DIGESTIVE SYSTEM. 



i8 7 



Crypt. 



Parietal cell. 



layer of longitudinal smooth muscle fibers. A liberal 

 supply of connective tissue is associated with this 

 muscle. This layer, therefore, offers resistance to 

 an invasion of bacteria, while the muscular contrac- 

 tion relieves pressure to the rich blood supply in the 

 submucosa just external to it, and at the same time 

 exerts pressure upon the gastric glands. 



Gastric Glands. 

 These are widely dis- 

 tributed and per- 

 haps the most impor- 

 tant structures of 

 the mucosa. They 

 are simple tubular, 

 except in the pyloric 

 region, where many 

 of them are 

 branched. Usually 

 several glands open 

 into each crypt, the 

 latter representing 

 a circular pit-like 

 evagination of the 

 epithelial surface . 

 The wall of each 

 gland consists of 

 simple epithelium and two kinds of cells are present : 

 (i) chief cells, which are by far the most numerous; 

 these are round or cuboid cells, with central nucleus 

 that stains blue with hematoxylin ; (2) parietal cells , 

 which are less numerous, larger, and have a granular 

 cytoplasm that takes the red eosin stain. They inter- 



Chief cell. 



Fig. 136. Simple tubular gland from 

 stomach. 



