Gastric acid

Definition

The term gastric juice is used to refer to the acidic liquid found in the stomach, which is very important for the digestion of any food constituents. A human body produces about 2 to 3 liters of gastric juice per day, depending on the amount.

  • Frequency
  • Amount of food intake and
  • Food composition

Composition of gastric acid

The gastric juice is composed of many different components. Its most important component is probably gastric acid. This is a 0.5% hydrochloric acid (in the fasting state), which is only formed by one cell type of the stomach lining, the proving cells.

How much hydrochloric acid is formed there depends on the food intake. The release of gastric acid occurs according to a very special principle: In order to protect the epithelial cells from being attacked and destroyed by gastric acid itself, the acid is only formed outside the cells. In the document cells, acid develops from: The resulting protons can now be transported into the inside of the stomach in exchange for potassium ions (K+) with the help of a pump.

The chloride ion that is now still needed for the stomach acid is obtained by the cell in exchange for the hydrogen carbonate ion from the blood plasma. The chloride ion can now also be passively transported from the cell to the stomach lumen, where it combines with the proton to form hydrochloric acid (HCl). This process requires a great deal of energy.

An increased secretion of chloride ions occurs under various influences, such as activation of the parasympathetic nervous system or the release of histamine or gastrin (i.e. following the ingestion of food).

  • Water (H2O)
  • Carbon dioxide (CO2)
  • Carbonic acid (H2CO3), (protons (H+ ions) and hydrogen carbonate ions (H2CO3-)

There are three phases in gastric secretion: 1. head phase (cephale phase): Here the stimulus for hydrochloric acid production is set by the vagus nerve, i.e. ultimately the sight, taste or smell of food. 2. stomach phase (gastric phase): the formation of hydrochloric acid is stimulated by the stretching of the stomach through the ingested food and special ingredients such as spices or proteins.

3. intestinal phase (intestinal phase)It is a negative feedback mechanism, so to speak, through which enzymes are released from the duodenum when the food chyme has migrated there, which ultimately limits the production of gastric acid. Apart from its main function, namely the denaturation (splitting) of proteins and thus the digestion of protein, gastric acid activates the enzyme pepsinogen to pepsin, which is then also able to split protein bonds. In addition, gastric acid is there to kill microorganisms with its low pH value of 1 to 1.5 on an empty stomach and 2 to 4 on a full stomach.

In addition to gastric acid, gastric juice contains other substances that are essential for digestion. These include, for example, a large number of enzymes, including pepsinogen or pepsin from the main cells of the stomach, which is responsible for breaking down bonds in protein. Furthermore, there are also lipases that help in the digestion of dietary fats.

Also important is the intrinsic factor, which is also produced in the supporting cells, which is needed for the proper absorption of vitamin B12 in the small intestine, forming a complex with it that protects the vitamin from being destroyed by stomach acid. Another important component of gastric juice is mucus. Mucins are produced in surface cells and secondary cells, among others.

These cover the entire inner wall of the stomach, protecting it from being digested by gastric acid. Bicarbonate, which is also produced by the surface cells, is an important contribution to the protection against gastric acid. If the protective mucous layer of the stomach is attacked by certain factors such as: acidity can lead to overacidification, whereby the cells of the stomach wall are attacked by the gastric acid, which can lead to the development of gastritis.

In the case of an attacked gastric mucosa, the development of stomach cancer is also favored. It is also possible that if the lower esophageal sphincter is not functioning properly or if there is an overproduction of gastric acid, it can enter the esophagus, leading to a burning pain, also known as heartburn. Permanent damage to the surface of the esophagus leads to the so-called reflux disease in the long term.In order to limit the secretion of gastric acid, one usually falls back on so-called proton pump inhibitors such as Omeprazol®, which prevent the transport of H+ ions from the cells in the stomach lumen and thus the formation of hydrochloric acid.

They are used both for gastric mucosa inflammation and heartburn. The condition of insufficient or completely missing production of gastric juice is called achylya. This disease usually develops in the context of complications of gastric carcinoma.

Since adequate digestion can no longer take place, those affected suffer from recurrent diarrhea and (due to the lack of absorption of the intrinsic factor and thus of vitamin B12, which is important for the formation of red blood cells) anemia (pernicious anemia).

  • Consumption of alcohol
  • Certain painkillers (e.g. Ibuprofen®)
  • Food components such as tannins (e.g. contained in coffee beans)
  • Pungent spices
  • Infection with the bacterium Helicobacter pylori