CHAPTER XIV 



PULMONARY RESPIRATION AND RESPIRATORY 

 ORGANS 



Respiration is the term used to express the interchange of gases 

 between the blood and the surrounding tissues, the gases being 

 oxygen and carbon dioxide. 



Pulmonary respiration takes place in the capillary system of the 

 lungs. The interchange is between the blood and the atmosphere, 

 or external air; hence, the process in the lungs is called external 

 respiration. 



The exchange which takes place in the capillaries of the tissues 

 elsewhere is, on the other hand, called internal respiration. As this 

 depends entirely upon the intake of oxygen by the lungs and the 

 removal of carbon dioxide in the same organs, the use of the word 

 respiration without qualifying, has come to signify pulmonary or 

 external respiration, commonly termed breathing. 



Inspiration is the act of drawing air into the lungs; expira- 

 tion is the act of expelling it. An inspiration and an expiration 

 together constitute a pulmonary respiration. 



By air is meant the atmospheric air by which we are surrounded. 

 It consists principally of the two gases, oxygen and nitrogen, one 

 hundred parts by weight of air containing a little more than twenty 

 of oxygen and a little less than eighty of nitrogen, or, in the pro- 

 portion of one of O to four of N, roughly speaking. It is the 

 oxygen which is the essential part of inspired air. 



The respiratory organs are the nose, pharynx, larynx, trachea, 

 bronchial tubes, and lungs, with the thorax and its muscles, in- 

 cluding the diaphragm; and the pulmonary blood-vessels. These 

 organs constitute the respiratory apparatus and they include the 

 respiratory tract, which is a series of channels or air-passages at 

 the termination of which the air comes into contact with the 

 respiratory epithelium. 



The nose. The external nose is a framework of bone, cartilage 

 and skin. The dorsum is formed by the meeting of the lateral 



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