280 



THE DIGESTIVE SYSTEM 



abundant at the deeper portion of the fundus, where they form a 

 complete lining for the tubule. In this portion the parietal cells are 

 crowded away from the lumen and consequently produce a bulg- 

 ing of the basement membrane. Toward the neck of the tubule 



the parietal cells are 

 more abundant and 

 draw progressively 

 nearer and nearer 

 a the lumen until, in 

 the neck of the 

 gland, they possess 

 a considerable free 

 surface which en- 

 croaches upon the 

 glandular lumen. 



The Chief Cells 

 (central, peptic, or 

 adelomorphous cells) 

 possess a cuboidal 

 or pyramidal shape 

 and a granular cyto- 

 plasm. The sphe- 

 roidal nucleus is sit- 

 uated in the proxi- 

 mal or attached end, 

 while the distal end 

 of the cell is its 

 most granular por- 

 tion. The breadth 

 of the granular zone 

 is dependent upon 

 the state of secre- 

 tory activity, the 

 coarse z y m o g e n 

 granules accumulat- 

 ing during periods 



of rest and disappearing by secretion during activity. Thus the 

 granular distal zone increases in breadth during rest and decreases 

 during activity. The whole cell, also, becomes shrunken after 

 prolonged secretion, but during rest it becomes so swollen that 

 with its neighbors it nearly occludes the lumen of the tubule. 



d e d 



FIG. 231. THE MUCOSA OF THE FUNDUS KEGION OF THE 



DOG'S STOMACH. 



a, gastric crypts ; >, neck region, and c, fundus por- 

 tions of the secreting glands, the parietal cells being 

 much more abundant in the former; d, muscularis mu- 

 <?, submucosa. Hematein and eosin. Photo, x 80. 



