132 MUSCLE TISSUE 



or grinding action. When the cheeks are distended 

 with air, the muscle contracts and expels it through the 

 lips as in playing the cornet, flute, etc. 



Nerve facial. 



Risorius. A small thin muscle arises from the fascia 

 over the masseter muscle, inserted into muscular and 

 subcutaneous tissue at the angle of the mouth. 



Action. Draws back the angle of the mouth as seen 

 in lockjaw, giving the peculiar expression to the face 

 known as the "sardonic grin or laugh;" also (both 

 sides) assists in retracting angles of mouth as in 

 smiling, associated with the other muscles at the 

 angle. 



Nerve facial. 



Muscles of Mastication 



Temporomandibular region. Pterygomandibular region. 

 Masseter. External Pterygoid. 



Temporal. Internal Pterygoid. 



The muscles of mastication aid in preparing the food 

 so that it can be easily swallowed. They bring the 

 jaws together, so that the teeth approximate and chew, 

 or by a lateral motion, grind the food. 



The Muscles of the Tongue (Lingual Region) 



The muscles of the tongue are divided into extrinsic, 

 those situated outside of the organ, yet are inserted 

 into it; and intrinsic, those contained within the organ, 

 forming its substance. 



The Extrinsic Muscles. These are: geniohyoglossus, 

 hyoglossus, styloglossus, palatoglossus, and chondroglossus. 



The Intrinsic Muscles. These are a series of inter- 

 lacing fibers making up the substance of the tongue 

 and are named according to their position and direc- 

 tion, called lingualis, presenting superior, inferior, 



