188 



ANATOMY FOR NURSES 



[Chap. XI 



either directly into the heart, or indirectly by means of the superior 



and inferior venie cavae. 



The aorta. — Tiie aorta is the main trunk of the arterial system. 



Springing from the left ventricle of the heart, it arches over the 



root of the left lung, de- 

 scends along the verte- 

 bral column, and after 

 passing through the dia- 

 phragm into the abdom- 

 inal cavity, ends opposite 

 the fourth lumbar verte- 

 bra by dividing into the 

 right and left common 

 iliac arteries. In this 

 course the aorta forms a 

 continuous single trunk, 

 which gradually dimin- 

 ishes in size from its 

 commencement to its 

 termination (from 28 to 

 17 mm.) and gives off 

 larger or smaller branches 

 at various points. 



It may be divided as 

 follows : — 



(1) The ascending 

 aorta is the short part 

 which is contained within 

 the pericardium. 



(2) The arch is the 

 part extending from the 

 ascending aorta and 

 forming a well-marked 



curve in front of the trachea, and around the root of the left 

 lung to the border of the fourth thoracic vertebra. 



(3) The descending thoracic aorta is the comparatively straight 

 part that extends from the lower border of the fourth thoracic 

 vertebra on the left side, to the opening in the diaphragm below 

 the last thoracic vertebra. It has a length of from seven to eight 

 inches (175 to 200 mm.). 



Fig. 119. — Thor.\cic Aort.\. (Gerrish.) 



