SURVEY QUESTIONS 



How does food and oxygen get to the body cells i* Why is blood from 

 arteries redder than blood from veins? How is the human heart built 

 and how does it work ? Why do we breathe more deeply after exercise ? 

 How do we get air into the lungs ? Why do we ventilate a room ? 



UNIT XIII 



HOW ARE FOODS CIRCULATED AND USED IN THE 



BODY? 



Preview. As we have thought of the digestive system as a 

 chemical laboratory, so we might think of the blood as a moving 

 chemical workshop. Not only is the blood the carrier of food from 

 the food tube to the cells of the body, but it also takes away the 

 waste products from these same cells to those parts of the body 

 that can expel them. It transports oxygen to the cells where 

 oxidation takes place, and carries away the waste products of 

 this oxidation. It conducts heat to all parts of the body, thus 

 keeping the temperature even. The white corpuscles in the blood 

 act as sanitary police, standing guard at all times to protect the 



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