1238 



THE ORGANS OF DIGESTION 



front of the aorta. On its left side, in the superior mediastinum, are the terminal part of the 

 arch of the aorta, the left subclavian artery, the thoracic duct, and left pleura, while running 

 upward in the angle between it and the trachea is the left recurrent laryngeal nerve; below, it 

 is in relation with the descending thoracic aorta. On its right side are the right pleura and the 

 vena azygos major, which it overlaps. The vagus nerves desceryd in close contact with it, the 

 right nerve passing down behind, and the left nerve in front of it; the two nerves uniting to form 

 a plexus (plexus gulae s. oesophageus) around the tube. 



In the lower part of the posterior mediastinum the thoracic duct lies to the right side of the 

 oesophagus; higher up, it is placed behind it, and, crossing about the level of the fourth thoracic 

 vertebra, is continued upward on its left side. 



THORACIC DUCT 



AZYGOS VEIN 



SUPERIOR. LARYN- 

 GEAL NERVE 



INTERNAL 

 JUGULAR VEIN 

 TRACHEA 

 INFERIOR 

 THYROID ARTERY 



RECURRENT 



NERVE 

 UBCLAVICULAR 



ARTERY 



RIGHT CEPHALIC 



TRUNK 



ESOPHAGUS 



VAGUS NERVE 



AZYGOS VEIN 



BRONCHIAL 

 ARTERY 



RIGHT PUL- 

 MONARY VEIN 



RIGHT LUNG 



INF. VENA CAVA 



DIAPHRAGM 



FIG. 955. The position and relation of the ossophagus in the cervical region and in the posterior mediastinum. 

 Seen from behind. (Poirier and Charpy.) 



Structure. The oesophagus has four coats an external or fibrous, a muscular, a sub- 

 mucous, and an internal or mucous coat. 



The fibrous coat consists of white fibrous connective tissue that supports the other coats and 

 assists in connecting the oesophagus to the surrounding tissues or organs. 



The muscular coat (tunica muscularis) is composed of two planes of considerable thickness, 

 an external longitudinal and an internal circular. 



The longitudinal fibres are arranged, at the commencement of the tube, in three fasciculi 

 one in front, which is attached to the vertical ridge on the posterior surface of the cricoid car- 

 tilage, and one at each side, which is continuous with the fibres of the Inferior constrictor of 

 the pharynx; as they descend they blend together and form a uniform layer, which covers the 

 outer surface of the tube. 



Accessory slips of muscle tissue pass between the oesophagus and the left pleura, where 

 the latter covers the thoracic aorta, or the root of the left bronchus, or the back of the 

 pericardium. 



