Which cells is pepsinogen excreted from?
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The most important substances secreted in the stomach to break down food are the protein-splitting enzyme pepsin (excreted by the stomach as a proenzyme pepsinogen) and hydrochloric acid. The acid is used to lower the pH value, as pepsin is only active below a pH value of 4. The crucial importance of hydrochloric acid for the decomposition of food and the formation of ulcers has long been known, but the causes were not understood for a long time.
The most obvious cause of gastric and duodenal ulcers seems to be the excessive production of hydrochloric acid (hypersecretion) in connection with a reduced resistance of the gastric mucosa. The hydrochloric acid is formed in the base and body of the stomach in order to initiate the rapid digestion of the food ingested. Acid production is increased by spicy foods, alcohol, nicotine, medication and psychological stress. This happens on the one hand through local irritation of the gastric mucosa, on the other hand via the gastric nerves (vagus nerve).
Stomach acid is released into the stomach cavity through certain stomach wall cells. These cells are coupled to nerves controlled by the autonomic nervous system. When the autonomic nervous system is stimulated, a signal is sent to the stomach wall cells, which culminates in the release of the neurotransmitter acetylcholine at the nerve endings. Acetylcholine bridges the gap between the nerve endings and the stomach wall cells and activates the cholinergic receptors of the stomach wall cells. This leads to the release of stomach acid into the stomach area. These processes are triggered by the sight, the smell or even the thought of food. As a result, stomach acid is produced even when no food has reached the stomach.
Other nerves stimulate a region in the stomach called the antrum (cavity). There are hormone-producing cells that produce the hormone gastrin. This hormone is also responsible for the secretion of gastric acid, so that blocking the gastrin or acetylcholine receptors should lead to a reduction in acid production.
Since the stomach acid serves to prepare the breakdown of proteins in food, the stomach wall must be protected against this process. It is commonly assumed that this is done on the one hand by a mucous membrane that protects the stomach wall through the strong secretion of mucus by mucus-producing cells, and on the other hand by the gastric glands, which also secrete gastric acid.
Furthermore, it is now considered certain that the infection with a bacterium called Helicobacter pylori plays a major causative role in the development of gastric ulcers. The infection with Helicobacter pylori is very common. About 30% of the German population are carriers of this germ. However, it is not yet known why only a small proportion of those affected develop an ulcer.
Fighting this bacterium with antibiotic treatment not only convincingly lowers the risk of developing a new ulcer, but also the risk of rebleeding.
The causes for the cell protection mechanisms of people who are not affected are not yet known. However, they are the subject of current research.
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