QUESTIONS AND ANSWERS 113 



Name two vascular glands. Give the function of each. 



Spleen: Red blood-corpuscles are formed in the spleen during 

 intra-uterine life, but after birth they are destroyed in it. This 

 organ is thought by some to produce an enzyme which converts 

 trypsinogen into trypsin and also to produce uric acid. It serves as 

 a reservoir for the abdominal circulation. 



Thyroid : This gland has an internal secretion which is directed 

 to the nutrition of the body. The nature of this secretion is not 

 well understood. 



Rbspieation 



Describe the process of respiration. Describe the changes that take 

 place in inspired air during the process of respiration. 



The act of respiration is divided into two parts, inspiration and 

 expiration. The former, by which the chest is filled with air, is a 

 purely muscular act; the diaphragm contracts and therefore re- 

 cedes, the ribs are rotated, being drawn forward and outward, their 

 posterior edges everted, and the intercostal space widened. By 

 these means the capacity of the chest is increased and the lungs 

 expand to fill the space, thus causing air to rush in. Expiration is 

 effected by the recoil of the lungs and the displaced abdominal 

 organs, the contraction of the abdominal muscles and the internal 

 intercostals. Through these movements the air is expelled from 

 the lungs. 



During respiration, part of the oxygen of the air is taken up 

 by the blood in exchange for carbon dioxide which is thrown off. 



How are the diameters of the chest enlarged during inspiration? 



By the recession of the diaphragm, the anteroposterior diameter 

 of the chest is lengthened from four to five inches and by the out- 

 ward rotation of the ribs, the transverse diameter, between the 

 eleventh and twelfth ribs, is increased one and one-half inches. 



Compare inspired air with expired air as to relative quantity of oxygen, 

 nitrogen and carbon dioxide. 



Inspired air contains more oxygen and less carbon dioxide than 

 expired air ; the amount of nitrogen is the same in both. 



Oxygen. 



Inspired air 20.96 



Expired air 16.02 



Mention the functions of respiration. 



Supplies oxygen to the blood and excretes carbon dioxide, solids, 



moisture, etc. 



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