THE RESPIRATORY SYSTEM 105 



the heart, the lungs being expanded laterally into the paired pleural 

 cavities. 



In addition to the carrying of air over the sensory, olfactory 

 surfaces, other accessory- functions more closely related to respira- 

 tion are the warming of the air and removal therefrom of particles 

 of foreign material, both of which are performed by the mucous 

 membrane of the nose, including that of the turbinated surfaces. 

 The sole functions of the true respiratory tract and lungs are 

 respiratory. 



Respiration as a Process 



In a mammal, respiration is both a physicochemical and a 

 mechanical process. The former is fundamental, and consists in 

 the supply of oxygen to the blood, and in this way to the tissues, 



X* 



r 



i 



"A 



- rn \ 



\% 



/ 





I W"'lJ '' 



Fig. 57. The heart and lungs from the ventral surface: ad. right atrium; 

 ao, aorta; ap, pulmonary artery; as, left atrium; d, right superior caval vein; 

 i', i", left and right inferior lobes of lung; 1, aortic ligament; m', m", middle 

 lobes; ml, medial lobule of right inferior lobe; s, left superior caval vein; 

 s', s", superior lobes; tr, trachea; vd, right ventricle; vi, inferior caval vein; 

 vp, pulmonary veins, vs, left ventricle. The right and left pulmonary 

 arteries and the arch of the aorta are represented too high up — compare 

 Fig. 62. 



