i854 



HUMAN ANATOMY. 



Portion of injected lung, showing relation of blooa- 

 vessels to bronchi; pulmonary arteries (blue) accompany- 

 ing bronchi (white) ; pulmonary veins (red) at periphery 

 of lobule. X 2 



near the bottom. They arise from the capillaries in the walls of the air-chambers, 



running first on the outside of the lung-units, unite with others, and ramify in the 



connective tissue about the lobules, so that, first in the lung-units and then in the 



lobules, the circulation is from the centre towards the periphery. As they ascend to 



the hilum they unite with others and form 



trunks that accompany the bronchi, lying Fig. 1578. 



in the main lower and to the inner side 



of the latter. Corrosion preparations 



(Fig. 1578) show very clearly that the 



small arteries travel in close company 



with the bronchi, while the veins course 



by themselves. 



The bro7ichial arteries carry the 

 blood for the nutrition of the lungs, es- 

 pecially that of the air-tubes, the lymph- 

 nodes, the walls of the blood-vessels, 

 and the areolar tissue about them ; hence 

 they follow the course of the bronchi. 

 They are in communication with the 

 interlobular system of the pulmonary 

 arteries. 



The bronchial veins are very irreg- 

 ular. Both anterior and posterior are 

 described. The former carry the blood 

 back from the bronchi and the tissues 

 about them, becoming perceptible at the 



bronchi of the third order {i.e., the branches of the first branches) and running 

 to the hilum anterior to the bronchi, two with each. The posterior bronchial veins 

 appear at the back of the hilum and, without any close connection with the bronchi, 

 anastomose with other veins at the back of the roots of the lungs. 



Anastomoses betzveen the 

 Fig. 1 579. Pulmonary and the Bron- 



Pieura ' chial SysteiHS. — Not only do 



/--"■'-''r-^^ the capillaries at some places 



drain into either system of 

 veins, but important com- 

 munications occur between 

 both the arteries and the 

 veins. (a) The bronchial 

 arteries as they enter the 

 lungs give off occasional 

 branches which, running for 

 some distance beneath the 

 pleura, suddenly plunge into 

 the lung to anastomose with 

 an interlobular artery. Such 

 a branch may arise from an 

 oesophageal artery. There 

 are also deep connections 

 between the arteries of the 

 two systems on or near the 

 secondary bronchi and their 

 branches. (3) The com- 

 munications between the two 

 systems of veins are very 

 extensive. Apparently all 

 the blood from the smallest branches of the bronchial arteries returns by the pul- 

 monary veins ; and, moreover, the bronchial veins about the larger bronchi have 

 free communication with those of the pulmonary system. According to Zucker- 



Pulmonary vein 



Lymph-vessel 



Section of injected lung, showing lymphatic accompanying peripheral 

 branch of pulmonary vein. X 60. (Miller.) 



