Why can t the stomach digest itself?

The stomach has a strong digestive function and relies on hydrochloric acid, pepsin, and mucus in the stomach. Hydrochloric acid is a very corrosive acid that kills bacteria when food enters the stomach. The concentration of hydrochloric acid in the stomach is high, which is enough to dissolve the metal zinc.

Pepsin breaks down proteins in food. Mucus wraps around food, lubricating and protecting the gastric mucosa from food-induced mechanical damage. The hydrochloric acid, pepsin, and mucus in the stomach combine to digest almost any food.

Since the stomach is so digestive, why can't it digest itself? This question was asked more than 100 years ago, and there has never been a complete answer. Some scientists believe that

The stomach cannot digest itself because there is a special substance in the gastric mucosa or gastric juice that resists the action of hydrochloric acid and pepsin. Scientists believe that: first, after the gastric wall secretes hydrochloric acid, hydrochloric acid will not flow backward and will not corrode the gastric wall because it is blocked by the epithelial cells on the mucosal surface.

In the event that the epithelial cells are destroyed, the mucosa secretes mucus, which has a certain buffering effect on hydrochloric acid and also prevents the hydrochloric acid that adheres to the surface of the gastric mucosa from entering the interior. The gastric mucosa also has the ability to "lose the pawn and protect the car", which allows the epithelial cells to constantly metabolize and renew, prevent pepsin from adsorbing on the mucosa, and achieve the purpose of protecting the stomach wall. In addition, the glycoproteins in the mucus, some of which contain a lot of sugar and have a large molecular weight, can inhibit the activity of pepsin.

Secondly, the human gastric mucosa cells are about 500,000 cells per minute, and they can all be renewed within three days, so that the strong regeneration ability can make up for the temporary damage caused by digestive juices to the stomach wall.

So, under normal conditions, the stomach cannot digest itself on its own. If there is too much stomach acid produced in the stomach, or if you take medicine on an empty stomach, the stomach wall is damaged, and the stomach begins to digest itself, and diseases such as gastric ulcers will occur.

The reason why the stomach can have the function of digestion is because of the presence of pepsin in the gastric juice. Gastric juice is acidic. The secretions of the stomach will only flow in the stomach. The stomach digests itself only when it has symptoms. For example, stomach ulcers.

Haha, such a question, at first glance, is asked by a twin or an aquarius.

The gastric wall can be roughly divided into five layers, from top to bottom, it is the mucosal layer, the mucosal layer, the mucus layer, the muscle layer and the serous layer, the mucosal layer is composed of epithelial cells, mucus cells, parietal cells, master cells, etc., what we call gastric acid is mainly secreted by parietal cells, so it will not corrode the function of stomach and gastric acid.

Stomach acid is made up of hydrochloric acid, which is less corrosive than other acids. Moreover, the concentration of gastric acid in the human body is low, which belongs to dilute acid, and the corrosion of dilute acid on objects is weak;

On the other hand, under normal circumstances, the proteins on the gastric mucosa have a certain resistance to gastric acid and cannot be digested by gastric acid, so they will not cause harm to people!

Digestion of the stomach is mainly done by gastric juice, which is a liquid similar to hydrochloric acid. Gastric juice is actually very acidic, but the surface of the stomach wall forms a protective film that protects the stomach wall from erosion.

ps The following is a personal input, and any similarities are purely coincidental: The digestion of the stomach is mainly based on gastric juice, which is a liquid similar to hydrochloric acid. Gastric juice is actually very acidic, but the surface of the stomach wall forms a protective film to protect the stomach wall from erosion, which may be the structure of the evolutionary species.

But there is a situation where gastric juice can still harm itself, that is, when gastric juice refluxes, it enters the esophagus, you will have a heartburn feeling, commonly known as "nausea", this example should be experienced by most people, this is because there is no protective film in the esophagus. People with "reflux esophagitis" often feel sick to their stomachs. In addition, if the stomach wall is broken, gastric juice flows into the abdominal cavity, which will also cause you a lot of damage.

This is a more popular way to explain, if you ask what the structure of the membrane is, you need to explain the anatomy, tissue composition, etc. This membrane is simply a simple analogy, "with Durex can be used for contraception", which is almost the same. ]

Although the acidity of gastric acid is very high, the cells above the stomach wall can secrete a mucus that forms a bicarbonate barrier to buffer the acidity of gastric juice, so the cells on the inside of the stomach can resist gastric acid. But the cushioning of this barrier is limited. ]

The stomach digests itself, and when it digests itself, it is when there is no food in the stomach. If there is something in the stomach, it will not digest itself, because the stomach has the protection of the mucous membrane. ]

The gastric mucosa has its own barrier function and can secrete mucus to protect the lining, but if you get an ulcer or other disease, it may perforate.

The stomach will not be corroded by itself, because there is a layer of fatty matter on the surface of the cell membrane of the stomach wall, which can effectively resist the corrosion of hydrochloric acid, and secondly, the columnar epithelial cells that make up the stomach wall are arranged very closely, and there is no space in the middle, which can prevent the invasion of gastric acid solution.

When talking about the structure and function of the stomach, one student asked, "The human stomach can digest the cow's stomach, so why can't it digest itself?" ”

This is an interesting question, so let's make some **.

The stomach has the function of digesting food, which means that the stomach can secrete gastric juice, and the hydrochloric acid in the gastric juice can activate pepsin and make it become pepsin, and pepsin can digest the protein in food. After the cow's stomach is eaten into the human stomach, the protein it contains is gradually digested by the digestive juices produced by the human stomach.

The stomach can digest all kinds of meat, but it is safe and sound. To this end, Professor Deben of the Department of Medicine at the University of Michigan in the United States has done an interesting experiment. He put the stomach that had been removed from the human body into a large test tube, then added an appropriate amount of hydrochloric acid and pepsin prepared according to the concentration of the normal human stomach, and placed the test tube in a constant temperature environment of 37.

As a result, the stomach in the test tube was severely damaged, and a considerable part was dissolved. This experiment shows that the stomach is unable to resist the digestion of hydrochloric acid and pepsin. Professor Deben's further research has shown that the stomach can be damaged, but it can also be easily repaired, and it is this mechanism that performs the important function of protecting the surface of the stomach.

He pointed out that the lipids on the surface of the cell membrane of the gastric parietal cells have a lot to do with defending against digestion, and if the lipids on the cell surface are removed with detergents, the gastric parietal cells will be attacked by acid. In addition, the cells of the stomach parietal are constantly renewed, and the old cells are constantly shedding from the surface and replaced by new cells within the tissue. Professor Deben estimates that about 500,000 cells are shed in the human stomach every minute, and the gastric mucosal layer is all renewed every three days.

So, even if the lining of the stomach is violated to some extent, it can be completely repaired within a few days or hours. So it's not that the stomach in the human body doesn't digest itself, but it renews itself as soon as it's digested to a certain extent.

There are also some scientists who have confirmed after years of research that the formation of local gastric ulcers is the result of the digestion of gastric wall tissue by gastric acid and pepsin; This process of self-digestion is the direct cause of ulcer formation; The digestion of gastric juice is one of the important factors in ulcer formation.

Therefore, they questioned Professor Deben's view: how can a stomach ulcer arise if the stomach is in a constant process of self-digestion and self-repair. Therefore, it is reasonable to think that the human stomach may have other mechanisms that prevent digestion of itself. What exactly are these mechanisms?

Scientists predict that the twenty-first century will be the century of biological sciences. So, as the biological sciences continue to evolve, scientists will give a clear answer to this question.

The gastric mucosa is the innermost layer of the gastric wall, which is composed of the superficial epithelium, mucosa: muscle and intermuscular tissues, with a thickness of about 0 5 0 7 mm. Below the superficial epithelium are glands and membranes propria and contain connective tissue matrix, plasma cells, lymphocytes, a few eosinophils, mast cells, and nerves and blood vessels.

The glandular cells in the gastric mucosa include cervical mucus cells, master cells, parietal cells, and endocrine cells, which secrete mucus, pepsin, hydrochloric acid, intrinsic factor, and gastrin, respectively.

Functions of the gastric mucosa:

1. The secretion of mucus by epithelial cells has a lubricating effect and is easy for food to pass through.

2. Secrete internal factors to promote the absorption of vitamin B12.

3. Secrete hydrochloric acid to provide a suitable environment for pepsin, sterilization and bacteriostasis.

4. Secrete pepsin to promote protein digestion.

5. Form a gastric mucosal barrier to protect the stomach from acid erosion.