MUSCLES OF THE FACE AND HEAD 



309 



MasseteP. — A broad, thick, square muscle situated on the outer fece 

 of the lower jaw. It is largely intersected by tendinous layers and covered 

 l)y a strong fibrous membrane. 



Origin. — From the zygomatic ridge of the upper jaw-bone by a strong 

 broad tendon. 



Insertion. — Into the external surface of the upper broad portion of the 

 inferior maxilla or lower jaw. 



Action. — It brings the teeth of the lower jaw forcibly into contact with 

 those of the upper in grinding the food. It is the most powerful of the 

 muscles engaged in mastication. 



Pterygoideus Internus. — A broad, thick, fiat mu,scle situated on the 

 internal aspect of the superior broad portion of the lower jaw. 



