82 



APPLIED PHYSIOLOGY 



is b 



of an inch in diameter, extend into the mucous membrane. 



Each tube is lined with a layer of epithelial cells, which 



secrete a fluid called the intestinal juice. 



110. Villi. Each villus consists of an outer covering 



of epithelial cells, inclos- 

 ing a loose meshwork of 

 fine blood tubes, and also 

 of tubes called lacteals, 

 both of which take up 

 the food as it is di- 

 gested. Neither villi nor 

 valvulae conniventes are 

 found in the large intes- 

 tine. 



111. The pancreas. 

 From the duodenum there 

 extends a very short tube, 

 about the size of a small 

 quill. This divides into 

 two tubes, one of which 

 goes to the liver and the 

 other to the pancreas. 



Diagram of the essential parts of a villus. The pancreas IS a gland 



a epithelium which takes up food and trans- about an inch in diameter 



-.I, and six inches long, lying 

 behind the stomach. In 

 lower animals it is called the sweetbread. Its structure 

 resembles that of a salivary gland. It secretes a thin, 

 watery liquid called the pancreatic juice, which is poured 

 into the intestine at the rate of one and a half pints a 

 day. 



112. The liver. The liver is a firm, dark-red, wedge- 

 shaped organ, lying under the lowest ribs upon the right 



