1152 THE DIGESTIVE SYSTEM. 



to the deviation of the tube to the left in the inferior part of the neck, its relation 

 to the carotid sheath and thyreoid gland is much more intimate on the left than 

 on the right side. 



In the Thorax. The oesophagus passes successively through the superior and 

 posterior mediastina, in the former lying close to the vertebral column, but in 

 the latter advancing somewhat into the thoracic cavity and coming into contact 

 with the back of the pericardium. The trachea still lies anterior to it as far as the 

 fifth thoracic vertebra, where the trachea bifurcates. Immediately below that the 

 oesophagus is crossed by the left bronchus (Fig. 908, C), and in the rest of its 

 thoracic course it lies in the closest relation to the back of the pericardium. 

 Posteriorly, in the upper part of the thorax, it rests on the longus colli muscles and 

 the vertebral column ; but below the bifurcation of the trachea, as already explained, 

 it advances into the cavity of the posterior mediastinum, and is soon separated 

 from the vertebral column by the vena azygos, the thoracic duct, the upper five 

 aortic intercostal arteries of the right side, and in its lower part by the thoracic 

 aorta as well. 



On its left side, in the upper part of the thorax, lie the left pleura and the left 

 subclavian artery, with the thoracic duct in a plane posterior to the artery ; in the 

 middle region, the aorta, and lower down the left pleura again, for a little way, 

 before the oesophagus pierces the diaphragm. On the right side the tube conies 

 into relation with the arch ^of the vena azygos, whilst the right pleura clothes it 

 both below and above that level. 



The two vagus nerves, after forming the anterior and posterior pulmonary 

 plexuses descend to the oesophagus, where they form, by uniting with one another 

 and with the branches of the sympathetic, the anterior and posterior cesophageal 

 plexuses. Lower down the left nerve winds round to the anterior, whilst the right 

 turns to the posterior surface of the oesophagus, and in this relation they pass with 

 the tube through the diaphragm to reach the stomach. 



The diaphragmatic portion, about half an inch in length (1 to 1'5 cm.), corresponds to the 

 portion of the tube which lies in the cesophageal orifice (or canal) of the diaphragm. Tht 

 plane of this orifice is very oblique or almost vertical, and its abdominal opening looks forwards 

 and to the left, and but little downwards. Above and in front, where it is bounded either by tht 

 posterior edge of the central tendon or by a few decussating fibres of the muscular portion GJ 

 the diaphragm, which meet behind the tendon, the cesophageal orifice has practically no length 

 and consequently the oesophagus here passes into the abdominal cavity immediately after leaving 

 the thorax. At the sides and behind, on the other hand, the decussating bands from the twc 

 crura, which embrace the orifice, are so arranged that they turn a flat surface (not an edge 

 towards the opening, and thus, behind and at the sides, the orifice or canal is of some length 

 and on these aspects there is a portion of the tube in contact with the diaphragm for a distanct 

 of 1 to 1^ cm. But this contact takes place not around a horizontal line, but in a very obliqu< 

 plane corresponding to that of the orifice. 



The oesophagus, in passing through the orifice, is connected to its boundaries by a considerabl- 

 amount of strong connective tissue, but it is extremely difficult, or impossible, to demonstrate an? 

 direct naked-eye connexion between the cesophageal muscular fibres and those of the diaphragm 



The anterior or right boundary of the cesophageal orifice, formed of fibres derived from botJ 

 crura of the diaphragm, is strongly developed and prominent, and usually lies in the cesophagea 

 groove, on the back of the left lobe of the liver, which groove is rarely due to the pressure of th 

 O3sophagus alone. 



The pars abdominalis of the oesophagus is very short, for immediately after piercing th 

 diaphragm the tube expands into the stomach. However, when the empty stomach is draw; 

 forcibly downwards, a portion of the front and left side of the tube, about half an inch in length 

 (1 to 1'5 cm.), is seen, to which the above term is applied. This part is covered with peritoneun 

 derived from the great sac in front and on the left, whilst its right and posterior surfaces ar 

 uncovered. It is generally described as lying against the cesophageal groove and the left triangula 

 ligament of the liver in front, but it never actually comes in contact with the latter of thes 

 structures, which is attached to the upper surface of the left lobe of the liver by one edge, an 

 to the diaphragm, over an inch in front of the oesophagus, by the other. As regards the forme 

 the cesophageal groove of the liver is generally occupied by the prominent right margin of t 

 cesophageal orifice of the diaphragm and occasionally by the oesophagus as well. Possibly th 

 margin is so strongly developed and so prominent in order that it may bear the pressure of the li 

 off the gullet, which otherwise might be interfered with in its dilatation during the passage of fc 



When the stomach is fully distended the abdominal part of the oesophagus almost disappear 

 being absorbed into the stomach in its distension. 



The portion of the oesophagus which adjoins the stomach is sometimes described as consis 

 of two parts, namely, the ampulla phrenica and the antrum cardiacum. The former n 



