THE USE OF FOOD 



383 



valve 



'.valve 



.muscle 



they form a network of tiny blood vessels which run close 



around the cells in the tissues all over the body. These 



small blood vessels are 



called capillaries and 



from the blood in them 



the cells get food and 



oxygen, and take up 



wastes. The capillaries 



in turn lead into tiny 



veins, thin-walled vessels 



which get larger and 



larger as they return 



blood to the heart. 



There are two complete 



circulations of blood in 



the body, one from the 



right side of the heart 



to the lungs, returning 



to the left side of the 



heart, from which it 



passes, as has just been 



described, to all parts 



of the body. The blood returns to the right side of the 



heart, thus completing the circulation. 



each Vialf of the 

 hectrt, is a pump 



The heart is a double force pump. Can 

 you prove it from the diagram? The thick 

 muscular part of the heart is called ventricle, 

 the thin-walled upper portion auricle. De- 

 scribe the heart's action, using the above 

 terms. 



SELF-TESTING EXERCISE 



Select from the following list those words which best fill the blank spaces 

 in the sentences below and arrange the words in proper numerical order. 

 A word may be used more than once. 



digested 



waste 



liver 



enzymes 



kidneys 



used 



lungs 



carbon dioxide 



same 



energy 



wasted 



soluble 



stomach 



oxidized 



absorbed 



vitamins 



different 



blood 



cells 



unites 



bones 



fuel 



oxygen 



separates 



