CHAO: DIGESTIVE SYSTEM OF CUNNER 



MUCOSA. — The epithelium of the anterior 

 esophagus is a modified transitional type (Fig- 

 ure 9) with large mucous cells extending to 

 various depths from the surface. While the 

 esophagus proceeds posteriorly, the stratified 

 epithelium gradually becomes simple columnar 

 in the transitional zone between the esophagus 

 and intestine. The flattened nucleus of each 

 mucous cell is pressed against the base by the 

 large vacuole. The mucous secreting cells do 

 not narrow appreciably where they open into 

 the lumen. They can occupy nearly the entire 

 surface and thickness of the epithelium, and 

 they decrease in numbers from anterior to 

 posterior. Also, smaller mucous cells with large 

 vacuoles filled with mucous were found among 

 the basal cells in the anterior half of the 

 esophagus (Figure 9). The columnar epithelium 

 appears gradually while the mucous cells de- 

 crease toward the transitional zone. The large 

 oval nuclei of columnar cells are located at 

 the basal level under the level of the mucous 

 cells in the transitional zone. The basal cell 

 layer appears to maintain a uniform thickness 

 throughout the esophagus. These cells are small 

 with relatively large nuclei. Occasionally, taste 

 bud like structures were found at the tip of 

 major folds in the most anterior part of the 

 esophagus. No cilia are j^resent on the epi- 

 thelium of the esophagus. The mucosal layer 



of the esophageal-intestinal valve is similar to 

 that of the transitional zone, except for an 

 increased number of mucous secreting cells, 

 especially, in the distal i)ortion of the valve 

 (Figure 10). 



SUBMUCOSA.— The submucosal layer is an 

 areolar connective tissue between the epithelium 

 and the muscularis. The stratum compactum 

 (Figure 9) is a layer of compacted fibrous 

 connective tissue attached to the basal mem- 

 brane of the epithelium. The rest of the areolar 

 connective tissue is highly vascularized. Longi- 

 tudinal bundles of striated muscles extend from 

 the pharynx to the base of the esophageal- 

 intestinal valve in the connective tissue. Also, 

 in the anterior half of the esophagus, these 

 longitudinal muscles are dispersed irregularly 

 up to half of the depth of the folds in the sub- 

 mucosa (Figures 7, 9). Collagen fibers constitute 

 the framework of the submucosal layer. The 

 vascular system is scattered in this framework, 

 and leucocytes, lymphocytes, fibrocytes, and 

 granular cells are present. The granulocytes 

 first appear in the i)osterior half of the esopha- 

 gus (Figure 8). The submucosa becomes much 

 thicker on both sides of the esophageal-intestinal 

 valve. Increasing numbers of granulocytes 

 appear in the submucosa of the intestinal side 

 of the valve. 



Figure 9. — Mucosa and submucosa 

 of the anterior esophagus of a 200-mm 

 SL cunner (X 400, x.s.). m, mucous 

 secreting cell; sc. stratum compactum; 

 St, striated muscle. 



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