RIBBON MUSCLES 91 



The internal pterygoid. In the infra-temporal fossa covered by the 

 ramus of the mandible on which it is inserted. 



Action. It closes the mouth and moves the jaw forward and sideways. 



External pterygoid. Also in the infra-temporal fossa and inserted on the 

 mandible. 



Action. It moves the jaw forward and sideways. 



Nerve. Fifth cranial. 



Buccinator. Origin, from both the maxilla and the mandible on the 

 alveolar borders. The fibers approach each other, interlacing and running for- 

 ward; some of them join the lip muscles, constituting the insertion (Fig. 78). 



Action. It helps to close the mouth, and keeps the food between the teeth 

 during the act of mastication. 



Nerves. Fifth and seventh cranial. 



Temporal 



Buccinator 



FIG. 77. THE TEMPORAL MUSCLE. (Morris.) 



By the action of the first four muscles the food is divided and 

 crushed, and also ground; the external pterygoid is especially a 

 grinding muscle. The function or use of these four would be 

 somewhat limited without the aid of the buccinator. 



MUSCLES IN THE FRONT OF THE NECK 



The ribbon muscles, thin and flat, connecting the larynx and 

 hyoid bone above, with the sternum, rib, and clavicula below. 



