layers of stomach wall

 

Layers of Stomach Wall

Walls of stomach consists of 4 layers of tissue. From deep (external) to superficial (internal) are-

1. Serosa (outermost layer)

2. Muscularis externa

3. Submucosa

4. Mucus membrane or mucosa (innermost layer)

1. Serosa

Serous is outermost layer which covers the stomach. Covering stomach consist of visceral peritoneum.

At greater curvature, visceral peritoneum continues inferiorly as greater omentum (fatty apron; contains large amount of fat) protecting and insulating abdominal organ.

Greater Omentum 

Greater omentum extensive folded membrane that extends from greater curvature of stomach to the back wall and down to pelvic cavity.

Greater omentum rich supply with blood and lymph vessels and lymph nodes.

Greater omentum have ability to isolate area slowly developing inflammation.

For example - Chronic appendicitis preventing the spread of infection to the peritoneal cavity.

Lesser Omentum

Lesser curvature of stomach, visceral peritoneum extends up to liver as lesser omentum (double layer of peritoneum).

2.Muscularis externa; Smooth muscle

Muscularis is a layer of muscle.

1. Outmost longitudinal layer

Continuous with muscles of esophagus.

2. Middle circular layer

 Wrapped around body of stomach.

Thickest muscular layer- forms pyloric sphincter (strongest).

3.Innermost oblique layer

Primarily to body of stomach.

Arrangement allows for churning motion, gastric activity and peristaltic movement.

3. Submucosa

Submucosa composed of areolar connective tissue. It rich in blood vessels, lymphatic vessels, and nerves.

Submucosa attaches the mucosa to the muscularis externa. This layer supports the mucosa. Submucosa connect mucosa to muscularis externa.

4. Mucus membrane or mucosa

Mucosa is stomach innermost layer or lining. It contains the glands; produce enzyme and acid; hydrochloric acid and pepsin which help digest food.

When stomach empty, mucus membrane contain longitudinal folds (branching wrinkle) called rugae.

Stomach line with simple columnar epithelial cells. Simple columnar epithelium have million of gastric pits (Small pore). Each gastric pits are 3-8 types of gastric gland.

Gastric Glands

There are three types of gastric glands. Gastric pits are opening for these glands-

1. Cardiac gland

Near cardiac orifice.

2. Pyloric gland

In pyloric canal.

3. Fundus gland

In fundus and body of the stomach.

Secretion from gastric gland flow- into gastric pits- then into lumen of the stomach.

Epithelial Cell of Stomach Wall

Secretion of the Stomach; Gastric juice/Gastric acid/Stomach acid.

Epithelial cell of stomach divided into five groups-

1. Surface mucus cells

Cell on the surface and lines the gastric pit, produce mucus.

2. Mucus neck cells

Secrete mucus, located near opening of glands.

3. Parietal cells

Produce hydrochloric acid, and intrinsic factor.

4. Chief cells

Secrete pepsinogen and gastric lipase.

Mucus neck, parietal cell and chief cell are exocrine gland cell that secrete their product into lumen of stomach. Secretion of mucus, parietal cell and chief cell are collectively called Gastric juice.

5. Enteroendocrine cells (G-cells)

Cell produce hormone gastrin, cell located at pyloric antrum.

Characteristic of Gastric Juice

Stomach acid or gastric acid is a watery, colorless fluid that secreted by stomach mucosa in response to food.

Amount of gastric juice secretion - gastric mucosa secretes 1.5 litres of gastric juice daily.

Composition of Gastric Juice

Major component of gastric juice are-

1. Water

2. Mineral salt

3. Mucus

4. Hydrochloric acid

5. Intrinsic factor

6. Enzyme; pepsinogen, gastric lipais (LIPF)