the jaw and the temporal styloid process, forming the stylomandibular ligament. It is complemented by the pterygospinous ligament, which stretches from the upper part of the posterior border of the lateral pterygoid plate to the spinous process of the sphenoid. It occasionally ossifies, and in such cases, between its upper border and the base of the skull, a foramen is formed which transmits the branches of the mandibular nerve to the muscles of mastication. Inferior extent of the investing fascia Below, the fascia is attached to the thoracic outlet (acromion, clavicle, and manubrium). In doing so, it bifurcates into two layers, superficial and deep. The former is attached to the anterior border of the manubrium, the latter to its posterior border and to the interclavicular ligament. Between these two layers is a slit-like interval, the suprasternal space (space of Burns); it contains a small quantity of areolar tissue, the lower portions of the anterior jugular veins and their transverse connecting branch, the sternal heads of the sternocleidomastoid, and sometimes a lymph gland. Deeper fascial layers The fascia which lines the deep surface of the sternocleidomastoideus gives off the following processes: A process envelops the tendon at the omohyoideus, and binds it down to the sternum and first costal cartilage. A strong sheath, the carotid sheath, encloses the carotid artery, internal jugular vein, and vagus nerve. The prevertebral fascia extends medialward behind the carotid vessels, where it assists in forming their sheath, and passes in front of the prevertebral muscles. The pretracheal fascia extends medially in front of the carotid vessels, and assists in forming the carotid sheath. References External links Sagittal Section Showing Deep Cervical Fascial Layers Infrahyoid Cross-Section Showing Layers of Deep Cervical Fascia Suprahyoid Cross-Section Showing Layers of Deep Cervical Fascia Fascial spaces of the head and neck