GASTRIC GLANDS 



113 



The mucous coat is a pink membrane which is not elastic, 

 and, though smooth when the stomach is fully distended, 

 is thrown into folds when the organ is empty. This mem- 

 brane derives its pink appearance from the blood vessels 

 underlying it and becomes much redder 

 during digestion, as these submucous 

 capillaries become distended with blood. 

 When examined with a lens the mucous 

 membrane is seen to be covered with 

 shallow pits. These pits are the mouths 

 of many simple tubular glands (the gas- 

 tric glands) which secrete the digestive 

 fluid of the stomach. This fluid is 

 called the gastric juice. Between these 

 special glands are the ordinary mucous 

 glands which secrete the lubricating 

 mucus. 



Gastric glands. — These glands (see 

 Fig. 38) are simple tubes lined with 

 epithelial cells, formed by the folding of 

 the mucous membrane. Between suc- 

 cessive tubes project layers of the sub- 

 mucous capillaries. These capillaries 

 furnish the food out of which the cells 

 manufacture the fluids and ferments 

 used in stomach digestion. The cells 

 of these glands are of two kinds. Those which secrete 

 the enzymes, pepsin and rennin, are called the chief cells 

 tgdistinguish them from another group called the border 

 ceZZswhich are supposed to secrete hydrochloric acid. The 

 exact function of these border cells is still unknown. (For 

 arrangement of these cells see Fig. 38.) 



EDDY. PHYS. — 8 



Fig. 38 — a peptic 

 gland, from cardiac 

 end of stomacli. 

 Very mucli magni- 

 fied. Af central or 

 chief cells, which 

 make pepsin ; 5, 

 herder or parietal 

 cells, which make 

 acid. [From Miller's 

 Histology.] 



