2 34 Ho%v a Complex Aimual Uses Food unit iv 



lungs do not take on their full load. At ribs contract, enlarging the chest cavity, 

 first this causes a feeling of well-being, so They relax, diminishing the size of the 

 the flier who is climbing in his plane is cavity. As a result of this contraction and 

 not aware of his danger, and fails to use relaxation air enters and leaves the lungs, 

 his oxygen mask. As he goes higher the The air that enters has a larger percent- 

 lack of oxygen afl^ects his vision and age of oxygen and a smaller percentage 

 hearing; coordination and judgment be- of carbon dioxide than the air that leaves, 

 come poor; he becomes unconscious. This is because the air sacs are w^ell fitted 

 With oxygen masks fliers may now fly for an exchange of gases between the 

 at altitudes of well over 40,000 feet. blood and outside air. They have a large 

 How did we answer the problem ques- surface, their walls are thin and moist and 

 tion? The movements of the chest cavity plentifully supplied with capillaries. With 

 are responsible for the passage of air into blood to transport the oxygen you can 

 and out of the lungs. The muscular dia- see how our cells are provided with a 

 phragm and the muscles attached to the constant supply of oxygen. 



Questions 



1. Of what use to a man are his lungs? 



2. Name in order the openings and passages through which air passes 

 on its way to the lungs. Describe the structure of the windpipe and 

 explain how each part is useful. 



3. Explain the relation to one another of bronchus, bronchial tubes, air 

 sacs. Describe the structure of an air sac. 



4. When our chest cavity grows larger what happens to the air sacs? 

 Why can they do this? 



5. Explain two ways in which you can make your chest cavit\" larger. 

 Explain how the chest cavity becomes smaller. 



6. Explain the connection between air pressure and the filling of a 

 fountain pen. Explain how your lungs become filled with air and how 

 air is moved out of the lungs. 



7. To what extent are the air sacs emptied in breathing? To what ex- 

 tent is the air within them changed? 



8. How does the composition of the air that leaves the lungs differ from 

 that which enters? Account for the two important changes just given. 



9. In what difl^crent ways is the term respiration used? 



10. What makes the chest muscles work in ordinar\' quiet breathing? 

 What causes them to move faster after vicforous exercise? What else 

 may cause them to move faster? 



1 1 . Describe two methods of giving artificial respiration. Explain the 

 sequence of events within the body when you give artificial respira- 

 tion. 



12. State two possible results of high altitude flying. At about what alti- 

 tude does anoxia occur? What arc its symptoms? 



