Adenoid 

 Tonsil 



Bronchial 

 tubes 



Right 

 lung 



Dia- 

 phragm 



Alveoh 



LUNGS IN MAN 



The main windpipe from the throat divides into main branches, the bronchi, one to 

 each lung. The bronchi divide again and again, the smallest air tubules ending in 

 the alveoli, or tiny sacs. The epiglottis drops over the trachea when food is being 

 swallowed from the pharynx to the esophagus 



diaphragm. This separates the chest cavity from the abdominal cavity (see 

 illustration above). Inspiration and expiration are caused by the alternate 

 expansion and contraction of the thoracic cavity. 



Blood-Red We have seen that the circulating blood takes part in dis- 

 tributing oxygen and carbon dioxide, as well as foods, wastes, and other sub- 

 stances. And that the actual oxygen-carrier is the yellowish hemoglobin of the 

 red corpuscles, since it combines readily with oxygen, forming oxyhemo- 

 globin (see page 189). When oxygen is relatively scarce, it gives up oxygen. 



205 



