156 



NORMAL HISTOLOGY. 



Lymph-nodule 

 in niucosa 



and constitute a constant narrow zone surrounding the termination of the 

 oesophagus. Lying entirely within the tunica propria, their bases abutting 

 against the muscularis mucosae, they open on the free surface by wavy 

 ducts that pierce the summit of the papillae and traverse the epithelium. 

 Less definite and much less constant groups of similar tubules occur within 

 the mucosa, along the sides, at the upper end of the oesophagus; these have 

 been described as the superior cardiac glands. 



The muscular coat of the oesophagus includes an inner circular and 

 an outer longitudinal layer, although the individual bundles are often irregu- 

 larly and obliquely disposed, and above somewhat intermingled. The histo- 

 logical character of the muscular tissue varies in different parts of the tube. 



Thus in a general way, within 

 approximately the lower half of 

 the oesophagus the muscle is 

 entirely unstriped; within the 

 second quarter both striated 

 and unstriped muscle appear; 

 while within the first quarter 

 striated muscle almost exclu- 

 sively is present. Although 

 within the longitudinal layer 

 unstriped fibres do not appear 

 within the upper fourth or fifth, 

 the zone of purely striated 

 fibres within the circular layer 

 includes only about the first 

 2. 5 cm. , below which level un- 

 striped fibres gradually become 

 more abundant. 



The fibrous coat is poor- 

 ly developed above the dia- 

 phragm, consisting of areolar 

 tissue that attaches the oesophagus to the surrounding structures, aided in 

 places by strands of unstriped muscle. After piercing the diaphragm, the 

 peritoneum contributes a limited serous coat, which, with its connective 

 tissue stroma and surface mesothelium, constitutes a more definite investment 

 for the alimentary tube from this point on. 



The blood-vessels of the oesophagus, after sending twigs directly for 

 the supply of the muscular tissue, gain the loose submucous layer, within 

 which lie branches of considerable size. From these, in addition to small 

 vessels for the circular muscle and the glands within the submucosa, twigs 

 are given off that enter the mucous membrane and break up into capillary 

 networks from which terminal loops invade the papillae. The venous radi- 

 cles of the mucosa are tributary to the veins within the submucous tissue, 

 from which the larger trunks accompany the arteries. 



The lymphatics are represented by networks within the submucous 

 and muscular coats. The former take up the fluid collected by the lymph- 

 spaces of the mucous membrane. These networks are connected by inde- 

 pendent trunks with neighboring lymph-nodes, those from the lower end 

 of the oesophagus passing to the upper nodes of the coeliac group. 



The nerves of the oesophagus include both medullated and nonmedul- 

 lated fibres. The former, largely from the vagi, contribute fibres supplying 

 the striated muscle, in which they end in motor plates. The nonmed- 



Submucous layer 



Muscle 



FIG. 195. Section of mucous membrane of oesophagus, 

 showing lymph-nodule. X 55. 



