Page 571 - Atlas of Histology with Functional Correlations

called chyme. The reduction of bolus is performed by strong, muscular

peristaltic contractions of the stomach wall when food enters the stomach.
With the pylorus closed, the muscular contractions churn and mix the
stomach contents with gastric juices produced by the gastric glands.
Neurons and axons located in the submucosal nerve plexus and myenteric
nerve plexus of the stomach wall regulate the peristaltic activity. In addition,

the stomach also performs some absorption; however, this is limited to
absorption of water, alcohol, salts, and certain drugs.

GASTRIC GLAND CELLS IN CARDIA,

BODY, AND FUNDUS OF STOMACH

Cardiac glands are limited to the narrow cardiac region of the stomach that
surrounds the esophageal opening. They are primarily mucous cells. The
mucus produced by these glands and the cardiac glands of the esophagus
neutralize the gastric reflux and protect the esophageal lining.

Chemical reduction or digestion of food in the stomach is the main

function of gastric secretions produced by different cells in the gastric glands,
especially by cells in the fundus and body of the stomach. The main
components of the gastric secretions are pepsin, hydrochloric acid, mucus,

gastric intrinsic factor, water, lysozyme, and different electrolytes.

The surface or luminal epithelial cells of the stomach and the mucous
neck cells of the gastric pits secrete thick layers of mucus. This secretion
covers, lubricates, and protects the stomach surface from the corrosion by
acidic gastric juices secreted by the gastric glands and the ingested material.

The major component of gastric juice is the hydrochloric acid (HCL)

produced by parietal cells of the gastric glands. In humans, parietal cells also
produce gastric intrinsic factor, a glycoprotein that is necessary for the
absorption of vitamin B from the terminal portion of the small intestine.
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Vitamin B is necessary for erythrocyte (red blood cell) production
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(erythropoiesis) in the red bone marrow. Deficiency of this vitamin leads to

the development of pernicious anemia, a disorder of erythrocyte formation.

Chief (zymogenic) cells are filled with granules that contain the
proenzyme pepsinogen, an inactive precursor of pepsin. Release of
pepsinogen during gastric secretion into the acidic environment of the
stomach converts the inactive pepsinogen into the highly active, proteolytic

enzyme pepsin. This enzyme digests large protein molecules into smaller

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