LECTURE IX. 

 RESPIRATION. 



Definition. — Respiration is the process by which the various 

 tissues gain oxygen and give off impurities. Apparently, the plain 

 simple purpose of respiration is two-fold : ( I ) to get oxygen into 

 the blood and various body tissues, and (2) to get CO2 and vari- 

 ous other organic impurities out of the blood and body tissues. 

 It is a common mistake to suppose that respiration is confined to 

 the lungs. A very important portion of the true respiration 

 occurs between the blood and individual tissue cells apart from 

 the lungs. 



Stages. — There are four stages in the complete act of res- 

 piration : (a) air comes into the lungs; (b) blood takes out part 

 of the oxygen; (c) tissues take part of the oxygen away from 

 the blood and give back to the blood carbon dioxide gas in ex- 

 change; and (d) the blood trades off its carbon dioxide to the 

 air for oxygen. 



Parts. — Respiratory system consists of nasal chambers, pha- 

 rynx, larynx, trachea, bronchi, and lungs. These organs are all 

 lined with mucous membrane. Function is to bring blood and 

 air so near each other that the exchange may be rapid and the 

 blood take away oxygen and leave waste matters. 



Nostrils. — Two in number. These are openings at the front 

 of the nasal cavities. The skin covering the nostrils is compara- 

 tively thin, quite sensitive and supported by cartilages. The 

 mucous membrane lining the nasal chambers is divided for study 

 into two portions, the upper in which are distributed the termina- 

 tions of the olfactory nerves and the lower, the Schneiderian. 



The inferior turbinated bones are located on the outer wall 

 of each nasal cavity, two in number, scroll shaped. 



Nasal cavities. — Two in number, one on each side of a me- 

 dian partition. This partition is composed of the vomer, a por- 

 tion of the ethmoid, and the median cartilage. Each cavity con- 



Vet. Studies— 3. 



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