102 THORAX 



and to the left, across the anterior aspect of the descending 

 aorta and posterior to the pericardium (Figs. 12 and 21). 



Posterior Relations. In the superior mediastinum it is an- 

 terior to the left longus colli muscle and the vertebral column. 

 In the upper part of the posterior mediastinum it is separated 

 from the vertebral column by (i) the posterior part of the ceso- 

 phageal plexus, (2) the upper six right aortic intercostal arteries, 

 (3) the thoracic duct, (4) the vena azygos, (5) the vena hemi- 

 azygos and the accessory hemiazygos vein; and in the lower part 

 by (6) the cesophageal plexus and (7) the descending aorta. 



Anterior Relations. Anterior to it, in the superior media- 

 stinum^ lie the trachea, the left recurrent nerve, the upper 

 part of the left common carotid artery, the left subclavian 

 artery, the arch of the aorta, and the structures which lie 

 anterior to those already mentioned. As it passes from the 

 superior to the posterior mediastinum its anterior relations are 

 first the commencement of the left bronchus and then the 

 right pulmonary artery. 1 In the posterior mediastinum, the 

 cesophageal plexus is on its anterior surface, intervening 

 between it and the posterior wall of the pericardium, which 

 separates both the plexus and the oesophagus from the 

 posterior wall of the left atrium ; and at a lower level the 

 oesophagus lies posterior to the diaphragm (Fig. 21). 



Right Lateral Relations. In the superior mediastinum, it is 

 in relation with the right pleura and lung and with the arch 

 of the vena azygos (Figs. 12 and 22), and in the posterior 

 mediastinum with the cesophageal plexus and right pleura 

 and lung, until it passes anteriorly and to the left, anterior to 

 the descending aorta. 



Left Lateral Relations. In the superior mediastinum, it is 

 in relation on the left side with the thoracic duct, the left 

 subclavian artery, the left pleura and lung, and the termination 

 of the arch of the aorta. From the fifth to the seventh thoracic 

 vertebra its left lateral relations are the cesophageal plexus and 

 the descending aorta ; and at its lower end, as it lies anterior to 

 the descending aorta, it comes again into relation with the 

 left pleura and lung. 



The dissector should note (i) that, after death, the 

 oesophagus is somewhat compressed antero- posteriorly by 

 the structures, between which it lies. It probably has a 

 similar form during life when empty and flaccid, but becomes 



1 Verify this statement by replacing the heart in situ. 



