery and passes anterior to the anterior scalene muscle.
Transverse cervical and suprascapular veins travel with each of the similarly named arteries. These veins become tributaries to either the external jugular vein or the initial part of the subclavian vein.
A variety of nerves pass through or are within the posterior triangle. These include the accessory nerve [XI], branches of the cervical plexus, components forming the brachial plexus, and branches of the brachial plexus. |
The accessory nerve [XI] exits the cranial cavity through the jugular foramen. It descends through the neck in a posterior direction, to reach the anterior border of the sternocleidomastoid muscle. Passing either deep to or through and innervating the sternocleidomastoid muscle, the accessory nerve [XI] continues to descend and enters the posterior triangle (Fig. 8.187). It crosses the posterior triangle, still in an obliquely downward direction, within the investing layer of cervical fascia as this fascia crosses between the sternocleidomastoid and trapezius muscles. When the accessory nerve [XI] reaches the anterior border of the trapezius muscle, it continues on the deep surface of the trapezius and innervates it. The superficial location of the accessory nerve as it crosses the posterior triangle makes it susceptible to injury.
The cervical plexus is formed by the anterior rami of cervical nerves C1 to C4 (Fig. 8.188).
The cervical plexus forms in the substance of the muscles making up the floor of the posterior triangle within the prevertebral layer of cervical fascia, and consists of: muscular (or deep) branches, and cutaneous (or superficial) branches.
The cutaneous branches are visible in the posterior triangle emerging from beneath the posterior border of the sternocleidomastoid muscle (Fig. 8.187).
Muscular (deep) branches of the cervical plexus distribute to several groups of muscles. A major branch is the phrenic nerve, which supplies the diaphragm with both sensory and motor innervation (Fig. 8.188). It arises from the anterior rami of cervical nerves C3 to C5. Hooking around the upper lateral border of the anterior scalene muscle, the nerve continues inferiorly across the anterior surface of the anterior scalene within the prevertebral fascia to enter the thorax (Fig. 8.189). As the nerve descends in the neck, it is “pinned” to the anterior scalene muscle by the transverse cervical and suprascapular arteries.
Several muscular branches of the cervical plexus supply prevertebral and lateral vertebral muscles, including the rectus capitis anterior, rectus capitis lateralis, longus colli, and longus capitis (Fig. 8.189 and Table 8.16).
The cervical plexus also contributes to the formation of the superior and inferior roots of the ansa cervicalis (Fig. 8.188). This loop of nerves receives contributions from the anterior rami of the cervical nerves C1 to C3 and innervates the infrahyoid muscles.
Cutaneous (superficial) branches of the cervical plexus are visible in the posterior triangle as they pass outward from the posterior border of the sternocleidomastoid muscle (Figs. 8.187 and 8.188):
The lesser occipital nerve consists of contributions from cervical nerve C2 (Fig. 8.188), ascends along the posterior border of the sternocleidomastoid muscle, and distributes to the skin of the neck and scalp posterior to the ear.
The great auricular nerve consists of branches from cervical nerves C2 and C3, emerges from the posterior border of the sternocleidomastoid muscle, and ascends across the muscle to the base of the ear, supplying the skin of the parotid region, the ear, and the mastoid area.
The transverse cervical nerve consists of branches from the cervical nerves C2 and C3, passes around the midpart of the sternocleidomastoid muscle, and continues horizontally across the muscle to supply the lateral and anterior parts of the neck.
The supraclavicular nerves are a group of cutaneous nerves from cervical nerves C3 and C4 that, after emerging from beneath the posterior border of the sternocleidomastoid muscle, descend and supply the skin over the clavicle and shoulder as far inferiorly as rib II. |
The brachial plexus forms from the anterior rami of cervical nerves C5 to C8 and thoracic nerve T1. The contributions of each of these nerves, which are between the anterior and middle scalene muscles, are the roots of the brachial plexus. As the roots emerge from between these muscles, they form the next component of the brachial plexus (the trunks) as follows: the anterior rami of C5 and C6 form the upper trunk, the anterior ramus of C7 forms the middle trunk, the anterior rami of C8 and T1 form the lower trunk.
The trunks cross the base of the posterior triangle (see Fig. 8.186). Several branches of the brachial plexus may be visible in the posterior triangle (see Fig. 7.54 on pg. 730). These include the: dorsal scapular nerve to the rhomboid muscles, long thoracic nerve to the serratus anterior muscle, nerve to the subclavius muscle, and suprascapular nerve to the supraspinatus and infraspinatus muscles.
Root of the neck
The root of the neck (Fig. 8.190) is the area immediately superior to the superior thoracic aperture and axillary inlets. It is bounded by: the top of the manubrium of the sternum and superior margin of the clavicle anteriorly, and the top of the thoracic vertebra TI and the superior margin of the scapula to the coracoid process posteriorly.
It contains structures passing between the neck, thorax, and upper limb. There is also an extension of the thoracic cavity projecting into the root of the neck (Fig. 8.190). This consists of an upward projection of the pleural cavity, on both sides, and includes the cervical part of the parietal pleura (cupula), and the apical part of the superior lobe of each lung.
Anteriorly, the pleural cavity extends above the top of the manubrium of the sternum and superior border of rib I, while posteriorly, due to the downward slope of the superior thoracic aperture, the pleural cavity remains below the top of vertebra TI.
The subclavian arteries on both sides arch upward out of the thorax to enter the root of the neck (Fig. 8.191).
The right subclavian artery begins posterior to the sternoclavicular joint as one of two terminal branches of the brachiocephalic trunk. It arches superiorly and laterally to pass anterior to the extension of the pleural cavity in the root of the neck and posterior to the anterior scalene muscle. Continuing laterally across rib I, it becomes the axillary artery as it crosses its lateral border.
The left subclavian artery begins lower in the thorax than the right subclavian artery as a direct branch of the arch of the aorta. Lying posterior to the left common carotid artery and lateral to the trachea, it ascends and arches laterally, passing anterior to the extension of the pleural cavity and posterior to the anterior scalene muscle. It continues laterally over rib I, and becomes the axillary artery as it crosses the lateral border of rib I.
Both subclavian arteries are divided into three parts by the anterior scalene muscle (Fig. 8.191):
The first part extends from the origin of the artery to the anterior scalene muscle.
The second part is the part of the artery posterior to the anterior scalene muscle.
The third part is the part lateral to the anterior scalene muscle before the artery reaches the lateral border of rib I.
All branches from the right and left subclavian arteries arise from the first part of the artery, except in the case of one branch (the costocervical trunk) on the right side (Fig. 8.191). The branches include the vertebral artery, the thyrocervical trunk, the internal thoracic artery, and the costocervical trunk. |
The vertebral artery is the first branch of the subclavian artery as it enters the root of the neck (Fig. 8.191). A large branch, arising from the first part of the subclavian artery medial to the anterior scalene muscle, it ascends and enters the foramen in the transverse process of vertebra CVI. Continuing to pass superiorly, the vertebral artery passes through the foramina of vertebrae CV to CI. At the superior border of vertebra CI, the artery turns medially and crosses the posterior arch of vertebra CI. From here it passes through the foramen magnum to enter the posterior cranial fossa.
The second branch of the subclavian artery is the thyrocervical trunk (Fig. 8.191). It arises from the first part of the subclavian artery medial to the anterior scalene muscle, and divides into three branches—the inferior thyroid, the transverse cervical, and the suprascapular arteries.
Inferior thyroid artery. The inferior thyroid artery (Fig. 8.191) is the superior continuation of the thyrocervical trunk. It ascends, anterior to the anterior scalene muscle, and eventually turns medially, crossing posterior to the carotid sheath and its contents and anterior to the vertebral artery. Reaching the posterior surface of the thyroid gland it supplies the thyroid gland.
When the inferior thyroid artery turns medially, it gives off an important branch (the ascending cervical artery), which continues to ascend on the anterior surface of the prevertebral muscles, supplying these muscles and sending branches to the spinal cord.
Transverse cervical artery. The middle branch of the thyrocervical trunk is the transverse cervical artery (Fig. 8.191). This branch passes laterally, across the anterior surface of the anterior scalene muscle and the phrenic nerve, and enters and crosses the base of the posterior triangle of the neck. It continues to the deep surface of the trapezius muscle, where it divides into superficial and deep branches:
The superficial branch continues on the deep surface of the trapezius muscle.
The deep branch continues on the deep surface of the rhomboid muscles near the medial border of the scapula.
Suprascapular artery. The lowest branch of the thyrocervical trunk is the suprascapular artery (Fig. 8.191). This branch passes laterally, crossing anterior to the anterior scalene muscle, the phrenic nerve, the third part of the subclavian artery, and the trunks of the brachial plexus. At the superior border of the scapula, it crosses over the superior transverse scapular ligament and enters the supraspinatus fossa.
The third branch of the subclavian artery is the internal thoracic artery (Fig. 8.191). This artery branches from the inferior edge of the subclavian artery and descends.
It passes posterior to the clavicle and the large veins in the region and anterior to the pleural cavity. It enters the thoracic cavity posterior to the ribs and anterior to the transversus thoracis muscle and continues to descend giving off numerous branches.
The final branch of the subclavian artery in the root of the neck is the costocervical trunk (Fig. 8.191). It arises in a slightly different position, depending on the side:
On the left, it arises from the first part of the subclavian artery, just medial to the anterior scalene muscle.
On the right, it arises from the second part of the subclavian artery.
On both sides, the costocervical trunk ascends and passes posteriorly over the dome of the pleural cavity and continues in a posterior direction behind the anterior scalene muscle. Eventually it divides into two branches—the deep cervical and the supreme intercostal arteries:
The deep cervical artery ascends in the back of the neck and anastomoses with the descending branch of the occipital artery. |
The supreme intercostal artery descends anterior to rib I and divides to form the posterior intercostal arteries for the first two intercostal spaces.
Numerous veins pass through the root of the neck. Small veins accompany each of the arteries described above, and large veins form major drainage channels.
The subclavian veins begin at the lateral margin of rib I as continuations of the axillary veins. Passing medially on each side, just anterior to the anterior scalene muscles, each subclavian vein is joined by the internal jugular vein to form the brachiocephalic veins.
The only tributary to each subclavian vein is an external jugular vein.
The veins accompanying the numerous arteries in this region empty into other veins.
Several nerves and components of the nervous system pass through the root of the neck.
The phrenic nerves are branches of the cervical plexus and arise on each side as contributions from the anterior rami of cervical nerves C3 to C5 come together. Passing around the upper lateral border of each anterior scalene muscle, the phrenic nerves continue inferiorly across the anterior surface of each anterior scalene muscle within the prevertebral layer of cervical fascia (Fig. 8.192). Leaving the lower edge of the anterior scalene muscle each phrenic nerve passes between the subclavian vein and artery to enter the thorax and continue to the diaphragm.
The vagus nerves [X] descend through the neck within the carotid sheath, posterior to and just between the common carotid artery and the internal jugular vein.
In the lower part of the neck, the vagus nerves [X] give off cardiac branches, which continue downward and medially, passing posterior to the subclavian arteries to disappear into the thorax.
In the root of the neck, each vagus nerve [X] passes anterior to the subclavian artery and posterior to the subclavian vein as it enters the thorax (Fig. 8.192).
The right and left recurrent laryngeal nerves are visible as they originate in (the right recurrent laryngeal nerve), or pass through (the left recurrent laryngeal nerve), the root of the neck.
The right recurrent laryngeal nerve is a branch of the right vagus nerve [X] as it reaches the lower edge of the first part of the subclavian artery in the root of the neck. It passes around the subclavian artery and upward and medially in a groove between the trachea and the esophagus as it heads to the larynx.
The left recurrent laryngeal nerve is a branch of the left vagus nerve [X] as it crosses the arch of the aorta in the superior mediastinum. It passes below and behind the arch of the aorta and ascends beside the trachea to the larynx (Fig. 8.192).
Various components of the sympathetic nervous system are visible as they pass through the root of the neck (Fig. 8.193). These include: the cervical part of the sympathetic trunk, the ganglia associated with the cervical part of the sympathetic trunk, and cardiac nerves branching from the cervical part of the sympathetic trunk.
The sympathetic trunks are two parallel cords that run from the base of the skull to the coccyx. Along the way they are punctuated by ganglia, which are collections of neuronal cell bodies outside the CNS.
Cervical part of the sympathetic trunk
The cervical part of the sympathetic trunk is anterior to the longus colli and longus capitis muscles, and posterior to the common carotid artery in the carotid sheath and the internal carotid artery. It is connected to each cervical spinal nerve by a gray ramus communicans (Fig. 8.194). There are no white rami communicantes in the cervical region. |
Three ganglia are usually described along the course of the sympathetic trunk in the cervical region, and in these ganglia ascending preganglionic sympathetic fibers from upper thoracic spinal cord levels synapse with postganglionic sympathetic fibers. The postganglionic sympathetic fibers are distributed in branches from these ganglia.
Superior cervical ganglion. A very large superior cervical ganglion in the area of cervical vertebrae CI and CII marks the superior extent of the sympathetic trunk (Figs. 8.193 and 8.194). Its branches pass to: the internal carotid and external carotid arteries, forming plexuses around these vessels, cervical spinal nerves C1 to C4 through gray rami communicantes, the pharynx, and the heart as superior cardiac nerves.
Middle cervical ganglion. A second ganglion inferior to the superior cervical ganglion along the course of the sympathetic trunk (the middle cervical ganglion) is encountered at about the level of cervical vertebra CVI (Figs. 8.193 and 8.194). Branches from this ganglion pass to: cervical spinal nerves C5 and C6 through gray rami communicantes, and the heart as middle cardiac nerves.
Inferior cervical ganglion. At the lower end of the cervical part of the sympathetic trunk is another ganglion (the inferior cervical ganglion), which becomes very large when it combines with the first thoracic ganglion and forms the cervicothoracic ganglion (stellate ganglion). The inferior cervical ganglion (Figs. 8.193 and 8.194) is anterior to the neck of rib I and the transverse process of cervical vertebra CVII, and posterior to the first part of the subclavian artery and the origin of the vertebral artery.
Branches from this ganglion pass to: spinal nerves C7 to T1 through gray rami communicantes, the vertebral artery, forming a plexus associated with this vessel, and the heart as inferior cardiac nerves.
This ganglion may also receive white rami communicantes from thoracic spinal nerve T1, and occasionally, from T2.
The thoracic duct is a major lymphatic channel that begins in the abdomen, passes superiorly through the thorax, and ends in the venous channels in the neck.
It passes through the lower thoracic cavity in the midline with: the thoracic aorta on the left, the azygos vein on the right, and the esophagus anteriorly.
At about the level of thoracic vertebra TV the thoracic duct passes to the left and continues to ascend just to the left of the esophagus. It passes through the superior mediastinum and enters the root of the neck to the left of the esophagus (Fig. 8.195). Arching laterally, it passes posterior to the carotid sheath and turns inferiorly in front of the thyrocervical trunk, the phrenic nerve, and the vertebral artery.
The thoracic duct terminates in the junction between the left internal jugular and the left subclavian veins (Fig. 8.195). Near its junction with the venous system it is joined by: the left jugular trunk, which drains lymph from the left side of the head and neck, the left subclavian trunk, which drains lymph from the left upper limb, and occasionally, the left bronchomediastinal trunk, which drains lymph from the left half of the thoracic structures (Fig. 8.196).
A similar confluence of three lymphatic trunks occurs on the right side of the body. Emptying into the junction between the right internal jugular and right subclavian veins are: the right jugular trunk from the head and neck, the right subclavian trunk from the right upper limb, and occasionally, the right bronchomediastinal trunk carrying lymph from the structures in the right half of the thoracic cavity and the right upper intercostal spaces (Fig. 8.196). |
There is variability in how these trunks enter the veins. They may combine into a single right lymphatic duct to enter the venous system or enter as three separate trunks.
Lymphatics of the neck
A description of the organization of the lymphatic system in the neck becomes a summary of the lymphatic system in the head and neck. It is impossible to separate the two regions. The components of this system include superficial nodes around the head, superficial cervical nodes along the external jugular vein, and deep cervical nodes forming a chain along the internal jugular vein (Fig. 8.197).
The basic pattern of drainage is for superficial lymphatic vessels to drain to the superficial nodes. Some of these drain to the superficial cervical nodes on their way to the deep cervical nodes and others drain directly to the deep cervical nodes.
Five groups of superficial lymph nodes form a ring around the head and are primarily responsible for the lymphatic drainage of the face and scalp. Their pattern of drainage is very similar to the area of distribution of the arteries near their location.
Beginning posteriorly these groups (Fig. 8.197) are: occipital nodes near the attachment of the trapezius muscle to the skull and associated with the occipital artery—lymphatic drainage is from the posterior scalp and neck; mastoid nodes (retro-auricular/posterior auricular nodes) posterior to the ear near the attachment of the sternocleidomastoid muscle and associated with the posterior auricular artery—lymphatic drainage is from the posterolateral half of the scalp; pre-auricular and parotid nodes anterior to the ear and associated with the superficial temporal and transverse facial arteries—lymphatic drainage is from the anterior surface of the auricle, the anterolateral scalp, the upper half of the face, the eyelids, and the cheeks; submandibular nodes inferior to the body of the mandible and associated with the facial artery—lymphatic drainage is from structures along the path of the facial artery as high as the forehead, as well as the gingivae, the teeth, and the tongue; submental nodes inferior and posterior to the chin—lymphatic drainage is from the center part of the lower lip, the chin, the floor of the mouth, the tip of the tongue, and the lower incisor teeth.
Lymphatic flow from these superficial lymph nodes passes in several directions:
Drainage from the occipital and mastoid nodes passes to the superficial cervical nodes along the external jugular vein.
Drainage from the pre-auricular and parotid nodes, the submandibular nodes, and the submental nodes passes to the deep cervical nodes.
The superficial cervical nodes are a collection of lymph nodes along the external jugular vein on the superficial surface of the sternocleidomastoid muscle (Fig. 8.197). They primarily receive lymphatic drainage from the posterior and posterolateral regions of the scalp through the occipital and mastoid nodes, and send lymphatic vessels in the direction of the deep cervical nodes.
The deep cervical nodes are a collection of lymph nodes that form a chain along the internal jugular vein (Fig. 8.197). They are divided into upper and lower groups where the intermediate tendon of the omohyoid muscle crosses the common carotid artery and the internal jugular vein.
The most superior node in the upper deep cervical group is the jugulodigastric node (Fig. 8.197). This large node is where the posterior belly of the digastric muscle crosses the internal jugular vein and receives lymphatic drainage from the tonsils and tonsillar region.
Another large node, usually associated with the lower deep cervical group because it is at or just inferior to the intermediate tendon of the omohyoid muscle, is the jugulo-omohyoid node (Fig. 8.197). This node receives lymphatic drainage from the tongue. |
The deep cervical nodes eventually receive all lymphatic drainage from the head and neck either directly or through regional groups of nodes.
From the deep cervical nodes, lymphatic vessels form the right and left jugular trunks, which empty into the right lymphatic duct on the right side or the thoracic duct on the left side.
The pharynx is a musculofascial half-cylinder that links the oral and nasal cavities in the head to the larynx and esophagus in the neck (Fig. 8.198). The pharyngeal cavity is a common pathway for air and food.
The pharynx is attached above to the base of the skull and is continuous below, approximately at the level of vertebra CVI, with the top of the esophagus. The walls of the pharynx are attached anteriorly to the margins of the nasal cavities, oral cavity, and larynx. Based on these anterior relationships the pharynx is subdivided into three regions, the nasopharynx, oropharynx, and laryngopharynx:
The posterior apertures (choanae) of the nasal cavities open into the nasopharynx.
The posterior opening of the oral cavity (oropharyngeal isthmus) opens into the oropharynx.
The superior aperture of the larynx (laryngeal inlet) opens into the laryngopharynx.
In addition to these openings, the pharyngeal cavity is related anteriorly to the posterior one-third of the tongue and to the posterior aspect of the larynx. The pharyngotympanic tubes open into the lateral walls of the nasopharynx.
Lingual, pharyngeal, and palatine tonsils are on the deep surface of the pharyngeal walls.
The pharynx is separated from the posteriorly positioned vertebral column by a thin retropharyngeal space containing loose connective tissue.
Although the soft palate is generally considered as part of the roof of the oral cavity, it is also related to the pharynx. The soft palate is attached to the posterior margin of the hard palate and is a type of “flutter valve” that can: swing up (elevate) to close the pharyngeal isthmus, and seal off the nasopharynx from the oropharynx, and swing down (depress) to close the oropharyngeal isthmus and seal off the oral cavity from the oropharynx.
The superior and anterior margins of the pharyngeal wall are attached to bone and cartilage, and to ligaments. The two sides of the pharyngeal wall are welded together posteriorly in the midline by a vertically oriented cord-like ligament (the pharyngeal raphe). This connective tissue structure descends from the pharyngeal tubercle on the base of the skull to the level of cervical vertebra CVI where the raphe blends with connective tissue in the posterior wall of the esophagus.
There is an irregular C-shaped line of pharyngeal wall attachment on the base of the skull (Fig. 8.200). The open part of the C faces the nasal cavities. Each arm of the C begins at the posterior margin of the medial plate of the pterygoid process of the sphenoid bone, just inferior to the cartilaginous part of the pharyngotympanic tube. The line crosses inferior to the pharyngotympanic tube and then passes onto the petrous part of the temporal bone where it is just medial to the roughening for the attachment of one of the muscles (levator veli palatini) of the soft palate. From here, the line swings medially onto the occipital bone and joins the line from the other side at a prominent elevation of bone in the midline (the pharyngeal tubercle).
Anterior vertical line of attachment for the lateral pharyngeal walls
The vertical line of attachment for the lateral pharyngeal walls to structures related to the nasal and oral cavities and larynx is discontinuous and in three parts (Fig. 8.201). |
On each side, the anterior line of attachment of the lateral pharyngeal wall begins superiorly on the posterior edge of the medial pterygoid plate of the sphenoid bone just inferior to where the pharyngotympanic tube lies against this plate. It continues inferiorly along the edge of the medial plate of the pterygoid process and onto the pterygoid hamulus. From this point, the line descends along the pterygomandibular raphe to the mandible where this part of the line terminates.
The pterygomandibular raphe is a linear cord-like connective tissue ligament that spans the distance between the tip of the pterygoid hamulus and a triangular roughening immediately posterior to the third molar on the mandible. It joins a muscle of the lateral pharyngeal wall (superior constrictor) with a muscle of the lateral wall of the oral cavity (buccinator).
The second part of the line of attachment of the lateral pharyngeal wall is related to the hyoid bone. It begins on the lower aspect of the stylohyoid ligament, which connects the tip of the styloid process of the temporal bone to the lesser horn of the hyoid bone. The line continues onto the lesser horn and then turns and runs posteriorly along the entire upper surface of the greater horn of the hyoid where it terminates.
The most inferior and third part of the line of attachment of the lateral pharyngeal wall begins superiorly on the superior tubercle of the thyroid cartilage, and descends along the oblique line to the inferior tubercle.
From the inferior tubercle, the line of attachment continues over the cricothyroid muscle along a tendinous thickening of fascia to the cricoid cartilage where it terminates.
The pharyngeal wall is formed by skeletal muscles and by fascia. Gaps between the muscles are reinforced by the fascia and provide routes for structures to pass through the wall.
The muscles of the pharynx are organized into two groups based on the orientation of muscle fibers.
The constrictor muscles have fibers oriented in a circular direction relative to the pharyngeal wall, whereas the longitudinal muscles have fibers oriented vertically.
The three constrictor muscles on each side are major contributors to the structure of the pharyngeal wall (Fig. 8.202 and Table 8.17) and their names indicate their position—superior, middle, and inferior constrictor muscles. Posteriorly, the muscles from each side are joined together by the pharyngeal raphe. Anteriorly, these muscles attach to bones, cartilages, and ligaments related to the lateral margins of the nasal and oral cavities and the larynx.
The constrictor muscles overlap each other in a fashion resembling the walls of three flower pots stacked one on the other. The inferior constrictors overlap the lower margins of the middle constrictors and, in the same way, the middle constrictors overlap the superior constrictors.
Collectively, the muscles constrict or narrow the pharyngeal cavity.
When the constrictor muscles contract sequentially from top to bottom, as in swallowing, they move a bolus of food through the pharynx and into the esophagus.
All of the constrictors are innervated by the pharyngeal branch of the vagus nerve [X].
The superior constrictor muscles together bracket the upper part of the pharyngeal cavity (Fig. 8.202).
Each muscle is attached anteriorly to the pterygoid hamulus, pterygomandibular raphe, and adjacent bone of the mandible. From these attachments, the muscle fans out posteriorly and joins with its partner muscle from the other side at the pharyngeal raphe.
A special band of muscle (the palatopharyngeal sphincter) originates from the anterolateral surface of the soft palate and circles the inner aspect of the pharyngeal wall, blending with the inner aspect of the superior constrictor. |
When the superior constrictor constricts during swallowing, it forms a prominent ridge on the deep aspect of the pharyngeal wall that catches the margin of the elevated soft palate, which then seals closed the pharyngeal isthmus between the nasopharynx and oropharynx.
The middle constrictor muscles are attached to the lower aspect of the stylohyoid ligament, the lesser horn of the hyoid bone, and the entire upper surface of the greater horn of the hyoid (Fig. 8.202).
Like the superior constrictors, the middle constrictor muscles fan out posteriorly and attach to the pharyngeal raphe.
The posterior part of the middle constrictors overlaps the superior constrictors.
The inferior constrictor muscles attach anteriorly to the oblique line of the thyroid cartilage, the cricoid cartilage, and a ligament that spans between these two attachments to cartilage and crosses the cricothyroid muscle (Fig. 8.202).
Like the other constrictor muscles, the inferior constrictor muscles spread out posteriorly and attach to the pharyngeal raphe.
The posterior part of the inferior constrictors overlaps the middle constrictors. Inferiorly, the muscle fibers blend with and attach into the wall of the esophagus.
The parts of the inferior constrictors attached to the cricoid cartilage bracket the narrowest part of the pharyngeal cavity.
The three longitudinal muscles of the pharyngeal wall (Fig. 8.203 and Table 8.18) are named according to their origins—stylopharyngeus from the styloid process of the temporal bone, salpingopharyngeus from the cartilaginous part of the pharyngotympanic tube (salpinx is Greek for “tube”), and palatopharyngeus from the soft palate. From their sites of origin, these muscles descend and attach into the pharyngeal wall.
The longitudinal muscles elevate the pharyngeal wall, or during swallowing, pull the pharyngeal wall up and over a bolus of food being moved through the pharynx and into the esophagus.
The cylindrical stylopharyngeus muscle (Fig. 8.203A) originates from the base of the medial surface of the styloid process of the temporal bone and descends between the superior and middle constrictor muscles to fan out on, and blend with, the deep surface of the pharyngeal wall. It is innervated by the glossopharyngeal nerve [IX].
The salpingopharyngeus (Fig. 8.203B) is a small muscle originating from the inferior aspect of the pharyngotympanic tube, descending on, and blending into, the deep surface of the pharyngeal wall. It is innervated by the vagus nerve [X].
The palatopharyngeus (Fig. 8.203B), in addition to being a muscle of the pharynx, is also a muscle of the soft palate (see pp. 1098–1099). It is attached to the upper surface of the palatine aponeurosis, and passes posteriorly and inferiorly to blend with the deep surface of the pharyngeal wall.
The palatopharyngeus forms an important fold in the overlying mucosa (the palatopharyngeal arch). This arch is visible through the oral cavity and is a landmark for finding the palatine tonsil, which is immediately anterior to it on the oropharyngeal wall.
In addition to elevating the pharynx, the palatopharyngeus participates in closing the oropharyngeal isthmus by depressing the palate and moving the palatopharyngeal fold toward the midline.
The palatopharyngeus is innervated by the vagus nerve [X].
The pharyngeal fascia is separated into two layers, which sandwich the pharyngeal muscles between them: |
A thin layer (buccopharyngeal fascia) coats the outside of the muscular part of the wall and is a component of the pretracheal layer of cervical fascia (see p. 991).
A much thicker layer (pharyngobasilar fascia) lines the inner surface.
The fascia reinforces the pharyngeal wall where muscle is deficient. This is particularly evident above the level of the superior constrictor where the pharyngeal wall is formed almost entirely of fascia (Fig. 8.203). This part of the wall is reinforced externally by muscles of the soft palate (tensor and levator veli palatini).
Gaps in the pharyngeal wall and structures passing through them
Gaps between muscles of the pharyngeal wall provide important routes for muscles and neurovascular tissues (Fig. 8.204).
Above the margin of the superior constrictor, the pharyngeal wall is deficient in muscle and completed by pharyngeal fascia.
The tensor and levator veli palatini muscles of the soft palate initially descend from the base of the skull and are lateral to the pharyngeal fascia. In this position, they reinforce the pharyngeal wall:
The levator veli palatini passes through the pharyngeal fascia inferior to the pharyngotympanic tube and enters the soft palate.
The tendon of the tensor veli palatini turns medially around the pterygoid hamulus and passes through the origin of the buccinator muscle to enter the soft palate.
One of the largest and most important apertures in the pharyngeal wall is between the superior and middle constrictor muscles of the pharynx and the posterior border of the mylohyoid muscle, which forms the floor of the mouth (Fig. 8.204). This triangular-shaped gap (oropharyngeal triangle) not only enables the stylopharyngeus to slip into the pharyngeal wall, but also allows muscles, nerves, and vessels to pass between regions lateral to the pharyngeal wall and the oral cavity, particularly to the tongue.
The gap between the middle and inferior constrictor muscles allows the internal laryngeal vessels and nerve access to the aperture in the thyrohyoid membrane to enter the larynx.
The recurrent laryngeal nerves and accompanying inferior laryngeal vessels enter the larynx posterior to the inferior horn of the thyroid cartilage deep to the inferior margin of the inferior constrictor muscle.
The nasopharynx is behind the posterior apertures (choanae) of the nasal cavities and above the level of the soft palate (Fig. 8.205). Its ceiling is formed by the sloping base of the skull and consists of the posterior part of the body of the sphenoid bone and the basal part of the occipital bone. The ceiling and lateral walls of the nasopharynx form a domed vault at the top of the pharyngeal cavity that is always open.
The cavity of the nasopharynx is continuous below with the cavity of the oropharynx at the pharyngeal isthmus. The position of the pharyngeal isthmus is marked on the pharyngeal wall by a mucosal fold caused by the underlying palatopharyngeal sphincter, which is part of the superior constrictor muscle.
Elevation of the soft palate and constriction of the palatopharyngeal sphincter closes the pharyngeal isthmus during swallowing and separates the nasopharynx from the oropharynx.
There is a large collection of lymphoid tissue (the pharyngeal tonsil) in the mucosa covering the roof of the nasopharynx. Enlargement of this tonsil, known then as adenoids, can occlude the nasopharynx so that breathing is only possible through the oral cavity (Fig. 8.205A). |
The most prominent features on each lateral wall of the nasopharynx are: the pharyngeal opening of the pharyngotympanic tube, and mucosal elevations and folds covering the end of the pharyngotympanic tube and the adjacent muscles.
The opening of the pharyngotympanic tube is posterior to and slightly above the level of the hard palate, and lateral to the top of the soft palate (Fig. 8.205A).
Because the pharyngotympanic tube projects into the nasopharynx from a posterolateral direction, its posterior rim forms an elevation or bulge on the pharyngeal wall. Posterior to this tubal elevation (torus tubarius) is a deep recess (pharyngeal recess) (Fig. 8.205A).
Mucosal folds related to the pharyngotympanic tube include: the small vertical salpingopharyngeal fold, which descends from the tubal elevation and overlies the salpingopharyngeus muscle, and a broad fold or elevation (torus levatorius) that appears to emerge from just under the opening of the pharyngotympanic tube, continues medially onto the upper surface of the soft palate, and overlies the levator veli palatini muscle.
The oropharynx is posterior to the oral cavity, inferior to the level of the soft palate, and superior to the upper margin of the epiglottis (Fig. 8.205). The palatoglossal folds (arches), one on each side, that cover the palatoglossal muscles, mark the boundary between the oral cavity and the oropharynx. The arched opening between the two folds is the oropharyngeal isthmus. Just posterior and medial to these folds are another pair of folds (arches), the palatopharyngeal folds, one on each side, that overlie the palatopharyngeus muscles.
The anterior wall of the oropharynx inferior to the oropharyngeal isthmus is formed by the upper part of the posterior one-third or pharyngeal part of the tongue. Large collections of lymphoid tissue (the lingual tonsils) are in the mucosa covering this part of the tongue. A pair of mucosal pouches (valleculae), one on each side of the midline, between the base of the tongue and epiglottis, are depressions formed between a midline mucosal fold and two lateral folds that connect the tongue to the epiglottis.
The palatine tonsils are on the lateral walls of the oropharynx. On each side, there is a large ovoid collection of lymphoid tissue in the mucosa lining the superior constrictor muscle and between the palatoglossal and palatopharyngeal arches. The palatine tonsils are visible through the oral cavity just posterior to the palatoglossal folds.
When holding liquid or solids in the oral cavity, the oropharyngeal isthmus is closed by depression of the soft palate, elevation of the back of the tongue, and movement toward the midline of the palatoglossal and palatopharyngeal folds. This allows a person to breathe while chewing or manipulating material in the oral cavity.
On swallowing, the oropharyngeal isthmus is opened, the palate is elevated, the laryngeal cavity is closed, and the food or liquid is directed into the esophagus. A person cannot breathe and swallow at the same time because the airway is closed at two sites, the pharyngeal isthmus and the larynx.
The laryngopharynx extends from the superior margin of the epiglottis to the top of the esophagus at the level of vertebra CVI (Fig. 8.205).
The laryngeal inlet opens into the anterior wall of the laryngopharynx. Inferior to the laryngeal inlet, the anterior wall consists of the posterior aspect of the larynx. |
There is another pair of mucosal recesses (piriform fossae) between the central part of the larynx and the more lateral lamina of the thyroid cartilage. The piriform fossae form channels that direct solids and liquids from the oral cavity around the raised laryngeal inlet and into the esophagus.
Collections of lymphoid tissue in the mucosa of the pharynx surrounding the openings of the nasal and oral cavities (Waldeyer’s tonsillar ring) are part of the body’s defense system. The largest of these collections form distinct masses (tonsils). Tonsils occur mainly in three areas (Fig. 8.205):
The pharyngeal tonsil, known as adenoids when enlarged, is in the midline on the roof of the nasopharynx.
The palatine tonsils are on each side of the oropharynx between the palatoglossal and palatopharyngeal arches just posterior to the oropharyngeal isthmus. (The palatine tonsils are visible through the open mouth of a patient when the tongue is depressed.)
The lingual tonsils refer collectively to numerous lymphoid nodules on the posterior one-third of the tongue.
Small lymphoid nodules also occur in the pharyngotympanic tube near its opening into the nasopharynx, and on the upper surface of the soft palate.
Numerous vessels supply the pharyngeal wall (Fig. 8.206).
Arteries that supply upper parts of the pharynx include: the ascending pharyngeal artery, the ascending palatine and tonsillar branches of the facial artery, and numerous branches of the maxillary and the lingual arteries.
All these vessels are from the external carotid artery.
Arteries that supply the lower parts of the pharynx include pharyngeal branches from the inferior thyroid artery, which originates from the thyrocervical trunk of the subclavian artery.
The major blood supply to the palatine tonsil is from the tonsillar branch of the facial artery, which penetrates the superior constrictor muscle.
Veins of the pharynx form a plexus, which drains superiorly into the pterygoid plexus in the infratemporal fossa, and inferiorly into the facial and internal jugular veins (Fig. 8.207).
Lymphatic vessels from the pharynx drain into the deep cervical nodes and include retropharyngeal (between the nasopharynx and vertebral column), paratracheal, and infrahyoid nodes (Fig. 8.207).
The palatine tonsils drain through the pharyngeal wall into the jugulodigastric nodes in the region where the facial vein drains into the internal jugular vein (and inferior to the posterior belly of the digastric muscle).
Motor and most sensory innervation (except for the nasal region) of the pharynx is mainly through branches of the vagus [X] and glossopharyngeal [IX] nerves, which form a plexus in the outer fascia of the pharyngeal wall (Fig. 8.208A).
The pharyngeal plexus is formed by: the pharyngeal branch of the vagus nerve [X], branches from the external laryngeal nerve from the superior laryngeal branch of the vagus nerve [X], and pharyngeal branches of the glossopharyngeal nerve [IX].
The pharyngeal branch of the vagus nerve [X] originates from the upper part of its inferior ganglion above the origin of the superior laryngeal nerve and is the major motor nerve of the pharynx.
All muscles of the pharynx are innervated by the vagus nerve [X] mainly through the pharyngeal plexus, except for the stylopharyngeus, which is innervated directly by a branch of the glossopharyngeal nerve [IX] (Fig. 8.208B). |
Each subdivision of the pharynx has a different sensory innervation:
The nasopharynx is innervated by a pharyngeal branch of the maxillary nerve [V2] that originates in the pterygopalatine fossa and passes through the palatovaginal canal in the sphenoid bone to reach the roof of the pharynx.
The oropharynx is innervated by the glossopharyngeal nerve [IX] via the pharyngeal plexus.
The laryngopharynx is innervated by the vagus nerve [X] via the internal branch of the superior laryngeal nerve.
The glossopharyngeal nerve [IX] is related to the pharynx throughout most of its course outside the cranial cavity.
After exiting the skull through the jugular foramen, the glossopharyngeal nerve [IX] descends on the posterior surface of the stylopharyngeus muscle (Fig. 8.208B), passes onto the lateral surface of the stylopharyngeus, and then passes anteriorly through the gap (oropharyngeal triangle) between the superior constrictor, middle constrictor, and mylohyoid muscles to eventually reach the posterior aspect of the tongue.
As the glossopharyngeal nerve [IX] passes under the free edge of the superior constrictor, it is just inferior to the palatine tonsil lying on the deep surface of the superior constrictor.
Pharyngeal branches to the pharyngeal plexus and a motor branch to the stylopharyngeus muscle are among branches that originate from the glossopharyngeal nerve [IX] in the neck. Because sensory innervation of the oropharynx is by the glossopharyngeal nerve [IX], this nerve carries sensory innervation from the palatine tonsil and is also the afferent limb of the gag reflex (see “In the clinic” on p. 889).
The larynx is a hollow musculoligamentous structure with a cartilaginous framework that caps the lower respiratory tract.
The cavity of the larynx is continuous below with the trachea, and above opens into the pharynx immediately posterior and slightly inferior to the tongue and the posterior opening (oropharyngeal isthmus) of the oral cavity (Fig. 8.209A,B).
The larynx is both a valve (or sphincter) to close the lower respiratory tract, and an instrument to produce sound. It is composed of: three large unpaired cartilages (cricoid, thyroid, and epiglottis), three pairs of smaller cartilages (arytenoid, corniculate, and cuneiform), and a fibro-elastic membrane and numerous intrinsic muscles.
The larynx is suspended from the hyoid bone above and attached to the trachea below by membranes and ligaments. It is highly mobile in the neck and can be moved up and down and forward and backward by the action of extrinsic muscles that attach either to the larynx itself or to the hyoid bone.
During swallowing, the dramatic upward and forward movements of the larynx facilitate closing the laryngeal inlet and opening the esophagus.
Motor and sensory innervation of the larynx is provided by the vagus nerve [X].
The cricoid cartilage is the most inferior of the laryngeal cartilages and completely encircles the airway (Fig. 8.210). It is shaped like a signet ring with a broad lamina of cricoid cartilage posterior to the airway and a much narrower arch of cricoid cartilage circling anteriorly.
The posterior surface of the lamina is characterized by two shallow oval depressions separated by a vertical ridge. The esophagus is attached to the ridge and the depressions are for attachment of the posterior crico-arytenoid muscles.
The cricoid cartilage has two articular facets on each side for articulation with other laryngeal cartilages: |
One facet is on the sloping superolateral surface of the lamina and articulates with the base of an arytenoid cartilage.
The other facet is on the lateral surface of the lamina near its base and is for articulation with the medial surface of the inferior horn of the thyroid cartilage.
The thyroid cartilage (Fig. 8.211) is the largest of the laryngeal cartilages. It is formed by a right and a left lamina, which are widely separated posteriorly, but converge and join anteriorly. The most superior point of the site of fusion between the two broad flat laminae projects forward as the laryngeal prominence (Adam’s apple). The angle between the two laminae is more acute in men (90°) than in women (120°) so the laryngeal prominence is more apparent in men than women.
Just superior to the laryngeal prominence, the superior thyroid notch separates the two laminae as they diverge laterally. Both the superior thyroid notch and the laryngeal prominence are palpable landmarks in the neck. There is a less distinct inferior thyroid notch in the midline along the base of the thyroid cartilage.
The posterior margin of each lamina of the thyroid cartilage is elongated to form a superior horn and an inferior horn:
The medial surface of the inferior horn has a facet for articulation with the cricoid cartilage.
The superior horn is connected by a lateral thyrohyoid ligament to the posterior end of the greater horn of the hyoid bone.
The lateral surface of each thyroid lamina is marked by a ridge (the oblique line), which curves anteriorly from the base of the superior horn to a little short of midway along the inferior margin of the lamina.
The ends of the oblique line are expanded to form superior and inferior thyroid tubercles. The oblique line is a site of attachment for the extrinsic muscles of the larynx (sternothyroid, thyrohyoid, and inferior constrictor).
The epiglottis is a leaf-shaped cartilage attached by its stem to the posterior aspect of the thyroid cartilage at the angle (Fig. 8.212) and projects posterosuperiorly from its attachment to the thyroid cartilage. The attachment is via the thyro-epiglottic ligament in the midline approximately midway between the laryngeal prominence and the inferior thyroid notch. The upper margin of the epiglottis is behind the pharyngeal part of the tongue.
The inferior half of the posterior surface of the epiglottis is raised slightly to form an epiglottic tubercle.
The two arytenoid cartilages are pyramid-shaped cartilages with three surfaces, a base of arytenoid cartilage and an apex of arytenoid cartilage (Fig. 8.213):
The base is concave and articulates with the sloping articular facet on the superolateral surface of the lamina of cricoid cartilage.
The apex articulates with a corniculate cartilage.
The medial surface of each cartilage faces the other.
The anterolateral surface has two depressions, separated by a ridge, for muscle (vocalis) and ligament (vestibular ligament) attachment.
The posterior surface is covered by the transverse arytenoid muscle (see Fig. 8.223).
The anterior angle of the base is elongated into a vocal process to which the vocal ligament is attached. The lateral angle is similarly elongated into a muscular process for attachment of the posterior and lateral crico-arytenoid muscles.
The corniculate cartilages (Fig. 8.214) are two small conical cartilages whose bases articulate with the apices of the arytenoid cartilages. Their apices project posteromedially toward each other. |
These two small club-shaped cartilages (Fig. 8.214) lie anterior to the corniculate cartilages and are suspended in the part of the fibro-elastic membrane of the larynx that attaches the arytenoid cartilages to the lateral margin of the epiglottis.
The thyrohyoid membrane is a tough fibro-elastic ligament that spans between the superior margin of the thyroid cartilage below and the hyoid bone above (Fig. 8.215). It is attached to the superior margin of the thyroid laminae and adjacent anterior margins of the superior horns, and ascends medial to the greater horns and posterior to the body of the hyoid bone to attach to the superior margins of these structures.
An aperture in the lateral part of the thyrohyoid membrane on each side is for the superior laryngeal artery, the internal branch of the superior laryngeal nerve, and lymphatics.
The posterior borders of the thyrohyoid membrane are thickened to form the lateral thyrohyoid ligaments. The membrane is also thickened anteriorly in the midline to form the median thyrohyoid ligament.
Occasionally, there is a small cartilage (triticeal cartilage) in each lateral thyrohyoid ligament.
The hyo-epiglottic ligament (Fig. 8.215) extends from the midline of the epiglottis, anterosuperiorly to the body of the hyoid bone.
The cricotracheal ligament (Fig. 8.215) runs from the lower border of the cricoid cartilage to the adjacent upper border of the first tracheal cartilage.
Fibro-elastic membrane of the larynx
The fibro-elastic membrane of the larynx links together the laryngeal cartilages and completes the architectural framework of the laryngeal cavity. It is composed of two parts—a lower conus elasticus and an upper quadrangular membrane.
The conus elasticus (Fig. 8.216) is attached to the arch of cricoid cartilage and extends superiorly to end in a free upper margin within the space enclosed by the thyroid cartilage. On each side, this upper free margin attaches: anteriorly to the thyroid cartilage, and posteriorly to the vocal processes of the arytenoid cartilages.
The free margin between these two points of attachment is thickened to form the vocal ligament, which is under the vocal fold (true vocal cord) of the larynx.
The conus elasticus is also thickened anteriorly in the midline to form a distinct median cricothyroid ligament, which spans the distance between the arch of cricoid cartilage and the inferior thyroid notch and adjacent deep surface of the thyroid cartilage up to the attachment of the vocal ligaments.
In emergency situations, when the airway is blocked above the level of the vocal folds, the median cricothyroid ligament can be perforated to establish an airway. Except for small vessels and the occasional presence of a pyramidal lobe of the thyroid gland, normally there are few structures between the median cricothyroid ligament and skin.
The quadrangular membrane on each side runs between the lateral margin of the epiglottis and the anterolateral surface of the arytenoid cartilage on the same side (Fig. 8.217). It is also attached to the corniculate cartilage, which articulates with the apex of arytenoid cartilage.
Each quadrangular membrane has a free upper margin, between the top of the epiglottis and the corniculate cartilage, and a free lower margin. The free lower margin is thickened to form the vestibular ligament under the vestibular fold (false vocal cord) of the larynx.
The vestibular ligament is attached posteriorly to the superior depression on the anterolateral surface of the arytenoid cartilage and anteriorly to the thyroid angle just superior to the attachment of the vocal ligament. |
On each side, the vestibular ligament of the quadrangular membrane is separated from the vocal ligament of the cricothyroid ligament below by a gap. Because the vestibular ligament attaches to the anterolateral surface of the arytenoid cartilage and the vocal ligament attaches to the vocal process of the same cartilage, the vestibular ligament is lateral to the vocal ligament when viewed from above (Fig. 8.218).
The joints between the inferior horns of the thyroid cartilage and the cricoid cartilage, and between the cricoid cartilage and arytenoid cartilages are synovial. Each is surrounded by a capsule and is reinforced by associated ligaments. The cricothyroid joints enable the thyroid cartilage to move forward and tilt downward on the cricoid cartilage (Fig. 8.219).
Because the vocal ligaments pass between the posterior aspect of the thyroid angle and the arytenoid cartilages that sit on the lamina of cricoid cartilage, forward movement and downward rotation of the thyroid cartilage on the cricoid cartilage effectively lengthens and puts tension on the vocal ligaments.
The crico-arytenoid joints between articular facets on the superolateral surfaces of the cricoid cartilage and the bases of the arytenoid cartilages enable the arytenoid cartilages to slide away or toward each other and to rotate so that the vocal processes pivot either toward or away from the midline. These movements abduct and adduct the vocal ligaments (Fig. 8.220).
Cavity of the larynx
The central cavity of the larynx (Fig. 8.221) is tubular and lined by mucosa. Its architectural support is provided by the fibro-elastic membrane of the larynx and by the laryngeal cartilages to which it is attached.
The superior aperture of the cavity (laryngeal inlet) opens into the anterior aspect of the pharynx just below and posterior to the tongue (Fig. 8.221A):
Its anterior border is formed by mucosa covering the superior margin of the epiglottis.
Its lateral borders are formed by mucosal folds (ary-epiglottic folds), which enclose the superior margins of the quadrangular membranes and adjacent soft tissues, and two tubercles on the more posterolateral margin of the laryngeal inlet on each side mark the positions of the underlying cuneiform and corniculate cartilages.
Its posterior border in the midline is formed by a mucosal fold that forms a depression (interarytenoid notch) between the two corniculate tubercles.
The inferior opening of the laryngeal cavity is continuous with the lumen of the trachea, is completely encircled by the cricoid cartilage, and is horizontal in position unlike the laryngeal inlet, which is oblique and points posterosuperiorly into the pharynx. In addition, the inferior opening is continuously open, whereas the laryngeal inlet can be closed by downward movement of the epiglottis.
Two pairs of mucosal folds, the vestibular and vocal folds, which project medially from the lateral walls of the laryngeal cavity, constrict it and divide it into three major regions—the vestibule, a middle chamber, and the infraglottic cavity (Fig. 8.221B):
The vestibule is the upper chamber of the laryngeal cavity between the laryngeal inlet and the vestibular folds, which encloses the vestibular ligaments and associated soft tissues.
The middle part of the laryngeal cavity is very thin and is between the vestibular folds above and the vocal folds below.
The infraglottic space is the most inferior chamber of the laryngeal cavity and is between the vocal folds (which encloses the vocal ligaments and related soft tissues) and the inferior opening of the larynx. |
On each side, the mucosa of the middle cavity bulges laterally through the gap between the vestibular and vocal ligaments to produce an expanded trough-shaped space (a laryngeal ventricle) (Fig. 8.221A). An elongate tubular extension of each ventricle (laryngeal saccule) projects anterosuperiorly between the vestibular fold and thyroid cartilage and may reach as high as the top of the thyroid cartilage. Within the walls of these laryngeal saccules are numerous mucous glands. Mucus secreted into the saccules lubricates the vocal folds.
When viewed from above (Fig. 8.221C,D), there is a triangular opening (the rima vestibuli) between the two adjacent vestibular folds at the entrance to the middle chamber of the laryngeal cavity. The apex of the opening is anterior and its base is formed by the posterior wall of the laryngeal cavity.
Inferior to the vestibular folds, the vocal folds (true vocal cords) and adjacent mucosa-covered parts of the arytenoid cartilages form the lateral walls of a similar, but narrower, triangular opening (the rima glottidis between the two adjacent vocal folds). This opening separates the middle chamber above from the infraglottic cavity below. The base of this triangular opening is formed by the fold of mucosa (interarytenoid fold) at the bottom of the interarytenoid notch.
Both the rima glottidis and the rima vestibuli can be opened and closed by movement of the arytenoid cartilages and associated fibro-elastic membranes.
The intrinsic muscles of the larynx (Table 8.19) adjust tension in the vocal ligaments, open and close the rima glottidis, control the inner dimensions of the vestibule, close the rima vestibuli, and facilitate closing of the laryngeal inlet. They do this mainly by: acting on the cricothyroid and crico-arytenoid joints, adjusting the distance between the epiglottis and arytenoid cartilages, pulling directly on the vocal ligaments, and forcing soft tissues associated with the quadrangular membranes and vestibular ligaments toward the midline.
The fan-shaped cricothyroid muscles are attached to the anterolateral surfaces of the arch of the cricoid cartilage and expand superiorly and posteriorly to attach to the thyroid cartilage (Fig. 8.222).
Each muscle has an oblique part and a straight part:
The oblique part runs in a posterior direction from the arch of the cricoid cartilage to the inferior horn of the thyroid cartilage.
The straight part runs more vertically from the arch of the cricoid cartilage to the posteroinferior margin of the thyroid lamina.
The cricothyroid muscles move the cricothyroid joints. They pull the thyroid cartilage forward and rotate it down relative to the cricoid cartilage. These actions lengthen the vocal folds.
The cricothyroid muscles are the only intrinsic muscles of the larynx innervated by the superior laryngeal branches of the vagus nerves [X]. All other intrinsic muscles are innervated by the recurrent laryngeal branches of the vagus nerves [X].
There is a right and a left posterior crico-arytenoid muscle (Fig. 8.223). The fibers of each muscle originate from a large shallow depression on the posterior surface of the lamina of the cricoid cartilage, and run superiorly and laterally to converge on the muscular processes of the arytenoid cartilage.
The posterior crico-arytenoid muscles abduct and externally (laterally) rotate the arytenoid cartilages, thereby opening the rima glottidis. These muscles are the primary abductors of the vocal folds. They are innervated by the recurrent laryngeal branches of the vagus nerves [X]. |
The lateral crico-arytenoid muscle on each side originates from the upper surface of the arch of the cricoid cartilage, and runs posteriorly and superiorly to insert on the muscular process of the arytenoid cartilage (Fig. 8.223).
The lateral crico-arytenoid muscles internally rotate the arytenoid cartilages. These movements result in adducted (closed) vocal folds.
The lateral crico-arytenoids are innervated by the recurrent laryngeal branches of the vagus nerves [X].
The single transverse arytenoid muscle spans the distance between adjacent lateral margins of the arytenoid cartilages and covers the posterior surfaces of these cartilages (Fig. 8.223). It adducts the arytenoid cartilages and is innervated by the recurrent laryngeal branches of the vagus nerves [X].
Each of the two oblique arytenoid muscles runs from the posterior surface of the muscular process of one arytenoid cartilage to the apex of the arytenoid cartilage on the other side (Fig. 8.223). Some fibers of the muscle continue laterally around the margin of the arytenoid cartilage and into the ary-epiglottic fold where they continue as the ary-epiglottic part of the muscle (Fig. 8.224).
The oblique arytenoids can narrow the laryngeal inlet by constricting the distance between the arytenoid cartilages and the epiglottis. They are innervated by the recurrent laryngeal branches of the vagus nerves [X].
The vocalis muscles are elongate muscles lateral to and running parallel with each vocal ligament (Fig. 8.223). The fibers in each muscle are attached posteriorly to the lateral surface of the vocal process and adjacent depression on the anterolateral surface of the arytenoid cartilage, and anteriorly insert along the length of the vocal ligament to the thyroid angle.
The vocalis muscles adjust tension in the vocal folds and are innervated by the recurrent laryngeal branches of the vagus nerves [X].
The two thyro-arytenoid muscles are broad flat muscles lateral to the fibro-elastic membrane of the larynx and the laryngeal ventricles and saccules (Fig. 8.224). Each muscle runs from a vertical line of origin on the lower half of the thyroid angle and adjacent external surface of the cricothyroid ligament to the anterolateral surface of the arytenoid cartilage. Some of the fibers may continue into the ary-epiglottic fold and reach the margin of the epiglottis. These fibers are the thyro-epiglottic part of the muscle.
Because the thyro-arytenoid muscles are broad and lateral to the quadrangular membrane, they act as a sphincter of the vestibule by pushing soft tissues medial to the muscles toward the midline. The muscles also narrow the laryngeal inlet by pulling the arytenoid cartilages forward while simultaneously pulling the epiglottis toward the arytenoid cartilages.
The thyro-arytenoid muscles are innervated by the recurrent laryngeal branches of the vagus nerves [X].
Function of the larynx
The larynx is an elaborate sphincter for the lower respiratory tract and provides a mechanism for producing sounds. Adjustments of the size of the central cavity of the larynx result from changes in the dimensions of the rima glottidis, the rima vestibuli, the vestibule, and the laryngeal inlet (Fig. 8.225). These changes result from muscle actions and laryngeal mechanics. |
During quiet respiration, the laryngeal inlet, vestibule, rima vestibuli, and rima glottidis are open. The arytenoid cartilages are abducted and the rima glottidis is triangular shaped (Fig. 8.225A). During forced inspiration (Fig. 8.225B), the arytenoid cartilages are rotated laterally, mainly by the action of the posterior crico-arytenoid muscles. As a result, the vocal folds are abducted and the rima glottidis widens into a rhomboid shape, which effectively increases the diameter of the laryngeal airway.
When phonating, the arytenoid cartilages and vocal folds are adducted and air is forced through the closed rima glottidis (Fig. 8.225C). This action causes the vocal folds to vibrate against each other and produce sounds, which can then be modified by the upper parts of the airway and oral cavity. Tension in the vocal folds can be adjusted by the vocalis and cricothyroid muscles.
Effort closure of the larynx (Fig. 8.225D) occurs when air is retained in the thoracic cavity to stabilize the trunk, for example during heavy lifting, or as part of the mechanism for increasing intra-abdominal pressure. During effort closure, the rima glottidis is completely closed, as is the rima vestibuli and lower parts of the vestibule. The result is to completely and forcefully shut the airway.
During swallowing, the rima glottidis, rima vestibuli, and vestibule are closed and the laryngeal inlet is narrowed. In addition, the larynx moves up and forward. This action causes the epiglottis to swing downward toward the arytenoid cartilages and to effectively narrow or close the laryngeal inlet (Fig. 8.225E). The up and forward movement of the larynx also opens the esophagus, which is attached to the posterior aspect of the lamina of the cricoid cartilage. All these actions together prevent solids and liquids from entry into the airway and facilitate their movement through the piriform fossae into the esophagus.
The major blood supply to the larynx is by the superior and inferior laryngeal arteries (Fig. 8.226):
The superior laryngeal artery originates near the upper margin of the thyroid cartilage from the superior thyroid branch of the external carotid artery, and accompanies the internal branch of the superior laryngeal nerve through the thyrohyoid membrane to reach the larynx.
The inferior laryngeal artery originates from the inferior thyroid branch of the thyrocervical trunk of the subclavian artery low in the neck and, together with the recurrent laryngeal nerve, ascends in the groove between the esophagus and trachea—it enters the larynx by passing deep to the margin of the inferior constrictor muscle of the pharynx.
Veins draining the larynx accompany the arteries:
Superior laryngeal veins drain into superior thyroid veins, which in turn drain into the internal jugular veins (Fig. 8.227).
Inferior laryngeal veins drain into inferior thyroid veins, which drain into the left brachiocephalic vein.
Lymphatics drain regions above and below the vocal folds:
Those above the vocal folds follow the superior laryngeal artery and terminate in deep cervical nodes associated with the bifurcation of the common carotid artery.
Those below the vocal folds drain into deep nodes associated with the inferior thyroid artery or with nodes associated with the front of the cricothyroid ligament or upper trachea.
Sensory and motor innervation of the larynx is by two branches of the vagus nerves [X]—the superior laryngeal nerves and the recurrent laryngeal nerves (Fig. 8.228). |
The superior laryngeal nerves originate from the inferior vagal ganglia high in the neck (Fig. 8.228). On each side, the nerve descends medial to the internal carotid artery and divides into internal and external branches just above the level of the superior horn of the hyoid bone:
The external branch (external laryngeal nerve) descends along the lateral wall of the pharynx to supply and penetrate the inferior constrictor of the pharynx and ends by supplying the cricothyroid muscle.
The internal branch (internal laryngeal nerve) passes anteroinferiorly to penetrate the thyrohyoid membrane—it is mainly sensory and supplies the laryngeal cavity down to the level of the vocal folds.
The recurrent laryngeal nerves are (Fig. 8.228): sensory to the laryngeal cavity below the level of the vocal folds, and motor to all intrinsic muscles of the larynx except for the cricothyroid.
The left recurrent laryngeal nerve originates in the thorax, whereas the right recurrent laryngeal nerve originates in the root of the neck. Both nerves generally ascend in the neck in the groove between the esophagus and trachea and enter the larynx deep to the margin of the inferior constrictor. They may pass medial to, lateral to, or through the lateral ligament of the thyroid gland, which attaches the thyroid gland to the trachea and lower part of the cricoid cartilage on each side.
The two nasal cavities are the uppermost parts of the respiratory tract and contain the olfactory receptors. They are elongated wedge-shaped spaces with a large inferior base and a narrow superior apex (Figs. 8.229 and 8.230) and are held open by a skeletal framework consisting mainly of bone and cartilage.
The smaller anterior regions of the cavities are enclosed by the external nose, whereas the larger posterior regions are more central within the skull. The anterior apertures of the nasal cavities are the nares, which open onto the inferior surface of the nose. The posterior apertures are the choanae, which open into the nasopharynx.
The nasal cavities are separated: from each other by a midline nasal septum, from the oral cavity below by the hard palate, and from the cranial cavity above by parts of the frontal, ethmoid, and sphenoid bones.
Lateral to the nasal cavities are the orbits.
Each nasal cavity has a floor, roof, medial wall, and lateral wall (Fig. 8.230A).
The lateral wall is characterized by three curved shelves of bone (conchae), which are one above the other and project medially and inferiorly across the nasal cavity (Fig. 8.230B). The medial, anterior, and posterior margins of the conchae are free.
The conchae divide each nasal cavity into four air channels (Fig. 8.230C,D): an inferior nasal meatus between the inferior concha and the nasal floor, a middle nasal meatus between the inferior and middle concha, a superior nasal meatus between the middle and superior concha, and a spheno-ethmoidal recess between the superior concha and the nasal roof.
These conchae increase the surface area of contact between tissues of the lateral wall and the respired air.
The openings of the paranasal sinuses, which are extensions of the nasal cavity that erode into the surrounding bones during childhood and early adulthood, are on the lateral wall and roof of the nasal cavities (Fig. 8.231). In addition, the lateral wall also contains the opening of the nasolacrimal duct, which drains tears from the eye into the nasal cavity.
Each nasal cavity consists of three general regions—the nasal vestibule, the respiratory region, and the olfactory region (Fig. 8.232):
The nasal vestibule is a small dilated space just internal to the naris that is lined by skin and contains hair follicles. |
The respiratory region is the largest part of the nasal cavity, has a rich neurovascular supply, and is lined by respiratory epithelium composed mainly of ciliated and mucous cells.
The olfactory region is small, is at the apex of each nasal cavity, is lined by olfactory epithelium, and contains the olfactory receptors.
In addition to housing receptors for the sense of smell (olfaction), the nasal cavities adjust the temperature and humidity of respired air by the action of a rich blood supply, and trap and remove particulate matter from the airway by filtering the air through hair in the vestibule and by capturing foreign material in abundant mucus. The mucus normally is moved posteriorly by cilia on epithelial cells in the nasal cavities and is swallowed.
Innervation of the nasal cavities is by three cranial nerves:
Olfaction is carried by the olfactory nerve [I].
General sensation is carried by the trigeminal nerve [V], the anterior region by the ophthalmic nerve [V1], and the posterior region by the maxillary nerve [V2].
All glands are innervated by parasympathetic fibers in the facial nerve [VII] (greater petrosal nerve), which join branches of the maxillary nerve [V2] in the pterygopalatine fossa.
Sympathetic fibers are ultimately derived from the
T1 spinal cord level. They synapse mainly in the superior cervical sympathetic ganglion, and postganglionic fibers reach the nasal cavities along blood vessels, or by joining branches of the maxillary nerve [V2] in the pterygopalatine fossa.
Blood supply to the nasal cavities is by: terminal branches of the maxillary and facial arteries, which originate from the external carotid artery, and ethmoidal branches of the ophthalmic artery, which originates from the internal carotid artery.
Bones that contribute to the skeletal framework of the nasal cavities include: the unpaired ethmoid, sphenoid, frontal, and vomer bones, and the paired nasal, maxillary, palatine, and lacrimal bones and inferior conchae.
Of all the bones associated with the nasal cavities, the ethmoid is a key element.
The single ethmoid bone is one of the most complex bones in the skull. It contributes to the roof, lateral wall, and medial wall of both nasal cavities, and contains the ethmoidal cells (ethmoidal sinuses).
The ethmoid bone is cuboidal in overall shape (Fig. 8.233A) and is composed of two rectangular box- shaped ethmoidal labyrinths, one on each side, united superiorly across the midline by a perforated sheet of bone (the cribriform plate). A second sheet of bone (the perpendicular plate) descends vertically in the median sagittal plane from the cribriform plate to form part of the nasal septum.
Each ethmoidal labyrinth is composed of two delicate sheets of bone, which sandwich between them the ethmoidal cells.
The lateral sheet of bone (the orbital plate) is flat and forms part of the medial wall of the orbit.
The medial sheet of bone forms the upper part of the lateral wall of the nasal cavity and is characterized by two processes and a swelling (Fig. 8.233B)—the two processes are curved shelves of bone (the superior and middle conchae), which project across the nasal cavity and curve downward ending in free medial margins, while inferior to the origin of the middle concha, the middle ethmoidal cells form a prominent bulge (the ethmoidal bulla), on the medial wall of the labyrinth. |
Extending anterosuperiorly from just under the bulla is a groove (the ethmoidal infundibulum), which continues upward, and narrows to form a channel that penetrates the ethmoidal labyrinth and opens into the frontal sinus. This channel is for the frontonasal duct, which drains the frontal sinus.
The superior surface of the ethmoidal labyrinth articulates with the frontal bone, which usually completes the roof of the ethmoidal cells, while the anterior surface articulates with the frontal process of the maxilla and with the lacrimal bone. The inferior surface articulates with the upper medial margin of the maxilla.
A delicate irregularly shaped projection (the uncinate process) on the anterior aspect of the inferior surface of the ethmoidal labyrinth extends posteroinferiorly across a large defect (maxillary hiatus) in the medial wall of the maxilla to articulate with the inferior concha.
The cribriform plate is at the apex of the nasal cavities and fills the ethmoidal notch in the frontal bone (Fig. 8.233) and separates the nasal cavities below from the cranial cavity above. Small perforations in the bone allow the fibers of the olfactory nerve [I] to pass between the two regions.
A large triangular process (the crista galli) at the midline on the superior surface of the cribriform plate anchors a fold (falx cerebri) of dura mater in the cranial cavity.
The perpendicular plate of the ethmoid bone is quadrangular in shape, descends in the midline from the cribriform plate, and forms the upper part of the median nasal septum (Fig. 8.233). It articulates: posteriorly with the sphenoidal crest on the body of the sphenoid bone, anteriorly with the nasal spine on the frontal bone and with the site of articulation at the midline between the two nasal bones, and inferiorly and anteriorly with the septal cartilage and posteriorly with the vomer.
The external nose extends the nasal cavities onto the front of the face and positions the nares so that they point downward (Fig. 8.234). It is pyramidal in shape with its apex anterior in position. The upper angle of the nose between the openings of the orbits is continuous with the forehead.
Like posterior regions, the anterior parts of the nasal cavities found within the nose are held open by a skeletal framework, which is composed partly of bone and mainly of cartilage:
The bony parts are where the nose is continuous with the skull—here the nasal bones and parts of the maxillae and frontal bones provide support.
Anteriorly, and on each side, support is provided by lateral processes of the septal cartilage, major alar and three or four minor alar cartilages, and a single septal cartilage in the midline that forms the anterior part of the nasal septum.
There are four paranasal air sinuses—the ethmoidal cells, and the sphenoidal, maxillary, and frontal sinuses (Fig. 8.235A,B). Each is named according to the bone in which it is found.
The paranasal sinuses develop as outgrowths from the nasal cavities and erode into the surrounding bones. All of the paranasal sinuses: are lined by respiratory mucosa, which is ciliated and mucus secreting, open into the nasal cavities, and are innervated by branches of the trigeminal nerve [V].
The frontal sinuses, one on each side, are variable in size and are the most superior of the sinuses (Fig. 8.235A–C). Each is triangular in shape and is in the part of the frontal bone under the forehead. The base of each triangular sinus is oriented vertically in the bone at the midline above the bridge of the nose and the apex is laterally approximately one-third of the way along the upper margin of the orbit. |
Each frontal sinus drains onto the lateral wall of the middle meatus via the frontonasal duct, which penetrates the ethmoidal labyrinth and continues as the ethmoidal infundibulum at the front end of the semilunar hiatus.
The frontal sinuses are innervated by branches of the supra-orbital nerve from the ophthalmic nerve [V1]. Their blood supply is from branches of the anterior ethmoidal arteries.
The ethmoidal cells on each side fill the ethmoidal labyrinth (Fig. 8.235A,B). Each cluster of cells is separated from the orbit by the thin orbital plate of the ethmoidal labyrinth, and from the nasal cavity by the medial wall of the ethmoidal labyrinth.
The ethmoidal cells are formed by a variable number of individual air chambers, which are divided into anterior, middle, and posterior ethmoidal cells based on the location of their apertures on the lateral wall of the nasal cavity:
The anterior ethmoidal cells open into the ethmoidal infundibulum or the frontonasal duct.
The middle ethmoidal cells open onto the ethmoidal bulla, or onto the lateral wall just above this structure.
The posterior ethmoidal cells open onto the lateral wall of the superior nasal meatus.
Because the ethmoidal cells often erode into bones beyond the boundaries of the ethmoidal labyrinth, their walls may be completed by the frontal, maxillary, lacrimal, sphenoid, and palatine bones.
The ethmoidal cells are innervated by: the anterior and posterior ethmoidal branches of the nasociliary nerve from the ophthalmic nerve [V1], and the maxillary nerve [V2] via orbital branches from the pterygopalatine ganglion.
The ethmoidal cells receive their blood supply through branches of the anterior and posterior ethmoidal arteries.
The maxillary sinuses, one on each side, are the largest of the paranasal sinuses and completely fill the bodies of the maxillae (Fig. 8.235A,B). Each is pyramidal in shape with the apex directed laterally and the base deep to the lateral wall of the adjacent nasal cavity. The medial wall or base of the maxillary sinus is formed by the maxilla, and by parts of the inferior concha and palatine bone that overlie the maxillary hiatus.
The opening of the maxillary sinus is near the top of the base, in the center of the semilunar hiatus, which grooves the lateral wall of the middle nasal meatus.
Relationships of the maxillary sinus are as follows:
The superolateral surface (roof) is related above to the orbit.
The anterolateral surface is related below to the roots of the upper molar and premolar teeth and in front to the face.
The posterior wall is related behind to the infratemporal fossa.
The maxillary sinuses are innervated by infra-orbital and alveolar branches of the maxillary nerve [V2], and receive their blood through branches from the infra-orbital and superior alveolar branches of the maxillary arteries.
The sphenoidal sinuses, one on either side within the body of the sphenoid, open into the roof of the nasal cavity via apertures on the posterior wall of the spheno-ethmoidal recess (Fig. 8.235C,D). The apertures are high on the anterior walls of the sphenoid sinuses.
The sphenoidal sinuses are related: above to the cranial cavity, particularly to the pituitary gland and to the optic chiasm, laterally, to the cranial cavity, particularly to the cavernous sinuses, and below and in front, to the nasal cavities. |
Because only thin shelves of bone separate the sphenoidal sinuses from the nasal cavities below and hypophyseal fossa above, the pituitary gland can be surgically approached through the roof of the nasal cavities by passing first through the anteroinferior aspect of the sphenoid bone and into the sphenoidal sinuses and then through the top of the sphenoid bone into the hypophyseal fossa.
Innervation of the sphenoidal sinuses is provided by: the posterior ethmoidal branch of the ophthalmic nerve [V1], and the maxillary nerve [V2] via orbital branches from the pterygopalatine ganglion.
The sphenoidal sinuses are supplied by branches of the pharyngeal arteries from the maxillary arteries.
Walls, floor, and roof
The medial wall of each nasal cavity is the mucosa-covered surface of the thin nasal septum, which is oriented vertically in the median sagittal plane and separates the right and left nasal cavities from each other.
The nasal septum (Fig. 8.236) consists of: the septal nasal cartilage anteriorly, posteriorly, mainly the vomer and the perpendicular plate of the ethmoid bone, small contributions by the nasal bones where they meet in the midline, and the nasal spine of the frontal bone, and contributions by the nasal crests of the maxillary and palatine bones, rostrum of the sphenoid bone, and the incisor crest of the maxilla.
The floor of each nasal cavity (Fig. 8.237) is smooth, concave, and much wider than the roof. It consists of: soft tissues of the external nose, and the upper surface of the palatine process of the maxilla and the horizontal plate of the palatine bone, which together form the hard palate.
The naris opens anteriorly into the floor, and the superior aperture of the incisive canal is deep to the mucosa immediately lateral to the nasal septum near the front of the hard palate.
The roof of the nasal cavity is narrow and is highest in central regions where it is formed by the cribriform plate of the ethmoid bone (Fig. 8.238).
Anterior to the cribriform plate the roof slopes inferiorly to the nares and is formed by: the nasal spine of the frontal bone and the nasal bones, and the lateral processes of the septal cartilage and major alar cartilages of the external nose.
Posteriorly, the roof of each cavity slopes inferiorly to the choana and is formed by: the anterior surface of the sphenoid bone, the ala of the vomer and adjacent sphenoidal process of the palatine bone, and the vaginal process of the medial plate of the pterygoid process.
Underlying the mucosa, the roof is perforated superiorly by openings in the cribriform plate, and anterior to these openings by a separate foramen for the anterior ethmoidal nerve and vessels.
The opening between the sphenoidal sinus and the spheno-ethmoidal recess is on the posterior slope of the roof.
The lateral wall of each nasal cavity is complex and is formed by bone, cartilage, and soft tissues.
Bony support for the lateral wall (Fig. 8.239A) is provided by: the ethmoidal labyrinth, superior concha, middle concha and uncinate process, the perpendicular plate of the palatine bone, the medial pterygoid plate of the sphenoid bone, the medial surfaces of the lacrimal bones and maxillae, and the inferior concha.
In the external nose, the lateral wall of the cavity is supported by cartilage (lateral process of the septal cartilage and major and minor alar cartilages) and by soft tissues. The surface of the lateral wall is irregular in contour and is interrupted by the three nasal conchae. |
The inferior, middle, and superior conchae (Fig. 8.239B) extend medially across the nasal cavity, separating it into four air channels, an inferior, middle, and superior meatus and a spheno-ethmoidal recess. The conchae do not extend forward into the external nose. The anterior end of each concha curves inferiorly to form a lip that overlies the end of the related meatus.
Immediately inferior to the attachment of the middle concha and just anterior to the midpoint of the concha, the lateral wall of the middle meatus elevates to form the dome-shaped ethmoidal bulla (Fig. 8.239C). This is formed by the underlying middle ethmoidal cells, which expand the medial wall of the ethmoidal labyrinth.
Inferior to the ethmoidal bulla is a curved gutter (the semilunar hiatus), which is formed by the mucosa covering the lateral wall as it spans a defect in the bony wall between the ethmoidal bulla above and the uncinate process below.
The anterior end of the semilunar hiatus forms a channel (the ethmoidal infundibulum), which curves upward and continues as the frontonasal duct through the anterior part of the ethmoidal labyrinth to open into the frontal sinus.
The nasolacrimal duct and most of the paranasal sinuses open onto the lateral wall of the nasal cavity (Fig. 8.239C):
The nasolacrimal duct opens onto the lateral wall of the inferior nasal meatus under the anterior lip of the inferior concha—it drains tears from the conjunctival sac of the eye into the nasal cavity and originates at the inferior end of the lacrimal sac on the anteromedial wall of the orbit.
The frontal sinus drains via the frontonasal duct and ethmoidal infundibulum into the anterior end of the semilunar hiatus on the lateral wall of the middle nasal meatus—the anterior ethmoidal cells drain into the frontonasal duct or ethmoidal infundibulum (in some cases, the frontal sinus drains directly into the anterior end of the middle nasal meatus and the frontonasal duct ends blindly in the anterior ethmoidal cells).
The middle ethmoidal cells open onto or just above the ethmoidal bulla.
The posterior ethmoidal cells usually open onto the lateral wall of the superior nasal meatus.
The large maxillary sinus opens into the semilunar hiatus, usually just inferior to the center of the ethmoidal bulla—this opening is near the roof of the maxillary sinus.
The only paranasal sinus that does not drain onto the lateral wall of the nasal cavity is the sphenoidal sinus, which usually opens onto the sloping posterior roof of the nasal cavity.
The nares are oval apertures on the inferior aspect of the external nose and are the anterior openings of the nasal cavities (Fig. 8.240A). They are held open by the surrounding alar cartilages and septal cartilage, and by the inferior nasal spine and adjacent margins of the maxillae.
Although the nares are continuously open, they can be widened further by the action of the related muscles of facial expression (nasalis, depressor septi nasi, and levator labii superioris alaeque nasi muscles; Fig. 8.240B).
The choanae are the oval-shaped openings between the nasal cavities and the nasopharynx (Fig. 8.241). Unlike the nares, which have flexible borders of cartilage and soft tissues, the choanae are rigid openings completely surrounded by bone, and their margins are formed: inferiorly by the posterior border of the horizontal plate of the palatine bone, laterally by the posterior margin of the medial plate of the pterygoid process, and medially by the posterior border of the vomer.
The roof of the choanae is formed: anteriorly by the ala of the vomer and the vaginal process of the medial plate of the pterygoid process, and posteriorly by the body of the sphenoid bone. |
There are a number of routes by which nerves and vessels enter and leave the soft tissues lining each nasal cavity (Fig. 8.242), and these include the cribriform plate, sphenopalatine foramen, incisive canal, and small foramina in the lateral wall, and around the margin of the nares.
The fibers of the olfactory nerve [I] exit the nasal cavity and enter the cranial cavity through perforations in the cribriform plate. In addition, small foramina between the cribriform plate and surrounding bone allow the anterior ethmoidal nerve, a branch of the ophthalmic nerve [V1], and accompanying vessels to pass from the orbit into the cranial cavity and then down into the nasal cavity.
In addition, there is a connection in some individuals between nasal veins and the superior sagittal sinus of the cranial cavity through a prominent foramen (the foramen cecum) in the midline between the crista galli and frontal bone.
One of the most important routes by which nerves and vessels enter and leave the nasal cavity is the sphenopalatine foramen in the posterolateral wall of the superior nasal meatus. This foramen is just superior to the attachment of the posterior end of the middle nasal concha and is formed by the sphenopalatine notch in the palatine bone and the body of the sphenoid bone.
The sphenopalatine foramen is a route of communication between the nasal cavity and the pterygopalatine fossa. Major structures passing through the foramen are: the sphenopalatine branch of the maxillary artery, the nasopalatine branch of the maxillary nerve [V2], and superior nasal branches of the maxillary nerve [V2].
Another route by which structures enter and leave the nasal cavities is through the incisive canal in the floor of each nasal cavity. This canal is immediately lateral to the nasal septum and just posterosuperior to the root of the central incisor in the maxilla. The two incisive canals, one on each side, both open into the single unpaired incisive fossa in the roof of the oral cavity and transmit: the nasopalatine nerve from the nasal cavity into the oral cavity, and the terminal end of the greater palatine artery from the oral cavity into the nasal cavity.
Small foramina in the lateral wall
Other routes by which vessels and nerves get into and out of the nasal cavity include the nares and small foramina in the lateral wall:
Internal nasal branches of the infra-orbital nerve of the maxillary nerve [V2] and alar branches of the nasal artery from the facial artery loop around the margin of the naris to gain entry to the lateral wall of the nasal cavity from the face.
Inferior nasal branches from the greater palatine branch of the maxillary nerve [V2] enter the lateral wall of the nasal cavity from the palatine canal by passing through small foramina on the lateral wall.
The nasal cavities have a rich vascular supply for altering the humidity and temperature of respired air. In fact, the submucosa of the respiratory region, particularly that related to the conchae and septum, is often described as “erectile” or “cavernous” because the tissue enlarges or shrinks depending on the amount of blood flowing into the system.
Arteries that supply the nasal cavity include vessels that originate from both the internal and external carotid arteries (Fig. 8.243):
Vessels that originate from branches of the external carotid artery include the sphenopalatine, greater palatine, superior labial, and lateral nasal arteries.
Vessels that originate from branches of the internal carotid artery are the anterior and posterior ethmoidal arteries. |
The largest vessel supplying the nasal cavity is the sphenopalatine artery (Fig. 8.243), which is the terminal branch of the maxillary artery in the pterygopalatine fossa. It leaves the pterygopalatine fossa and enters the nasal cavity by passing medially through the sphenopalatine foramen and onto the lateral wall of the nasal cavity.
Posterior lateral nasal branches supply a large part of the lateral wall and anastomose anteriorly with branches from the anterior and posterior ethmoidal arteries, and with lateral nasal branches of the facial artery.
Posterior septal branches of the sphenopalatine artery pass over the roof of the cavity and onto the nasal septum where they contribute to the blood supply of the medial wall. One of these latter branches continues forward down the nasal septum to anastomose with the terminal end of the greater palatine artery and septal branches of the superior labial artery.
The terminal end of the greater palatine artery enters the anterior aspect of the floor of the nasal cavity by passing up through the incisive canal from the roof of the oral cavity (Fig. 8.243).
Like the sphenopalatine artery, the greater palatine artery arises in the pterygopalatine fossa as a branch of the maxillary artery. It passes first onto the roof of the oral cavity by passing down through the palatine canal and greater palatine foramen to the posterior aspect of the palate, then passes forward on the undersurface of the palate, and up through the incisive fossa and canal to reach the floor of the nasal cavity. The greater palatine artery supplies anterior regions of the medial wall and adjacent floor of the nasal cavity, and anastomoses with the septal branch of the sphenopalatine artery.
The superior labial artery and the lateral nasal artery originate from the facial artery on the front of the face.
The superior labial artery originates from the facial artery near the lateral end of the oral fissure and passes medially in the lip, supplying the lip and giving rise to branches that supply the nose and nasal cavity. An alar branch supplies the region around the lateral aspect of the naris and a septal branch passes into the nasal cavity and supplies anterior regions of the nasal septum.
The lateral nasal artery originates from the facial artery in association with the margin of the external nose and contributes to the blood supply of the external nose. Alar branches pass around the lateral margin of the naris and supply the nasal vestibule.
The anterior and posterior ethmoidal arteries (Fig. 8.243) originate in the orbit from the ophthalmic artery, which originates in the cranial cavity as a major branch of the internal carotid artery. They pass through canals in the medial wall of the orbit between the ethmoidal labyrinth and frontal bone, supply the adjacent paranasal sinuses, and then enter the cranial cavity immediately lateral and superior to the cribriform plate.
The posterior ethmoidal artery descends into the nasal cavity through the cribriform plate and has branches to the upper parts of the medial and lateral walls.
The anterior ethmoidal artery passes forward, with the accompanying anterior ethmoidal nerve, in a groove on the cribriform plate and enters the nasal cavity by descending through a slit-like foramen immediately lateral to the crista galli. It gives rise to branches that supply the medial (septal) and lateral wall of the nasal cavity and then continues forward on the deep surface of the nasal bone, and terminates by passing between the nasal bone and lateral nasal cartilage to emerge on the external nose as the external nasal branch to supply skin and adjacent tissues. |
Vessels that supply the nasal cavities form extensive anastomoses with each other. This is particularly evident in the anterior region of the medial wall where there are anastomoses between branches of the greater palatine, sphenopalatine, superior labial, and anterior ethmoidal arteries, and where the vessels are relatively close to the surface (Fig. 8.243B). This area is the major site of nosebleeds, or epistaxis.
Veins draining the nasal cavities generally follow the arteries (Fig. 8.244):
Veins that pass with branches that ultimately originate from the maxillary artery drain into the pterygoid plexus of veins in the infratemporal fossa.
Veins from anterior regions of the nasal cavities join the facial vein.
In some individuals, an additional nasal vein passes superiorly through a midline aperture (the foramen cecum), in the frontal bone anterior to the crista galli, and joins with the anterior end of the superior sagittal sinus. Because this nasal vein connects an intracranial venous sinus with extracranial veins, it is classified as an emissary vein. Emissary veins in general are routes by which infections can track from peripheral regions into the cranial cavity.
Veins that accompany the anterior and posterior ethmoidal arteries are tributaries of the superior ophthalmic vein, which is one of the largest emissary veins and drains into the cavernous sinus on either side of the hypophyseal fossa.
Nerves that innervate the nasal cavities (Fig. 8.245) are: the olfactory nerve [I] for olfaction, and branches of the ophthalmic [V1] and maxillary [V2] nerves for general sensation.
Secretomotor innervation of mucous glands in the nasal cavities and paranasal sinuses is by parasympathetic fibers from the facial nerve [VII], which mainly join branches of the maxillary nerve [V2] in the pterygopalatine fossa.
The olfactory nerve [I] is composed of axons from receptors in the olfactory epithelium at the top of each nasal cavity. Bundles of these axons pass superiorly through perforations in the cribriform plate to synapse with neurons in the olfactory bulb of the brain.
Branches from the ophthalmic nerve [V1]
Branches from the ophthalmic nerve [V1] that innervate the nasal cavity are the anterior and posterior ethmoidal nerves, which originate from the nasociliary nerve in the orbit.
The anterior ethmoidal nerve (Fig. 8.245) travels with the anterior ethmoidal artery and leaves the orbit through a canal between the ethmoidal labyrinth and the frontal bone. It passes through and supplies the adjacent ethmoidal cells and frontal sinus, and then enters the cranial cavity immediately lateral and superior to the cribriform plate. It then travels forward in a groove on the cribriform plate and enters the nasal cavity by descending through a slit-like foramen immediately lateral to the crista galli. It has branches to the medial and lateral wall of the nasal cavity and then continues forward on the undersurface of the nasal bone. It passes onto the external surface of the nose by traveling between the nasal bone and lateral nasal cartilage, and then terminates as the external nasal nerve, which supplies skin around the naris, in the nasal vestibule, and on the tip of the nose.
Like the anterior ethmoidal nerve, the posterior ethmoidal nerve leaves the orbit through a similar canal in the medial wall of the orbit. It terminates by supplying the mucosa of the ethmoidal cells and sphenoidal sinus and normally does not extend into the nasal cavity itself.
Branches from the maxillary nerve [V2] |
A number of nasal branches from the maxillary nerve [V2] innervate the nasal cavity. Many of these nasal branches (Fig. 8.245) originate in the pterygopalatine fossa, which is just lateral to the lateral wall of the nasal cavity, and leave the fossa to enter the nasal cavity by passing medially through the sphenopalatine foramen or through smaller foramina in the lateral wall:
A number of these nerves (posterior superior lateral nasal nerves) pass forward on and supply the lateral wall of the nasal cavity.
Others (posterior superior medial nasal nerves) cross the roof to the nasal septum and supply both these regions.
The largest of these nerves is the nasopalatine nerve, which passes forward and down the medial wall of the nasal cavity to pass through the incisive canal onto the roof of the oral cavity, and terminates by supplying the oral mucosa posterior to the incisor teeth.
Other nasal nerves (posterior inferior nasal nerves) originate from the greater palatine nerve, descending from the pterygopalatine fossa in the palatine canal just lateral to the nasal cavity, and pass through small bony foramina to innervate the lateral wall of the nasal cavity.
A small nasal nerve also originates from the anterior superior alveolar branch of the infra-orbital nerve and passes medially through the maxilla to supply the lateral wall near the anterior end of the inferior concha.
Secretomotor innervation of glands in the mucosa of the nasal cavity and paranasal sinuses is by preganglionic parasympathetic fibers carried in the greater petrosal branch of the facial nerve [VII]. These fibers enter the pterygopalatine fossa and synapse in the pterygopalatine ganglion (see Fig. 8.157 and pp. 986–987). Postganglionic parasympathetic fibers then join branches of the maxillary nerve [V2] to leave the fossa and ultimately reach target glands.
Sympathetic innervation, mainly involved with regulating blood flow in the nasal mucosa, is from spinal cord level T1. Preganglionic sympathetic fibers enter the sympathetic trunk and ascend to synapse in the superior cervical sympathetic ganglion. Postganglionic sympathetic fibers pass onto the internal carotid artery, enter the cranial cavity, and then leave the internal carotid artery to form the deep petrosal nerve, which joins the greater petrosal nerve of the facial nerve [VII] and enters the pterygopalatine fossa (see Figs. 8.156 and 8.157 and pp. 984–986).
Like the parasympathetic fibers, the sympathetic fibers follow branches of the maxillary nerve [V2] into the nasal cavity.
Lymph from anterior regions of the nasal cavities drains forward onto the face by passing around the margins of the nares (Fig. 8.246). These lymphatics ultimately connect with the submandibular nodes.
Lymph from posterior regions of the nasal cavity and the paranasal sinuses drains into upper deep cervical nodes. Some of this lymph passes first through the retropharyngeal nodes.
The oral cavity is inferior to the nasal cavities (Fig. 8.247A). It has a roof and floor and lateral walls, opens onto the face through the oral fissure, and is continuous with the cavity of the pharynx at the oropharyngeal isthmus.
The roof of the oral cavity consists of the hard and soft palates. The floor is formed mainly of soft tissues, which include a muscular diaphragm and the tongue. The lateral walls (cheeks) are muscular and merge anteriorly with the lips surrounding the oral fissure (the anterior opening of the oral cavity).
The posterior aperture of the oral cavity is the oropharyngeal isthmus, which opens into the oral part of the pharynx. |
The oral cavity is separated into two regions by the upper and lower dental arches consisting of the teeth and alveolar bone that supports them (Fig. 8.247B):
The outer oral vestibule, which is horseshoe shaped, is between the dental arches and the deep surfaces of the cheeks and lips—the oral fissure opens into it and can be opened and closed by muscles of facial expression, and by movements of the lower jaw.
The inner oral cavity proper is enclosed by the dental arches.
The degree of separation between the upper and lower arches is established by elevating or depressing the lower jaw (mandible) at the temporomandibular joint.
The oropharyngeal isthmus at the back of the oral cavity proper can be opened and closed by surrounding soft tissues, which include the soft palate and tongue.
The oral cavity has multiple functions:
It is the inlet for the digestive system involved with the initial processing of food, which is aided by secretions from salivary glands.
It manipulates sounds produced by the larynx and one outcome of this is speech.
It can be used for breathing because it opens into the pharynx, which is a common pathway for food and air. For this reason, the oral cavity can be used by physicians to access the lower airway, and dentists use “rubber dams” to prevent debris such as tooth fragments from passing through the oropharyngeal isthmus and pharynx into either the esophagus or the lower airway.
Multiple nerves innervate the oral cavity
General sensory innervation is carried predominantly by branches of the trigeminal nerve [V]:
The upper parts of the cavity, including the palate and the upper teeth, are innervated by branches of the maxillary nerve [V2].
The lower parts, including the teeth and oral part of the tongue, are innervated by branches of the mandibular nerve [V3].
Taste (special afferent [SA]) from the oral part or anterior two-thirds of the tongue is carried by branches of the facial nerve [VII], which join and are distributed with branches of the trigeminal nerve [V].
Parasympathetic fibers to the glands within the oral cavity are also carried by branches of the facial nerve [VII], which are distributed with branches of the trigeminal nerve [V].
Sympathetic fibers in the oral cavity ultimately come from spinal cord level T1, synapse in the superior cervical sympathetic ganglion, and are eventually distributed to the oral cavity along branches of the trigeminal nerve [V] or directly along blood vessels.
All muscles of the tongue are innervated by the hypoglossal nerve [XII], except the palatoglossus, which is innervated by the vagus nerve [X].
All muscles of the soft palate are innervated by the vagus nerve [X], except for the tensor veli palatini, which is innervated by a branch from the mandibular nerve [V3]. The muscle (mylohyoid) that forms the floor of the oral cavity is also innervated by the mandibular nerve [V3].
Bones that contribute to the skeletal framework of the oral cavity or are related to the anatomy of structures in the oral cavity include: the paired maxillae, palatine, and temporal bones, and the unpaired mandible, sphenoid, and hyoid bones.
In addition, the cartilaginous parts of the pharyngotympanic tubes on the inferior aspect of the base of the skull are related to the attachment of muscles of the soft palate.
The two maxillae contribute substantially to the architecture of the roof of the oral cavity. The parts involved are the alveolar and palatine processes (Fig. 8.248A). |
The palatine process is a horizontal shelf that projects from the medial surface of each maxilla. It originates just superior to the medial aspect of the alveolar process and extends to the midline where it is joined, at a suture, with the palatine process from the other side. Together, the two palatine processes form the anterior two-thirds of the hard palate.
In the midline on the inferior surface of the hard palate and at the anterior end of the intermaxillary suture is a single small fossa (incisive fossa) just behind the incisor teeth. Two incisive canals, one on each side, extend posterosuperiorly from the roof of this fossa to open onto the floor of the nasal cavity. The canals and fossae allow passage of the greater palatine vessels and the nasopalatine nerves.
The parts of each L-shaped palatine bone that contribute to the roof of the oral cavity are the horizontal plate and the pyramidal process (Fig. 8.248A).
The horizontal plate projects medially from the inferior aspect of the palatine bone and is joined by sutures to its partner in the midline and, on the same side, with the palatine process of the maxilla anteriorly.
A single posterior nasal spine is formed at the midline where the two horizontal plates join and projects backward from the margin of the hard palate. The posterior margin of the horizontal plates and the posterior nasal spine are associated with attachment of the soft palate.
The greater palatine foramen, formed mainly by the horizontal plate of the palatine bone and completed laterally by the adjacent part of the maxilla, opens onto the posterolateral aspect of the horizontal plate. This foramen is the inferior opening of the palatine canal, which continues superiorly into the pterygopalatine fossa and transmits the greater palatine nerve and vessels to the palate.
Also opening onto the palatine bone is the lesser palatine foramen. This foramen is the inferior opening of the short lesser palatine canal, which branches from the greater palatine canal and transmits the lesser palatine nerve and vessels to the soft palate.
The pyramidal process projects posteriorly and fills the space between the inferior ends of the medial and lateral plates of the pterygoid process of the sphenoid bone.
The pterygoid processes and spines of the sphenoid bone are associated with structures related to the soft palate, which forms part of the roof of the oral cavity (Fig. 8.248A).
The pterygoid processes descend, one on each side, from the lateral aspect of the body of the sphenoid bone. Each process has a medial and a lateral plate. These two vertically oriented plates project from the posterior aspect of the process. The V-shaped gap that occurs inferiorly between the two plates is filled by the pyramidal process of the palatine bone.
Projecting posterolaterally from the inferior margin of the medial plate of the pterygoid process is an elongate hook-shaped structure (the pterygoid hamulus). This hamulus is immediately behind the alveolar arch and inferior to the posterior margin of the hard palate. It is: a “pulley” for one of the muscles (tensor veli palatini) of the soft palate, and the attachment site for the upper end of the pterygomandibular raphe, which is attached below to the mandible and joins together the superior constrictor of the pharynx and the buccinator muscle of the cheek.
At the root of the medial plate of the pterygoid process on the base of the skull is a small canoe-shaped fossa (scaphoid fossa), which begins just medial to the foramen ovale and descends anteriorly and medially to the root of the medial plate of the pterygoid process (Fig. 8.248A). This fossa is for the attachment of one of the muscles of the soft palate (tensor veli palatini).
The spines of the sphenoid, one on each side, are vertical projections from the inferior surfaces of the greater wings of the sphenoid bone (Fig. 8.248A). Each spine is immediately posteromedial to the foramen spinosum. |
The medial aspect of the spine provides attachment for the most lateral part of the tensor veli palatini muscle of the soft palate.
The styloid process and inferior aspect of the petrous part of the temporal bone provide attachment for muscles associated with the tongue and soft palate, respectively.
The styloid process projects anteroinferiorly from the underside of the temporal bone. It can be as long as 1 inch (2.5 cm) and points toward the lesser horn of the hyoid bone to which it is attached by the stylohyoid ligament (Fig. 8.248B). The root of the styloid process is immediately anterior to the stylomastoid foramen and lateral to the jugular foramen. The styloglossus muscle of the tongue attaches to the anterolateral surface of the styloid process.
The inferior aspect of the temporal bone has a triangular roughened area immediately anteromedial to the opening of the carotid canal (Fig. 8.248A). The levator veli palatini muscle of the soft palate is attached here.
Cartilaginous part of the pharyngotympanic tube
The trumpet-shaped cartilaginous part of the pharyngotympanic tube is in a groove between the anterior margin of the petrous part of the temporal bone and the posterior margin of the greater wing of the sphenoid (Fig. 8.248A).
The medial and lateral walls of the cartilaginous part of the pharyngotympanic tube are formed mainly of cartilage, whereas the more inferolateral wall is more fibrous and is known as the membranous lamina.
The apex of the cartilaginous part of the pharyngotympanic tube connects laterally to the opening of the bony part in the temporal bone.
The expanded medial end of the cartilaginous part of the pharyngotympanic tube is immediately posterior to the upper margin of the medial plate of the pterygoid process and opens into the nasopharynx.
The cartilaginous part of the pharyngotympanic tube is lateral to the attachment of the levator veli palatini muscle and medial to the spine of the sphenoid. The tensor veli palatini muscle is attached, in part, to the membranous lamina.
The mandible is the bone of the lower jaw (Fig. 8.249). It consists of a body of right and left parts, which are fused anteriorly in the midline (mandibular symphysis), and two rami. The site of fusion is particularly visible on the external surface of the bone as a small vertical ridge in the midline.
The upper surface of the body of the mandible bears the alveolar arch (Fig. 8.249B), which anchors the lower teeth, and on its external surface on each side is a small mental foramen (Fig. 8.249B).
Posterior to the mandibular symphysis on the internal surface of the mandible are two pairs of small spines, one pair immediately above the other pair. These are the superior and inferior mental spines (superior and inferior genial spines) (Fig. 8.249A,C), and are attachment sites for a pair of muscles that pass into the tongue and a pair of muscles that connect the mandible to the hyoid bone.
Extending from the midline and originating inferior to the mental spines is a raised line or ridge (the mylohyoid line) (Fig. 8.249C), which runs posteriorly and superiorly along the internal surface of each side of the body of the mandible to end just below the level of the last molar tooth.
Above the anterior one-third of the mylohyoid line is a shallow depression (the sublingual fossa) (Fig. 8.249C), and below the posterior two-thirds of the mylohyoid line is another depression (the submandibular fossa) (Fig. 8.249C).
Between the last molar tooth and the mylohyoid line is a shallow groove for the lingual nerve. |
Immediately posterior to the last molar tooth on the medial upper surface of the body of the mandible is a small triangular depression (retromolar triangle) (Fig. 8.249A,C). The pterygomandibular raphe attaches just medial to the apex of this triangle and extends from here to the tip of the pterygoid hamulus above.
The ramus of the mandible, one on each side, is quadrangular shaped and oriented in the sagittal plane. On the medial surface of the ramus is a large mandibular foramen for transmission of the inferior alveolar nerve and vessels (Fig. 8.249C).
The hyoid bone is a small U-shaped bone in the neck between the larynx and the mandible. It has an anterior body of hyoid bone and two large greater horns, one on each side, which project posteriorly and superiorly from the body (Fig. 8.250). There are two small conical lesser horns on the superior surface where the greater horns join with the body. The stylohyoid ligaments attach to the apices of the lesser horns.
The hyoid bone is a key bone in the neck because it connects the floor of the oral cavity in front with the pharynx behind and the larynx below.
Walls: the cheeks
The walls of the oral cavity are formed by the cheeks.
Each cheek consists of fascia and a layer of skeletal muscle sandwiched between skin externally and oral mucosa internally. The thin layer of skeletal muscle within the cheeks is principally the buccinator muscle.
The buccinator muscle is one of the muscles of facial expression (Fig. 8.251). It is in the same plane as the superior constrictor muscle of the pharynx. In fact, the posterior margin of the buccinator muscle is joined to the anterior margin of the superior constrictor muscle by the pterygomandibular raphe, which runs between the tip of the pterygoid hamulus of the sphenoid bone above and a roughened area of bone immediately behind the last molar tooth on the mandible below.
The buccinator and superior constrictor muscles therefore provide continuity between the walls of the oral and pharyngeal cavities.
The buccinator muscle, in addition to originating from the pterygomandibular raphe, also originates directly from the alveolar part of the mandible and alveolar process of the maxilla.
From its three sites of origin, the muscle fibers of the buccinator run forward to blend with those of the orbicularis oris muscle and to insert into the modiolus, which is a small button-shaped nodule of connective tissue at the interface between the muscles of the lips and cheeks on each side.
The buccinator muscle holds the cheeks against the alveolar arches and keeps food between the teeth when chewing.
The buccinator is innervated by the buccal branch of the facial nerve [VII]. General sensation from the skin and oral mucosa of the cheeks is carried by the buccal branch of the mandibular nerve [V3].
The floor of the oral cavity proper is formed mainly by three structures: a muscular diaphragm, which fills the U-shaped gap between the left and right sides of the body of the mandible and is composed of the paired mylohyoid muscles; two cord-like geniohyoid muscles above the diaphragm, which run from the mandible in front to the hyoid bone behind; and the tongue, which is superior to the geniohyoid muscles.
Also present in the floor of the oral cavity proper are salivary glands and their ducts. The largest of these glands, on each side, are the sublingual gland and the oral part of the submandibular gland.
The two thin mylohyoid muscles (Table 8.20), one on each side, together form a muscular diaphragm that defines the inferior limit of the floor of the oral cavity (Fig. 8.252A). Each muscle is triangular in shape with its apex pointed forward. |
The lateral margin of each triangular muscle is attached to the mylohyoid line on the medial side of the body of the mandible. From here, the muscle fibers run slightly downward to the medial margin at the midline where the fibers are joined together with those of their partner muscle on the other side by a raphe. The raphe extends from the posterior aspect of the mandibular symphysis in front to the body of the hyoid bone behind.
The posterior margin of each mylohyoid muscle is free except for a small medial attachment to the hyoid bone.
The mylohyoid muscles: contribute structural support to the floor of the oral cavity, participate in elevating and pulling forward the hyoid bone, and therefore the attached larynx, during the initial stages of swallowing, and when the hyoid bone is fixed in position, depress the mandible and open the mouth.
Like the muscles of mastication, the mylohyoid muscles are innervated by the mandibular nerve [V3]. The specific branch that innervates the mylohyoid muscles is the nerve to the mylohyoid from the inferior alveolar nerve.
The geniohyoid muscles (Table 8.20) are paired cord-like muscles that run, one on either side of the midline, from the inferior mental spines on the posterior surface of the mandibular symphysis to the anterior surface of the body of the hyoid bone (Fig. 8.252B,C). They are immediately superior to the mylohyoid muscles in the floor of the mouth and inferior to the genioglossus muscles that form part of the root of the tongue.
The geniohyoid muscles: mainly pull the hyoid bone, and therefore the attached larynx, up and forward during swallowing; and because they pass posteroinferiorly from the mandible to the hyoid bone, when the hyoid bone is fixed, they can act with the mylohyoid muscles to depress the mandible and open the mouth.
Unlike other muscles that move the mandible at the temporomandibular joint, the geniohyoid muscles are innervated by a branch of cervical nerve C1, which “hitchhikes” from the neck along the hypoglossal nerve [XII] into the floor of the oral cavity.
Gateway into the floor of the oral cavity
In addition to defining the lower limit of the floor of the oral cavity, the free posterior border of the mylohyoid muscle on each side forms one of the three margins of a large triangular aperture (oropharyngeal triangle), which is a major route by which structures in the upper neck and infratemporal fossa of the head pass to and from structures in the floor of the oral cavity (Fig. 8.253). The other two muscles that complete the margins of the aperture are the superior and middle constrictor muscles of the pharynx.
Most structures that pass through the aperture are associated with the tongue and include muscles (hyoglossus, styloglossus), vessels (lingual artery and vein), nerves (lingual, hypoglossal [XII], glossopharyngeal [IX]), and lymphatics.
A large salivary gland (the submandibular gland) is “hooked” around the free posterior margin of the mylohyoid muscle and therefore also passes through the opening.
The tongue is a muscular structure that forms part of the floor of the oral cavity and part of the anterior wall of the oropharynx (Fig. 8.254A). Its anterior part is in the oral cavity and is somewhat triangular in shape with a blunt apex of the tongue. The apex is directed anteriorly and sits immediately behind the incisor teeth. The root of the tongue is attached to the mandible and the hyoid bone.
The superior surface of the oral or anterior two-thirds of the tongue is oriented in the horizontal plane. |
The pharyngeal surface or posterior one-third of the tongue curves inferiorly and becomes oriented more in the vertical plane. The oral and pharyngeal surfaces are separated by a V-shaped terminal sulcus of the tongue. This terminal sulcus forms the inferior margin of the oropharyngeal isthmus between the oral and pharyngeal cavities. At the apex of the V-shaped sulcus is a small depression (the foramen cecum of the tongue), which marks the site in the embryo where the epithelium invaginated to form the thyroid gland. In some people a thyroglossal duct persists and connects the foramen cecum on the tongue with the thyroid gland in the neck.
The superior surface of the oral part of the tongue is covered by hundreds of papillae (Fig. 8.254B):
Filiform papillae are small cone-shaped projections of the mucosa that end in one or more points.
Fungiform papillae are rounder in shape and larger than the filiform papillae, and tend to be concentrated along the margins of the tongue.
The largest of the papillae are the vallate papillae, which are blunt-ended cylindrical papillae invaginations in the tongue’s surface—there are only about 8 to 12 vallate papillae in a single V-shaped line immediately anterior to the terminal sulcus of the tongue.
Foliate papillae are linear folds of mucosa on the sides of the tongue near the terminal sulcus of tongue.
The papillae in general increase the area of contact between the surface of the tongue and the contents of the oral cavity. All except the filiform papillae have taste buds on their surfaces.
Inferior surface of tongue
The undersurface of the oral part of the tongue lacks papillae, but does have a number of linear mucosal folds (see Fig. 8.265). A single median fold (the frenulum of the tongue) is continuous with the mucosa covering the floor of the oral cavity, and overlies the lower margin of a midline sagittal septum, which internally separates the right and left sides of the tongue. On each side of the frenulum is a lingual vein, and lateral to each vein is a rough fimbriated fold.
The mucosa covering the pharyngeal surface of the tongue is irregular in contour because of the many small nodules of lymphoid tissue in the submucosa. These nodules are collectively the lingual tonsil.
There are no papillae on the pharyngeal surface.
The bulk of the tongue is composed of muscle (Fig. 8.254 and Table 8.21).
The tongue is completely divided into left and right halves by a median sagittal septum composed of connective tissue. This means that all muscles of the tongue are paired. There are intrinsic and extrinsic lingual muscles.
Except for the palatoglossus, which is innervated by the vagus nerve [X], all muscles of the tongue are innervated by the hypoglossal nerve [XII].
The intrinsic muscles of the tongue (Fig. 8.255) originate and insert within the substance of the tongue. They are divided into superior longitudinal, inferior longitudinal, transverse, and vertical muscles, and they alter the shape of the tongue by: lengthening and shortening it, curling and uncurling its apex and edges, and flattening and rounding its surface.
Working in pairs or one side at a time the intrinsic muscles of the tongue contribute to precision movements of the tongue required for speech, eating, and swallowing.
Extrinsic muscles of the tongue (Fig. 8.255 and Table 8.21) originate from structures outside the tongue and insert into the tongue. There are four major extrinsic muscles on each side, the genioglossus, hyoglossus, styloglossus, and palatoglossus. These muscles protrude, retract, depress, and elevate the tongue. |
The thick fan-shaped genioglossus muscles make a substantial contribution to the structure of the tongue. They occur on either side of the midline septum that separates left and right halves of the tongue.
The genioglossus muscles originate from the superior mental spines on the posterior surface of the mandibular symphysis immediately superior to the origin of the geniohyoid muscles from the inferior mental spines (Fig. 8.256). From this small site of origin, each muscle expands posteriorly and superiorly. The most inferior fibers attach to the hyoid bone. The remaining fibers spread out superiorly to blend with the intrinsic muscles along virtually the entire length of the tongue.
The genioglossus muscles: depress the central part of the tongue, and protrude the anterior part of the tongue out of the oral fissure (i.e., stick the tongue out).
Like most muscles of the tongue, the genioglossus muscles are innervated by the hypoglossal nerves [XII].
Asking a patient to “stick your tongue out” can be used as a test for the hypoglossal nerves [XII]. If the nerves are functioning normally, the tongue should protrude evenly in the midline. If the nerve on one side is not fully functional, the tip of the tongue will point to that side.
The hyoglossus muscles are thin quadrangular muscles lateral to the genioglossus muscles (Fig. 8.257).
Each hyoglossus muscle originates from the entire length of the greater horn and the adjacent part of the body of the hyoid bone. At its origin from the hyoid bone, the hyoglossus muscle is lateral to the attachment of the middle constrictor muscle of the pharynx. The muscle passes superiorly and anteriorly through the gap (oropharyngeal triangle) between the superior constrictor, middle constrictor, and mylohyoid to insert into the tongue lateral to the genioglossus and medial to the styloglossus.
The hyoglossus muscle depresses the tongue and is innervated by the hypoglossal nerve [XII].
An important landmark. The hyoglossus muscle is an important landmark in the floor of the oral cavity:
The lingual artery from the external carotid artery in the neck enters the tongue deep to the hyoglossus, between the hyoglossus and genioglossus.
The hypoglossal nerve [XII] and lingual nerve (branch of the mandibular nerve [V3]), from the neck and infratemporal fossa of the head, respectively, enter the tongue on the external surface of the hyoglossus.
The styloglossus muscles originate from the anterior surface of the styloid processes of the temporal bones. From here, each muscle passes inferiorly and medially through the gap (oropharyngeal triangle) between the middle constrictor, superior constrictor, and mylohyoid muscles to enter the lateral surface of the tongue where they blend with the superior margin of the hyoglossus and with the intrinsic muscles (Fig. 8.258).
The styloglossus muscles retract the tongue and pull the back of the tongue superiorly. They are innervated by the hypoglossal nerves [XII].
The palatoglossus muscles are muscles of the soft palate and the tongue. Each originates from the undersurface of the palatine aponeurosis and passes anteroinferiorly to the lateral side of the tongue (Fig. 8.259).
The palatoglossus muscles: elevate the back of the tongue, move the palatoglossal arches of mucosa toward the midline, and depress the soft palate.
These movements facilitate closing of the oropharyngeal isthmus and as a result separate the oral cavity from the oropharynx.
Unlike other muscles of the tongue, but similar to most other muscles of the soft palate, the palatoglossus muscles are innervated by the vagus nerves [X].
The major artery of the tongue is the lingual artery (Fig. 8.260). |
On each side, the lingual artery originates from the external carotid artery in the neck adjacent to the tip of the greater horn of the hyoid bone. It forms an upward bend and then loops downward and forward to pass deep to the hyoglossus muscle, and accompanies the muscle through the aperture (oropharyngeal triangle) formed by the margins of the mylohyoid, superior constrictor, and middle constrictor muscles, and enters the floor of the oral cavity.
The lingual artery then travels forward in the plane between the hyoglossus and genioglossus muscles to the apex of the tongue.
In addition to the tongue, the lingual artery supplies the sublingual gland, gingiva, and oral mucosa in the floor of the oral cavity.
The tongue is drained by dorsal lingual and deep lingual veins (Fig. 8.260).
The deep lingual veins are visible through the mucosa on the undersurface of the tongue. Although they accompany the lingual arteries in anterior parts of the tongue, they become separated from the arteries posteriorly by the hyoglossus muscles. On each side, the deep lingual vein travels with the hypoglossal nerve [XII] on the external surface of the hyoglossus muscle and passes out of the floor of the oral cavity through the aperture (oropharyngeal triangle) formed by the margins of the mylohyoid, superior constrictor, and middle constrictor muscles. It joins the internal jugular vein in the neck.
The dorsal lingual vein follows the lingual artery between the hyoglossus and genioglossus muscles and, like the deep lingual vein, drains into the internal jugular vein in the neck.
Innervation of the tongue is complex and involves a number of nerves (Figs. 8.260 and 8.261).
Taste (SA) and general sensation from the pharyngeal part of the tongue are carried by the glossopharyngeal nerve [IX].
The glossopharyngeal nerve [IX] leaves the skull through the jugular foramen and descends along the posterior surface of the stylopharyngeus muscle. It passes around the lateral surface of the stylopharyngeus and then slips through the posterior aspect of the gap (oropharyngeal triangle) between the superior constrictor, middle constrictor, and mylohyoid muscles. The nerve then passes forward on the oropharyngeal wall just below the inferior pole of the palatine tonsil and enters the pharyngeal part of the tongue deep to the styloglossus and hyoglossus muscles. In addition to taste and general sensation on the posterior one-third of the tongue, branches creep anterior to the terminal sulcus of the tongue to carry taste (SA) and general sensation from the vallate papillae.
General sensory innervation from the anterior two-thirds or oral part of the tongue is carried by the lingual nerve, which is a major branch of the mandibular nerve [V3]. It originates in the infratemporal fossa and passes anteriorly into the floor of the oral cavity by passing through the gap (oropharyngeal triangle) between the mylohyoid, superior constrictor, and middle constrictor muscles (Fig. 8.262). As it travels through the gap, it passes immediately inferior to the attachment of the superior constrictor to the mandible and continues forward on the medial surface of the mandible adjacent to the last molar tooth and deep to the gingiva. In this position, the nerve can be palpated against the bone by placing a finger into the oral cavity.
The lingual nerve then continues anteromedially across the floor of the oral cavity, loops under the submandibular duct, and ascends into the tongue on the external and superior surface of the hyoglossus muscle. |
In addition to general sensation from the oral part of the tongue, the lingual nerve also carries general sensation from the mucosa on the floor of the oral cavity and gingiva associated with the lower teeth. The lingual nerve also carries parasympathetic and taste fibers from the oral part of the tongue that are part of the facial nerve [VII].
Taste (SA) from the oral part of the tongue is carried into the central nervous system by the facial nerve [VII]. Special sensory (SA) fibers of the facial nerve [VII] leave the tongue and oral cavity as part of the lingual nerve. The fibers then enter the chorda tympani nerve, which is a branch of the facial nerve [VII] that joins the lingual nerve in the infratemporal fossa (Fig. 8.262; also see p. 976).
All muscles of the tongue are innervated by the hypoglossal nerve [XII] except for the palatoglossus muscle, which is innervated by the vagus nerve [X].
The hypoglossal nerve [XII] leaves the skull through the hypoglossal canal and descends almost vertically in the neck to a level just below the angle of the mandible (Fig. 8.263). Here it angles sharply forward around the sternocleidomastoid branch of the occipital artery, crosses the external carotid artery, and continues forward, crossing the loop of the lingual artery, to reach the external surface of the lower one-third of the hyoglossus muscle.
The hypoglossal nerve [XII] follows the hyoglossus muscle through the gap (oropharyngeal triangle) between the superior constrictor, middle constrictor, and mylohyoid muscles to reach the tongue.
In the upper neck, a branch from the anterior ramus of C1 joins the hypoglossal nerve [XII]. Most of these C1 fibers leave the hypoglossal nerve [XII] as the superior root of the ansa cervicalis (Fig. 8.263). Near the posterior border of the hyoglossus muscle, the remaining fibers leave the hypoglossal nerve [XII] and form two nerves: the thyrohyoid branch, which remains in the neck to innervate the thyrohyoid muscle, and the branch to the geniohyoid, which passes into the floor of the oral cavity to innervate the geniohyoid.
All lymphatic vessels from the tongue ultimately drain into the deep cervical chain of nodes along the internal jugular vein:
The pharyngeal part of the tongue drains through the pharyngeal wall directly into mainly the jugulodigastric node of the deep cervical chain.
The oral part of the tongue drains both directly into the deep cervical nodes, and indirectly into these nodes by passing first through the mylohyoid muscle and into submental and submandibular nodes.
The submental nodes are inferior to the mylohyoid muscles and between the digastric muscles, while the submandibular nodes are below the floor of the oral cavity along the inner aspect of the inferior margins of the mandible.
The tip of the tongue drains through the mylohyoid muscle into the submental nodes and then into mainly the jugulo-omohyoid node of the deep cervical chain.
Salivary glands are glands that open or secrete into the oral cavity. Most are small glands in the submucosa or mucosa of the oral epithelium lining the tongue, palate, cheeks, and lips, and open into the oral cavity directly or via small ducts. In addition to these small glands are much larger glands, which include the paired parotid, submandibular, and sublingual glands. |
The parotid gland (see pp. 900–901) on each side is entirely outside the boundaries of the oral cavity in a shallow triangular-shaped trench (Fig. 8.264) formed by: the sternocleidomastoid muscle behind, the ramus of the mandible in front, and superiorly, the base of the trench is formed by the external acoustic meatus and the posterior aspect of the zygomatic arch.
The gland normally extends anteriorly over the masseter muscle, and inferiorly over the posterior belly of the digastric muscle.
The parotid duct passes anteriorly across the external surface of the masseter muscle and then turns medially to penetrate the buccinator muscle of the cheek and open into the oral cavity adjacent to the crown of the second upper molar tooth.
The parotid gland encloses the external carotid artery, the retromandibular vein, and the origin of the extracranial part of the facial nerve [VII].
The elongate submandibular glands are smaller than the parotid glands but larger than the sublingual glands. Each is hook shaped (Fig. 8.265A,B):
The larger arm of the hook is directed forward in the horizontal plane below the mylohyoid muscle and is therefore outside the boundaries of the oral cavity—this larger superficial part of the gland is directly against a shallow impression on the medial side of the mandible (submandibular fossa) inferior to the mylohyoid line.
The smaller arm of the hook (or deep part) of the gland loops around the posterior margin of the mylohyoid muscle to enter and lie within the floor of the oral cavity where it is lateral to the root of the tongue on the lateral surface of the hyoglossus muscle.
The submandibular duct emerges from the medial side of the deep part of the gland in the oral cavity and passes forward to open on the summit of a small sublingual caruncle (papilla) beside the base of the frenulum of the tongue (Fig. 8.265C,D).
The lingual nerve loops under the submandibular duct, crossing first the lateral side and then the medial side of the duct, as the nerve descends anteromedially through the floor of the oral cavity and then ascends into the tongue.
The sublingual glands are the smallest of the three major paired salivary glands. Each is almond shaped and is immediately lateral to the submandibular duct and associated lingual nerve in the floor of the oral cavity (Fig. 8.265).
Each sublingual gland lies directly against the medial surface of the mandible where it forms a shallow groove (sublingual fossa) superior to the anterior one-third of the mylohyoid line.
The superior margin of the sublingual gland raises an elongate fold of mucosa (sublingual fold), which extends from the posterolateral aspect of the floor of the oral cavity to the sublingual papilla beside the base of the frenulum of the tongue at the midline anteriorly (Fig. 8.265D).
The sublingual gland drains into the oral cavity via numerous small ducts (minor sublingual ducts), which open onto the crest of the sublingual fold. Occasionally, the more anterior part of the gland is drained by a duct (major sublingual duct) that opens together with the submandibular duct on the sublingual caruncle.
Vessels that supply the parotid gland originate from the external carotid artery and from its branches that are adjacent to the gland. The submandibular and sublingual glands are supplied by branches of the facial and lingual arteries.
Veins from the parotid gland drain into the external jugular vein, and those from the submandibular and sublingual glands drain into lingual and facial veins.
Lymphatic vessels from the parotid gland drain into nodes that are on or in the gland. These parotid nodes then drain into superficial and deep cervical nodes. |
Lymphatics from the submandibular and sublingual glands drain mainly into submandibular nodes and then into deep cervical nodes, particularly the jugulo-omohyoid node.
Parasympathetic innervation to all salivary glands in the oral cavity is by branches of the facial nerve [VII], which join branches of the maxillary [V2] and mandibular [V3] nerves to reach their target destinations.
The parotid gland, which is entirely outside the oral cavity, receives its parasympathetic innervation from fibers that initially traveled in the glossopharyngeal nerve [IX], which eventually join a branch of the mandibular nerve [V3] in the infratemporal fossa (Fig. 8.266).
All salivary glands above the level of the oral fissure, as well as all mucus glands in the nose and the lacrimal gland in the orbit, are innervated by parasympathetic fibers carried in the greater petrosal branch of the facial nerve [VII] (Fig. 8.266). Preganglionic parasympathetic fibers carried in this nerve enter the pterygopalatine fossa and synapse with postganglionic parasympathetic fibers in the pterygopalatine ganglion formed around branches of the maxillary nerve [V2]. Postganglionic parasympathetic fibers join general sensory branches of the maxillary nerve, such as the palatine nerves, destined for the roof of the oral cavity, to reach their target glands.
All glands below the level of the oral fissure, which include those small glands in the floor of the oral cavity, in the lower lip, and in the tongue, and the larger submandibular and sublingual glands, are innervated by parasympathetic fibers carried in the chorda tympani branch of the facial nerve [VII] (Fig. 8.266).
The chorda tympani joins the lingual branch of the mandibular nerve [V3] in the infratemporal fossa and passes with it into the oral cavity. On the external surface of the hyoglossus muscle, preganglionic parasympathetic fibers leave the inferior aspect of the lingual nerve to synapse with postganglionic parasympathetic fibers in the submandibular ganglion, which appears to hang off the lingual nerve (Fig. 8.267). Postganglionic parasympathetic fibers leave the ganglion and pass directly to the submandibular and sublingual glands while others hop back onto the lingual nerve and travel with branches of the lingual nerve to target glands.
Sympathetic innervation to the salivary glands is from spinal cord level T1. Preganglionic sympathetic fibers enter the sympathetic trunk and ascend to synapse in the superior cervical sympathetic ganglion (Fig. 8.268). Postganglionic fibers hop onto adjacent blood vessels and nerves to reach the glands.
The roof of the oral cavity consists of the palate, which has two parts—an anterior hard palate and a posterior soft palate (Fig. 8.269).
The hard palate separates the oral cavity from the nasal cavities. It consists of a bony plate covered above and below by mucosa:
Above, it is covered by respiratory mucosa and forms the floor of the nasal cavities.
Below, it is covered by a tightly bound layer of oral mucosa and forms much of the roof of the oral cavity (Fig. 8.269).
The palatine processes of the maxillae form the anterior three-quarters of the hard palate. The horizontal plates of the palatine bones form the posterior one-quarter. In the oral cavity, the upper alveolar arch borders the hard palate anteriorly and laterally. Posteriorly, the hard palate is continuous with the soft palate. |
The mucosa of the hard palate in the oral cavity possesses numerous transverse palatine folds (palatine rugae) and a median longitudinal ridge (palatine raphe), which ends anteriorly in a small oval elevation (incisive papilla). The incisive papilla (Fig. 8.269) overlies the incisive fossa formed between the horizontal plates of the maxillae immediately behind the incisor teeth.
The soft palate (Fig. 8.269) continues posteriorly from the hard palate and acts as a valve that can be: depressed to help close the oropharyngeal isthmus, and elevated to separate the nasopharynx from the oropharynx.
The soft palate is formed and moved by four muscles and is covered by mucosa that is continuous with the mucosa lining the pharynx and oral and nasal cavities.
The small tear-shaped muscular projection that hangs from the posterior free margin of the soft palate is the uvula.
Muscles of the soft palate
Five muscles (Table 8.22) on each side contribute to the formation and movement of the soft palate. Two of these, the tensor veli palatini and levator veli palatini, descend into the palate from the base of the skull. Two others, the palatoglossus and palatopharyngeus, ascend into the palate from the tongue and pharynx, respectively. The last muscle, the musculus uvulae, is associated with the uvula.
All muscles of the palate are innervated by the vagus nerve [X], except for the tensor veli palatini, which is innervated by the mandibular nerve [V3] (via the nerve to the medial pterygoid).
Tensor veli palatini and the palatine aponeurosis
The tensor veli palatini muscle is composed of two parts—a vertical muscular part and a more horizontal fibrous part, which forms the palatine aponeurosis (Fig. 8.270A).
The vertical part of the tensor veli palatini is thin and triangular in shape with its base attached to the skull and its apex pointed inferiorly. The base is attached along an oblique line that begins medially at the scaphoid fossa near the root of the pterygoid process of the sphenoid bone and continues laterally along the membranous part of the pharyngotympanic tube to the spine of the sphenoid bone.
The tensor veli palatini descends vertically along the lateral surface of the medial plate of the pterygoid process and pharyngeal wall to the pterygoid hamulus where the fibers converge to form a small tendon (Fig. 8.270A).
The tendon loops 90° medially around the pterygoid hamulus, penetrating the origin of the buccinator muscle as it does, and expands like a fan to form the fibrous horizontal part of the muscle. This fibrous part is continuous across the midline with its partner on the other side to form the palatine aponeurosis.
The palatine aponeurosis is attached anteriorly to the margin of the hard palate, but is unattached posteriorly where it ends in a free margin. This expansive aponeurosis is the major structural element of the soft palate to which the other muscles of the palate attach.
The tensor veli palatini: tenses (makes firm) the soft palate so that the other muscles attached to the palate can work more effectively, and opens the pharyngotympanic tube when the palate moves during yawning and swallowing as a result of its attachment superiorly to the membranous part of the pharyngotympanic tube.
The tensor veli palatini is innervated by the nerve to the medial pterygoid from the mandibular nerve [V3]. |
The levator veli palatini muscle originates from the base of the skull and descends to the upper surface of the palatine aponeurosis (Fig. 8.270B). On the skull, it originates from a roughened area on the petrous part of the temporal bone immediately anterior to the opening of the carotid canal. Some fibers also originate from adjacent parts of the pharyngotympanic tube.
The levator veli palatini passes anteroinferiorly through fascia of the pharyngeal wall, passes medial to the pharyngotympanic tube, and inserts onto the palatine aponeurosis (Fig. 8.270B). Its fibers interlace at the midline with those of the levator veli palatini on the other side.
Unlike the tensor veli palatini muscles, the levator veli palatini muscles do not pass around each pterygoid hamulus, but course directly from the base of the skull to the upper surface of the palatine aponeurosis. Therefore, they are the only muscles that can elevate the palate above the neutral position and close the pharyngeal isthmus between the nasopharynx and oropharynx.
The levator veli palatini is innervated by the vagus nerve [X] through the pharyngeal branch to the pharyngeal plexus. Clinically, the levator veli palatini can be tested by asking a patient to say “ah.” If the muscle on each side is functioning normally, the palate elevates evenly in the midline. If one side is not functioning, the palate deviates away from the abnormal side.
The palatopharyngeus muscle originates from the superior surface of the palatine aponeurosis and passes posterolaterally over its margin to descend and become one of the longitudinal muscles of the pharyngeal wall (Fig. 8.270C). It is attached to the palatine aponeurosis by two flat lamellae separated by the levator veli palatini muscle. The more anterior and lateral of these two lamellae is attached to the posterior margin of the hard palate as well as to the palatine aponeurosis.
The two palatopharyngeus muscles, one on each side, underlie the palatopharyngeal arches on the oropharyngeal wall. The palatopharyngeal arches lie posterior and medial to the palatoglossal arches when viewed anteriorly through the oral cavity (Fig. 8.271).
On each side, the palatine tonsil is between the palatopharyngeal and palatoglossal arches on the lateral oropharyngeal wall (Fig. 8.271A).
The palatopharyngeus muscles: depress the palate and move the palatopharyngeal arches toward the midline like curtains—both these actions help close the oropharyngeal isthmus; and elevate the pharynx during swallowing.
The palatopharyngeus is innervated by the vagus nerve [X] through the pharyngeal branch to the pharyngeal plexus.
The palatoglossus muscle attaches to the inferior (oral) surface of the palatine aponeurosis and passes inferiorly and anteriorly into the lateral surface of the tongue (Fig. 8.272).
The palatoglossus muscle underlies a fold of mucosa that arches from the soft palate to the tongue. These palatoglossal arches, one on each side, are lateral and anterior to the palatopharyngeal arches and define the lateral margins of the oropharyngeal isthmus (Fig. 8.271A).
The palatine tonsil is between the palatoglossal and palatopharyngeal arches on the lateral oropharyngeal wall (Figs. 8.271 and 8.272). |
The palatoglossus muscles depress the palate, move the palatoglossal arches toward the midline like curtains, and elevate the back of the tongue. These actions help close the oropharyngeal isthmus.
The palatoglossus is innervated by the vagus nerve [X] through the pharyngeal branch to the pharyngeal plexus.
The musculus uvulae originates from the posterior nasal spine on the posterior margin of the hard palate and passes directly posteriorly over the dorsal aspect of the palatine aponeurosis to insert into connective tissue underlying the mucosa of the uvula (Fig. 8.272). It passes between the two lamellae of the palatopharyngeus superior to the attachment of the levator veli palatini. Along the midline, the musculus uvulae blends with its partner on the other side.
The musculus uvulae elevates and retracts the uvula. This action thickens the central part of the soft palate and helps the levator veli palatini muscles close the pharyngeal isthmus between the nasopharynx and oropharynx.
The musculus uvulae is innervated by the vagus nerve [X] through the pharyngeal branch to the pharyngeal plexus.
Arteries of the palate include the greater palatine branch of the maxillary artery, the ascending palatine branch of the facial artery, and the palatine branch of the ascending pharyngeal artery. The maxillary, facial, and ascending pharyngeal arteries are all branches that arise in the neck from the external carotid artery (Fig. 8.273).
The ascending palatine artery of the facial artery ascends along the external surface of the pharynx. The palatine branch loops medially over the top of the superior constrictor muscle of the pharynx to penetrate the pharyngeal fascia with the levator veli palatini muscle and follow the levator veli palatini to the soft palate.
The palatine branch of the ascending pharyngeal artery follows the same course as the palatine branch of the ascending palatine artery from the facial artery and may replace the vessel.
The greater palatine artery originates from the maxillary artery in the pterygopalatine fossa. It descends into the palatine canal where it gives origin to a small lesser palatine branch, and then continues through the greater palatine foramen onto the inferior surface of the hard palate (Fig. 8.274). The greater palatine artery passes forward on the hard palate and then leaves the palate superiorly through the incisive canal to enter the medial wall of the nasal cavity where it terminates. The greater palatine artery is the major artery of the hard palate. It also supplies palatal gingiva. The lesser palatine branch passes through the lesser palatine foramen just posterior to the greater palatine foramen, and contributes to the vascular supply of the soft palate.
Veins from the palate generally follow the arteries and ultimately drain into the pterygoid plexus of veins in the infratemporal fossa (Fig. 8.275; also see pp. 980–981), or into a network of veins associated with the palatine tonsil, which drain into the pharyngeal plexus of veins or directly into the facial vein.
Lymphatic vessels from the palate drain into deep cervical nodes (Fig. 8.275).
The palate is supplied by the greater and lesser palatine nerves and the nasopalatine nerve (Figs. 8.274 and 8.276).
originate in the pterygopalatine fossa from the maxillary nerve [V2]. |
palate) fibers from a branch of the facial nerve [VII] join the nerves in the pterygopalatine fossa, as do the sympathetics (mainly to blood vessels) ultimately derived from the T1 spinal cord level.
The greater and lesser palatine nerves descend through the pterygopalatine fossa and palatine canal to reach the palate (Fig. 8.276):
The greater palatine nerve travels through the greater palatine foramen and turns anteriorly to supply the hard palate and gingiva as far as the first premolar.
The lesser palatine nerve passes posteromedially to supply the soft palate.
The nasopalatine nerve also originates in the pterygopalatine fossa, but passes medially into the nasal cavity. It continues medially over the roof of the nasal cavity to reach the medial wall, then anteriorly and obliquely down the wall to reach the incisive canal in the anterior floor, and descends through the incisive canal and fossa to reach the inferior surface of the hard palate (Fig. 8.276).
The nasopalatine nerve supplies gingiva and mucosa adjacent to the incisors and canine.
The oral fissure is the slit-like opening between the lips that connects the oral vestibule to the outside (Fig. 8.277). It can be opened and closed, and altered in shape by the movements of the muscles of facial expression associated with the lips and surrounding regions, and by movements of the lower jaw (mandible).
The lips are entirely composed of soft tissues (Fig. 8.277B). They are lined internally by oral mucosa and covered externally by skin. Externally, there is an area of transition from the thicker skin that covers the face to the thinner skin that overlies the margins of the lips and continues as oral mucosa onto the deep surfaces of the lips.
Blood vessels are closer to the surface in areas where the skin is thin and as a consequence there is a vermilion border that covers the margins of the lips.
The upper lip has a shallow vertical groove on its external surface (the philtrum) sandwiched between two elevated ridges of skin (Fig. 8.277A). The philtrum and ridges are formed embryologically by fusion of the medial nasal processes.
On the inner surface of both lips, a fold of mucosa (the median labial frenulum) connects the lip to the adjacent gum.
The lips enclose the orbicularis oris muscle, neurovascular tissues, and labial glands (Fig. 8.277B). The small pea-shaped labial glands are between the muscle tissue and the oral mucosa and open into the oral vestibule.
A number of muscles of facial expression control the shape and size of the oral fissure. The most important of these is the orbicularis oris muscle, which encircles the orifice and acts as a sphincter. A number of other muscles of facial expression blend into the orbicularis oris or other tissues of the lips and open or adjust the contours of the oral fissure. These include the buccinator, levator labii superioris, zygomaticus major and minor, levator anguli oris, depressor labii inferioris, depressor anguli oris, and platysma (see pp. 897–899).
The oropharyngeal isthmus is the opening between the oral cavity and the oropharynx (see Fig. 8.271). It is formed: laterally by the palatoglossal arches; superiorly by the soft palate; and inferiorly by the sulcus terminalis of the tongue that divides the oral surface of the tongue (anterior two-thirds) from the pharyngeal surface (posterior one-third).
The oropharyngeal isthmus can be closed by elevation of the posterior aspect of the tongue, depression of the palate, and medial movement of the palatoglossal arches toward the midline. |
Medial movement of the palatopharyngeal arches medial and posterior to the palatoglossal arches is also involved in closing the oropharyngeal isthmus. By closing the oropharyngeal isthmus, food or liquid can be held in the oral cavity while breathing.
The teeth are attached to sockets (alveoli) in two elevated arches of bone on the mandible below and the maxillae above (alveolar arches). If the teeth are removed, the alveolar bone is resorbed and the arches disappear.
The gingivae (gums) are specialized regions of the oral mucosa that surround the teeth and cover adjacent regions of the alveolar bone.
The different types of teeth are distinguished on the basis of morphology, position, and function (Fig. 8.278A).
In adults, there are 32 teeth, 16 in the upper jaw and 16 in the lower jaw. On each side in both maxillary and mandibular arches are two incisor, one canine, two premolar, and three molar teeth.
The incisor teeth are the “front teeth” and have one root and a chisel-shaped crown, which “cuts.”
The canine teeth are posterior to the incisors, are the longest teeth, have a crown with a single pointed cusp, and “grasp.”
The premolar teeth (bicuspids) have a crown with two pointed cusps, one on the buccal (cheek) side of the tooth and the other on the lingual (tongue) or palatal (palate) side, generally have one root (but the upper first premolar next to the canine may have two), and “grind.”
The molar teeth are behind the premolar teeth, have three roots and crowns with three to five cusps, and “grind.”
Two successive sets of teeth develop in humans, deciduous teeth (“baby” teeth) (Fig. 8.278B) and permanent teeth (“adult” teeth). The deciduous teeth emerge from the gingivae at between six months and two years of age. Permanent teeth begin to emerge and replace the deciduous teeth at around age six years, and can continue to emerge into adulthood.
The 20 deciduous teeth consist of two incisor, one canine, and two molar teeth on each side of the upper and lower jaws. These teeth are replaced by the incisor, canine, and premolar teeth of the permanent teeth. The permanent molar teeth erupt posterior to the deciduous molars and require the jaws to elongate forward to accommodate them.
All teeth are supplied by vessels that branch either directly or indirectly from the maxillary artery (Fig. 8.279).
All lower teeth are supplied by the inferior alveolar artery, which originates from the maxillary artery in the infratemporal fossa. The vessel enters the mandibular canal of the mandible, passes anteriorly in bone supplying vessels to the more posterior teeth, and divides opposite the first premolar into incisor and mental branches. The mental branch leaves the mental foramen to supply the chin, while the incisor branch continues in bone to supply the anterior teeth and adjacent structures.
All upper teeth are supplied by anterior and posterior superior alveolar arteries.
The posterior superior alveolar artery originates from the maxillary artery just after the maxillary artery enters the pterygopalatine fossa and it leaves the fossa through the pterygomaxillary fissure. It descends on the posterolateral surface of the maxilla, branches, and enters small canals in the bone to supply the molar and premolar teeth.
The anterior superior alveolar artery originates from the infra-orbital artery, which arises from the maxillary artery in the pterygopalatine fossa. The infra-orbital artery leaves the pterygopalatine fossa through the inferior orbital fissure and enters the inferior orbital groove and canal in the floor of the orbit. The anterior superior alveolar artery originates from the infra-orbital artery in the infra-orbital canal. It passes through bone and branches to supply the incisor and canine teeth. |
The gingivae are supplied by multiple vessels and the source depends on which side of each tooth the gingiva is—the side facing the oral vestibule or cheek (vestibular or buccal side), or the side facing the tongue or palate (lingual or palatal side):
Buccal gingiva of the lower teeth is supplied by branches from the inferior alveolar artery, whereas the lingual side is supplied by branches from the lingual artery of the tongue.
Buccal gingiva of the upper teeth is supplied by branches of the anterior and posterior superior alveolar arteries.
Palatal gingiva is supplied by branches from the nasopalatine (incisor and canine teeth) and greater palatine (premolar and molar teeth) arteries.
Veins from the upper and lower teeth generally follow the arteries (Fig. 8.279).
Inferior alveolar veins from the lower teeth, and superior alveolar veins from the upper teeth drain mainly into the pterygoid plexus of veins in the infratemporal fossa, although some drainage from the anterior teeth may be via tributaries of the facial vein.
The pterygoid plexus drains mainly into the maxillary vein and ultimately into the retromandibular vein and jugular system of veins. In addition, small communicating vessels pass superiorly, from the plexus, and pass through small emissary foramina in the base of the skull to connect with the cavernous sinus in the cranial cavity. Infection originating in the teeth can track into the cranial cavity through these small emissary veins.
Venous drainage from the teeth can also be via vessels that pass through the mental foramen to connect with the facial vein.
Veins from the gingivae also follow the arteries and ultimately drain into the facial vein or into the pterygoid plexus of veins.
Lymphatic vessels from the teeth and gingivae drain mainly into submandibular, submental, and deep cervical nodes (Fig. 8.280).
All nerves that innervate the teeth and gingivae are branches of the trigeminal nerve [V] (Figs. 8.281 and 8.282).
The lower teeth are all innervated by branches from the inferior alveolar nerve, which originates in the infratemporal fossa from the mandibular nerve [V3] (Figs. 8.281 and 8.282). The inferior alveolar nerve and its accompanying vessels enter the mandibular foramen on the medial surface of the ramus of the mandible and travel anteriorly through the bone in the mandibular canal. Branches to the back teeth originate directly from the inferior alveolar nerve.
Adjacent to the first premolar tooth, the inferior alveolar nerve divides into incisive and mental branches:
The incisive branch innervates the first premolar, the canine, and the incisor teeth, together with the associated vestibular (buccal) gingiva.
The mental nerve exits the mandible through the mental foramen and innervates the chin and lower lip.
Anterior, middle, and posterior superior
All upper teeth are innervated by the anterior, middle, and posterior superior alveolar nerves, which originate directly or indirectly from the maxillary nerve [V2] (Figs. 8.281 and 8.282).
The posterior superior alveolar nerve originates directly from the maxillary nerve [V2] in the pterygopalatine fossa, exits the pterygopalatine fossa through the pterygomaxillary fissure, and descends on the posterolateral surface of the maxilla. It enters the maxilla through a small foramen approximately midway between the pterygomaxillary fissure and the last molar tooth, and passes through the bone in the wall of the maxillary sinus. The posterior superior alveolar nerve then innervates the molar teeth through the superior alveolar plexus formed by the posterior, middle, and anterior alveolar nerves. |
The middle and anterior superior alveolar nerves originate from the infra-orbital branch of the maxillary nerve [V2] in the floor of the orbit:
The middle superior alveolar nerve arises from the infra-orbital nerve in the infra-orbital groove, passes through the bone in the lateral wall of the maxillary sinus, and innervates the premolar teeth via the superior alveolar plexus.
The anterior superior alveolar nerve originates from the infra-orbital nerve in the infra-orbital canal, passes through the maxilla in the anterior wall of the maxillary sinus, and via the superior alveolar plexus, supplies the canine and incisor teeth.
Innervation of gingivae
Like the teeth, the gingivae are innervated by nerves that ultimately originate from the trigeminal nerve [V] (Fig. 8.282):
Gingiva associated with the upper teeth is innervated by branches derived from the maxillary nerve [V2].
Gingiva associated with the lower teeth is innervated by branches of the mandibular nerve [V3].
The gingiva on the buccal side of the upper teeth is innervated by the anterior, middle, and superior alveolar nerves, which also innervate the adjacent teeth. Gingiva on the palatal (lingual) side of the same teeth is innervated by the nasopalatine and the greater palatine nerves:
The nasopalatine nerve innervates gingiva associated with the incisor and canine teeth.
The greater palatine nerve supplies gingiva associated with the remaining teeth.
The gingiva associated with the (buccal) side of the mandibular incisor, canine, and premolar teeth is innervated by the mental branch of the inferior alveolar nerve. Gingiva on the buccal side of the mandibular molar teeth is innervated by the buccal nerve, which originates in the infratemporal fossa from the mandibular nerve [V3]. Gingiva adjacent to the lingual surface of all lower teeth is innervated by the lingual nerve.
Skeletal landmarks in the head and neck are used for locating major blood vessels, glands, and muscles, and for locating points of access to the airway.
Neurological examination of the cranial and upper cervical nerves is carried out by assessing function in the head and neck.
In addition, information about the general status of body health can often be obtained by evaluating surface features, the eye and the oral cavity, and the characteristics of speech.
Anatomical position of the head
The head is in the anatomical position when the inferior margins of the bony orbits and the superior margins of the external acoustic meatuses are in the same horizontal plane (Frankfort plane).
In addition to the external acoustic meatus and the bony margin of the orbit, other features that are palpable include the head of the mandible, zygomatic arch, zygomatic bone, mastoid process, and external occipital protuberance (Fig. 8.283).
The head of the mandible is anterior to the external ear and behind and inferior to the posterior end of the zygomatic arch. It is best found by opening and closing the jaw and palpating the head of the mandible as it moves forward onto the articular tubercle and then back into the mandibular fossa, respectively.
The zygomatic arch extends forward from the region of the temporomandibular joint to the zygomatic bone, which forms a bony prominence lateral to the inferior margin of the anterior opening of the orbit.
The mastoid process is a large bony protuberance that is easily palpable posterior to the inferior aspect of the external acoustic meatus. The superior end of the sternocleidomastoid muscle attaches to the mastoid process.
The external occipital protuberance is palpable in the midline posteriorly where the contour of the skull curves sharply forward. This landmark marks the point superficially where the back of the neck joins the head. |
Another clinically useful feature of the head is the vertex. This is the highest point of the head in the anatomical position and marks the approximate point on the scalp where there is a transition from cervical to cranial innervation of the scalp. Anterior to the vertex, the scalp and face are innervated by the trigeminal nerve [V]. Posterior to the vertex, the scalp is innervated by branches from cervical spinal nerves.
Visualizing structures at the CIII/CIV and CVI vertebral levels
Two vertebral levels in the neck are associated with important anatomical features (Fig. 8.284).
The intervertebral disc between the CIII and CIV vertebrae is in the same horizontal plane as the bifurcation of the common carotid artery into the internal and external carotid arteries. This level is approximately at the upper margin of the thyroid cartilage.
Vertebral level CVI marks the transition from pharynx to esophagus and larynx to trachea. The CVI vertebral level therefore marks the superior ends of the esophagus and trachea and is approximately at the level of the inferior margin of the cricoid cartilage.
How to outline the anterior and posterior triangles of the neck
The boundaries of the anterior and posterior triangles on each side of the neck are easily established using readily visible bony and muscular landmarks (Fig. 8.285).
The base of each anterior triangle is the inferior margin of the mandible, the anterior margin is the midline of the neck, and the posterior margin is the anterior border of the sternocleidomastoid muscle. The apex of each anterior triangle points inferiorly and is at the suprasternal notch.
The anterior triangles are associated with structures such as the airway and digestive tract, and nerves and vessels that pass between the thorax and head. They are also associated with the thyroid and parathyroid glands.
The base of each posterior triangle is the middle one-third of the clavicle. The medial margin is the posterior border of the sternocleidomastoid muscle, and the lateral margin is the anterior border of the trapezius muscle. The apex points superiorly and is immediately posteroinferior to the mastoid process.
The posterior triangles are associated with nerves and vessels that pass into and out of the upper limbs.
How to locate the cricothyroid ligament
An important structure to locate in the neck is the median cricothyroid ligament (Fig. 8.286) because artificial penetration of this membrane in emergency situations can provide access to the lower airway when the upper airway above the level of the vocal folds is blocked.
The ligament can be easily found using palpable features of the larynx as landmarks.
Using a finger to gently feel laryngeal structures in the midline, first find the thyroid notch in the superior margin of the thyroid cartilage and then move the finger inferiorly over the laryngeal prominence and down the anterior surface of the thyroid angle. As the finger crosses the inferior margin of the thyroid cartilage in the midline, a soft depression is felt before the finger slides onto the arch of the cricoid cartilage, which is hard.
The soft depression between the lower margin of the thyroid cartilage and the arch of the cricoid is the position of the median cricothyroid ligament.
A tube passed through the median cricothyroid ligament enters the airway just inferior to the position of the vocal folds of the larynx.
Structures that may occur in or cross the midline between the skin and the median cricothyroid ligament include the pyramidal lobe of the thyroid gland and small vessels, respectively.
Inferior to the cricoid cartilage, the upper cartilage of the larynx can sometimes be palpated above the level of the isthmus of the thyroid gland that crosses the trachea anteriorly.
The landmarks used for finding the cricothyroid ligament are similar in men and women; however, because the laminae of the thyroid cartilage meet at a more acute angle in men, the structures are more prominent in men than in women.
How to find the thyroid gland |
The left and right lobes of the thyroid gland are in the anterior triangles in the lower neck on either side of the airway and digestive tract inferior to the position of the oblique line of the thyroid cartilage (Fig. 8.287). In fact, the sternothyroid muscles, which attach superiorly to the oblique lines, lie anterior to the lobes of the thyroid gland and prevent the lobes from moving upward in the neck.
The lobes of the thyroid gland can be most easily palpated by finding the thyroid prominence and arch of the cricoid cartilage and then feeling posterolateral to the larynx.
The isthmus of the thyroid gland crosses anterior to the upper end of the trachea and can be easily palpated in the midline inferior to the arch of the cricoid.
The presence of the isthmus of the thyroid gland makes palpating the tracheal cartilages difficult in the neck. Also, the presence of the isthmus of the thyroid gland and the associated vessels found in and crossing the midline makes it difficult to artificially enter the airway anteriorly through the trachea. This procedure, a tracheostomy, is a surgical procedure.
Estimating the position of the middle
The middle meningeal artery (Fig. 8.288) is a branch of the maxillary artery in the infratemporal fossa. It enters the skull through the foramen spinosum and is within the dura mater lining the cranial cavity.
In lateral blows to the head the middle meningeal artery can be ruptured, leading to extradural hemorrhage and eventual death if not treated.
The anterior branch of the middle meningeal artery is the part of the vessel most often torn. This branch is in the temple region of the head, approximately midway between the superior margin of the orbit and the upper part of the external ear in the pterion region. The pterion is a small circular area enclosing the region where the sphenoid, frontal, parietal, and temporal bones of the skull come together.
Lateral blows to the head can fracture the internal table of bone of the skull and tear the middle meningeal artery in the outer layer of dura mater that is fused to the cranium. Blood under pulsatile arterial pressure leaks out of the vessel and gradually separates the dura from the bone, forming a progressively larger extradural hematoma.
Major features of the face
The major features of the face are those related to the anterior openings of the orbit, the nasal cavities, and the oral cavity (Fig. 8.289).
The palpebral fissures are between the upper and lower eyelids and can be opened and closed. The oral fissure is the gap between the upper and lower lips and can also be opened and closed.
The sphincter muscles of the oral and palpebral fissures are the orbicularis oris and orbicularis oculi muscles, respectively. These muscles are innervated by the facial nerve [VII].
The nares are the anterior apertures of the nasal cavities and are continuously open.
The vertical groove in the midline between the external nose and the upper lip is the philtrum.
Sensory innervation of the face is carried by the trigeminal nerve [V]. The three divisions of this nerve are represented on the face and can be tested by touching the forehead (the ophthalmic nerve [V1]), the anterior cheek (the maxillary nerve [V2]), and skin over the anterior body of the mandible (the mandibular nerve [V3]).
The eye and lacrimal apparatus
Major features of the eye include the sclera, cornea, iris, and pupil (Fig. 8.290). The cornea is continuous with the sclera and is the clear circular region of the external covering of the eye through which the pupil and iris are visible. The sclera is not transparent and is normally white.
The upper and lower eyelids of each eye enclose between them the palpebral fissure. The eyelids come together at the medial and lateral palpebral commissures on either side of each eye. |
At the medial side of the palpebral fissure and lateral to the medial palpebral commissure is a small triangular soft tissue structure (the lacrimal lake).
The elevated mound of tissue on the medial side of the lacrimal lake is the lacrimal caruncle, and the lateral margin overlying the sclera is the lacrimal fold.
The lacrimal apparatus consists of the lacrimal gland and the system of ducts and channels that collects the tears and drain them into the nasal cavity. Tears hydrate and maintain the transparency of the cornea.
The lacrimal gland is associated with the upper eyelid and is in a small depression in the lateral roof of the orbit just posterior to the orbital margin. The multiple small ducts of the gland open into the upper margin of the conjunctival sac, which is the thin gap between the deep surface of the eyelid and the cornea.
Tears are swept medially over the eye by blinking and are collected in small openings (lacrimal puncta), one on each of the upper and lower eyelids near the lacrimal lake.
Each punctum is on a small raised mound of tissue (a lacrimal papilla), and is the opening of a small canal (lacrimal canaliculus) that connects with the lacrimal sac.
The lacrimal sac is in the lacrimal fossa on the medial side of the orbit. From the lacrimal sac, tears drain via the nasolacrimal duct into the nasal cavity.
The external ear (Fig. 8.291) consists of the auricle and the external acoustic meatus. The auricle is supported by cartilage and is covered by skin. The external acoustic meatus is near the anterior margin of the auricle.
The auricle is characterized by a number of depressions, eminences, and folds. The folded outer margin of the auricle is the helix, which ends inferiorly as the lobule.
A smaller fold (the antihelix) parallels the contour of the helix and is separated from it by a depression (the scaphoid fossa).
The tragus is a small eminence anteroinferior to the external acoustic meatus. Opposite the tragus and at the end of the antihelix is another eminence (the antitragus). The depression between the tragus and antitragus is the intertragic incisure.
The deepest depression (the concha) is bracketed by the antihelix and leads into the external acoustic meatus. Other depressions include the triangular fossa and the cymba conchae.
Arterial pulses can be felt at four locations in the head and neck (Fig. 8.292).
Carotid pulse—the common or external carotid artery can be palpated in the anterior triangle of the neck. This is one of the strongest pulses in the body. The pulse can be obtained by palpating either the common carotid artery posterolateral to the larynx or the external carotid artery immediately lateral to the pharynx midway between the superior margin of the thyroid cartilage below and the greater horn of the hyoid bone above.
Facial pulse—the facial artery can be palpated as it crosses the inferior border of the mandible immediately adjacent to the anterior margin of the masseter muscle.
Temporal pulse—the superficial temporal artery can be palpated anterior to the ear and immediately posterosuperior to the position of the temporomandibular joint.
Temporal pulse—the anterior branch of the superficial temporal artery can be palpated posterior to the zygomatic process of the frontal bone as it passes lateral to the temporal fascia and into anterolateral regions of the scalp. In some individuals pulsations of the superficial temporal artery can be seen through the skin.
Fig. 8.1 Major compartments of the head and neck.
Fig. 8.2 Areas of transition from one compartment of the head to another. |
Infratemporal fossaLateral plate ofpterygoid processMandibular nerve [V3]Pterygopalatine fossaMaxillary nerve [V2]Ramus of mandible
Fig. 8.3 Muscles of the face.
Fig. 8.4 Boundaries of the neck.
Vertebra CVIIMandibleMastoid processSuperior nuchal lineAcromionManubrium of sternumClavicle
Fig. 8.5 Major compartments of the neck.
Fig. 8.6 Specialized structures of the neck. A. Conceptual view. B. Anatomical view.
Fig. 8.7 Skull. A. Bones.
B. Sutures. C. Fontanelles and lambdoid suture.
Fig. 8.8 Cervical vertebrae. A. Typical features. B. Atlas—vertebra CI (superior view). C. Axis—vertebra CII (anterior view). D. Atlas and axis (anterolateral view). E. Atlanto-occipital joint (posterior view).
Foramen transversariumAnterior tuberclePosterior tubercleArchSuperior articular facetBodyTransverse processSpinous processDensAnterior archArticular facetfor densLateral massSuperior articular surface (for occipital condyle)Posterior archBodyAtlas (CI)Axis (CII)Articular facetfor densABCDForamenmagnumOccipital condyleOccipital boneApical ligamentof densSuperior longitudinal bandof cruciform ligamentInferior longitudinal bandof cruciform ligamentTransverseligament of atlasAlar ligamentsETectorial membrane (upper partof posterior longitudinal ligament)Posteriorlongitudinalligament
Fig. 8.9 Hyoid. A. Bone. B. Attachments.
ABLesser hornGreater hornBody of hyoid boneFloor of mouth (mylohyoid muscle)Thyrohyoid membraneStylohyoid ligamentMiddle pharyngeal constrictor muscleInferior pharyngeal constrictor muscleEpiglottis
Fig. 8.10 Soft palate. A. Position. B. Muscles.
Fig. 8.11 Superior thoracic aperture and axillary inlets.
Fig. 8.12 Important vertebral levels—CIII/CIV and CV/CVI.
Fig. 8.13 Larynx and associated structures in the neck.
Fig. 8.14 Cranial nerves and parasympathetic innervation.
Fig. 8.15 Cervical nerves. A. Structure. B. Dermatomes.
Phrenic nerveBrachial plexus(C5 to T1)Cervical plexus(C1 to C4)Cutaneous nervesAnsa cervicalis tostrap musclesAC3C4C2C2C3C4Ophthalmic nerve [V1]Trigeminal nerve [V]Maxillary nerve [V2]Mandibular nerve [V3]Anterior rami (C2 to C4) ClavicleAcromionPosterior rami (C2 to C4)External occipital protuberanceB
Fig. 8.16 Larynx, soft palate, epiglottis, and oropharyngeal isthmus. A. Overall design.
B. Normal breathing. C. Breathing with food or liquid in the oral cavity. D. Swallowing. E. In a newborn child. |
Soft palate(opens and closesoropharyngeal isthmus)Cranial cavityEarsChoanaeNasopharynxCVI vertebral levelPharynxEsophagusScapulaAxillary inletClavicleSuperior thoracic aperture(thoracic inlet)Manubrium of sternumTracheaVocal folds(together with other soft tissuestructures open and closecavity of larynx)Epiglottis(opens and closes laryngeal inlet)Oropharyngeal isthmusOral cavityNasal cavitiesOrbitsARib IVertebra TIOropharynxLaryngopharynxLaryngeal inletLarynx
Laryngeal inletand laryngealcavity openBack oftongue elevated,palate depressedOropharyngealisthmus closedLarynx andhyoid pulledup and forwardresulting in openingthe esophagusEpiglottisclosed overlaryngeal inletOropharyngealisthmus openOpening between nasal andoral parts of pharynx closedby soft palateSoft palatein neutral positionMilk pathwayTracheaNasal cavityEEsophagusSoft palateLaryngealinletBCD
Fig. 8.17 Anterior and posterior triangles of neck.
Fig. 8.18 Anterior view of the skull.
GlabellaNasal boneFrontal boneSuperciliary archSupra-orbital notch(foramen)Zygomatic process(of frontal bone)Zygomatic boneFrontal process (of maxilla)Infra-orbital foramenInferior nasal conchaMaxillaOblique lineMandibleMental foramenMental tubercleMental protuberanceAngle of mandibleAlveolar part of mandibleZygomatic process (of maxilla)NasionNasal crestPiriform apertureAlveolar processRamus of mandibleBody of mandibleAnterior nasal spine
Fig. 8.19 Lateral view of the skull.
Sphenoparietal sutureCoronal sutureFrontal bonePterionSphenosquamous sutureGreater wing(of sphenoid bone)ZygomaticofacialforamenZygomatic boneMaxillaMental foramenBody of mandibleTemporal process (of zygomatic bone)Alveolar part(of mandible)Condylar processAngleZygomatic process (of temporal bone)Coronoid process Ramus of mandibleStyloid processMastoid processTympanic part (of temporal bone)Mastoid part of temporal boneOccipitomastoidsutureOccipital boneAsterionLambdoidsutureParietomastoidsutureParietal boneSquamous sutureSquamous part (of temporal bone)Nasal boneLacrimal boneZygomaticotemporalforamen(on deep surface ofzygomatic bone)
Fig. 8.20 Posterior view of the skull.
Fig. 8.21 Superior view of the skull.
Fig. 8.22 Calvaria.
Fig. 8.23 Inferior view of the skull. |
Incisive fossaHard palate (maxilla)Hard palate (palatine bone)Greater palatine foramenHamulusLesser palatine foramenLateral plate of pterygoidprocessMedial plate of pterygoidprocessVomerBody of sphenoidArticular tubercleMandibular fossaForamen ovaleForamen spinosumPetrous part oftemporal boneSquamous part oftemporal boneStyloid processStylomastoid foramenJugular foramenCarotid canalInferior nuchal lineOccipital condyleExternal occipital protuberanceSuperior nuchal lineExternal occipital crestForamen magnumPharyngeal tubercleHypoglossal canalMastoid processMastoid notchBasilar part of occipital boneForamen lacerumGroove for auditory tubeOpening of pterygoid canalPterygoid processScaphoid fossaPterygoid fossaGreater wing (of sphenoid bone)Posterior nasal aperture (choana)Pyramidal process of palatine boneAlveolar archPosterior nasal spine
Fig. 8.24 Roof of the cranial cavity.
Frontal boneFrontal crestGroove for superiorsagittal sinusBregmaGranular foveolaeSagittal sutureLambdoid sutureOccipital boneLambdaParietal boneGrooves for middlemeningeal arteryCoronal sutureGroove for anterior branch of middle meningeal artery
Fig. 8.25 Anterior cranial fossa.
Foramen cecumForamina of cribriform plateBody of (sphenoid)Frontal crestOrbital part (of frontal bone)Crista galliCribriform plate (of ethmoid bone)Lesser wing (of sphenoid)Anterior clinoid process
Fig. 8.26 Middle cranial fossa.
Optic canalSuperior orbital fissureGreater wing (of sphenoid)Foramen rotundumGroove for middlemeningeal arteryForamen ovaleForamen spinosumForamen lacerumTegmen tympaniDorsum sellaeMiddle clinoid processPrechiasmatic sulcusTuberculum sellaeHypophyseal fossaPosterior clinoid processGroove and hiatus for lesser petrosal nerveGroove and hiatus for greater petrosal nerveArcuate eminenceTrigeminal impressionOpening of carotid canal
Fig. 8.27 Posterior cranial fossa.
Superior border of petrous part of temporal boneInternal acoustic meatusJugular foramenHypoglossal canalForamen magnumClivusJugular tubercleGroove for sigmoid sinusGroove for inferior petrosal sinusGroove for transverse sinusInternal occipital crestInternal occipital protuberance
Fig. 8.28 Summary of foramina and fissures through which major structures enter and leave the cranial cavity. A. Floor of cranial cavity.
Also indicated are the regions between which each foramen or fissure communicates. B. Inferior aspect of cranium. |
Foramen ovale:• [V3] Mandibular division of [V] (trigeminal nerve)Jugular foramen:• [IX] Glossopharyngeal nerve• [X] Vagus nerve• [XI] Accessory nerve• Internal jugular veinForamen magnum:• Spinal cord• Vertebral arteries Roots of accessory nerve [XI] pass from upper region of spinal cord through the foramen magnum into the cranial cavity and then leave the cranial cavity through the jugular foramenForamen spinosum:• Middle meningeal arteryStylomastoid foramen:• [VII] Facial nerveCarotid canal:• Internal carotid arteryHypoglossal canal:• [XII] Hypoglossal nerveCribriform plate: (anterior cranial fossa/nasal cavity)• [I] Olfactory nerves Optic canal:(middle cranial fossa/orbit)• [II] Optic nerve• Ophthalmic arterySuperior orbital fissure:(middle cranial fossa/orbit)• [V1] Ophthalmic division of [V] (trigeminal nerve)• [III] Oculomotor nerve• [IV] Trochlear nerve• [VI] Abducent nerve• Superior ophthalmic veinForamen rotundum:(middle cranial fossa/pterygopalatine fossa)• [V2] Maxillary division of [V] (trigeminal nerve)Foramen ovale:(middle cranial fossa/infratemporal fossa)• [V3] Mandibular division of [V] (trigeminal nerve)Foramen lacerum(filled with cartilage in life)Jugular foramen:(posterior cranial fossa/neck)• [IX] Glossopharyngeal nerve• [X] Vagus nerve• [XI] Accessory nerve• Internal jugular veinABForamen magnum:(posterior cranial fossa/neck)• Spinal cord• Vertebral arteries Roots of accessory nerve [XI] pass from upper region of spinal cord through the foramen magnum into the cranial cavity and then leave the cranial cavity through the jugular foramen Foramen spinosum:(middle cranial fossa/infratemporal fossa)• Middle meningeal arteryCarotid canal:(middle cranial fossa/neck)• Internal carotid arteryHypoglossal canal:(posterior cranial fossa/neck)• [XII] Hypoglossal nerveInternal acoustic meatus:(posterior cranial fossa/ear, and neckvia stylomastoid foramen)• [VII] Facial nerve• [VIII] Vestibulocochlear nerve Labyrnthine artery and vein
Fig. 8.29 Skull fracture seen on a skull radiograph (patient in supine position).
Fig. 8.30 Ultrasound scans. A. Normal carotid bifurcation. B. Internal carotid artery stenosis.
Fig. 8.31 Cranial meninges. A. Superior coronal view. B. Continuity with the spinal meninges.
Intracranial venous structure(superior sagittal sinus)Outer periosteal layer of dura materInner meningeal layer of dura materArachnoid materPia materDural partition (falx cerebri)SkullDura materSubarachnoid spaceABMeningeal layer of dura materForamen magnumPeriosteal layer of dura materSkullPeriosteumSpinal dura materSpinal extradural spaceVertebra CI
Fig. 8.32 Dural partitions. A. Diagram. B. Dissection.
Fig. 8.33 Dural arterial supply. |
Middle meningeal arteryPosition of pterionMeningeal branch(from occipital artery)Meningeal branch(from vertebral artery)Posterior meningeal artery(from ascendingpharyngeal artery)Meningeal branch(from ascendingpharyngeal artery)Middlemeningeal arteryOccipital arteryAscending pharyngeal arteryExternal carotid arteryMaxillary arteryAnterior meningeal arteries(from ethmoidal arteries)
Fig. 8.34 Dural innervation.
Ophthalmic divisionof trigeminal nerve[V1]Ophthalmic division of trigeminal nerve [V1](tentorium cerebelli)Maxillary division of trigeminal nerve [V2]Mandibular division of trigeminal nerve [V3]Cervical nervesOphthalmic division oftrigeminal nerve [V1](falx cerebri)
Fig. 8.35 Arrangement of the meninges and spaces.
Fig. 8.36 Lateral view of the brain.
Fig. 8.37 Sagittal section of the brain.
Fig. 8.38 Arterial supply to the brain. A. Diagram. B. Magnetic resonance angiogram showing normal carotid and vertebral arteries.
C. Enhanced CT scan of carotid vessels.
Fig. 8.39 Arteries on the base of the brain.
Fig. 8.40 Different imaging modalities used to evaluate a stroke (arrows). A. CT scan. B. T2weighted CT. C. Diffusion-weighted image (DWI). D. Apparent diffusion coefficient image (ADC).
Fig. 8.41 Basilar tip aneurysm. A. Three-dimensional cranial cutaway CT scan. B. Magnified view of aneurysm.
Fig. 8.42 Anterior communicating aneurysm. A. Left carotid angiogram. B. Left carotid angiogram after embolization.
Fig. 8.43 Dural venous sinuses.
Fig. 8.44 Veins, meninges, and dural venous sinuses.
Sigmoid sinusInferior sagittal sinusSuperior petrosal sinusBasilar sinusSphenoparietal sinusIntercavernous sinusCavernous sinusOphthalmic veinPterygoid plexus of veinsSuperior petrosal sinusSigmoid sinusInferior petrosal sinusRight transverse sinusGreat cerebral veinConfluence of sinusesStraight sinusSuperior sagittal sinus
Fig. 8.45 Cavernous sinuses.
Pituitary glandInternal carotid arteryDura materAbducent nerve [VI]Maxillary division of trigeminal nerve [V2]Cavernous (venous) sinusesSphenoidal (paranasal) sinusesOphthalmic division of trigeminal nerve [V1]Trochlear nerve [IV]Oculomotor nerve [III]Diaphragma sellae
Fig. 8.46 Lateral view of right cavernous sinus with meningeal layer of dura removed to show contents.
Trochlea nerve [IV]Abducent nerve [VI]Abducent nerve [VI]Oculomotor nerve [III]Oculomotor nerve [III]Infundibulum (stalk of pituitary gland)Anterior clinoid processPosterior clinoid processTentorium cerebelliCut edge of dura materMaxillary nerve [V2]Ophthalmic nerve [V1]Trigeminal ganglionMandibular nerve [V3]Internal carotid arteryOptic nerve [III]Trochlea nerve [IV]Trigeminal nerve [V]
Fig. 8.47 Scalp and meninges. |
Neurovascular bundleV1V2Connected togetheras a structural unitSkinAponeurosisPeriosteum1234BoneOutertableInnertableDiploëAnterior cerebral arteryInternal carotidarteryDiploic veinSuperior sagittal sinusCavernous sinusOptic tractsDuraPeriostial layerMeningeal layerArachnoidSubarachnoid spacePiaEmissary vein: can spread infection fromthe scalp into the cranial cavityConnective tissue:contains majornerves and vesselsof the scalpFractureLoose connective tissue (danger area)• In scalping injuries, this is the layer in which separation occurs.• Infection can easily spread in this layer.• Blunt trauma can result in hemorrhage in this layer (blood can spread forward into the face, resulting in “black eyes”).Rupture of the middle meningeal artery (branches) by fracture of the inner table of boneresults in extradural hematoma. Under pressure, the blood progressively separates dura from the bone.Aneurysm• Ruptured aneurysms of vessels of the cerebral arterial circle hemorrhage directly into the subarachnoid space and CSF.Tear to cerebral vein where it crosses dura to enter cranial venous sinus can result in subdural hematoma. The tearseparates a thin layer of meningeal dura from that which remains attached to the periosteal layer. As a result, thehematoma is covered by an inner limiting membrane derived from part of the meningeal dura. ExtraduralhematomaSubdural hematomaVIIVIII1234
Fig. 8.48 Extradural hematoma. Axial CT scan of brain.
Shift of the falx cerebriExtradural hematoma
Fig. 8.49 Chronic (low-density) subdural hematoma. Axial CT scan of brain.
Fig. 8.50 Subarachnoid hemorrhage. Axial CT scan of brain.
Fig. 8.51 MRI of the brain shows peripherally enhancing tuberculosis lesions in the left temporal lobe and cerebral peduncle.
Fig. 8.52 MRI of the brain reveals an incidental Chiari I malformation with herniation of the the cerebellar tonsils through the foramen magnum, giving rise to a cone shape.
Fig. 8.53 Cranial nerves exiting the cranial cavity.
Fig. 8.54 Cranial nerves on the base of the brain.
Fig. 8.56 Facial muscles.
Fig. 8.57 Orbital group of facial muscles.
Fig. 8.58 Nasal group of facial muscles.
Fig. 8.59 Oral group of facial muscles.
Fig. 8.60 Buccinator muscle.
Fig. 8.61 Auricular muscles.
Fig. 8.62 Parotid gland. A. Lateral view. B. Cross section.
Fig. 8.63 Tumor in parotid gland. Axial CT scan.
Fig. 8.64 Trigeminal nerve [V] leaving the skull.
Fig. 8.65 Cutaneous distribution of the trigeminal nerve [V]. |
Third occipital(from posterior ramus of C3)Lesser occipitaland great auricular(from cervical plexus)Great auricular nerve(from anterior ramusof C2 and C3)Lesser occipital nerveZygomaticotemporalnervesSupra-orbital nerveAuriculotemporalnerveGreater occipital(from posteriorramus of C2)Supratrochlear nerveOphthalmic nerve [V1]Maxillary nerve [V2]Mandibular nerve [V3]External nasalnerveInfratrochlear nerveZygomaticofacial nerveInfra-orbital nerveBuccal nerveMental nerveTransverse cervical(from anterior ramus of C2 and C3)Transverse cervical
Fig. 8.66 Facial nerve [VII] on the face. A. Terminal branches. B. Branches before entering the parotid gland.
Fig. 8.67 Vasculature of the face. A. Lateral view. B. Branches of the maxillary artery.
Fig. 8.68 Intracranial venous connections.
Fig. 8.69 Lymphatic drainage of the face.
Fig. 8.70 SCALP.
Fig. 8.71 Layers of the scalp.
Fig. 8.72 Occipitofrontalis muscle. A. Frontal belly. B. Occipital belly.
Fig. 8.73 Innervation of the scalp.
Fig. 8.74 Vasculature of the scalp.
Fig. 8.75 Lymphatic drainage of the scalp.
Fig. 8.76 Bones of the orbit.
Optic canalFrontal boneEthmoidal foraminaEthmoid boneLacrimalgrooveLacrimal bonePalatine boneMaxillaInferior orbital fissureZygomatic boneGreater wing of sphenoidSuperior orbital fissureLesser wing of sphenoid
Fig. 8.77 Eyelids.
PeriosteumLevator palpebraesuperioris muscleSuperior conjunctival fornixConjunctivaTarsusSebaceous glandof eyelashTarsal glandOrbital septumSuperior tarsal muscle(smooth muscle)Tendon of levator palpebrae superioris muscleOrbicularis oculimuscle
Fig. 8.78 Orbicularis oculi muscle.
Fig. 8.79 Orbital septum.
PeriosteumOrbital septumOrbital septumPeriosteumTendon of levator palpebrae superioris muscle
Fig. 8.80 Tarsal plates.
Tendon of levatorpalpebrae superioris muscleSuperior tarsusAnterior lacrimal crestMedial palpebral ligamentInferior tarsusOrbital septumLateral palpebral ligamentOrbital septum
Fig. 8.81 Vasculature of the eyelids.
Fig. 8.82 Innervation of the eyelids.
Fig. 8.83 Lacrimal gland, anterior view.
MedialPunctaLacrimal sacNasolacrimal ductLacrimalcanaliculiLacrimal glandTendon of levator palpebrae superioris muscle
Fig. 8.84 Lacrimal gland and levator palpebrae superioris.
Orbital part of lacrimal glandLacrimal vessels and nervePalpebral part oflacrimal glandTendon oflevator palpebrae superiorisOrbital septum
Fig. 8.85 The lacrimal sac.
Fig. 8.86 Position of lacrimal sac. |
Medial palpebral ligamentLacrimal part of orbicularis oculi muscleOrbital septum Posterior lacrimal crestLacrimal sacAnterior lacrimal crestPeriosteumAnteriorPosteriorLateral
Fig. 8.87 Innervation of the lacrimal gland.
Lacrimal nerveLacrimal glandForamen rotundumMaxillary nerve [V2]Pterygoid canalGreater petrosal nerveDeep petrosal nerveNerve ofpterygoid canalSympathetic plexusInternal carotid arteryBranch of zygomaticotemporal nerveZygomatic nervePterygopalatine ganglionSensory fibersSympathetic postganglionic fibersParasympathetic preganglionic fibersParasympathetic postganglionic fibersZygomaticotemporal nerveZygomaticofacial nerve
Fig. 8.88 Openings into the bony orbit.
Nasolacrimal canalInferior orbital fissure Optic canalFrontal boneEthmoidal foraminaEthmoid boneLacrimal bonePalatine boneMaxillaInfra-orbital grooveZygomatic boneGreater wing of sphenoidSuperior orbital fissureLesser wing of sphenoid
Fig. 8.89 Optic canal and superior orbital fissure.
Lacrimal branch of the ophthalmic nerve [V1]Nasociliary branch of ophthalmic nerve [V1]Frontal branch of the ophthalmic nerve [V1]Optic nerveOptic canalInferior ophthalmic veinSuperior ophthalmic veinOphthalmic arteryInferior branch of oculomotor nerve [III]Abducent nerve [VI]Trochlear nerve [IV]Superior branch of oculomotor nerve [III]Superior orbital fissureInferior orbital fissureLateralMedial
Fig. 8.90 Periorbita. A. Lateral view. B. Common tendinous ring.
Fig. 8.91 Fascial sheath of the eyeball.
Fig. 8.92 Check ligaments. A. Anterior view. B. Superior view.
Medial rectus muscleMedial rectus muscleLateral rectus muscleLateral rectus muscleInferior rectus muscleInferior oblique muscleMedial check ligamentCheck ligament of medial rectusmuscleCheck ligament of lateral rectus muscleLateral check ligamentSuspensory ligamentSuspensory ligamentSuspensoryligamentFascial sheathFascial sheathPeriosteumPeriorbitaLacrimal sacAB
Fig. 8.93 Movements of the eyeball.
Fig. 8.94 Axes of the eyeball and orbit.
Axis of eyeballAxis of orbitMedial
Fig. 8.95 Muscles of the eyeball. A. Superior view. B. Lateral view. C. Coronal magnetic resonance image through the eye.
Fig. 8.96 Origins of muscles of the eyeball, coronal view.
Superior orbital fissureInferior orbital fissureLacrimal nerveFrontal nerveNasociliary nerveOptic nerveLateral rectusMedial rectusSuperior rectusSuperior obliqueLevator palpebrae superiorisInferior rectusInferior ophthalmic veinOphthalmic arteryInferior division of oculomotor nerve [III]Superior division of oculomotor nerve [III]Abducent nerve [VI]Trochlear nerve [IV]LateralMedial
Fig. 8.97 Actions of muscles of the eyeball. A. Action of individual muscles (anatomical action). B. Movement of eye when testing specific muscle (clinical testing). |
AbductionAdductionElevationDepressionInferiorobliqueSuperiorobliqueSuperiorrectusInferiorrectusLateralrectusMedialrectusMuscle testedDirection to moveeye when testingmuscleSuperior rectusInferior rectusLateral rectusMedial rectusInferior obliqueSuperior obliqueLook laterally and upwardLook laterally and downwardLook laterally Look mediallyLook medially and upwardLook medially and downwardABMedialLateral
Fig. 8.98 The “H-test.”
Right eyeLateral rectus [VI]Superior rectus [III]Inferior rectus [III]Medial rectus [III]Superior oblique [IV]Inferior oblique [III]1.2.3.4.5.6.Medial rectus [III]Inferior oblique [III]Superior oblique [IV]Lateral rectus [VI]Inferior rectus [III]Superior rectus [III]Left eye142635
Fig. 8.99 Arterial supply to the orbit and eyeball.
Fig. 8.100 Venous drainage of the orbit and eyeball.
Fig. 8.101 Innervation of the orbit and eyeball.
Lacrimal branch of ophthalmic nerve [V1]Nasociliary branchof ophthalmic nerve [V1]Frontal branch of ophthalmic nerve [V1]Optic nerveOptic canalInferior ophthalmic veinSuperior ophthalmic veinOphthalmic arteryInferior branch of oculomotor nerve [III]Superior branch of oculomotor nerve [III]Abducent nerve [VI]Trochlear nerve [IV]Common tendinous ringLateralMedial
Fig. 8.102 Oculomotor nerve [III] and its divisions.
Fig. 8.103 Trochlear nerve [IV] in the orbit.
Fig. 8.104 Ophthalmic nerve [V1] and its divisions.
Fig. 8.105 Relationship of the ophthalmic nerve [V1] and its divisions to the muscles of the eyeball.
Fig. 8.106 Course of the nasociliary nerve (from [V1]) in the orbit.
Long ciliary nervesShort ciliary nervesLacrimal glandLacrimal nerve (from [V1])Lateral rectus Ciliary ganglionAbducent nerve[VI]Inferior branch of the oculomotor nerve [III]Superior branch of the oculomotor nerve [III]Medial rectus muscleNasociliary nerve (from [V1])Posterior ethmoidal nerveAnterior ethmoidal nerveInfratrochlear nerveLateral
Fig. 8.107 Ciliary ganglion.
Fig. 8.108 Eyeball.
Fig. 8.109 Ophthalmoscopic view of posterior chamber of the right eye.
Fig. 8.110 Ciliary body.
Fig. 8.111 Layers of the retina in a healthy eye. A. HD-OCT scan of a healthy eye. B. Schematic indicating the layers of the retina on an HD-OCT scan of a healthy eye. C. Diagram illustrating the layers of the retina.
Fig. 8.112 High-definition optical coherence tomography (HD-OCT). A. Diseased eye. B. Healthy eye.
Fig. 8.113 Right ear.
Fig. 8.114 Auricle.
Fig. 8.115 Sensory innervation of the auricle.
Auriculotemporalbranch of themandibular nerve [V3]Great auricular nerve(C2,C3)Facial nerve [VII]Vagus nerve [X]Lesser occipitalnerve (C2) |
Fig. 8.116 External acoustic meatus.
Fig. 8.117 Middle ear.
Fig. 8.118 Tympanic membrane (right ear). A. Diagram. B. Otoscopic view.
ABPars flaccidaPosteriormalleolar foldHandle ofmalleusUmboCone of lightAnteriormalleolar foldLateral process(of malleus)
Fig. 8.119 Parts of the middle ear.
Fig. 8.120 Boundaries of the right middle ear.
Tegmen tympaniTensor tympani musclePharyngotympanic tubeLesser petrosal nerveBranch from internalcarotid plexusSympathetic plexusInternal carotid arteryChorda tympani nerveTympanic branch of the glossopharyngeal nerve [IX]Internal jugular veinPromontoryRound windowFacial nerve [VII]Chorda tympani nervePyramidal eminenceAditus tomastoid antrumProminence of facial canalProminence of lateral semicircular canalOval window
Fig. 8.121 Mastoid antrum and surrounding bone. A. Diagram.
B. High-resolution CT scan of left ear (petrous temporal bone).
BAditus to mastoid antrumTegmen tympaniEpitympanic recessPharyngotympanic tubeMiddle earMastoid processCochleaMiddle earExternal auditorymeatusMastoid air cellsMastoid air cellsMastoid antrumA
Fig. 8.122 Pharyngotympanic tube.
Fig. 8.123 Auditory ossicles. A. Malleus. B. Incus. C. Stapes.
Head of malleusNeck ofmalleusABCAnterior processHandle of malleusLateralprocessIncus articulationShort limbMalleus articulationLong limbBody ofincusBase of stapesAnterior limbHead of stapesPosterior limb
Fig. 8.124 Muscles associated with the auditory ossicles (right ear).
MalleusIncusPyramidal eminenceTendon ofstapedius muscleFootplate of stapesTympanic membranePharyngotympanic tubeTensor tympani muscle
Fig. 8.125 Innervation of the middle ear.
Prominence of lateralsemicircular canalTensor tympani musclePromontoryLesser petrosal nervePharyngotympanic tubeBranch from internal carotid plexus(caroticotympanic nerve)Tympanic nerve(from glossopharyngeal nerve [IX])Tympanic plexusRound windowStapesProminence of facial canal
Fig. 8.126 Grooves and hiatuses for the greater and lesser petrosal nerves.
Fig. 8.127 Location of the internal ear in temporal bone.
Fig. 8.128 Internal ear.
Fig. 8.129 Bony labyrinth.
SacculeHelicotremaDura materCochleaCochlear ductScala tympaniScala vestibuliPharyngotympanic tubeRound windowOpening of cochlear canaliculusTympanic membraneVestibuleUtricleAmpullaAnterior semicircular canal and ductVestibular aqueductLateral semicircular canal and ductPosterior semicircular canal and ductStapes in oval window
Fig. 8.130 Cochlea.
ModiolusScala vestibuliScalatympaniCochlear ductLamina of modiolusCochlear nerveSpiral ganglionHelicotrema
Fig. 8.131 Membranous labyrinth.
Fig. 8.132 Membranous labyrinth, cross section. |
Vestibular membraneScala vestibuliModiolusLamina of modiolusScala tympaniBasilar membraneSpiral ligamentSpiral organ
Fig. 8.133 A. Facial nerve in the temporal bone. B. Chorda tympani in the temporal bone.
Fig. 8.134 Transmission of sound.
Fig. 8.135 Temporal and infratemporal fossae.
Zygomatic archArticular tubercleMandibular fossaGroove for middletemporal arteryRamus of mandibleExternal acousticmeatusSupramastoid crestTemporal fossaInfratemporal fossaMasseter muscle
Fig. 8.136 Bony features related to the temporal and infratemporal fossae.
Greater wingof sphenoid boneFrontal boneFrontal process ofzygomatic boneZygomaticofacialforamenZygomaticotemporalforamen(on deep surface ofzygomatic bone)Posterior surfaceof maxillaZygomatic boneMaxillary process ofzygomatic boneLateral plate of pterygoidprocess of sphenoid bonePalatine bonePterygopalatinefossaTympanomastoidfissureMastoid processTympanic plateSpine of sphenoidStyloid processPterygomaxillary fissure(leading into pterygopalatine fossa)PterygoidhamulusExternal acousticmeatusSupramastoid crestGroove for middletemporal arteryMandibular fossaArticular tubercleForamen spinosumInfratemporal crestForamen ovaleInfratemporalsurface of maxillaAlveolar foramenPetrotympanic fissureSquamous part oftemporal bone
Fig. 8.137 Mandible. A. Lateral view of left side. B. Medial view of left side.
Fig. 8.138 Temporomandibular joint. A. Mouth closed. B. Mouth open.
ABUpper joint cavityArticular discArticular tubercleFibrocartilage onarticular surfaceCapsuleLower joint cavitySynovialmembraneMandibular fossaForward movement of discand mandible at upper jointLateral pterygoidmuscleProtrusionDepressionHinge movementat lower joint
Fig. 8.139 Ligaments associated with the temporomandibular joint.
Fig. 8.140 Movements of the temporomandibular joint.
Protrusion• Lateral pterygoid assisted by medial pterygoidRetraction• Posterior fibers of temporalis, deep part of masseter, and geniohyoid and digastricDepression• Gravity• Digastric, geniohyoid, and mylohyoid musclesElevation• Temporalis, masseter, medial pterygoid
Fig. 8.141 Masseter muscle.
Fig. 8.142 Temporal fossa. A. Lateral view. B. Lateral view showing the infratemporal fossa.
Fig. 8.143 Temporalis muscle. Lateral view.
Fig. 8.144 Nerves and arteries of the temporal fossa.
Temporal fasciaZygomaticotemporal nerve(branch of maxillary nerve [V2])Deep temporal arteriesMandibular nerve [V3]Deep temporal nervesZygomaticofacial nerveInfratemporal crestMaxillary artery in infratemporal fossaExternal carotid arterySuperficial temporal arteryMiddle temporal arteryTemporalis muscle
Fig. 8.145 Borders of the infratemporal fossa. |
Foramen spinosumInfratemporal crestForamen ovaleTensor veli palatiniLevator veli palatiniAlveolar foramenLateral plate of pterygoid processPterygomaxillary fissure(leading into pterygopalatine fossa)Posterior surface of maxillaPterygopalatine fossaGreater wing of sphenoid boneMasseterMylohyoidHyoglossusMiddle constrictorSuperior constrictorPharynxSpine of sphenoidHead and neck of mandiblePetrotympanic fissurePterygomandibular raphe
Fig. 8.146 Medial pterygoid muscle.
Foramen spinosumInfratemporal crestForamen ovaleTensor veli palatiniLevator veli palatiniDeep headmedial pterygoidSuperficial headmedial pterygoidSpine of sphenoidPetrotympanic fissureLingulaMandibular canalSphenomandibular ligament
Fig. 8.147 Lateral pterygoid muscle.
Infratemporal crestUpper head of lateral pterygoidDeep head medial pterygoidSuperficial headmedial pterygoidLower headlateral pterygoidCapsuleArticular discSphenomandibular ligament
Fig. 8.148 Mandibular nerve [V3]—anterior trunk. Meningeal branch and nerve to medial pterygoid.
Deep headmedial pterygoidTrigeminal ganglionUpper head lateral pterygoid (cut )Lower head lateral pterygoid (cut )Nerve to medial pterygoidBranch to tensor veli palatiniMeningeal branchPosterior trunkBranch to tensor tympaniAnterior trunkDeep temporal nervesBuccal nerveNerve to lateral pterygoidMasseteric nerve
Fig. 8.149 Mandibular nerve [V3]—posterior trunk. A. Lateral view.
B. Anterior view. C. Anteromedial view.
Petrotympanic fissureChorda tympani nerveLingual nerveAIncisive nerveMental nerveNerve to mylohyoidInferior alveolar nerveAuriculotemporal nerve
Medial pterygoidmuscleLingulaLingual nerveMental nerveIncisive nerveInferior alveolar nerveSphenomandibular ligamentChorda tympaniInferior alveolar nerveSphenomandibular ligamentSuperior constrictor muscleSubmandibular ganglionNerve to mylohyoidGreater horns of hyoid boneHyoglossus muscleGenioglossus muscleGeniohyoid muscleLingual nerveTemporalis tendonPterygomandibular raphe (cut )Buccal nerve (branch of anterior trunk)BCFacial nerve [VII]Trigeminal nerve [V]Mandibular nerve [V3]
Fig. 8.150 Chorda tympani and lesser petrosal nerves. A. Course after emerging from the skull. B. Course of parasympathetic fibers.
APetrotympanic fissureChorda tympani nerve from [VII]Lesser petrosal nerve [IX]Lingual nerveOtic ganglion (medial to [V3])TongueLingual nerveSublingual glandMylohyoidSubmandibular glandSubmandibular ganglionPreganglionic parasympathetic fibers from glossopharyngeal nerve [IX]Postganglionic parasympathetic fibers from otic ganglionPreganglionic parasympathetic fibers from facial nerve [VII]Postganglionic parasympathetic fibers from submandibular ganglionAuriculotemporal nerveTop of parotid glandAuriculotemporal nerve |
Preganglionic parasympathetic fibers from glossopharyngeal nerve [IX]Postganglionic parasympathetic fibers from otic ganglionPreganglionic parasympathetic fibers from facial nerve [VII]Postganglionic parasympathetic fibers from submandibular ganglionTympanic plexusLesser petrosal nerveOtic ganglionChorda tympani (carries taste fromthe anterior 2/3 of the tongue)Sublingual glandSubmandibularglandChorda tympanicarries parasympatheticinnervation to all glandsbelow the oral fissureSubmandibularganglionLingual nerveAuriculotemporal nerveParotid glandTympanic membraneChorda tympaniTympanic nerveInferior ganglionGreater petrosal nerveBGlossopharyngeal nerve [IX]Facial nerve [VII]Mandibular nerve [V3]Maxillary nerve [V2]Ophthalmic nerve [V1]Trigeminal nerve [V]
Fig. 8.151 Maxillary artery.
Branches of middlemeningeal in cranial cavityMiddle meningeal arteryArtery to masseterUpper head oflateral pterygoid (cut )Pterygoid arteryPterygopalatine fossaLower head of lateralpterygoid (cut )Buccal arteryMental arteryInferior alveolar arteryExternal carotidMaxillary arteryAuriculotemporal nerveSuperficial temporal arteryDeep temporal arteries
Fig. 8.152 Pterygoid plexus of veins.
Maxillary veinEmissary veins(connect with cavernous sinus)Inferior ophthalmic veinDeep facial veinFacial veinInferior alveolar veinSuperficial temporal veinExternal jugular veinInternal jugular veinPosterior auricular veinRetromandibular vein
Fig. 8.153 Pterygopalatine fossa. A. Anterolateral view. B. Lateral view.
Fig. 8.154 Sphenoid bone. A. Anterior view. B. Posterosuperior view.
AForamen rotundumSurface related topterygopalatine fossaPterygoid canalPalatovaginal grooveBLesser wingGreater wingForamen rotundumPosterior opening of bony part of pterygoid canalPterygoid processPart of pterygoid canal incartilage of foramen lacerumCartilage filling foramen lacerumGreater petrosal nerve of VIIMaxillary nerve [V2]Internal carotid arterySuperior orbital fissure
Fig. 8.155 Gateways of the pterygopalatine fossa.
Sphenopalatine foramennasal cavityInferior orbital fissurefloor of orbitPterygomaxillary fissureinfratemporal fossaPalatine canalroof of oral cavity (palate)Pterygoid canalcranial cavity(middle cranial fossa)Foramen rotundumcranial cavity(middle cranial fossa)Palatovaginal canalnasopharynx
Fig. 8.156 Maxillary nerve [V2]. A. Terminal branches. B. In relationship to the pterygopalatine ganglion.
Fig. 8.157 Nerve of the pterygoid canal. A. Overview. B. In relationship to the pterygopalatine ganglion. |
ABLacrimal nerveLacrimal glandParasympathetic nerves in branch of zygomaticotemporal nerveZygomatic nerveNerve of pterygoid canalCartilage filling foramen lacerumDeep petrosal nerveInternal carotid nerveFacialnerve [VII]Preganglionic sympathetic nerves from T1Superior cervical sympathetic ganglionSympathetic trunkGeniculate ganglionGreater petrosal nerveInternal carotid plexus[V1][V2][V3]Internal carotid arteryPterygopalatine fossaInferior orbital fissureInfra-orbital nervePreganglionic parasympathetic nervesPostganglionic parasympathetic nervesPreganglionic sympathetic nervesPostganglionic sympathetic nervesNerve of pterygoid canal
Fig. 8.158 Maxillary artery in the pterygopalatine fossa.
Pharyngeal arterySphenopalatine arteryInfra-orbital arterySeptal part of greater palatine arteryAnterior superior alveolar arteryPosterior superior alveolar arteryGreater palatine arteryLesser palatine arteryMaxillary artery ininfratemporal fossaNasopharynxArtery of pterygoid canalCartilage filling foramen lacerum
Fig. 8.159 Veins of the pterygopalatine fossa.
Fig. 8.160 Compartments of the neck.
Fig. 8.161 Anterior and posterior triangles of the neck.
Inferior border of mandibleAnteriortriangleSternocleidomastoid muscleClavicleTrapezius musclePosteriortriangle
Fig. 8.162 Fascia of neck, transverse view.
Fig. 8.163 Fascia of the neck, sagittal view.
Investing layerInfrahyoid musclesPretracheal fasciaManubrium of sternumPretracheal spaceFascial space within prevertebral layerRetropharyngeal spacePrevertebral layerBuccopharyngeal fascia(posterior portion ofpretracheal layer)
Fig. 8.164 Superficial veins of neck.
Fig. 8.165 Placing a central venous catheter in the neck. A. Clinical procedure. B. Chest radiograph showing that the tip of the catheter is in the origin of the right atrium.
Fig. 8.166 Borders and subdivisions of the anterior triangle of the neck.
Submandibular triangleAnterior belly ofdigastric muscleSubmental triangleHyoid boneSuperior belly of omohyoid muscleMuscular triangleSternocleidomastoid muscleTrapezius musclePosterior triangleCarotid triangleStylohyoid musclePosterior belly of digastric muscle
Fig. 8.167 Suprahyoid muscles. A. Lateral view. B. Inferior view.
Fig. 8.168 Infrahyoid muscles.
Fig. 8.169 Origin of common carotid arteries.
TracheaEsophagusLeft common carotid arteryLeft internal jugular veinLeft subclavian arteryLeft subclavian veinClavicleSuperior vena cavaRight subclavian veinRight subclavian arteryRight internal jugular veinRight common carotid arteryArch of aortaLeft brachiocephalic veinRight brachiocephalic vein
Fig. 8.170 Carotid triangle.
SternocleidomastoidmuscleCarotid triangleSuperior belly ofomohyoid muscleCommon carotid arteryPosterior belly of digastric muscleInternal carotid arteryExternal carotid artery
Fig. 8.171 Carotid system.
Fig. 8.172 Glossopharyngeal nerve [IX] in the anterior triangle of the neck. |
Fig. 8.173 Vagus nerve [X] in the anterior triangle of the neck.
Fig. 8.174 Accessory nerve [XI] in the posterior triangle of the neck.
Fig. 8.175 Hypoglossal nerve [XII]. A. Surgical view of hypoglossal nerve in anterior triangle of the neck. B. Diagram.
Hyoglossus muscleExternal carotidarterySuperior root ofansa cervicalisSuperior thyroid arteryInternal jugular veinInternal jugularveinPosterior belly ofdigastric muscle (cut )Stylohyoid muscleSternocleidomastoidbranch of occipital arteryHypoglossal nerveHypoglossal nerveSternocleidomastoid branchof occipital arteryPosterior belly of digastric muscleOccipital arteryAB
Fig. 8.176 Transverse cervical nerve in the anterior triangle of the neck.
Fig. 8.177 Ansa cervicalis.
Hypoglossal nerveC1C3C2Superior root of ansa cervicalisInferior root of ansa cervicalisOmohyoid muscle(superior belly)Sternohyoid muscleSternothyroid muscleThyrohyoid muscleOmohyoid muscle(inferior belly)
Fig. 8.178 Thyroid gland in the anterior triangle of neck. A. Anterior view. B. Transverse view. C. Ultrasound scan—compound axial view of the neck. D. Ultrasound scan—axial view of the neck. E. Nuclear medicine scan—normal thyroid uptake of pertechnetate in the neck.
Fig. 8.179 Vasculature of the thyroid: anterior view.
Fig. 8.180 Superior and inferior thyroid arteries and left and right recurrent laryngeal nerves and thyroid and parathyroid glands. A. Posterior view. B. Surgical (anterolateral) view of parathyroid gland with left lobe of thyroid retracted.
BLeft lobe of thyroid glandParathyroid gland
Fig. 8.181 Surgical view of left lobe of enlarged thyroid (goiter) retracted to show close association with recurrent laryngeal nerve.
Left lobe of thyroid glandLeft recurrent laryngeal nerve
Fig. 8.182 Ectopic parathyroid adenoma in superior mediastinum. Noncontrast hybrid single photon emission computed tomography/computed tomography (SPECT/CT). A. Transverse view. B. Sagittal view. C. Coronal view.
Fig. 8.183 Borders of the posterior triangle of the neck.
Sternocleidomastoid muscleTrapezius muscleOmoclavicular orsubclavian triangleOccipital triangleHyoid bonePosteriortriangleSuperior belly ofomohyoid muscleInferior belly of omohyoid muscle
Fig. 8.184 Muscles of the posterior triangle of the neck.
Sternocleidomastoid muscleClavicleInferior belly of omohyoid muscleAcromion ofscapulaTrapezius muscleAnterior scalene muscleMiddle scalene musclePosterior scalene muscleLevator scapulae muscleSplenius capitis muscle
Fig. 8.185 External jugular vein in the posterior triangle of the neck.
Fig. 8.186 Arteries in the posterior triangle of the neck.
Trapezius muscleMiddle scalene muscleTransverse cervical arteryBrachial plexusSuprascapular artery3rd part of subclavian arteryPhrenic nerveAnterior scalene muscleSubclavian veinExternal jugular veinInternal jugular veinClavicle1st part of subclavian arteryVagus nerveCommon carotid arteryThyrocervical trunkInferior thyroid arterySternocleidomastoid muscle |
Fig. 8.187 Accessory nerve and cutaneous branches of the cervical plexus in the posterior triangle of the neck.
Fig. 8.188 Cervical plexus.
Fig. 8.189 Prevertebral and lateral vertebral muscles supplied by cervical plexus.
Fig. 8.190 Root of the neck.
TracheaRib IManubrium of sternumCervical pleuraTI vertebraEsophagus
Fig. 8.191 Vasculature of the root of the neck.
Fig. 8.192 Nerves in the root of the neck.
Fig. 8.193 Components of the sympathetic nervous system in the root of the neck.
Fig. 8.194 Cervical part of the sympathetic trunk.
Fig. 8.195 Thoracic duct in the root of the neck.
Fig. 8.196 Termination of lymphatic trunks in the root of the neck.
Fig. 8.197 Lymphatic system in the neck.
Fig. 8.198 Pharynx.
Fig. 8.199 Neck regions (levels) that are used clinically to evaluate lymph nodes.
Fig. 8.200 Line of attachment of the pharynx to the base of the skull.
Cartilaginous position of pharyngotympanic tubeChoanae (posterior openings of nasal cavities)Pterygoid hamulusLine of attachment of pharynxRoughening on petrous part of temporal bone for attachment of levator veli palatiniExternal acoustic meatusPharyngeal tubercleJugular foramenCarotid canalMedial plate of pterygoid process of sphenoidPetrous part of temporal boneScaphoid fossa on sphenoid bone (for attachment of tensor veli palatini)
Fig. 8.201 Attachments of the lateral pharyngeal wall.
Fig. 8.202 Constrictor muscles of the pharynx. A. Lateral view. B. Posterior view.
ABPosition of palatopharyngeal sphincteron deep surface of superior constrictorSuperior constrictorMiddle constrictorInferior constrictorEsophagusPharyngeal tuberclePharyngeal fasciaStylohyoid ligamentStylopharyngeus musclePharyngeal rapheStyloid process
Fig. 8.203 Longitudinal muscles of the pharynx. A. Stylopharyngeus muscle. B. Medial view.
Fig. 8.204 Gaps between muscles in the pharyngeal wall.
Pharyngeal fasciaStylopharyngeusSuperior constrictorMiddle constrictorInferior constrictorOropharyngealtriangle:structures (muscles,nerves, vessels)passing into and outof the oral cavityInternal laryngealnerve and vesselsEsophagusRecurrent laryngealnerve and vesselsTracheaMylohyoidBuccinator
Fig. 8.205 Mucosal features of the pharynx. A. Lateral view. B. Posterior view with the pharyngeal wall opened. C. Superior view. |
ABCFold overlyingpalatopharyngealsphincterTorus levatorius(fold overlyinglevator veli palatini)Torus tubariusPharyngeal recessPharyngeal tonsilPharyngeal opening of thepharyngotympanic tubeSalpingopharyngeal foldPalatine tonsilPalatopharyngeal arch(overliespalatopharyngeusmuscle)Laryngeal inletEsophagusTracheaValleculaLingual tonsilsPalatoglossal arch(margin of oropharyngeal isthmus)TongueNasal cavityNasopharynxOropharynxLaryngopharynxOropharyngealisthmusPharyngeal tonsilChoanaeTorus tubariusTorus levatoriusSoft palatePalatopharyngeal archPalatopharyngeal archPalatine tonsilValleculae (anterior to epiglottis)Laryngeal inletEsophagusPiriform fossaLingual tonsilLingual tonsilPalatine tonsilEpiglottisValleculaPiriform fossaSalpingopharyngealfoldPharyngealrecessesNasal cavityOral cavityTracheaLarynxPharynxEsophagus
Fig. 8.206 Arterial supply of the pharynx.
Pharyngeal branch(supplies roof of nasopharynx)Superficial temporal arteryAscending palatinearteryAscending pharyngeal arteryInternal carotid arteryCommon carotid arteryPharyngeal branchesInferior thyroid arteryThyrocervical trunkSubclavian arteryLingual arteryExternal carotid arteryFacial arteryTonsillar branchMaxillary artery
Fig. 8.207 Venous and lymphatic drainage of the pharynx.
Fig. 8.208 Innervation of the pharynx. A. Lateral view. B. Posterior view showing innervation of stylopharyngeus muscle.
ABPharyngeal branch of [V2]Nasopharynx–sensory [V2]Oropharynx–sensory [IX]Laryngopharynx–sensory [X]Superiorlaryngeal nerveInferiorganglion of [X]External laryngeal nerve(branch of superior laryngealnerve from [X])Internal laryngeal nerve(branch of superiorlaryngeal nervefrom [X])Pharyngealbranch of [IX]Pharyngealbranch of [X][IX][V2]IXMotor branch to stylopharyngeus
Fig. 8.209 Larynx. A. Relationship to other cavities. B. Lateral view.
Fig. 8.210 Cricoid cartilage. A. Anterolateral view. B. Posterior view.
Facet for articulation witharytenoid cartilageFacet for articulation withinferior horn of thyroid cartilageTracheaCricoidcartilageLaminaArchAirwayAFacet for articulation witharytenoid cartilageRidgeFacet for articulation with inferior horn of thyroid cartilageDepressionsB
Fig. 8.211 Thyroid cartilage. A. Anterolateral view. B. Superior view.
Fig. 8.212 Epiglottis. A. Anterolateral view. B. Posterior surface.
CricoidTracheaEpiglottic tubercleThyro-epiglottic ligamentRight thyroid laminaAnterior surface of epiglottisPosterior surface of epiglottisAB
Fig. 8.213 Arytenoid cartilages. |
ApexPosterior surfaceMedial surfaceRidge on anterolateral surfaceMuscular processArytenoidcartilageDepression for attachment of vocalis musclesDepression for attachment of vestibular ligamentBase (concave – for articulation with cricoid)Vocal processArticular facet forcorniculate cartilageAnterolateral surface
Fig. 8.214 Corniculate and cuneiform cartilages.
Fig. 8.215 Extrinsic ligaments of the larynx.
Lateral thyrohyoid ligamentsAperture for internal branch of superior laryngeal nerve and associated arteryThyrohyoid membraneCricotracheal ligamentMedian thyrohyoid ligamentHyo-epiglottic ligamentHyoid boneTriticeal cartilage
Fig. 8.216 Cricothyroid ligament.
Fig. 8.217 Quadrangular membrane.
Fig. 8.218 Fibro-elastic membrane of the larynx (superior view).
EpiglottisVestibular ligamentQuadrangular membraneConus elasticusMuscular process of arytenoidVocal process of arytenoidCorniculate cartilageVocal ligament
Fig. 8.219 Movements of the cricothyroid joints.
Fig. 8.220 Movements of the crico-arytenoid joints.
Fig. 8.221 Laryngeal cavity. A. Posterolateral view. B. Posterior view (cut away). C. Superior view through the laryngeal inlet. D. Labeled photograph of the larynx, superior view.
EpiglottisEpiglottisEpiglottisAry-epiglottic foldAry-epiglottic foldCut edge of mucosaLaryngeal sacculeVestibuleVestibuleCut edge of right thyroid laminaLaryngeal ventricleInfraglottic spaceInterarytenoid notchCorniculate tubercleCorniculate tubercleCuneiform tubercleCuneiform tubercleCuneiform tubercleLaryngeal inletLaryngeal inletVestibular fold(mucosa overlying vestibular ligament)Vestibular fold (false vocal cord)Vocal fold (mucosa overlying vocal ligament)Vocal fold (true vocal cord)TracheaCricoid archMiddle part of cavityLaryngeal sacculeRima vestibuliRima glottidisRima glottidis (opening between vocal cords)Interarytenoid foldCorniculate tubercleVestibular foldAry-epiglottic foldVocal fold ABCDLaryngopharynx (closed)Piriform recessTongueAnteriorPosterior
Fig. 8.222 Cricothyroid muscle.
Fig. 8.223 Crico-arytenoid, oblique and transverse arytenoid, and vocalis muscles.
Fig. 8.224 Thyro-arytenoid muscle.
Superior thyroid notchAry-epiglottic part ofoblique arytenoid muscleSacculeThyro-arytenoid muscleThyro-epiglotticpart of thyro-arytenoid muscle
Fig. 8.225 Laryngeal function. A. Quiet respiration. B. Forced inspiration. C. Phonation. D. Effort closure. E. Swallowing. |
Quiet respirationForced inspirationPhonationEffort closureSwallowingVocal foldVocal foldsclosedVestibular foldVestibularfolds closedAry-epiglottic foldLaryngeal inletLaryngealinlet narrowedEpiglottis swingsdown to arytenoidsEpiglottis• Vocal folds abducted and rima glottidis wide open• Vestibule open• Vocal folds adducted and stridulating as air is forced between them• Vestibule open• Vocal folds and vestibular folds adducted• Rima glottidis and vestibule closedABCDE
Fig. 8.226 Arterial supply of the larynx, left lateral view.
Fig. 8.227 Venous drainage of the larynx, anterior view.
Superior laryngeal veinMiddle thyroid veinSuperior thyroid veinThyrohyoid membraneMedian cricothyroid ligamentInferior thyroid veinThyroid glandManubrium of sternumRight subclavian veinInferior laryngeal veinRight internal jugular veinHyoid bone
Fig. 8.228 Innervation of the larynx.
Inferior vagal ganglionLeft vagus nerveThyrohyoid membranePosition of vocal foldsMedian cricothyroid ligamentLeft recurrent laryngeal nerveTracheaLeft subclavian arteryAortic archLeft pulmonary arteryRight pulmonary arteryLigamentum arteriosumPulmonary trunkEsophagusManubriumRight subclavian arteryRight recurrent laryngeal nerveCricothyroid muscleRight vagus nerveExternal laryngeal nerveSuperior laryngeal nerveInternal laryngeal nerve
Fig. 8.229 Nasal cavities (anterolateral view). Relationship to other cavities.
Fig. 8.230 Nasal cavities. A. Floor, roof, and lateral walls. B. Conchae on lateral walls. C. Coronal section. D. Air channels in right nasal cavity.
Fig. 8.231 Paranasal sinuses and nasolacrimal duct.
Fig. 8.232 Regions of the nasal cavities.
Fig. 8.233 Ethmoid bone. A. Overall shape. B. Coronal section through skull.
ABAnteriorPosteriorCrista galliLeft ethmoidal labyrinthOrbital plateUncinate processMiddle conchaPerpendicular plateChannel for frontonasal ductopening into frontal sinusRight ethmoidal labyrinthCribriform plateSuperior conchaEthmoidal bullaMiddle conchaUncinate processInfundibulumCranial cavityCribriform platePerpendicular plateNasal cavitiesOrbitOrbitMiddle ethmoidal cellsSuperior conchaEthmoidal bullaMiddle conchaUncinate processInferior concha boneVomerOral cavityPalatine process of maxillary boneMaxillarysinusMaxillarysinusOrbital plate ofethmoidal labyrinthOrbital plate offrontal boneCrista galli
Fig. 8.234 External nose.
Nasal boneFrontal process of maxillaLacrimal boneNasolacrimal grooveMinor alar cartilagesSeptal cartilageNarisMajor alarcartilageSuperior margin ofseptal cartilageLateral process ofseptal cartilage
Fig. 8.235 Paranasal sinuses. A. Anterior view. B. Posteroanterior skull radiograph.
C. Paramedian view of right nasal cavity. D. Lateral skull radiograph. |
ABEthmoidalcellsFrontal sinusesZygomatic process of frontal boneSuperior orbital fissureFrontalsinusesEthmoidal cellsMaxillarysinusesMaxillary sinusRoots of posteriorupper molarsOrbital plate ofethmoid boneNasal septumForamen rotundum
Fig. 8.236 Medial wall of the nasal cavity—the nasal septum.
Nasal spine of frontal bonePerpendicular plate of ethmoid bonePituitary fossaSphenoidal sinusVomerNasal crest ofmaxillary andpalatine bonesIncisor crestSeptalcartilageNasal bone
Fig. 8.237 Floor of the nasal cavity (superior view).
Septal cartilageNarisAnterior nasal spineIncisive canalPalatine process of maxillaHorizontal plate of palatineSoft palateNasal crestsMaxillary sinus
Fig. 8.238 Roof of the nasal cavity.
Cribriform plateOpening of sphenoidal sinusAla of vomerVomerSphenoidal rostrum(articulates in themidline with the vomer)Nasal bonesNasal spine of frontal bone
Fig. 8.239 Lateral wall of the nasal cavity. A. Bones.
B. Covered with mucosa. C. Conchae broken away at attachment to lateral wall.
AFrontal process of maxillaSuperior conchaMiddle conchaMedial pterygoid plate ofsphenoid boneUncinate process of ethmoidPerpendicular plateof palatine boneInferior conchaMinor alar cartilageMajor alar cartilageLateral process ofseptal cartilageLacrimal boneNasal bone
BCOpening ofpharyngotympanic tubeNasopharynxSoft palateInferior conchaMiddle conchaSuperior conchaOpening of posterior ethmoidalcells into lateral wall of superior meatusOpening of sphenoidal sinusinto spheno-ethmoidal recessOpening of middle ethmoidalcells onto ethmoidal bullaSemilunar hiatusOpening of maxillary sinus infloor of semilunar hiatus Opening of nasolacrimal ductInfundibulum opening of frontonasalduct that drains the frontal sinusand anterior ethmoidal cells
Fig. 8.240 Nares. A. Inferior view. B. Associated muscles.
NaresAMajor alar cartilageMinor alar cartilagesInferior nasal spine of maxillaConnective tissueSeptal cartilageBOrbitAttachment to frontalprocess of maxillaNasalis muscleAttachment to maxillaDepressor septi nasiNarisLevator labii superioris alaeque nasi
Fig. 8.241 Choanae (posterior view). A. Overview. B. Magnified view.
Ala of vomerSphenoidal rostrumSphenoidal process of palatine bonePalatine boneMaxillaPalatovaginal canalVomerBAVomerSphenoid boneMedial pterygoidplate of sphenoidHorizontal plate of palatine bonePyramidal process of palatine boneOral cavityChoanaeChoanaeVaginal process of medial pterygoid plate
Fig. 8.242 Gateways to the nasal cavities.
Fig. 8.243 Arterial supply of the nasal cavities. A. Lateral wall of the right nasal cavity. B. Septum (medial wall of right nasal cavity). |
ABAnterior ethmoidal arteryPosterior ethmoidal arterySuperior conchaMiddle conchaInferior conchaGreater palatine arteryPosterior lateral nasalbranches of sphenopalatine arterySphenopalatine arteryAlar branch oflateral nasal arteryExternal nasalartery from anteriorethmoidal arterySeptal branch ofanterior ethmoidal arterySeptal branch ofposterior ethmoidal arteryArea of significantanastomoses (proneto “nosebleeds”)Posterior septal branch ofsphenopalatine arteryTerminal part ofgreater palatine arterySeptal branch from nasalartery from superior labial artery
Fig. 8.244 Venous drainage of the nasal cavities.
Nasal vein in foramen cecumDrainage to cavernoussinus in cranial cavityDrainage to pterygoid plexusin infratemporal fossaDrainage to facial vein
Fig. 8.245 Innervation of the nasal cavities. A. Lateral wall of right nasal cavity. B. Medial wall of right nasal cavity.
ABPosterior inferiorlateral nasal nervesInternal nasal branchesof infra-orbital nerveExternal nasalbranch of anteriorethmoidal nerveSeptal branch ofanterior ethmoidal nerveOlfactory nerve [I](septal branches)Olfactory bulbAnterior ethmoidal nerveOlfactory nerve [I]Sphenopalatine foramenPosterior superiorlateral nasal nervesNasal branch of anteriorsuperior alveolar nerveNasopalatine nerve
Fig. 8.246 Lymphatic drainage of the nasal cavities.
Fig. 8.247 Oral cavity. A. Relationship to other cavities. B. Oral vestibule and oral cavity proper.
Fig. 8.248 Base and lateral aspects of the skull. A. Features in the base of the skull related to structures associated with the oral cavity.
B. Styloid process of the temporal bone.
Petrous part of temporal boneScaphoid fossaForamen ovaleSpine of sphenoidOpening to bony partof pharyngotympanic tubeForamen spinosumCarotid canalStyloid process of temporal boneMastoid processStylomastoid foramenJugular foramenRoughening for attachment of levator veli palatiniForamen lacerum (closed by cartilage)Cartilaginous part of pharyngotympanic tubeGreater wing of sphenoidMembranous lamina ofcartilaginous part of pharyngotympanic tubeAIncisive fossaPalatine process of maxillaAlveolar process of maxillaHorizontal plate of palatine boneGreater palatine foramenLesser palatine foramenLateral plate of pterygoid processMedial plate of pterygoid processIntermaxillary suturePosterior nasal spinePyramidal process of palatine bonePterygoid hamulus
Fig. 8.249 Mandible. A. Superior view. B. Lateral view. C. Medial view.
Fig. 8.250 Hyoid bone. A. Anterior view. B. Lateral view.
Fig. 8.251 Buccinator muscle.
Attachment to maxillaSuperior constrictorPterygomandibular rapheAttachment to mandibleBuccinatorOrbicularis orisModiolus
Fig. 8.252 A. Mylohyoid muscles. B. Geniohyoid muscles. C. Lateral view.
Superior mental spinesGeniohyoidGeniohyoidMylohyoidMylohyoidSuperior mental spinesMylohyoid lineInferior mental spinesRapheGreater hornBody of hyoidFree posterior marginSubmandibular fossaSublingual fossa ABC
Fig. 8.253 Gateway into the floor of the oral cavity. |
Superiorconstrictorof pharynxMiddleconstrictorof pharynxMylohyoidTriangular aperture (oropharyngeal triangle) between mylohyoid,superior constrictor, and middle constrictor
Fig. 8.254 Tongue. A. Paramedian sagittal section. B. Superior view.
AOral part (anterior two-thirds)Foramen cecumand terminal sulcusPharyngeal part (posterior one-third)Hyoid boneRoot of tongueMylohyoid muscleGeniohyoid muscleMandibleInferior surfaceLower lipOral vestibuleFiliform papillaeTerminal sulcusForamen cecumBOropharynxPharyngeal part of tongueVallate papillaeFoliate papillaeFungiform papillae
Fig. 8.255 Muscles of the tongue.
Fig. 8.256 Genioglossus muscles. A. Posterior view. B. Lateral (left) view.
Fig. 8.257 Hyoglossus muscles. A. Posterior view. B. Lateral (left) view.
Fig. 8.258 Styloglossus muscles.
Fig. 8.259 Palatoglossus muscles.
Hard palatePalatine aponeurosisof soft palatePalatoglossus muscle (underliesthe palatoglossusarch of mucosa)Uvula
Fig. 8.260 Arteries, veins, and nerves of the tongue.
Lingual nerve(from [V3])Chorda tympani (from [VII])Hypoglossalnerve [XII]OccipitalarterySternocleidomastoid branch of occipital arteryLingual arteryCommon carotid arteryInternal jugular veinDorsal lingual veinDeep lingual veinHyoglossusGlossopharyngealnerve [IX]
Fig. 8.261 Innervation of the tongue.
Fig. 8.262 Lingual nerve in the floor of the oral cavity (medial view).
Fig. 8.263 Hypoglossal nerve and C1 fibers.
Hypoglossal nerveC1C1 fibersC3C2ThyrohyoidSuperior root ofansa cervicalisNerve to thyrohyoid(C1)GeniohyoidNerve to geniohyoid (C1)
Fig. 8.264 Parotid gland.
MasseterBuccinatorParotid duct(penetrates buccinator oppositecrown of 2nd upper molar tooth)SternocleidomastoidParotid glandExternal acoustic meatus
Fig. 8.265 Submandibular and sublingual glands. A. Medial view. B. Posterior view. C. Anterior view. D. Anterosuperior view.
Superior constrictor musclePterygomandibular rapheSmall ducts of sublingual glandSubmandibular ductSublingual glandSublingual glandSubmandibular ductGenioglossus muscleHyoglossus muscleSuperficialDeepSuperficialDeepSubmandibularglandLingual nerveABSubmandibular ductSublingual fold overlyingsublingual glandSublingual caruncleOpening ofsubmandibular ductOpening of leftsubmandibular ductSublingual carunclesLingual veinFrenulum of tongueOpening of ducts from sublingual glandCDDeep lingual veinFimbriated foldFrenulum of tongue
Fig. 8.266 Summary of parasympathetic (secretomotor) innervation of glands in the head. |
Lacrimal glandGlands onpalatePterygopalatine ganglionPalatine nerveLabial glandsLingual glandsSublingual glandSubmandibular glandSubmandibular ganglionOtic ganglionAuriculotemporal nerve (from [V3])Parotid gland innervated by [IX]Chorda tympani[V][VII][IX]Preganglionic parasympathetic fibers from [IX]Greater petrosal nerveAll glands abovelevel of oral fissureinnervated by greater petrosal of [VII]All glands below level of oral fissureinnervated bychorda tympani of [VII]
Fig. 8.267 Course of parasympathetic fibers carried in the chorda tympani nerve.
Fig. 8.268 Summary of sympathetic innervation of glands in the head.
Fig. 8.269 Palate.
Fig. 8.270 A. Tensor veli palatini muscles and the palatine aponeurosis. B. Levator veli palatini muscles. C. Palatopharyngeus muscles.
Muscular part of tensor veli palatiniCartilaginous part ofpharyngotympanic tubeFibrous part of pharyngotympanic tubePalatine aponeurosisPterygoid hamulusPosition of palatopharyngealsphincterPharyngeal rapheSuperior constrictor of pharynxPterygomandibular rapheBuccinator musclePterygopalatine fossaABCNasal cavityMedial pterygoid plateLateral pterygoid plateNasal septumLevator veli palatiniPalatopharyngeus
Fig. 8.271 Open mouth with soft palate. A. Oropharyngeal isthmus opened. B. Oropharyngeal isthmus closed.
ABPalatoglossal archPalatopharyngeal archPosterior wall of oropharynxSoft palateSoft palateTongueUvulaPalatine tonsilAnterior margin oforopharyngeal isthmus(palatoglossal arch)Closure of oropharyngeal isthmus• Medial and downward movement of palatoglossal arches• Medial and downward movement of palatopharyngeal arches• Upward movement of tongue• Downward and forward movement of soft palate
Fig. 8.272 Palatoglossus muscles and musculus uvulae.
Musculus uvulaePalatoglossusfrom underside of aponeurosisPalatine tonsil
Fig. 8.273 Arteries of the palate.
Fig. 8.274 Palatine nerves and arteries.
Incisive fossaNasopalatine nerveGreater palatine nerveGreater palatine foramenLesser palatine foramenLesser palatine nerveUvulaBranches from ascending palatine artery of facial artery and palatine branch of ascending pharyngeal arteryLesser palatine arteryGreater palatine artery
Fig. 8.275 Venous and lymphatic drainage of the palate.
Fig. 8.276 Innervation of the palate.
Greater petrosal nerve (preganglionic parasympatheticand special sensory [taste])[VII]Deep petrosal nerve (postganglionic sympathetic)Superior cervical sympathetic ganglionSympathetic trunkPreganglionicsympathetic from T1UvulaInternal carotid arteryNerve of pterygoid canalLesser palatine nerveLesser palatine foramenGreater palatine nerveNasopalatine nerveGreater palatine foramenPalatine canalPterygopalatine ganglionNasopalatine nerveMaxillary nerve[V] |
Fig. 8.277 Oral fissure and lips. A. Anterior view. B. Sagittal section.
PhiltrumVestibuleOrbicularis oris muscleOral fissureVermilion border of lipFacial arterySuperior and inferior labial arteriesABLabial salivary glandsArtery and veinVermilion bordersOrbicularis oris muscleBuccinator muscle
Fig. 8.278 Teeth. A. Adult upper and lower permanent teeth. B. Deciduous (“baby”) teeth.
AIncisorsCaninesPremolarsMolarsMolarsPremolarsCaninesIncisorsMaxillary sinusRoots related to maxillary sinusPremolars3212132121Roots related tomandibular canalMolarsCanineIncisorsUpperLowerMolarsIncisorsCaninesBUpperLower
Fig. 8.279 Arteries and veins of the teeth.
Cavernous sinusin cranial cavityEmissary veinsInfra-orbitalartery and veinPosterior superior alveolarartery and veinAnterior superior alveolarartery and veinInferior alveolar artery andvein in mandibular canalFacial veinInternal jugular veinExternal jugular veinExternal carotid arteryPterygoid plexus of veinsRetromandibular veinMaxillary veinMaxillary artery
Fig. 8.280 Lymphatic drainage of the teeth and gums.
Fig. 8.281 Innervation of the teeth.
Fig. 8.282 Innervation of the teeth and gums.
TeethAnterior superior alveolar nerve (from [V2])Middle superior alveolar nerve (from [V2])Posterior superioralveolar nerve (from [V2])UpperLowerMain trunk of inferioralveolar nerve (from [V3])Incisive branch of inferioralveolar nerve (from [V3])Nasopalatine nerve (from [V2])Greater palatine nerve (from [V2])GingivaeAnterior superior alveolar nerve (from [V2])Middle superior alveolar nerve (from [V2])Posterior superior alveolar nerve (from [V2]) Lingual nerve (from [V3])Buccal nerve (from [V3])Mental nerve from inferior alveolar nerve (from [V3])
Fig. 8.283 Anatomical position of the head and major landmarks. Lateral head and neck of a man.
External occipitalprotuberanceCervical spinal nervesExternal acoustic meatusSternocleidomastoid muscleAngle of mandibleMastoid processVertexZygomatic boneFrankfort lineInferior margin of orbitPosition of head of mandiblePosition of zygomatic arch[V1][V2][V3]
Fig. 8.284 Visualizing structures at the CIII/IV and CVI vertebral levels. Lateral head and neck of a man.
Vertebral level CVI• Arch of cricoid cartilage• Superior end of esophagus• Superior end of tracheaVertebral level CIII/IV• Upper margin of thyroid cartilage• Bifurcation of common carotid arteryBifurcation of common carotidFrankfort lineEsophagusArch of cricoidPharynx
Fig. 8.285 How to outline the anterior and posterior triangles of the neck. A. In a woman, anterolateral view. The left anterior triangle is indicated. B. In a man, anterior view of the posterior triangle.
ABMidline of neckAnterior margin ofsternocleidomastoidAnterior margin oftrapeziusClaviclePosterior margin ofsternocleidomastoidPosterior triangleAnterior triangleInferior margin of mandibleStructures coursing betweenhead and thorax are associatedwith the anterior trianglesStructures coursing betweenthorax/neck and upper limb areassociated with the posterior triangles |
Fig. 8.286 How to locate the median cricothyroid ligament. A. In a man, lateral view of head and neck. B. In a woman, lateral view of head and neck. C. In a man, anterior neck with the chin elevated. D. In a woman, anterior neck with the chin elevated.
ABThyroid notchLaryngeal prominencePosition of mediancricothyroid ligamentArch of cricoid cartilage
Thyroid notchLaryngeal prominencePosition of median cricothyroid ligamentArch of cricoidcartilageIsthmus of thyroid glandCD
Fig. 8.287 How to find the thyroid gland. A. In a woman, anterior view of neck. B. In a man, anterior view of neck.
Position of oblique line on thyroid cartilageHyoid boneThyroid notchLaryngeal prominenceMedian cricothyroidligamentArch of cricoidLeft lobe of thyroid glandRight lobe of thyroid glandIsthmus of thyroid glandAB
Fig. 8.288 Estimating the position of the middle meningeal artery. Lateral head and neck of a man.
External earExternal acoustic meatusPterionFrankfort lineInferior margin of orbitSuperior margin of orbit
Fig. 8.289 Major features of the face. Anterior head and neck of a woman.
Region for testing [V1]Palpebral fissureOral fissureNostril[V1][V2][V3]Region fortesting [V2]Region for testingsensory of [V3]Orbicularis orisPhiltrumOrbicularis oculi
Fig. 8.290 Eye and lacrimal apparatus. A. Face of a woman. Lacrimal apparatus and the flow of tears are indicated. B. Left eye and surrounding structures. C. Left eye and surrounding structures with lower eyelid pulled down to reveal the lacrimal papilla and lacrimal punctum.
ALacrimal glandFlow of tearsNasolacrimal ductInferior canaliculusLacrimal sacUpper eyelidLower eyelidLacrimal lakeScleraPupilPalpebral fissureLacrimal foldLacrimal caruncleIrisMedial commissureLateral commissureLacrimal papillaLacrimal punctumBC
Fig. 8.291 External ear. Lateral view of the right ear of a woman.
Fig. 8.292 Where to take arterial pulses in the head and neck.
Fig. 8.293 Coronal CT scan demonstrating an orbital blowout fracture.
eFig. 8.294 Ultrasound scan (axial view) demonstrating a stone in a dilated parotid duct.
eFig. 8.295 Coronal MRI showing pituitary macroadenoma.
Table 8.1 External foramina of the skull
Table 8.2 Internal foramina of the skull
Table 8.3 Dural venous sinuses
Table 8.4 Cranial nerve functional components
Other terminology used when describing functional components: *Special sensory, or special visceral afferent (SVA): smell, taste. Special somatic afferent (SSA): vision, hearing, balance.
**Special visceral efferent (SVE) or branchial motor.
Table 8.5 Cranial nerves (see Table 8.4 for abbreviations)
Table 8.6 Parasympathetic ganglia of the head
Table 8.7 Muscles of the face
Table 8.8 Extrinsic (extra-ocular) muscles
Table 8.9 Intrinsic muscles of the eye
Table 8.10 Muscles of the middle ear
Table 8.11 Muscles of mastication
Table 8.12 Anterior triangle of neck (suprahyoid and infrahyoid muscles)
Table 8.13 Branches of the external carotid artery |
Table 8.14 Subdivisions of the anterior triangle of the neck—a regional approach
Table 8.15 Muscles associated with the posterior triangle of the neck; parentheses indicate possible involvement
Table 8.16 Prevertebral and lateral vertebral muscles
Table 8.17 Constrictor muscles of the pharynx
Table 8.18 Longitudinal muscles of the pharynx
Table 8.19 Intrinsic muscles of the larynx
Table 8.20 Muscles in the floor of the oral cavity
Table 8.21 Muscles of the tongue
Table 8.22 Muscles of the soft palate
In the clinic
Some babies can be born with ossified fusion (synostosis) of one or more of the cranial sutures. This can result in an irregular head shape because the pattern and direction of skull growth are altered. In the majority of cases the cause is unknown, and in a minority of cases it may be caused by a genetic syndrome.
In the clinic
Medical imaging of the head
Until recently, the standard method of imaging the head was plain radiography. The radiographs are taken in three standard projections—the posteroanterior view, the lateral view, and the Towne’s view (anteroposterior [AP] axial—head in anatomical position). Additional views are obtained to assess the foramina at the base of the skull and the facial bones. Currently, skull radiographs are used in cases of trauma, but such use is declining. Skull fractures are relatively easily detected (Fig. 8.29). The patient is assessed and treatment is based upon the underlying neurological or potential neurological complications.
Since the development of computed tomography (CT), cerebral CT has become the “workhorse” of neuroradiological examination. It is ideally used for head injury because the brain and its coverings can be easily and quickly examined and blood is easily detected. By altering the mathematical algorithm of the data set the bones can also be demonstrated.
With intravenous contrast, CT angiography can be used to demonstrate the position and the size of an intracerebral aneurysm before endovascular treatment.
Magnetic resonance imaging (MRI) is unsurpassed by other imaging techniques in its ability for contrast resolution. The brain and its coverings, cerebrospinal fluid (CSF), and vertebral column can be easily and quickly examined. Newer imaging sequences permit CSF suppression to define periventricular lesions.
Magnetic resonance angiography has been extremely useful in determining the completeness of the intracranial vasculature (circle of Willis), which is necessary in some surgical conditions.
MRI is also a powerful tool in the assessment of carotid stenosis.
It is now possible to carry out intracranial Doppler studies, which enable a surgeon to detect whether a patient is experiencing cerebral embolization from a carotid plaque.
Extracranial ultrasound is extremely important in tumor staging and in assessing neck masses and the carotid bifurcation (Fig. 8.30).
Ultrasound is useful in children because they have an acoustic window through the fontanelles.
In the clinic
Fractures of the skull vault
The skull vault is a remarkably strong structure because it protects our most vital organ, the brain. The shape of the skull vault is of critical importance and its biomechanics prevent fracture. From a clinical standpoint skull fractures alert clinicians to the nature and force of an injury and potential complications. The fracture itself is usually of little consequence (unlike, say, a fracture of the tibia). Of key importance is the need to minimize the extent of primary brain injury and to treat potential secondary complications, rather than focusing on the skull fracture. Skull fractures that have particular significance include depressed skull fractures, compound fractures, and pterion fractures. |
In a depressed skull fracture a bony fragment is depressed below the normal skull convexity. This may lead to secondary arterial and venous damage with hematoma formation. A primary brain injury can also result from this type of fracture.
In a compound fracture there is a fracture of the bone together with a breach of the skin, which may allow an infection to enter. Typically these fractures are associated with scalp lacerations and can usually be treated with antibiotics.
Important complications of compound fractures include meningitis, which may be fatal.
A more subtle type of compound fracture involves fractures across the sinuses. These may not be appreciated on first inspection, but are an important potential cause of morbidity and should be considered in patients who develop intracranial infections secondary to trauma.
The pterion is an important clinical point on the lateral aspect of the skull. At the pterion the frontal, parietal, greater wing of the sphenoid, and temporal bones come together. Importantly, deep to this structure is the middle meningeal artery. An injury to this point of the skull is extremely serious because damage to this vessel may produce a significant extradural hematoma, which can be fatal.
In the clinic
Hydrocephalus is a dilation of the cerebral ventricular system, which is due to either an obstruction to the flow of CSF, an overproduction of CSF, or a failure of reabsorption of CSF.
Cerebrospinal fluid is secreted by the choroid plexus within the lateral, third, and fourth ventricles of the brain. As it is produced it passes from the lateral ventricles through the interventricular foramina (the foramina of Monro) to enter the third ventricle. From the third ventricle it passes through the cerebral aqueduct (aqueduct of Sylvius) into the fourth ventricle, and from here it passes into the subarachnoid space via the midline foramen or the two lateral foramina (foramen of Magendie and foramina of Luschka).
The CSF passes around the spinal cord inferiorly, envelops the brain superiorly, and is absorbed through the arachnoid granulations in the walls of the dural venous sinuses. In adults almost half a liter of CSF is produced per day.
In adults the commonest cause of hydrocephalus is an interruption of the normal CSF absorption through the arachnoid granulations. This occurs when blood enters the subarachnoid space after subarachnoid hemorrhage, passes over the brain, and interferes with normal CSF absorption. To prevent severe hydrocephalus it may be necessary to place a small catheter through the brain into the ventricular system to relieve the pressure.
Other causes of hydrocephalus include congenital obstruction of the aqueduct of Sylvius and a variety of tumors (e.g., a midbrain tumor), where the mass obstructs the aqueduct. Rare causes include choroid plexus tumors that secrete CSF.
In children, hydrocephalus is always dramatic in its later stages. The hydrocephalus increases the size and dimensions of the ventricle, and as a result the brain enlarges. Because the skull sutures are not fused, the head expands. Cranial enlargement in utero may make a vaginal delivery impossible, and delivery then has to be by caesarean section.
Both CT and MRI enable a radiologist to determine the site of obstruction and in most cases the cause of the obstruction. A distinction must be made between ventricular enlargement due to hydrocephalus and that due to a variety of other causes (e.g., cerebral atrophy).
In the clinic
Leakage of CSF from the subarachnoid space may occur after any procedure in and around the brain, spinal cord, and meningeal membranes. These procedures include lumbar spine surgery, epidural injection, and CSF aspiration. |
In “cerebrospinal fluid leak” syndrome, CSF leaks out of the subarachnoid space and through the dura mater for no apparent reason. The clinical consequences of this include dizziness, nausea, fatigue, and a metallic taste in the mouth. Other effects also include facial nerve weakness and double vision.
In the clinic
Meningitis is a rare infection of the leptomeninges (the leptomeninges are a combination of the arachnoid mater and the pia mater). Infection of the meninges typically occurs via a blood-borne route, though in some cases it may be by direct spread (e.g., trauma) or from the nasal cavities through the cribriform plate in the ethmoid bone.
Certain types of bacterial inflammation of the meninges are so virulent that overwhelming inflammation and sepsis with cerebral irritation can cause the patient to rapidly pass into a coma and die.
Meningitis is usually treatable with antibiotics.
Certain types of bacteria that produce meningitis produce other effects; for example, subcutaneous hemorrhage (ecchymoses) is a feature of meningococcal meningitis.
The typical history of meningitis is nonspecific at first. The patient may have mild headache, fever, drowsiness, and nausea. As the infection progresses, photophobia (light intolerance) and ecchymosis may ensue. Straight leg raising causes marked neck pain and discomfort (Kernig’s sign) and an emergency hospital admission is warranted.
Immediate treatment consists of very-high-dose intravenous antibiotics and supportive management.
In the clinic
Determination of the anatomical structure from which a tumor arises is of the utmost importance, particularly when it arises within the cranial vault. Misinterpretation of the location of a lesion and its site of origin may have devastating consequences for the patient.
When assessing any lesion in the brain, it is important to define whether it is intra-axial (within the brain) or extra-axial (outside the brain).
Typical extra-axial tumors include meningiomas (tumors of the meninges) and acoustic neuromas. Meningiomas typically arise from the meninges, with preferred sites including regions at and around the falx cerebri, the free edge of the tentorium cerebelli, and the anterior margin of the middle cranial fossa. Acoustic neuromas are typically at and around the vestibulocochlear nerve [VIII] and in the cerebellopontine angle.
Intra-axial lesions are either primary or secondary. By far the commonest type are the secondary brain lesions, which in most cases are metastatic tumor deposits.
Metastatic tumor lesions are typically found in patients with either breast carcinoma or lung carcinoma, though many other malignancies can give rise to cerebral metastases.
Primary brain lesions are rare and range from benign tumors to extremely aggressive lesions with a poor prognosis. These tumors arise from the different cell lines and include gliomas, oligodendrocytomas, and choroid plexus tumors. Primary brain tumors may occur at any age, though there is a small peak incidence in the first few years of life followed by a later peak in early to middle age.
In the clinic |
A stroke, or cerebrovascular accident (CVA), is defined as the interruption of blood flow to the brain or brainstem resulting in impaired neurological function lasting more than 24 hours. Neurological impairment resolving within 24 hours is known as a transient ischemic attack (TIA) or mini-stroke. Based on their etiology, strokes are broadly classified as either ischemic or hemorrhagic. Ischemic strokes are further divided into those caused by thrombotic or embolic phenomena. The latter is by far the commonest type of stroke and is often caused by emboli that originate from atherosclerotic plaques in the carotid arteries that migrate into and block smaller intracranial vessels. Hemorrhagic strokes are caused by rupture of blood vessels.
The risk factors for stroke are those of cardiovascular disease, such as diabetes, hypertension, and smoking. In younger patients underlying clotting disorders, use of oral contraceptives, and illicit substance abuse (such as cocaine) are additional causes.
The symptoms and signs of a stroke depend on the distribution of impaired brain perfusion. Common presentations include rapid-onset hemiparesis or hemisensory loss, visual field deficits, dysarthria, ataxia, and a decreased level of consciousness.
Stroke is a neurological emergency. It is therefore important to establish the diagnosis as early as possible so that urgent and potentially life-saving treatment can be administered. Potent thrombolytic (blood-thinning) drugs can restore cerebral blood flow and improved patient outcome if administered within 3 to 4.5 hours of onset of the patient’s symptoms.
Following initial clinical history taking and neurological examination, all patients with suspected stroke should undergo urgent brain imaging with computed tomography (CT). This is to identify hemorrhagic strokes for which thrombolytic therapy is contraindicated and to exclude an alternative diagnosis such as malignancy. In ischemic stroke, early CT imaging may appear normal or can show a relatively darker area of low density that corresponds to the region of abnormal brain perfusion. Due to subsequent brain edema and swelling, the affected brain also loses its normal sulcal pattern (Fig. 8.40A). If thrombolysis is performed, a 24-hour follow-up CT scan is routinely carried out to evaluate for complications such as intracranial hemorrhage.
Additional diagnostic workup of stroke includes hematological and biochemical blood tests to identify causes such as hypoglycemia or underlying clotting disorders. A toxicology screen may be useful to identify substance intoxication, which can mimic stroke.
The full extent of neurological injury can be evaluated on subsequent magnetic resonance imaging (MRI) of the brain, which has better soft tissue resolution compared to CT. MRI is also useful for identifying strokes that may be too small to detect on a CT scan. MRI scans are produced by using complicated algorithms that create a series of images, also known as sequences. Various sequences can be obtained to assess different anatomical and physiological properties of the brain. A stroke, whether acute or chronic, will appear as a bright region on a sequence that is sensitive to fluid (T2 weighted) (Fig. 8.40B). To identify whether a stroke is acute, further sequences are obtained, known as diffusion-weighted imaging (DWI) (Fig. 8.40C) and the apparent diffusion coefficient (ADC) (Fig. 8.40D) map. These evaluate the diffusion of water molecules in the brain. If the region of abnormality appears bright on the DWI sequence and dark on the ADC map, this is known as restricted diffusion, which is compatible with an acute stroke. These changes can persist for up to a week after the initial insult.
Imaging of the carotid and vertebral arteries is also performed to assess for any treatable atherosclerotic changes and stenosis. This can be done with ultrasound, CT, or less frequently, MRI. |
Management of a stroke is multidisciplinary. Supportive treatment to stabilize the patient is a priority. Stroke specialists, speech and language therapists, occupational therapists, and physiotherapists have key roles in patient rehabilitation. Long-term use of antiplatelet drugs such as aspirin and modification of cardiovascular disease risk factors are important in the secondary prevention of stroke.
In the clinic
Endarterectomy is a surgical procedure to remove atheromatous plaque from arteries.
Atheromatous plaques occur in the subendothelial layer of vessels and consist of lipid-laden macrophages and cholesterol debris. The developing plaque eventually accumulates fibrous connective tissue and calcifies. Plaque commonly occurs around vessel bifurcations, limiting blood flow, and may embolize to distal organs.
During endarterectomy, plaque is removed and the vessel reopened. In many instances a patch of material is sewn over the hole in the vessel, enabling improved flow and preventing narrowing from the suturing of the vessel.
In the clinic
Cerebral aneurysms arise from the vessels in and around the cerebral arterial circle (of Willis). They typically occur in and around the anterior communicating artery, the posterior communicating artery, the branches of the middle cerebral artery, the distal end of the basilar artery (Fig. 8.41), and the posterior inferior cerebellar artery.
As the aneurysms enlarge, they have a significant risk of rupture. Typically patients have no idea that there is anything wrong. As the aneurysm ruptures, the patient complains of a sudden-onset “thunderclap” headache that produces neck stiffness and may induce vomiting. In a number of patients death ensues, but many patients reach the hospital, where the diagnosis is established. An initial CT scan demonstrates blood within the subarachnoid space, and this may be associated with an intracerebral bleed. Further management usually includes cerebral angiography, which enables the radiologist to determine the site, size, and origin of the aneurysm.
Usually patients undergo complex surgery to ligate the neck of the aneurysm. More recently radiological intervention has superseded the management of some aneurysms in specific sites. This treatment involves cannulation of the femoral artery, and placement of a long catheter through the aorta into the carotid circulation and thence into the cerebral circulation. The tip of the catheter is placed within the aneurysm and is packed with fine microcoils (Fig. 8.42), which seals the rupture.
In the clinic
Summary of relationships and clinical significance of the scalp and meninges (Fig. 8.47).
In the clinic
Head trauma is a common injury and is a significant cause of morbidity and death. Head injury may occur in isolation, but often the patient has other injuries; it should always be suspected in patients with multiple injuries. Among patients with multiple trauma, 50% die from the head injury.
At the time of the initial head injury two processes take place.
First the primary brain injury may involve primary axonal and cellular damage, which results from the shearing deceleration forces within the brain. These injuries are generally not repairable. Further primary brain injuries include intracerebral hemorrhage and penetrating injuries, which may directly destroy gray and white matter.
The secondary injuries are sequelae of the initial trauma. They include scalp laceration, fracture of the cranial vault, disruption of intracerebral arteries and veins, intracerebral edema, and infection. In most cases these can be treated if diagnosed early, and rapid and effective treatment will significantly improve the patient’s recovery and prognosis.
In the clinic
Types of intracranial hemorrhage
The many causes of a primary brain hemorrhage include aneurysm rupture, hypertension (intracerebral hematoma secondary to high blood pressure), and bleeding after cerebral infarction. |
An extradural hemorrhage (Fig. 8.48) is caused by arterial damage and results from tearing of the branches of the middle meningeal artery, which typically occurs in the region of the pterion. Blood collects between the periosteal layer of the dura and the calvaria and under arterial pressure slowly expands.
The typical history is of a blow to the head (often during a sporting activity) that produces a minor loss of consciousness. Following the injury the patient usually regains consciousness and has a lucid interval for a period of hours. After this, rapid drowsiness and unconsciousness ensue, which may lead to death.
A subdural hematoma (Fig. 8.49) results from venous bleeding, usually from torn cerebral veins where they enter the superior sagittal sinus. The tear and resulting seepage of blood separates the thin layer of dural border cells from the rest of the dura as the hematoma develops.
Patients at most risk of developing a subdural hematoma are the young and elderly. The increased CSF space in patients with cerebral atrophy results in a greater than normal stress on the cerebral veins entering the sagittal sinus. The clinical history usually includes a trivial injury followed by an insidious loss of consciousness or alteration of personality.
Subarachnoid hemorrhage (Fig. 8.50) may occur in patients who have undergone significant cerebral trauma, but typically it results from a ruptured intracerebral aneurysm arising from the vessels supplying and around the arterial circle (of Willis).
In the clinic
Tuberculosis of the central nervous system
Tuberculosis (TB) may invade the central nervous system, including the brain, spinal cord, and meninges (Fig. 8.51). Symptoms of brain TB include headache, neck stiffness, weight loss, and fever. Symptoms of spinal cord TB include leg weakness and fecal and urinary incontinence. Meningitis can cause altered mental status, fever, and seizures. Treatment usually requires a cocktail of drugs for 1 year, but treatment for brain TB can require 2 years.
In the clinic
Emissary veins connect extracranial veins with intracranial veins and are important clinically because they can be a conduit through which infections can enter the cranial cavity. Emissary veins lack valves, as do the majority of veins in the head and neck.
In the clinic
Concussion (mild traumatic brain injury [MTBI]) is the most common type of traumatic brain injury. The injury typically results from a rapid deceleration of the head or by a rotation of the brain within the cranial cavity. General symptoms of MTBI can include posttraumatic amnesia, confusion, loss of consciousness, headache, dizziness, vomiting, lack of motor coordination, and light sensitivity. The diagnosis of concussion, MTBI, is based on the event, the current neurological status, and the state of consciousness of the patient.
In the clinic
Clinical assessment of patients with head injury
Clinical assessment of patients with head injury always appears relatively straightforward. In reality it is usually far from straightforward.
Patients may have a wide spectrum of modes of injury from a simple fall to complex multiple trauma. The age of the patient and ability to communicate about the injuries are important factors.
The circumstances in which the injury may have occurred should be documented because some head injuries result from a serious assault, and the physician may be required to give evidence to a court of law.
Determining the severity of head injury may be difficult because some injuries occur as a result of or in association with alcohol intoxication.
Even when the diagnosis has been made and the correct management has been instigated, the circumstances in which the injury occurred and the environment to which the patient will return after treatment need to be reviewed to prevent further injuries (e.g., an elderly person tripping on loose carpet on a staircase). |
A thorough clinical examination includes all systems, but with a special focus on the central and peripheral nervous systems. The level of consciousness must also be assessed and accurately documented using the Glasgow Coma Scale, which allows clinicians to place a numerical value upon the level of consciousness so that any deterioration or improvement can be measured and quantified.
The Glasgow Coma Scale was proposed in 1974 and is now widely accepted throughout the world. There is a total score of 15 points, such that 15/15 indicates that the patient is alert and fully oriented, whereas 3/15 indicates a severe and deep coma. The points score comprises a best motor response (total of 6 points), best verbal response (total of 5 points), and best eye movement response (total of 4 points).
In the clinic
Treatment of head injury
Treatment of primary brain injury is extremely limited. Axonal disruption and cellular death are generally irrecoverable. Whenever the brain is injured, like most tissues, it swells. Because the brain is encased within a fixed space (the skull), swelling impairs cerebral function and has two other important effects.
First, the swelling compresses the blood supply into the skull, resulting in a physiologically dramatic increase in blood pressure.
Second, the cerebral swelling may be diffuse, eventually squeezing the brain and brainstem through the foramen magnum (coning). This compression and disruption of the brainstem may lead to a loss of basic cardiorespiratory function, and death will ensue. Focal cerebral edema may cause one side of the brain to herniate beneath the falx cerebri (falcine herniation).
Simple measures to prevent the swelling include hyperventilation (which alters the intracerebral acid–base balance and decreases swelling) and intravenous corticosteroids (though their action is often delayed).
Extracerebral hematoma may be removed surgically.
The outcome of patients with head injury depends on how the secondary injury is managed. Even with a severe primary injury, patients may recover to lead a normal life.
In the clinic
The skull is a closed bony compartment, and the brain and cerebrospinal fluid are maintained physiologically within a narrow intracranial pressure range. Any new space-occupying lesion, such as a hematoma, an injury that leads to brain swelling, or a brain tumor, can increase intracranial pressure and compress the brain. In severe cases, the brain may be squeezed down into the foramen magnum, giving it a cone shape, termed cerebral herniation, or “coning.” This may in turn compress the brainstem and upper cervical spinal cord, which can be fatal.
Congenital herniation or coning of the cerebellar tonsils through the foramen magnum can also occur if the posterior fossa is too small, a condition known as Chiari I malformation (Fig. 8.52). This often causes no problems in childhood and may only start causing symptoms in adulthood.
In the clinic
In the clinic
Overview of cranial nerves
Afferent—Trigeminal nerve (CN V)
Efferent—Facial nerve (CN VII)
Afferent—Glossopharyngeal nerve (CN IX)
Efferent—Vagus nerve (CN X)
Afferent—optic nerve (CN II)
Efferent—oculomotor nerve (CN III)
Fig. 8.55 Overview of cranial nerves. |
Glossopharyngeal nerve [IX]Special sensory – taste (posterior 1/3 of tongue)Somatic sensory – posterior 1/3 of tongue, oropharynx,palatine tonsil, middle ear, pharyngotympanic tube, andmastoid air cellsBranchial motor – stylopharyngeusVisceral motor – (parasympathetic) – secretomotor to theparotid glandVisceral sensory – from carotid body and sinusFacial nerve [VII] Branchial motor – all muscles of facial expression, andstapedius, stylohyoid, and posterior belly of digastricEfferent (motor) fibersV3V3V2V1Afferent (sensory) fibersFacial nerve [VII] (intermediate nerve)Special sensory – taste (anterior 2/3 of tongue)Somatic sensory – part of external acoustic meatus anddeeper parts of auricleVisceral motor (parasympathetic) – secretomotor to allsalivary glands except for parotid gland; all mucous glandsassociated with the oral and nasal cavities; lacrimal glandVestibulocochlear nerve [VIII]Special sensory – hearing and balanceOlfactory nerve [I]Special sensory – smellOptic nerve [II]Special sensory – visionTrigeminal nerve [V] sensory rootSomatic sensory – eyes, orbital contents, face, sinuses, teeth, nasal cavities, oral cavity, anterior 2/3 of tongue, nasopharynx, dura, anterior part of external ear,and part of external acoustic meatusTrigeminal nerve [V] motor rootBranchial motor – the four muscles of mastication(medial pterygoid, lateral pterygoid, masseter, temporalis)and mylohyoid, anterior belly of digastric, tensor tympani,and tensor veli palatiniOculomotor nerve [III]Somatic motor – five extra-ocular muscles (superior rectus, medial rectus,inferior oblique, inferior rectus, and levator palpebrae superioris)Visceral motor – ciliary muscles and sphincter pupillae musclesTrochlear nerve [IV]Somatic motor – one extra-ocularmuscle (superior oblique)Abducent nerve [VI]Somatic motor – one extra-ocularmuscle (lateral rectus)Hypoglossal nerve [XII]Somatic motor – all muscles of thetongue except palatoglossusAccessory nerve [XI]Branchial motor – sternocleidomastoidand trapeziusVagus nerve [X]Somatic sensory – larynx, laryngopharynx, deeper parts ofauricle, and part of external acoustic meatusSpecial sensory – taste from epiglottis and pharynxBranchial motor – all muscles of pharynx except for stylopharyngeus; all muscles of the soft palate except for tensor veli palatini, all intrinsic muscles of larynxVisceral motor – (parasympathetic) – thoracic viscera andabdominal viscera to end of midgutVisceral sensory – thoracic viscera and abdominal viscerato end of midgut, chemoand baroreceptors(and in some cases carotid body)
In the clinic
Facelift surgery (rhytidectomy) aims to lift up and pull back the skin in the lower half of the face and neck to make the face more taught. Careful placement of the incisions is important to ensure there is no skin or facial distortion and to avoid hair loss. The commonest incisions are placed in the temporal region on each side, extending to the helices of the ears, then tracking behind the tragus, around the earlobes, and then to the occiput. |
Botox is derived from the toxin produced by the bacterium Clostridium botulinum, which blocks neuromuscular junctions resulting in muscle relaxation. It is used in many therapies including strabismus (crossed eyes) where it is injected into extra-ocular muscles. Its injection is also used to treat uncontrolled blinking (blepharospasm), spastic muscle conditions, and overactive bladder disorders, as well as to relax facial muscles to improve the cosmetic appearances of lines and wrinkles and to treat patients with excessive sweating (hyperhidrosis).
In the clinic
The parotid gland is the largest of the paired salivary glands and is enclosed within the split investing layer of deep cervical fascia.
The parotid gland produces a watery saliva and salivary amylase, which are necessary for food bolus formation, oral digestion, and smooth passage of the bolus into the upper gastrointestinal tract.
Tumors of the parotid gland
The commonest tumors of the parotid gland (Fig. 8.63) are benign and typically involve the more superficial part of the gland. These include pleomorphic adenoma and adenolymphoma. Their importance is in relation to their anatomical position. The relationship of any tumor to the branches of the facial nerve [VII] must be defined because resection of the tumor may damage the nerve.
It is not uncommon for stones to develop within the parotid gland. They typically occur within the main confluence of the ducts and within the main parotid duct. The patient usually complains of intense pain when salivating and tends to avoid foods that produce this symptom. The pain can be easily reproduced in the clinic by squirting lemon juice into the patient’s mouth.
Surgery depends upon where the stone is. If it is within the anterior aspect of the duct, a simple incision in the buccal mucosa with a sphincterotomy may allow removal. If the stone is farther back within the main duct, complete gland excision may be necessary.
In the clinic
The complexity of the facial nerve [VII] is demonstrated by the different pathological processes and sites at which these processes occur.
The facial nerve [VII] is formed from the nuclei within the brainstem emerging at the junction of the pons and the medulla. It enters the internal acoustic meatus, passes to the geniculate ganglion (which gives rise to further branches), and emerges from the skull base after a complex course within the temporal bone, leaving through the stylomastoid foramen. It enters the parotid gland and gives rise to five terminal groups of branches that supply muscles in the face and a number of additional branches that supply deeper or more posterior muscles. A series of lesions may affect the nerve along its course, and it is possible, with good clinical expertise, to determine the exact site of the lesion in relation to the course of the nerve.
A primary brainstem lesion affecting the motor nucleus of the facial nerve [VII] would lead to ipsilateral (same side) weakness of the whole face. However, because the upper part of the nucleus receives motor input from the left and right cerebral hemispheres a lesion occurring above the nucleus leads to contralateral lower facial weakness. In this example, motor innervation to the upper face is spared because the upper part of the nucleus receives input from both hemispheres. Preservation and loss of the special functions are determined by the extent of the lesion.
Lesions at and around the geniculate ganglion
Typically lesions at and around the geniculate ganglion are accompanied by loss of motor function on the whole of the ipsilateral (same) side of the face. Taste to the anterior two-thirds of the tongue, lacrimation, and some salivation also are likely to be affected because the lesion is proximal to the greater petrosal and chorda tympani branches of the nerve.
Lesions at and around the stylomastoid foramen |
Subsets and Splits