94 



DIGESTION 



called the u^Tila. The hard palate separates the buccal 

 cavity from the nasal cavity. .The uvula, which .can be 

 seen easily by opening the mouth and examining it with a 

 mirror, forms a curtain which guards the opening from the 

 mouth cavity into the pharynx or throat cavity. This 

 opening at the back of the mouth cavity is flanked on either 

 side by two swollen masses of flesh called the tonsils. All 



these cavities are 

 lined with a thin 

 membrane which is 

 continuous with the 

 outside skin and of 

 the same kind of 

 tissue (epithelial). 

 This membrane con- 

 sists of a network of 

 cells carrying blood 

 vessels and nerves, 

 and secretes a liquid 

 called the mucus 

 which moistens and 

 lubricates the surface 

 of the cavities. It is 

 called the mucous 

 membrane. 



In the mouth are 

 two structures, the 

 teeth and the tongue, which have a purely mechanical 

 action in digestion; while connected with the mouth 

 cavity are several outgrowths (the salivary glands) which 

 secrete and pour into it a digestive fluid called saliva. 

 The teeth. — (See Fig. 25 and Ex. XXXIV.) The 



Fis. 25- 



■ Teetli in place, showing place of nerve 

 supply. 



