stomach functions

Stomach location

Located in the left upper quadrant, immediately inferior to the diaphragm.

Overall function of the stomach

Churns and mixes food with gastric secretions, continuing mechanical and chemical digestion and converting the bolus into chyme.

Four main regions of the stomach

Cardia, fundus, body, and pylorus.

Cardia location and function

• Small, narrow region where the esophagus enters the stomach;

• receives the swallowed bolus.

Fundus

• Dome-shaped region superior and lateral to the esophageal connection;

• contains gastric glands involved in gastric secretion and digestion.

Body of the stomach

• Largest region, located inferior to the cardiac orifice and fundus;

• major region for churning, mixing, and chemical digestion.

Pylorus

• Narrow, funnel-shaped terminal region of the stomach leading toward the duodenum;

• helps regulate the movement of chyme into the small intestine.

Two subdivisions of the pylorus

Pyloric antrum and pyloric canal.

Pyloric sphincter

• Thick ring of circular smooth muscle surrounding the pyloric orifice that

• regulates when chyme enters the small intestine.

Rugae

Folds of the stomach lining visible when empty; allow the stomach to expand as it fills.

Greater curvature

Long, inferior convex border of the stomach; provides attachment for the greater omentum.

Lesser curvature

Superior concave border of the stomach; provides attachment for the lesser omentum.

Greater omentum

Peritoneal fold attached to the greater curvature that hangs over the intestines, forming a protective apron over abdominal organs.

Lesser omentum

Thin peritoneal fold extending between the lesser curvature of the stomach and the liver, connecting the two organs.

Epithelium lining the stomach

Simple columnar epithelium.

Gastric pits

Depressions in the stomach lining continuous with branched tubular gastric glands; provide access to gastric gland secretions.

Three layers of smooth muscle in the stomach's muscularis

Inner oblique, middle circular, and outer longitudinal.

Function of the stomach's three muscular layers

Produce strong contractions that churn and blend food with gastric secretions.

Secretion and function of surface mucous cells

Secrete mucin and bicarbonate to form a thick alkaline mucus that protects the stomach lining from acid and digestive enzymes.

Secretion and function of mucous neck cells

Secrete a thinner, less-alkaline mucus that lubricates and protects the stomach from mechanical injury.

Secretions and functions of parietal cells

Secrete hydrochloric acid ($HCl$), which denatures proteins, and intrinsic factor, which binds vitamin $B_{12}$ to assist its absorption in the ileum.

Secretion and function of chief cells

Secrete pepsinogen, which is converted by stomach acid into pepsin to digest denatured proteins.

Secretion and function of enteroendocrine cells

Secrete gastrin, which stimulates gastric secretions and increases gastric muscle contractility.

Stomach regions containing all five major cell types

Fundus and body.

Path of material movement through the stomach

$$\text{Esophagus} \rightarrow \text{Cardia} \rightarrow \text{Fundus/Body} \rightarrow \text{Pylorus} \rightarrow \text{Pyloric Sphincter} \rightarrow \text{Duodenum}$$

Structural distinction between the greater and lesser omenta

Greater omentum attaches to the greater curvature and hangs over the intestines; lesser omentum connects the lesser curvature to the liver.