1 82 APPLIED PHYSIOLOGY 



SUMMARY 



1. The tubes carrying blood away from the heart are 



called arteries. They are thick-walled and elastic, 

 and in them the blood is under considerable pressure. 

 Each heart beat causes a perceptible wave in the 

 artery, which is called the pulse. 



2. The arteries divide and finally break up into fine 



tubes called capillaries, which touch each cell of the 

 body. 



3. In the capillaries some of the plasma passes outside the 



tubes and bathes the cells in nourishment. Some of 

 the oxygen leaves the red blood corpuscles to go to 

 the cells of the body. Some carbonic acid gas also 

 leaves the cells of the body and combines with the 

 plasma within the capillary. 



4. The capillaries join together to form thin-walled vessels 



called veins, which return the blood to the heart. 



5. The plasma which has left the capillaries is called 



lymph. It is returned to the blood by means of a 

 set of fine tubes called lymphatics. 



6. The lymphatics unite to form a tube called the thoracic 



duct, which runs up the backbone and opens into a 

 vein at the root of the neck. 



7. The right side of the heart sends the venous blood to 



the lungs, where it passes through the capillaries 

 and is freed from its impurities, and then returned to 

 the left side of the heart as arterial blood ready for 

 another circuit of the body. This is called the pul- 

 monary circulation. 



9. The venous blood from the stomach and intestine passes 

 through a second set of capillaries in the liver. This 

 is called the portal circulation. 



