Respiration 351 



The principal organs of respiration are the diaphragm, the 

 ribs, the lungs, the red corpuscles of the blood, and the cells of 

 the body. 



The diaphragm is a dome-shaped muscle attached to the ribs, 

 forming the floor of the chest. By expanding and contracting, 

 it aids in breathing. 



The lungs are two sponge-like organs composed of minute air 

 tubes, air sacs, and capillaries. They are located in the chest and 

 are protected by the ribs, the breast bone, and the pleura. They 

 are flexible to allow for expansion and contraction in breathing. 



The red corpuscles are blood cells that carry oxygen. 



The nose, pharynx, larynx, trachea, and bronchi form a con- 

 tinuous passage through which air reaches the air sacs of the 

 lungs. The trachea is the main portion of this passage. At its 

 lower end it divides into the bronchi which give off branches end- 

 ing in the air sacs of the lungs. 



Artificial respiration is the production of respiration by some 

 means outside the body. 



Tobacco smoke irritates the throat. If inhaled into the lungs, 

 nicotine, a poisonous substance in the tobacco, may be absorbed 

 into the system. 



Alcohol causes enlargement of the capillaries of the lungs, 

 producing congestion. 



Healthy respiration depends on the free access of oxygen to 

 all the cells of the body. 



Breathing through the mouth should be avoided. Deep breath- 

 ing should be practiced. 



The principal diseases of the respiratory system are colds, 

 catarrh, diphtheria, tuberculosis, pneumonia, and whooping 

 cough. 



Ventilation is necessary in order that fresh air may constantly 

 be brought into, and foul air removed from, the rooms where 

 people live. 



FACT AND THOUGHT QUESTIONS 



1. Why is respiration necessary? 



2. Describe the action of the ribs and the diaphragm in breathing. 



3. Describe the lungs. Show their adaptation to their work. 



