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CHAPTER XIV 



DIGESTION 

 AND ABSORPTION 





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Large globules of fat. 



Separated in an emulsion. 



What changes does the food undergo in the stomach and intestines f 

 What is the importance of gastric juice in digestion f How is the 

 small intestine adapted for carrying on digestive activities f What is 

 the importance of absorption f 



The stomach. The esophagus ends in the stomach, a collapsible, 

 saclike enlargement of the alimentary canal, which serves as a 

 temporary receptacle for food. When contracted, the shape of 

 the stomach is comparable to a sickle blade or a sausage. When 

 distended with food, it is more pouchlike. The stomach has two 

 openings ; one where the esophagus joins it, known as the cardiac 

 opening, the other which communicates with the small intestine 

 and is known as the pylorus (gateway). Both the cardiac and 

 pyloric entrances are guarded by ringlike muscles known as 

 sphincters. These muscles contract and keep the openings closed, 

 except when food is passing through them. Food is kept in the 

 stomach until it is ready for intestinal digestion ; then the circu- 

 lar fibers guarding the pyloric valve relax. 



The walls of the stomach are made of muscle and other tissues. 

 The inner coat (mucous membrane) of the stomach is honeycombed 

 by tiny, shallow pits, which are the openings or mouths of the 

 gastric glands from which the gastric juice is discharged. The 

 gastric or digestive juice is composed of water, hydrochloric acid, 



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