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THE RESPIRATORY SYSTEM. 



The bloodvessels of the lungs comprise two distinct sets of 

 arteries, capillaries, and veins : the pulmonary vessels and the 

 bronchial vessels. 



The pulmonary vessels are far the larger of the two sets 

 and carry out the respiratory function of the lungs. The 

 pulmonary arteries convey the venous blood from the right 

 ventricle of the heart, and break up into capillaries which 



General appearance of lung under low magnification (Dunham), a, bronchus; 

 b, muscularis mucosae of bronchus: c, pulmonary veins ; d, e, infundibula. 



surround the air-vesicles in a close mesh work. The blood, 

 aerated and arterialized in these capillaries, is collected from 

 them and returned in the pulmonary veins to the left auricle. 

 The pulmonary arteries and veins accompany the bronchi 

 in their course throughout the lungs, lying in the same 

 sustentacnlar tract of peribronchial connective tissue, the 

 bronchus in the centre, a pulmonary artery on one side, and 

 a pulmonary vein, larger and with thinner walls than the 



