270 



THE DIGESTIVE ORGANS. 



is, however, no sharply defined boundary between fundus and 

 pylorus, but a transitional zone in which changes gradually take 

 place. Toward the pylorus the gastric crypts gradually become 

 deeper and the parietal cells decrease in number. Here also the 

 glands branch more freely. In the pylorus itself the crypts fre- 

 quently extend half-way through the thickness of the mucous 

 membrane, often even penetrating nearly to the muscularis mucosae, 

 in which case the corresponding tubules become tortuous and arch 

 over the muscularis mucosae. The glands of the pyloric region 

 are therefore to be classified as branched tubular glands (De Witt). 



Epithelium - 

 of fold be- 

 tween gas- 

 tric crypts. 



Pyloric - 

 gland. 



Mucosa. -~- 



Muscularis 

 mucosae. 



Fig. 211. From vertical section through human pylorus ; X about 60. 



Among the branched pyloric glands are found glands which show 

 no distinct branching. The most important feature is that in the 

 great majority of the tubules only a single variety of cell is pres- 

 ent in the pyloric gland. (Only here and there are found parietal 

 cells in the pyloric glands of the human stomach.) These cells 

 may be compared with the chief cells of the neck regions of the 

 fundus glands, in that they show no zymogen granules, and prozy- 

 mogen only in small quantity, and on staining with special stains, it 

 can be shown that their secretion is mucus. They are of colum- 

 nar shape, and more uniformly so than the chief cells of the fundus 



