296 ASCENDING AORTA. 



AORTA. 



The AORTA arises from the left ventricle, at the middle of the root 

 of the heart, and opposite the articulation of the fourth costal cartilage 

 with the sternum. At its commencement it presents three dilatations, 

 called the sinus aortici, which correspond with the three semilunar 

 valves. It ascends at first to the right, then curves backwards and 

 to the left, and descends on the left side of the vertebral column to 

 the fourth lumbar vertebra. Hence it is divided into ascending 

 arch and descending aorta. 



Relations. The ascending aorta has in relation with it, in front, 

 the trunk of the pulmonary artery, thoracic fascia, and pericardium ; 

 Itehind, the right pulmonary veins and artery ; to the right side, the 

 right auricle and superior cava ; and to the left, the left auricle and 

 the trunk of the pulmonary artery. 



Plan of the Relations of the Ascending Aorta. 



In Front. 



Pericardium, 

 Thoracic fascia, 

 Pulmonary artery. 



Right Side. LeftSide. 



Pulmonary artery, 

 Left auricle. 



Behind. 



Right pulmonary artery, 

 Right pulmonary veins. 



Arch. The upper border of the arch of the aorta is parallel with 

 the upper border of the second sterno-costal articulation of the right 

 side in front, and the second dorsal vertebra behind, and terminates 

 opposite the lower border of the third. 



The anterior surface of the arch is crossed by the left pneumogas- 

 tric nerve, and by the cardiac branches of that nerve and of the sym- 

 pathetic. The posterior surface of the arch is in relation with the bi- 

 furcation of the trachea and great cardiac plexus, the cardiac nerves, 

 left recurrent nerve, and the thoracic duct. The superior border gives 

 the three great arteries, viz. the innominata, left carotid, and left 

 subclavian. The inferior border, or concavity of the arch, is in rela- 

 tion with the remains of the ductus arteriosus, the cardiac ganglion 

 and left recurrent nerve, and has passing beneath it the right pulmo- 

 nary artery and left bronchus. 



