Gastric juice or chyme is the clear liquid secreted in abundance by numerous microscopic glands scattered throughout the mucosa of the stomach .
Functionally, it can be said that gastric juice is a very strong acid that is found in the stomach and that serves to eliminate the part of the food that is useless, that is, that part that cannot be transformed into energy for the body .
Gastric acid is a product of the secretion of gastric parietal or oxyntic cells, it fulfills essential biological roles for body homeostasis. The production of gastric acid depends on a cellular effector process consisting of histamine , acetylcholine and gastrin at the first level, constituting the first messengers of said process.
Summary
[ hide ]
- 1 Ingredients
- 2 Operation process
- 3 function
- 4 Power
- 5 Damage to the stomach
- 1 What protects the stomach itself from acid and enzymes?
- 6 Protect against bacteria
- 7 sources
Ingredients
- Water
- Hydrochloric acid
- Enzymes : pepsin , gastric renin and gastric lipase .
operation process
The secretory process described is set in motion, sequentially in three phases, two of them stimulatory -cephalic phase and gastric phase- and an inhibitory or intestinal phase. These stages are initiated by psychoneural phenomena ( thinking , seeing , smelling, or remembering); by food and other ingested substances; and by products of nutrient digestion.
Alterations in the regulation of acid secretion; in the constitution of the gastroduodenal mucosal barrier, protective against the potentially harmful action of food and pharmaceuticals or drugs; and enhancement of its action by the presence of H. pylori , constitute the etiopathogenic basis of acid-peptic disease, a nosographic entity where it plays a fundamental role.
These interact with specific receptors, which in turn activates second messengers represented by cAMP and the calcium-calmodulin system. These then sequentially activate a protein kinase that phosphorylates a specific protein, activating it, which initiates acid synthesis.
A proton pump located at the luminal pole of the parietal cell finally extrudes the synthesized acid into the gastric lumen.
Function
Its function is to act mainly on the digestion of proteins , due to the effect of the enzymes pepsin and renin, to favor the absorption of nutrients in the small intestine . Parietal cells produce hydrochloric acid (HCl) that activates the enzyme pepsinogen, which is subsequently converted to pepsin.
Due to the presence of hydrochloric acid, the pH takes a value between one and two. This acid medium facilitates the breakdown ( hydrolysis ) of proteins into smaller units.
Pepsin breaks down proteins into smaller subunits; other important digestive enzymes are trypsin and chymotrypsin .
Rennin (also known as rennet ferment) transforms casein ( milk protein) into a soluble protein (rennet) for pepsin action. This is necessary to keep it in the stomach long enough for pepsin to act on it, since if milk remained liquid it would pass through the stomach as quickly as water.
Can
Gastric juice is extremely powerful in humans. It is capable of digesting iron , most plastics, glass , virtually all metals among other things.
The gastric mucosa also secretes a protein called intrinsic factor, which is essential for the absorption of vitamin B12 .
When there is no intrinsic factor, this vitamin is not absorbed and then a severe form of anemia , called pernicious anemia, occurs.
The gastric epithelium also produces mucus (or mucin ), which plays an important role in self-protection: in this way it avoids the direct attack of hydrochloric acid on its surface.
stomach damage
The corrosive power of hydrochloric acid is a thousand times higher than that of saliva. The stomach makes about six glasses of gastric acid a day.
The stomach secretes gastric acid to break down food. One of the main components of these gastric juices is hydrochloric acid. And if this acid is capable of completely corroding a piece of zinc metal and killing any living cell, why doesn’t it corrode the stomach itself, which would then digest itself?
What protects the stomach itself from acid and enzymes?
Gastric juices cannot damage the stomach, which is lined by stomach mucosa on the inside, which lines the inside of the stomach with the necessary thickness and texture so that our digestive organ par excellence does not suffer the effects of its own juices. corrosive
Of course, acids damage this mucosa to a certain extent, but the stomach itself constantly regenerates it in order to always have a new and more resistant layer. In addition, this mucosa generates its own antacid, which contains the necessary dose of bicarbonate to stop the destructive action of the juices.
Stomach juices contain more than just acid. This is found dissolved in a mixture of water, electrolytes (sodium, potassium and calcium) and enzymes called pepsin , which destroy proteins.
Eating food triggers a series of mechanisms aimed at facilitating digestion. The body releases some hormones into the bloodstream, among which lagastrin stands out, whose function is to stimulate the acid-producing cells of the stomach. These combine hydrogen atoms with the chlorine present in the salt to produce hydrochloric acid. Meanwhile, other cells secrete a substance called pepsinogen, which, thanks to the intervention of hydrochloric acid, is transformed into pepsin, an enzyme that is also lethal to living cells.
Well, it is protected by the mucus that lines the inside of the stomach. This mucus lubricates the food bolus so that it circulates easily through the digestive tract and also forms a thick lining on the inner wall of the stomach to prevent it from being digested by its own juices.
Acids attack, of course, this mucosal wall, but the stomach septum continuously regenerates them. In addition, the stomach lining makes its own antacid, secreting bicarbonate to neutralize the acid.
protective against bacteria
From a microbiological point of view, most bacteria cannot survive for long in a highly acidic environment. Constantly and inevitably, common bacteria enter our bodies through the nose and mouth.
Normally, when these bacteria reach the stomach, they would die as they are at a very low pH. However, if gastric acid is deficient, many of these microbes can live, multiply and infect us. Most of these bacteria that enter through these routes are harmless, but there are some such as salmonella, escherichia coli and vibrium cholerae that can cause serious illness and even death when stomach acid levels are low.