LECTUEE XI 

 DIGESTIVE APPARATUS 



Definition. — The digestive apparatus consists of various or- 

 gans which carry on the processes of food reception, digestion, 

 and absorption. The digestive apparatus also expels various 

 undigested and waste materials. The organs of digestion are 

 the mouth, pharynx, esophagus, stomach, and intestines, together 

 with certain other organs ; viz., the salivary glands at the mouth, 

 and the liver and pancreas in the abdominal cavity. 



Mouth. — At the mouth we find the lips, teeth, tongue, and 

 palate. 



The horse has a freely movable and sensitive upper lip, which 

 is used in selecting food. The cow has hard cartilaginous lips 

 and selects her food mainly by the tongue. 



The tongue is used by the cow to select and gather her food, 

 and by all animals to control the food while in the mouth and 

 assist in swallowing. This organ is composed largely of muscu- 

 lar tissue with some connective tissue, and is covered by the 

 common mucous membrane. Its surface is studded with several 

 kinds of papillae, similar to those on the human tongue. These 

 aid in controlling the food while in the mouth and have to do 

 with the sense of taste. They are especially prominent and 

 strong on the cow's tongue. 



The hard palate forms the roof of the mouth, and consists of 

 portions of the superior maxillary and palate bones covered by 

 tough connective tissue, and overlaid with mucous membrane. 

 This connective tissue and its covering of mucous membrane is 

 thrown up into a series of transverse ridges, easily seen on the 

 roof of a horse's mouth, sometimes called "bars." 



The soft palate is a membranous structure containing some 

 muscular tissue. Its function is to separate the posterior open- 

 ing of the nose chamber and pharynx from the mouth. 



The principal salivary glands on each side are: one parotid, 

 one submaxillary, and one sublingual. They secrete saliva which 

 helps to change insoluble and useless starch into a soluble and 



57 



