The deep cervical fascia (or fascia colli in older texts) lies under cover of the platysma, and invests the muscles of the neck; it also forms sheaths for the carotid vessels, and for the structures situated in front of the vertebral column. Its attachment to the hyoid bone prevents the formation of a dewlap. The investing portion of the fascia is attached behind to the ligamentum nuchæ and to the spinous process of the seventh cervical vertebra. The alar fascia is a portion of the deep cervical fascia. Divisions The deep cervical fascia is often divided into a superficial, middle, and deep layer. The superficial layer is also known as the investing layer of deep cervical fascia. It envelops the trapezius, sternocleidomastoid, and muscles of facial expression. It also contains the submandibular and parotid salivary gland as well as the muscles of mastication (the masseter, pterygoid, and temporalis muscles). The middle layer is also known as the pretracheal fascia. It envelopes the strap muscles (sternohyoid, sternothyroid, thyrohyoid, and omohyoid muscles). It also surrounds the pharynx, larynx, trachea, esophagus, thyroid, parathyroids, buccinators, and constrictor muscles of the pharynx. The deep layer is also known as the prevertebral fascia. It surrounds the paraspinous muscles and cervical vertebrae. The carotid sheath is also considered a component of the deep cervical fascia. Superior extent of the investing fascia Above, the fascia is attached to the superior nuchal line of the occipital bone, to the mastoid process of the temporal bone, and to the whole length of the inferior border of the body of the mandible. Opposite the angle of the mandible the fascia is very strong, and binds the anterior edge of the sternocleidomastoideus firmly to that bone. Between the mandible and the mastoid process it ensheathes the parotid gland—the layer which covers the gland extends upward under the name of the parotideomasseteric fascia and is fixed to the zygomatic arch. It also contributes to the sheath of the digastric. At the level of the jaw, it splits to enclose the submandibular gland, with the upper leaflet inserting on the mylohyoid line just inferior to mylohyoid and the inferior leaflet inserting onto the lower margin of the jaw. The posterior portion of the upper leaflet helps separate the parotid gland from the submandibular gland where the mylohyoid is deficient while the posterior border is thickened into a strong band extending between the angle of