THE ORGANS OF RESPIRATION IN MAN 



403 



(15) contracts. Blood pressure is caused by the (16) 



of the tiny 

 (18). 



. (17) against the blood forced from the 



PROBLEM IV. WHAT IS RESPIRATION? 





Laboratory Exercise. A comparison of the respiratory tract of a 

 frog and a mammal. Open a frog's mouth and find the slitlike open- 

 ing (glottis) just back of the tongue. Insert a blowpipe or a glass tube 

 and blow down the short windpipe (trachea) which branches into two 

 divisions leading to the lungs (bronchial tubes). What happens to the 

 lungs ? 



Examine a section cut through a frog's lung. Is it hollow? Now 

 compare the baglike lungs of the frog with the more complicated lungs 

 of man (see diagram). Do you find the same structures leading to 

 the lungs of man? (Read your text.) Which part of the lungs of 

 man would be elastic ? Which part of the frog's ? Why? 



If blood vessels were found in the walls of these sacs, what gas might 

 be brought in the 



blood to this point? • / ^%|i(i& 



What gas might be lai^ri^^A„f8j| 



in the air? How Sricebc* Rj.iJ 



might the exchange t 3 



of these gases take trach«r...i. ,-J 



place ? Where might windpipe b; 



it take place ? 



The organs of 

 respiration in man. 

 We have noted the 

 fact that the lungs 

 are the organs which 

 give oxygen to the 

 blood and take from 

 it carbon dioxide. 

 Air passes through 

 the nostrils into the 

 windpipe. This 

 cartilaginous tube, 

 the top of which 

 may easily be felt 

 as -the Adam's apple 



of the throat, divides into two bronchi (bron'ki). The bronchi 

 within the lungs break up into a great number of smaller 



air- 5Yxc 

 bronchial 



The tissue is cut away from one of the lungs to show the air 

 tubes. Trace the course of air from the nose to the air sacs. 



