MUSCLES OF MASTICATION. 



457 



fovea pterygoidea on the anterior aspect of the neck of the mandible (Figs. 403 

 and 404, p. 455), and (2) the articular disc and capsule of the mandibular 

 articulation. 



This muscle is covered by the insertion of the temporal muscle and the coronoid 

 process of the mandible, and is usually crossed by the internal maxillary artery. 

 It conceals the mandibular branch of the trigeminal nerve, and the pterygoid origin 

 of the internal pterygoid muscle. 



M. Pterygoideus Internus. The internal pterygoid muscle, placed beneath 

 the external pterygoid muscle and the ramus of the mandible, has likewise a 

 double origin (1) from the medial surface of the lateral pterygoid lamina and the 

 Tamidal process of the palate bone, and (2) by a stout tendon from the tuberosity 



TEMPORAL MUSCLE (reflected 



EXTERNAL PTERYGOID 



INTERNAL PTERYGOID 



Pterygo-mandibiilar raphc 



BUCCINATOR 



FIG. 407. THE PTERYGOID MUSCLES OF THE RIGHT SIDE. 



the maxilla. Its two heads of origin embrace the inferior fibres of the external 

 pterygoid muscle. 



It is quadrilateral in form, and is directed downwards, laterally, and backwards 

 lateral to the auditory tube and the tensor and levator muscles of the palate, 

 to be inserted into a triangular impression on the medial surface of the mandible, 

 between the mylo-hyoid groove and the angle of the bone (Fig. 404, p. 455). 



This muscle is covered by the ramus of the mandible and temporal muscle, 

 and partially by the external pterygoid muscle. In contact with its superficial 

 surface are the spheno-mandibular ligament, and the inferior alveolar and lingual 

 nerves and their accompanying vessels. The muscle conceals the tensor veli 

 palatini and the wall of the pharynx (superior constrictor). 



Nerve-Supply. The mandibular division of the trigeminal nerve supplies all the muscles of 

 mastication except the buccinator, which is supplied by the facial nerve. The internal pterygoid 

 1vi uscle 13 supplied by the nerve before its division into anterior and posterior parts ; the other 

 les are innervated by the anterior trunk. 



muse 



mus : 



Actions. The above muscles, assisted by others in the neck, produce the various move- 

 ments of the mandible as follows : 





