FASCIA 



339 



^pral, masseter, and internal pterj^goid muscles have approximately vertical axes 

 of contraction and adduct the lower jaw, while the external pterj^goid has an 

 approximately horizontal axis of contraction and draws the jaw forward and, 

 when acting on one side, toward the opposite side. 



Fig. 346. — The Pterygoid Muscles. 



External pterygoid 



Internal pterygoid 



FASCItE 



The temporal fascia arises from the temporal line of the frontal bone and from the superior 

 temporal Une of the parietal and the periosteum immediately below this. It extends to the 

 zygomatic arch. In its inferior quarter the fascia divides into two lamellae, one of which passes 

 to the outer, the other to the inner, surface of the arch, but at the superior margin of the arch 

 these two lamellae are united by dense fibrous tissue. Between the two lamellae above the 

 arch lies a fatty areolar tissue in which the middle temporal artery often runs. The outer sur- 

 face of the fascia is covered by the superficial temporal and anterior and superior auricular 

 muscles, and by a thin layer of fascia from the galea aponeurotica, with which, toward the zygo- 

 matic arch, it becomes merged. The superficial temporal artery and auriculo-temporal nerve 

 cross it. 



The masseteric fascia represents essentially a continuation of the temporal fascia from the 

 inferior margin of the zygomatic arch over the masseter muscle which it covers. It is less thick 

 than the temporal fascia, but is firm and strong. It is attached dorsally to the dorsal margin 

 of the mandible, inferiorly to the inferior margin, and ventrally to the body and to the ventral 

 margin of the ramus and the coronoid process of the mandible. In part it extends over the fat 

 pad of the cheek to the buccinator fascia. The parotid gland, covered by the parotid extension 

 of the external cervical fascia, extends over the posterior portion of this fascia. The parotid 

 fascia becomes fused to its external surface at the anterior margin of the gland. Over it lie 

 the parotid duct, the transverse facial artery, branches of the facial nerve, the zygomaticus 

 (major), risorius, and platysma muscles. 



The pterygoid muscles are each surrounded by a delicate membrane. In addition an 

 interpterygoid fascia separates the two muscles. This arises from the sphenoidal spine and 

 follows the internal surface of the external pterj-goid to the mandible. MediaUj' it is attached 

 to the lateral lamella of the pterygoid process; posteriorly and laterally it presents a free margin 

 which forms with the neck of the mandibular condyle, an orifice for the passage of the internal 

 maxillary artery, the axiriculo-temporal nerve, and several veins. Its posterior margin is 

 strengthened into the spheno-mandibular ligament, which runs from the spine of the sphenoid 

 to the lingula of the mandible. 



The pharyngeal region is separated from the pterygoid by a dense membrane, the lateral 

 pharyngeal fascia. This extends from the depth of the pterygoid fossa to the prevertebral 

 fascia, and separates the tensor veli palatini from the internal pterj'goid muscle. It is attached 

 above along a fine extending from the external margin of the carotid canal to the internal margin 

 of the oval foramen. 



