The gastric mucosa is the protective lining of the stomach. Its cells, which produce mucus, enzymes and gastric acid, contribute significantly to the smooth process of digestion.
What is the gastric mucosa?
The gastric mucosa is the reddish-gray to pinkish-colored layer of mucous membrane that lines the inside of the stomach. The thick gastric mucosa protects the wall of the stomach from stomach acid. Stomach acid is a strong acid, with a pH of between 1 and 1.5 in the fasting state. This means that without the protective gastric mucosa, the stomach tissue would be severely damaged by stomach acid. Without this thick mucosal layer, the stomach would digest itself. The gastric mucosa is responsible for the production of gastric juice. This is a fluid that is essential for digestion and contains gastric acid as well as mucus and various enzymes such as pepsin. Pepsin is an enzyme that breaks down proteins ingested through food.
Anatomy and structure
Depending on the state of filling of the stomach, the gastric mucosa is more or less folded. In the empty stomach, these longitudinal folds are greatly expanded. The longitudinal folds converge at the gastric portal. This regulates the transport of food into the duodenum and is closed when at rest. The depressions of the gastric mucosa caused by the folds are also called gastric streets. Liquids can pass through the stomach quickly by means of these gastric streets. The gastric mucosa consists of three main layers. The mucosal epithelium contains cells that produce mucus and gastric acid. Directly following the epithelial layer is a connective tissue layer, the lamina propria, also called the intrinsic layer. The intrinsic layer has a large number of glands. This is followed by a muscle layer, which is composed of smooth muscle cells. Through this layer, there is contraction or regulation of the fold relief in the stomach.
Function and tasks
The function of the gastric mucosa depends on its location within the stomach. In the area of the entrance to the stomach, there is an increased number of cells that produce mucus. In addition, lysozyme is produced, which is helpful in defense against pathogens. The cells in the main part of the stomach are responsible for the majority of stomach acid production. The acidic environment in the stomach also kills many pathogens, preventing them from causing harm to the body. The cells and glands in the gastric mucosa are protected from the destructive effects of hydrochloric acid in the stomach by the thick layer of mucus. In the area of the stomach outlet, in turn, there are more mucus-producing cells so that the processed food pulp reaches the duodenum in a less acidic state. Basically, a distinction is made between three different cell types that are responsible for the function of the gastric mucosa. The vestibular cells produce gastric acid and intrinsic factor; this is a protein that enables the absorption of cobalamin (vitamin B12). Enzymes such as pepsinogen, a precursor of pepsin, are produced in the main cells. In addition to these protein-cleaving enzymes, enzymes that break down fat are also formed here. The accessory cells are mainly responsible for the production of mucus, which protects the wall of the stomach from gastric acid.
Diseases and ailments
A large proportion of people experience gastritis, or inflammation of the gastric mucosa, at least once in their lives. Depending on the severity of the inflammation, the entire stomach lining may be affected or only smaller areas. Inflammation of the gastric mucosa occurs when the balance that exists in the physiological state between factors that protect the gastric mucosa and factors that damage the gastric mucosa is upset. If for some reason the accessory cells are prevented from producing sufficient mucus, the stomach wall is no longer adequately protected from the hydrochloric acid in the gastric juice, resulting in damage to the deeper layers of the stomach and subsequently in an inflammatory reaction. There are many possible causes for this process. Among the most common are excessive alcohol consumption and smoking. Both are harmful to the stomach lining. Taking medications, such as painkillers, can also lead to stomach problems. The best-known drugs that damage the stomach lining include acetylsalicylic acid in aspirin and diclofenac in Voltaren.In bacterial food poisoning, toxins produced by the bacteria cause damage to the stomach lining, resulting in diarrhea and vomiting.
