A. Functions
1. Storage
2. Mechanical breakdown of food
3. Chemical breakdown of food
vitamin B12 in the small intestine]
5. Protection
B. Gross
Anatomy
1. The adult
stomach varies from 15–25 cm long; its diameter and volume vary depending on
the amount of food it contains.
a. The major
regions of the stomach include the cardiac region, fundus, body, and pyloric
region.
b. The convex
lateral surface of the stomach is its greater curvature, and its convex medial
surface is its lesser curvature.
c. Extending
from the curvatures are the lesser
omentum and the greater omentum,
which help to tie the stomach to other digestive organs and the body wall.
C. Microscopic Anatomy
1. The
surface epithelium of the stomach mucosa is a simple columnar epithelium composed of goblet cells, which produce a protective two-layer coat of alkaline
mucus.
2. The
gastric glands of the stomach produce gastric juice, which may be composed of a
combination of mucus, hydrochloric acid, intrinsic factor, pepsinogen,
and a variety of hormones.
a. Mucous neck cells; mucus
b. Parietal cells: hydrochloric acid and
intrinsic factor
c. Chief cells: pepsinogen
d. Enteroendocrine cells: histamine, serotonin,
somatostatin, gastrin, etc.
3. H. pylori [You da, man, Barry
Marshall!]
D. Digestive
Processes Occurring in the Stomach
1. Gastric
secretion is controlled by both neural and hormonal mechanisms and acts in
three distinct phases: the cephalic
phase, the gastric phase, and
the intestinal phase.
2. The
reflex-mediated relaxation of the stomach muscle and the plasticity of the visceral
smooth muscle allow the stomach to accommodate food and maintain internal
pressure.
3. The
interstitial cells of Cajal establish the stomach’s basic electrical rhythm of peristaltic waves.
4. Regulation
of Gastric Secretion
a. Phase 1: Cephalic [Reflex]
b. Phase 2:
Gastric
c. Phase 3:
Intestinal
5. Regulation of Gastric Emptying
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