144 



THE VITAL PROCESSES 



3. The Muscles of Mastication. These are attached to 

 the lower jaw and bring about its different movements. 

 The masseter muscles, which are the heavy muscles in the 

 cheeks, and the temporal muscles, located in the region of 

 the temples, raise the lower jaw and supply the force for 

 grinding the food. Small muscles situated below the chin 

 depress the jaw and open the mouth. 



4. The Salivary Glands. These glands are situated in 

 the tissues surrounding the mouth, and communicate with 

 it by means of ducts (Fig. 67). They secrete the saliva. 



The salivary glands are six 

 in number and are arranged 

 in three pairs. The largest, 

 called the parotid glands, 

 lie, one on either side, in 

 front of and below the ears. 

 A duct from each gland 

 passes forward along the 

 cheek until it opens in the, 

 interior of the mouth, oppo- 

 site the second molar tooth 

 in the upper jaw. Next 

 FIG. 67. -Salivary glands and the in size to the parot ids are 

 ducts connecting them with the mouth. , , ,, 



the suomaxtllary glands. 



These are located, one on either side, just below and in 

 front of the triangular bend in the lower jaw. The smallest 

 of the salivary glands are the sublingual. They are situated 

 in the floor of the mouth, on either side, at the front and 

 base of the tongue. Ducts from the submaxillary and 

 sublingual glands open into the mouth below the tip of 

 the tongue. 



The Saliva and its Uses. The saliva is a transparent 

 and somewhat slimy liquid which is slightly alkaline. It 



