334 A MANUAL OF ANATOMY. 



behind, right bronchus ; above, transverse aorta ; below, 

 the left auricle. 



In the root of the lung it is between the bronchus (above) 

 and the pulmonary veins (below) ; behind is the azygos 

 vein, pneumogastric nerve, and posterior pulmonary plexus. 



The Left Pulmonary Artery. 



Is shorter than the right, reaches to the left lung, and 

 divides into two branches. 



Relations. In front, phrenic nerve, anterior pulmonary 

 plexus, left pleura ; behind, descending aorta, left pneumo- 

 gastric nerve, posterior pulmonary plexus ; below (and in 

 front), pulmonary veins, left bronchus. 



The Aorta. (The description will be given here in full. 

 For dissection see page 352). Figs. 57, 58, 69 to 74. 



The outlet for the blood from the left ventricle. 



In the subject is seen to be contained in the pericardium 

 for its first two inches (or less). It presents to the right 

 of and behind the pulmonary artery and right auricle. Its 

 direction is upward, backward, and to the left, then down- 

 ward along the spinal column to leave the thorax through 

 the aortic opening. It is divided into the ascending, trans- 

 verse, descending, and thoracic portions. 



The Ascending- Aorta. Diag. 22. 



This is about two inches long. It begins at the left 

 ventricle of the heart, passes upward, curving slightly 

 to the right in its course ; it ends where the artery turns 

 to pass transversely into the left portion of the thorax. 

 From its base on the right and left sides are given off 

 the coronary arteries to the heart, the left coronary artery 

 supplying the left ventricle mostly, and the right, the right 

 ventricle. At the base of the aorta it is dilated into three 



