THE VILLI 



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The villi. But far more important for absorption are millions 

 of little projections which cover the inner surface of the small 

 intestine. So numerous are these projec- 

 tions that the whole surface presents a 

 velvety appearance. Collectively, these 

 structures are called the villi (sing, villus). 

 They form the chief organs of absorption in 

 the intestine, several thousand being dis- 

 tributed over every square inch of surface. 

 By means of the folds and the villi the 

 small intestine is estimated to have an 

 absorbing surface equal to twice that of 

 the surface of the body. Between the villi 

 are found the openings of the intestinal glands which secrete the 

 intestinal juice, which contains at least one hormone and several 

 enzymes with which it assists the pancreatic fluid to do its work. 



A section through the small 

 intestine. What are the tiny 

 projections. Of what use are 

 they? 



mixed e 



Explain this section through the small intestine, giving the uses of each part. 



The internal structure of a villus is best seen in a longitudinal 

 section. We find the outer wall made up of a thin layer of cells, 

 the epithelial layer. These cells absorb the fluid food from withiD 



