Gastric mucosa

Gastric mucosa is the mucous membrane layer of the stomach which contains the glands and the gastric pits. In humans, it is about 1 mm thick and its surface is smooth, soft, and velvety. It consists of epithelium, lamina propria, and muscularis mucosae.

Structure

The gastric mucosa is divided into two main regions: the body and the fundus, with the same structure, and the antrum, which has a slightly different organization. The surface of the mucosa is covered by a simple columnar epithelium which is composed of mucous cells. These cells secrete a bicarbonate-rich mucus that coats the stomach lining, providing a protective layer against the acidic environment of the stomach.

Beneath the epithelium is the lamina propria, a layer of connective tissue that contains blood vessels, nerves, and various cells of the immune system. This layer supports the epithelium and helps to regulate the exchange of substances between the epithelium and the underlying blood vessels.

The deepest layer of the gastric mucosa is the muscularis mucosae, a thin layer of smooth muscle that allows the stomach lining to fold and change shape as the stomach fills and empties.

Function

The primary function of the gastric mucosa is to secrete gastric juice, which is a mixture of hydrochloric acid (HCl), enzymes, and mucus. The acid and enzymes help to break down food, while the mucus protects the stomach lining from digestion by the acid. The gastric mucosa also contains specialized cells, including:

• Parietal cells, which secrete hydrochloric acid and intrinsic factor, the latter being essential for the absorption of vitamin B12.
• Chief cells, which secrete pepsinogen, the inactive precursor of the enzyme pepsin that digests proteins.
• G cells, which secrete the hormone gastrin into the bloodstream. Gastrin stimulates the parietal cells to increase acid secretion.

Clinical significance

The gastric mucosa can be affected by various conditions, including gastritis, peptic ulcer disease, and gastric cancer. Gastritis is an inflammation of the stomach lining, which can be caused by infection with Helicobacter pylori, excessive alcohol consumption, chronic vomiting, stress, or the use of certain medications such as aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs). Peptic ulcer disease involves the formation of ulcers, or sores, in the stomach lining or the upper part of the small intestine. Gastric cancer is a disease in which malignant (cancer) cells form in the lining of the stomach.

Diagnosis and treatment

Diagnosis of diseases affecting the gastric mucosa typically involves endoscopy, a procedure in which a flexible tube with a light and camera (endoscope) is inserted through the mouth and into the stomach to visualize the stomach lining. Treatment depends on the specific condition but may include medications to reduce acid production, antibiotics to treat Helicobacter pylori infection, or surgery in severe cases.