172 



THE DIGESTIVE SYSTEM 





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(Fig. 109.) Small pits, or gastric crypts, are easily visible with 

 slight magnification of the internal mucosal surface. The mucosa 

 is quite thick, due to the presence of simple tubular gastric glands 

 which are roughly divisible into three types: the cardiac, fundic, 

 and pyloric glands. 



Cardiac glands, found where the esophagus and the stomach join, 

 are relatively few in number. In these glands the cells are chiefly 



of the mucous type. Cardiac glands are 

 small, simple branched tubular in form, 

 with a short excretory duct lined by col- 

 umnar cells. The twisted secretory tubules 

 are formed from cuboidal or columnar 

 cells. There is great variation in the 

 number of cardiac glands, and in some 

 cases they are absent. 



Fundic glands are most numerous and 

 produce the essential elements of gastric 

 juice, the cardiac and pyloric glands may 

 function mainly as mucous glands. The 

 fundic glands are branched tubular in form, 

 with a relatively short excretory portion 

 extending into the gastric pit, and 

 glandular portions that are generally very 

 much longer. (Fig. 110.) The cells of the 

 gastric pit walls are columnar in type. 

 A constricted portion of the gland near 

 the gastric pit is called the neck, and 

 from it each secretory tubule leads to a 

 dilated end. Two types of cells, the chief 

 or central cells and the parietal cells make 

 up the secreting tubules. The chief cells 

 are roughly pyramidal, their cytoplasm 

 shows secretion grainiles in the end toward 

 the lumen, and nuclei are located in the 

 basal half. The secretory acti\ity of these 

 cells is associated with the production of zymogen granules, which 

 give rise to the pepsin of the gastric juice. Scattered along the 

 secreting tubule, between the chief cells and the basement mem- 

 brane, and more numerous toward the neck, are the parietal cells 



Fig. 110. — Diagram of 

 tissues in the body or fundus 

 of stomach of a mammal. 

 A, mucosa with simple, 

 branched tubular glands. 

 The black dots represent 

 parietal cells. Note mus- 

 cularis mucosa at base. B, 

 submucosa with artery and 

 vein. C, muscularis. This 

 being a longitudinal sec- 

 tion, the inner circular mus- 

 cle is cut across and the 

 outer longitudinal muscle is 

 cut lengthwise. D, adven- 

 titia, which is a serosa with 

 an external limiting mem- 

 brane of mesothelium. 



