326 



A YEAR IN SCIENCE 



Epithelium 



in the alimentary canal is commonly known as 

 absorption. By means of folds and finger-like pro- 

 jections, villi, the lining- of the small intestine is 



especially adapted for 

 absorption. In each 

 villus there are two sets 

 of small vessels. One 

 set contains blood, the 

 other contains a watery 

 fluid called lymph. 



The sugars and nitrog- 

 enous foods pass into 

 the blood vessels and 

 are then carried into 

 larger vessels through 

 the liver, and from there 

 to the heart. In passing 

 through the liver some of the sugar is left behind and 

 stored in the form of glycogen or "liver starch." Fats 

 pass into the lymph vessels. These enter larger vessels 

 which finally empty into a vein in the neck. From 

 there the fats enter the heart with the blood. From the 

 heart all these foodstuffs are then distributed to all 

 parts of the body. 



Questions 



1. Explain fully why it is necessary to have the 

 food digested. 



2. What is an enzyme? 



Fig. 156. Section of a villus, 

 highly magnified. 



