Gastric acid

Gastric juice is a more or less mucus -like fluid, a transparent but also distinctly yellow - greenish solution, which has a distinctive but slight odor. The gastric juice contains the stomach acid ( sober about 0.5 per cent hydrochloric acid), mucus, the proteolytic enzyme pepsin and intrinsic factor ( mucoprotein, which is necessary for the absorption of vitamin B12 in the intestine ). Stomach acid has a pH of about 1-1.5 with an empty stomach and a 2-4 when it is full. It serves the digestion of food ( hydrolysis of proteins in polypeptides), and has a bactericidal effect.

The stomach is made up of protons and extracellularly secreted by the gastric epithelium chloride ions together. The chloride ions are produced in the parietal cells of the gastric mucosa, which are sunk there in ducts and channels. Stimuli to increased secretion of chloride ions include the stimulation of the parasympathetic nervous system (can also be optically triggered by the so-called Pavlovian reflex), histamine and gastrin.

The epithelial cells of the gastric mucosa to prevent the gastric cell membranes and thus decomposed and digested the stomach itself.

A distinction is generally made between gastric secretion of three different phases:

• Cephalic phase (" head " phase ): Stimulation of the vagus nerve ( think, see and smell of food)
• Gastric phase (" gastric phase " ): by gastric distension and chemical stimulation by egg whites, spices etc.
• Intestinal phase (" gut " phase ): Hormonal blocking the formation of stomach acids (when the chyme has reached the duodenum)

The stomach acid flows into the esophagus (gastroesophageal reflux disease ), is this becomes apparent by heartburn. A frequent reflux leads to metaplasia of the epithelium of the esophagus, which can promote the development of esophageal cancer.

The pure gastric juice (percutaneous endoscopic jejunostomy ) are observable as reflux, for example, in people with PEJ tube.

Secretion

The hydrochloric acid as the stomach acid is made up to protect the gastric epithelium only extracellularly together. The parietal cells secrete while only chloride ions, which requires a complex and energy-intensive process. In a multistage process thereby oxonium ions are generated and incorporated and traded in a second process chloride ions from the blood plasma to a. In detail, the steps of:

• Carbonic anhydrase by catalyzed formation of H ions in the cells. The parietal cells of the gastric mucosa exhibit water ( H2O) and carbon dioxide ( CO2), protons (H ) and bicarbonate (HCO3-) ago.

• Exchange of H for K via a proton- potassium pump ( see below).
• Exchange of the formed HCO3- by Cl - from the blood plasma.
• Recirculation of K and Cl - by simultaneous delivery into the stomach by means of passive transport mechanisms.