DESCENDING THORACIC AORTA. 



481 



extent is from the lower border of the fourth dorsal vertebra, on extent; 

 the left side to the front of the last dorsal vertebra. 



Contained in the posterior mediastinum, the vessel is rather course ; 

 curved, lying at its upper end on the left, and below on the front 

 of the spinal column. Beneath it are the vertebrae and the smaller 

 azygos veins. In front of the vessel are the root of the left lung 

 and the pericardium. On its left side it is covered throughout by 



Sympathetic ganglion 

 (a part of the chain). 

 Superior intercostal vein. 



Aortic intercostal artery. 



Vena azygos major. 



Right vagus on the 

 oesophagus. 



Left lower azygos vein. 

 Left vagus. 

 Thoracic duct. 



Great splanchnic nerve, 



Kami to the lesser 

 splanchnic- nerve. 



FIG. 174. DIAGRAM OP STRUCTURES IK THE POSTERIOR MEDIASTINUM. 



the pleura ; and on its right side are the oesophagus, the thoracic 

 duct, and the large azygos vein, though near the diaphragm the 

 gullet is placed over the aorta (fig. 174). 



The BRANCHES of the vessels are distributed to the surrounding Branches, 

 parts, and are named from their destination bronchial, pericardial, 

 cesophageal, mediastinal, and intercostal. 



a. The bronchial arteries supply the structure of the lungs, and Arteries of 



adhere to the posterior part of the bronchial tubes, on which they 



. f . . , , i -, n i -11 distribu- 



raimty ; they give some twigs to the bronchial glands and the tion. 



oesophagus. 



D.A. I I 



