280 ABDOMINAL AORTA. 



The THORACIC AORTA is situated to the left side of the vertebral column, 

 but approaches the middle line as it descends, and at the aortic opening 

 of the diaphragm is altogether in front of the column. After entering the 

 abdomen it again falls back to the left side. 



Relations. It is in relation, behind, with the vertebral column and 

 lesser vena azygos ; in front, with the oesophagus and right pneumogastric 

 nerve ; to the left side, with the pleura ; and to the right, with the thoracic 

 duct. 



Plan oftfie Relations of the Thoracic Aorta. 



In Front. 



(Esophagus, 



Right pneumogastric nerve. 



Right Side. 

 Thoracic duct. 



Thoracic Aorta. 



Left Side. 

 Pleura. 



Behind. 



Lesser vena azygos, 

 Vertebral column. 



The ABDOMINAL AORTA enters the abdomen through the aortic opening 

 of the diaphragm, and descends, lying rather to the left side of the verte- 

 bral column, to the fourth lumbar vertebra, where it divides into the two 

 common iliac arteries. 



Relations. It is crossed in front, by the left renal vein, pancreas, trans- 

 verse duodenum, and mesentery, and is embraced by the aortic plexus ; 

 behind it is in relation with the thoracic duct, receptaculum chyli, and left 

 lumbar veins. 



On its left side is the left semilunar ganglion and sympathetic nerve ; 

 and on the right, the vena cava, right semilunar ganglion, and the com- 

 mencement of the vena azygos. 



Plan of the Relations of the Abdominal Aorta. 



In Front. 



Left renal vein, 



Pancreas, 



Transverse duodenum, 



Mesentery, 



Aortic plexus. 



Behind. 



Thoracic duct, 

 Receptaculum chyli, 

 Left lumbar veins. 



