STOMACH

Location: under the diaphragm.

Function: receives the bolus of macerated food from the esophagus. Mixing and partial digestion of the food produces a pulpy fluid mix -chyme that passes into the intestine for further digestion and absorption.

Anatomic featues

Consist of three anatomical segments: cardia (near the esophageal orifice), fundus - the larger part between the cardia and pylorus, pylorus (proximal to the pyloric sphincter).
Rugae -longitudinal folds and ridgers composed of the mucosa and underlying submucosa.
Mamillated areas - bulging irregular areas formed by grooves or shallow trenches.
Gastric pits or faveolae -numerous openings of fundic glands.

MUCOSA

Function:

secretory - the glands of stomach secrete nearly 2 liters of fluid each day
barrier - separates the lumen of the digestive tract, which is continuous with the environment, from the body of the organism.

Composition:

simple columnar epithelium with surface mucous cells.

Function: mucus secretion that provides protection to the epithelium against abrasion and from acid content of gastric juice.

lamina propria - loose connective tissue, blood capillaries and lymphatic capillaries, nerves, diffuse lymphatic tissue, lymphatic nodules, glands, smooth muscle cells.
muscularis mucosae - relatively thin inner circular and outer longitudinal layers of smooth muscle. In some regions a third layer may be present.

Function: facilitates the outflow of the gastric gland secretion.

FUNDIC (GAGTRIC) GLANDS

Location: lamina propria of gastric mucosa of fundus

Function: production of the digestive juice.

Composition: simple branched tubular glands that extend from the bottom of the gastric pit to the muscularis mucosae.

Mucous neck cells

Function: mucus secretion.

Chief cells

Function: secrete pepsinogen, that on contact with the acid of the gastric juice, convert to proteolytic enzyme - pepsin.

Parietal (oxyntic) cells

Function: secrete HCl and intrinsic factor - glycoprotein that complexes with vitamin B₁₂.

Enteroendocrine cells

Function: sample the contents of the gland lumen and release their hormones based on their sensing response.

Undifferentiated cells

Function: give rise to the mature cells.

Location: neck region of the gland.

CARDIAC GLANDS

Location: narrow region of the stomach - the cardia.

Function: mucus secretion.

Composition: simple tubular, occasionally branched glands.

Mucus-secreting cells

Enteroendocrine cells

Function: sample the contents of the gland lumen and release their hormones based on their sensing response.

PYLORIC GLANDS

Location: in the pyloric antrum and the pylorus.

Function: mucus secretion.

Composition: simple tubular branched glands.

Mucus-secreting cells

Enteroendocrine cells

Function: sample the contents of the gland lumen and release their hormones (among them - gastrin that stimulates acid secretion by parietal cells in fundic glands).

occasional Parietal (oxyntic) cells

Function: secrete HCl

SUBMUCOSA

Composition: moderately dense irregular connective tissue, blood vessels, lymphatic vessels, nerve network and ganglion neurons (Meissner's plexus), white adipose tissue.

MUSCULARIS EXTERNA

Function:

receiving the large volumes of ingested food and drink during the meal
mixing the ingested food with gastric juices so that digestion can occur

propelling the gastric contents into the small intestine.

Composition: Three layers of smooth muscle (outer - longitudinal, middle - circular and inner - oblique) may be difficult to discern, nerve network and ganglion neurons (Auerbach's plexus).

SEROSA (PERITONEUM)

Composition: simple squamous epithelium - mesothelium, small amount of loose connective tissue, white adipose tissue, large blood vessels, lymphatic vessels, nerve trunks.