CHAPTER XIII 



RESPIRATORY SYSTEM: NOSE; LARYNX; TRACHEA; BRONCHI; 

 LUNGS. — RESPIRATION ; ABNORMAL TYPES OF RESPIRATION. 

 MODIFIED RESPIRATORY MOVEMENTS 



The process of respiration is dependent upon the proper func- 

 tioning of certain organs, which we group together and call a res- 

 piratory system. A respiratory system consists essentially of a 

 moist and permeable membrane, with blood-vessels containing 



AIR 



THIN MUCOSA |- |- | . I ^ \ ^ \ — |_ |- 



CAPILLARV BLOOD VESSEL QD00Q(SC?Xg)O Q QGg)0<50 Q0QO ©gQ 



Fig. 139. — Diagram of the Essentials of a Respiratory System. 



(Gerrish.) 



a high percentage of carbon dioxide on one side, and air or fluid 

 containing a high percentage of oxygen on the other. In most 

 aquatic animals the respiratory organs are external in the form of 

 gills ; in terrestrial, or air-breathing animals, the respiratory organs 

 are situated internally in the form of lungs, and are placed in com- 

 munication with the nose and mouth by means of the bronchi, 

 trachea, and larynx. 



NOSE 



The nose is the special organ of the sense of smell, but it also 

 serves as a passageway for the entrance of air to the respiratory 

 organs. It consists of two parts, — the external feature, the nose, 

 and the internal cavities, the nasal fossae. 



The external nose is composed of a triangular framework of bone 

 and cartilage, covered by skin and lined by mucous membrane. 

 On its under surface are two oval-shaped openings — the nostrils, 

 which are the external openings of the nasal fossse. The margins 

 of the nostrils are provided with a number of stiff hairs, which ar- 



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