142 HANDBOOK OF ANATOMY 



The Ascending Aorta arises from the base of the left ven- 

 tricle opposite the lower border of the third left costal cartilage. 

 It passes upwards, forwards, and to the right, terminating in 

 the arch of the aorta at the level of the junction of the right 

 second costal cartilage with the sternum. 



Branches. Right and left coronary arteries, which supply the 

 heart muscle. 



The Arch of the Aorta lies behind the lower part of the nianu- 

 brium, and begins at the termination of the ascending aorta, 

 terminating as the descending aorta opposite the lower border 

 of the body of the fourth dorsal vertebra. The arch passes 

 upwards, backwards, arid to the left in front of the trachea, and 

 curving over the pulmonary artery ; it then passes backwards to 

 the left of the trachea and turns downwards. 



Branches of the Arch of the Aorta supply the head and neck 

 and upper limb. The branch on the right side the innominate 

 artery is a very short trunk, which divides almost at once into 

 right common carotid and right subclavian arteries; the left 

 common carotid and left subclavian arteries are given off from 

 the arch itself. 



The Descending Aorta extends from the termination of the 

 arch at the fourth dorsal vertebra, and ends at the opening in 

 the diaphragm opposite the twelfth dorsal vertebra, by becoming 

 the abdominal aorta. It lies on the vertebral column and is in 

 contact anteriorly with the root of the left lung, the pericardium,, 

 the oesophagus, and the crura of the diaphragm. 



The branches are divided into two sets, visceral and parietal, 

 supplying the muscles of the thorax and its contents. 



The Abdominal Aorta extends from the middle of the body 

 of the last dorsal vertebra to the left side of the body of the 

 fourth lumbar vertebra, where it divides into the two common 

 iliac arteries. The bifurcation^ in the intertubercular plane. 

 It lies on the vertebral column, and anteriorly is in contact with 

 the solar plexus, the third part of the duodenum, the mesentery, 

 peritoneum, and coils of small intestine. The pancreas is 

 separated from the aorta by the splenic vein and superior 

 mesenteric artery. 



Branches. The branches are divided into two sets visceral 



