THE DIGF.STI\'K SYSTEM 



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two distinct layers of smooth muscle, an inner circular and an outer 

 longitudinal. The latter is not continuous. 



4. The fibrous coat consists of bundles of white fibrous tissue with 

 many elastic fibres. It serves to connect the oesophagus with the 

 surrounding structures. 



Two kinds of glands occur in the oesophagus. 



Fig. 151. — Transverse Section through Wall of Dog's (Esophagus. X18. (Bohm 

 and von Davidoff.) a, Epithelium; b, stroma; c, muscularis mucosae; d, submucosa; e, 

 circular muscle layer; /, longitudinal muscle layer; g, fibrous layer. 



(i) Mucous Glands. — These are of the same structure as those 

 of the tongue, but much smaller. They lie in the submucosa and are 

 distributed throughout the entire oesophagus, though most numerous 

 in its upper third. The ducts pass obHquely downward on their way 

 to the surface. Just before entering the muscularis mucosae the duct 

 widens out to form a sort of ampulla. Beyond this it again becomes 

 narrow and enters the epithelium in the depression between two 

 adjacent papillae. A small lymph nodule is usually attached to the 

 duct as it passes through the tunica propria. 



(2) Simple Branched Tubular Glands. — These resemble the 

 glands of the cardiac end of the stomach, but branch much more 





