THE (ESOPHAGUS 958 



interval between tlie trachea and (esopliagns. The left nerve, as already deserihcd, 

 lies in front of the tube, and the riu;ht at some little distance from it. 



In the thorax the cesophagus descends through the superior and the ])osterior 

 mediastina. In the superior mediastinum its anterior relations are the trachea, 

 with the deep cardiac plexus in front of its bifurcation, the left subclavian and 

 carotid arteries crossing its left border oljliquely, the left recurrent laryngeal nerve 

 and the arch of the aorta. To the left are the left carotid and sul)clavian arteries, 

 the end of the arch of the aorta, and the left pleural sac. To the ritrht it is in 

 relation with the right vagus nerve and the right i)leural sac. Behind, it rests 

 upon the vertebral column, the left longus colli muscle, and it overla])s the 

 thoracic duct. As it enters the posterior mediastinum it passes behind the left 

 bronchus and the right pulmonary artery, resting posteriorly on the vertebral 

 column and thoracic duct. In the posterior mediastinum it has in front of it the 

 pericardium, which separates it from the left auricle of the heart and a portion of 

 diajiliragm; it rests upon the vertel:>ral column, the vena azygos minor, sujierior 

 and inferior, the right aortic intercostal arteries, and the thoracic duct. To 1h<' 

 right is the right pleural sac, the vena azygos major, which it ])artly overlaps, and 

 below the thoracic duct. To the left in the u])per part is the descending thoracic 

 aorta, and below the left pleural sac is separated from it by a little loose areolar 

 tissue. It is surrounded by the (esoi)hageal plexus formed by the vagi nerves, and 

 as they emerge from the lower part of the plexus the left vagus lies in front of the 

 oesophagus and the right vagus behind. 



In the abdomen the oesophagus lies in the epigastric region. In front of it is 

 the left lobe of the liver. To the left the left lobe of the liver and the fundus of the 

 stomach. To the right the Spigelian lobe of the liver, and Ijehind the decussating 

 fibres of the crura of the diaphragm and the left inferior phrenic artery. 



The arterial suii])ly of the oesophagus is derived from the inferior thyroid, the 

 oeso])hageal branches of the aorta, the intercostals, the inferior phrenic, and the 

 coronary arteries. 



The veins accompany the arteries. 



The nerves are filaments of the spinal accessory which pass to it by the vagus, 

 and the recurrent laryngeal nerves. 



After death the gullet is somewhat flattened from before backwards, but it is 

 more rounded during life. It is closed except during the passage of food, etc. 



Structure. — Tlie wall of the oesophagus is composed of three coats — muscular, 

 submucous, and mucous. It is surrounded wath elastic cellular tissue, loosely 

 connecting it with the neighbouring structures, and freely permitting its distension. 



The muscular coat is thick, red, and consists of striped muscular fil)res in its 

 upper thir<l or more. It is made up of two distinct layers. 



The longitudinal fibres commence as three flattened l)ands: a strong anterior 

 arising from the ridge on the back of the cricoid cartilage (fig. 526), and two lateral 

 bands wliich blend with the fibres of the pharynx. These all unite into a continu- 

 ous layer which passes below into the muscular coat of the stomach. Several 

 accessory bands have been described, connected with the trachea, left bronchus, 

 pericardium, and left pleura. 



The circular fibres are continuous above with the inferior constrictor, and l)elow 

 with the ol)li(|Ue Hl)res of the stomach; they form a uniform layer Avhich l)ecomes 

 .somewhat ()bli(jn(ly disposed towards the middle of the gullet. 



The submucous coat loosely connects the inner mucous and outer nniscular 

 coats. It is the seat of numerous racemose glands whose ducts open on the surface 

 of the mucous membrane. 



The mucous coat is thick, reddish above, paler l)elow. and deeply folded 

 longitudinally. It i)resents numerous jiapillte and contains racemose glands. It 

 is covered by a stratitied .squamous epithelium. 



