THE (ESOPHAGUS 



1141 



The submucosa (fig. 897) is a thick, very loose fibrous layer connecting the mucosa with the 

 muscularis. It contains numerous vessels and nerves, and mucous glands. The latter [gl. 

 oesophageae] are of the racemose type, like those of the mouth, and are variable in number. 

 There are also two sets of superficial glands, confined to the lamina propria, and resembling 

 the fundus glands of the stomach. The upper set (Rlidinger-Schaffer glands) are found in 70 

 per cent, of cases, occurring above the level of the fifth tracheal ring. The lower set (oesophageal 

 cardiac glands) form a ring around the oesophagus just above the cardiac aperture. A few small 

 lymph nodes also occur in the submucosa, often around the ducts of the mucous glands. 



The muscularis (fig. 897) is a thick reddish tunic with two distinct layers, approximately 

 equal in thickness. The fibres of the inner layer are arranged circularly and are continuous 

 with the inferior constrictor above and with the oblique fibres of the stomach below. The 

 fibres of the outer layer are longitudinal and commence above as three flattened bands: a strong 

 anterior band arising from the ridge on the back of the cricoid cartilage, and two lateral bands 

 blending with the fibres of the stylo-pharyngeus and the pharyngo-palatine. These all unite 

 into a continuous layer which below passes into the muscular coat of the stomach. The upper 

 third or fourth of the oesophagus contains exclusively cross-striated muscle fibres, like those 

 of the pharynx. Below this, there is a zone of intermingled smooth and cross-striated fibres. 

 The lower half of the oesophagus muscle is usually composed exclusively of smooth fibres. 



Around the muscular coat is a thin loose fibrous layer [tunica adventitial connecting the 

 CESophagus with neighbouring structures. 



Vessels and nerves. — The arterial supply of the oesophagus is derived from the inferior 

 thyreoid, the oesophageal branches of the aorta, the intercostals, the inferior phrenic and the 



Fig. 897." 



-Transverse Section op the Upper Third of the Human CEsophagus. 

 (Lewis and Stohr.) 



X5. 



Stratified epithelium 



Tunica propria 



Muscularis 

 / / mucosas 

 Submucosa 



Mucous 

 membrane 



Group of fat-cells' \.l^' 



" x\ Circular muscles 1 Muscu- 

 *'' Longitudinal muscles laris 



Tunica adventitia 



Lymph nodule 



Mucous gland 



left gastric arteries. Branches pierce the wall and supply the various coats. The veins 

 accompany the arteries. They form on the outer surface of the oesophagus a venous plexus 

 opening into the gastric coronary vein below and the azygos and thyreoid veins above (thus 

 estabhshing a communication between portal and systemic veins). There are also numerous 

 lymphatics in the oesophagus arising chiefly in the mucosa and draining into the lower deep 

 cervical, posterior mediastinal and superior gastric nodes. The nerves form two sympathetic 

 plexuses, the submucous and the myenteric, from which the walls are supplied as will be de- 

 scribed later for the stomach and intestine. Branches are received from the sympathetics, and 

 from the vagus, including the recurrent nerve. 



Development. — The embryonic oesophagus is at first relatively very short, but lengthens 

 rapidly in connection with the descent of the stomach. The upper end is still high in children, 

 corresponding to the higher vertebral level of the larynx. The lining epithelial cells are primi- 

 tively cylindrical in form, and irregular ciliated areas are found from the third foetal month up 

 to birth (F. T. Lewis). In the embryo of about 20 mm., there is a proliferation of the epithelium, 

 associated with the formation of vacuoles, but the lumen does not appear to be normally oc- 

 cluded. The primary longitudinal folds of the mucosa appear early (third month) and at the 

 lower end seem to participate in the rotation of the stomach (F. P. Johnson). The superficial 

 oesophageal glands appear about the fourth month (78 mm.), the deep glands at 240 mm. 

 (Johnson). Of the muscular layers, the circular appears first (at about 10 mm.) the longi- 

 tudinal slightly later (17 mm.). 



Variations. — LTsually a bundle of smooth muscle connects the oesophagus with the left 

 bronchus [m. broncho-oesophageus], and another similarly with the left mediastinal pleura [m. 

 pleuro-oesophageus]. More rarely there are similar bands connecting with the trachea, peri- 



