358 



THE DIGESTIVE SYSTEM 



other hand, is chiefly confined to the ducts, which occupy the superficial 

 two-thirds to three-fourths of the entire depth of the mucous membrane. 

 In the pyloric mucosa, therefore, three zones may be distinguished: a 

 superficial, middle, and deep. 



The superficial zone is narrow and contains the wide-mouthed crypts 

 or foveolse which are lined by tall columnar 

 cells similar to those of the f undus crypts. 



The middle zone contains the narrowed 

 portion of the ducts and is the broadest of 

 the three zones. Several of the narrow ducts 

 open into each foveola and further branch- 

 ing of the secreting tubnles occurs to a lim- 

 ited extent. The epithelium of the ducts is 

 of the low columnar variety, whose deeply 

 stained basal nuclei are spheroidal or ovoid, 

 and are progressively flattened as the se- 

 creting portion is approached. The super- 

 ficial cytoplasm of these cells stains readily 

 with muchematein and often has a coarsely 

 granular or reticular appearance. 



The deepest zone contains the convoluted 

 secreting portions and is sharply marked off 

 from the adjacent ducts, since in a transec- 

 tion of the stomach wall its tubules, owing 

 to their convolution, are nearly all cut 

 across, while the ducts are in longitudinal 

 section; the clear tall columnar epithelium 

 and broad lumen of the fundus also, contrast 



strongly with the low finely granular epithelium and narrow lumen 

 of the duct. It is this narrow zone of peculiar convoluted tubules, 

 lying just within the muscularis mucosae, by which the pyloric mucous 

 membrane is most readily distinguished from all other regions of the 

 alimentary canal. 



The tall columnar cells of the fundus possess a remarkably clear 

 cytoplasm which reacts distinctly, though feebly, to the specific stains 

 for mucus. The nuclei are flattened against the base of the cell and 

 thus contrast sharply with the spheroidal nuclei of the ducts and crypts. 

 During secretion the cells become shrunken and their nuclei approach 

 the center of the cell and become more nearly ovoid or spheroidal in 

 shape. 



FIG. 335. SECRETORY CAP- 

 ILLARIES OF THE FUNDUS 

 GLANDS OF THE DOG'S 

 STOMACH. 



Golgi stain. (After Miiller, 

 from Oppel.) 



