1 3 o THORAX 



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

 aorta and posterior to the pericardium (Figs. 65, 66, 68). 



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 

 cesophageal plexus, (2) the upper five right aortic intercostal 

 arteries, (3) the thoracic duct, (4) the vena azygos, (5) the 

 vena hemiazygos 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 

 still further forwards (pp. 35, 64). 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. 69). 



Right Relations. In the superior mediastinum, it is in re- 

 lation with the right pleura and lung, and with the arch of 

 the vena azygos (Figs. 22 and 13); and, in the posterior 

 mediastinum, with the cesophageal plexus and right pleura 

 and lung, until it passes forwards and towards the left, 

 anterior to the descending aorta (Figs. 68, 69). 



Left Relations. In the superior mediastinum, it is in rela- 

 tion on the left side with the thoracic duct, the left sub- 

 clavian 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; its lower part, which lies in front of 

 the descending aorta, is in relation on the left side with the 

 left pleura and lung. 



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

 phagus is generally somewhat compressed antero-posteriorly 

 by the structures between which it lies ; it probably has a 



1 Verify this statement by replacing the heart in situ (see also Figs, 48, 56). 



