PROBLEM 4. Hov: the Cells Are Provided with Oxygen 



Exercises 



1. Through what passages does the air travel in reaching the lungs? 

 Close vour mouth and inhale. Where does air enter? The nostrils open 

 into the throat. Put vour finger on the neck just under the chin, and 

 speak. What do vou feel? What pipe lies in the front of the neck? Does 

 this seem to have hard or soft walls? Compare with Figure 225. What 

 name is given to this portion of the tube? What are the advantages of 

 hard walls? Where does the food pipe lie with reference to the windpipe? 

 In reaching the food pipe food passes over the entrance to the windpipe. 

 Place vour fingers on vour voice box again and swallow. Describe. While 

 you are doincr this, the epiglottis, which vou see in the diagram, moves 

 from its upright to a horizontal position. Of what advantage is this in 

 swallowing? What fails to happen when vou "choke"? Whv can you not 

 speak and swallow at the same instant? When vou get a crumb into the 

 top of your voice box, how do you get rid of it? Explain. Examine the 

 diagram. Find the adenoids in the picture. How might a child give evi- 

 dence of having enlarged adenoids? Whv are children with large adenoids 

 sometimes listless and dull in school? 



2. Why is it better to breathe through the nasal cavities than through 

 the mouth? Air contains dust which is irritating. On the dust particles are 

 bacteria which may be injurious. Examine the entrance to your nasal 

 cavities. How are they fitted for stopping the entrance of dust? In the 

 upper part are microscopic cilia. Of what use might they be? The upper 

 part of the nasal cavities and the mouth are both lined with mucous mem- 

 brane. What characteristic of this membrane fits it for catchine dust? 

 Considering the width of the nasal cavities and the mouth cavitv, which 

 has a better chance of catching dust? Why? In winter when the outside 

 air is cold, which cavity is better fitted for warming up the air on its way 

 into the lungs? Explain. State three reasons why it is better to breathe 

 through the nose than through the mouth. 



3. What is the structure of a sheep or beef lung? Which of the struc- 

 tures mentioned in the text can you find in this specimen? What do you 

 observe that has not been mentioned? Feel the outer surface and describe. 

 This smooth membrane is part of the pleura. The pleura not only covers 

 the lungs but lines the inside of the chest cavity. Of what use is a smooth 

 membrane here? (In life it is moist.) What kind of tissue makes up this 

 membrane? What do you notice when you feel the windpipe? The sub- 

 stance in the walls is cartilage. How is the cartilage arranged? Of what 

 advantage is the cartilage? Are these lungs collapsed or expanded? If you 

 can, compare the weight of a piece of lung with the weight of a piece of 

 beefsteak of the same size. Explain, Lay a piece of beef lung in a pan 

 of water. Whv does it float? What color is the lung? Why? Write up 

 your observations. Compare them with others, 



4. How do the ribs move in breathing? A model mav be used to show 

 the rib movements. Use a board, one inch by two feet, to represent the 



3:) 



