What are Gastric Juices?

(Gastric juice) A general term for gastric secretions. These include water, electrolytes, lipids, proteins and peptide hormones. Pure gastric juice is a colorless transparent liquid with a pH of 0.9 to 1.5, a specific gravity of 1.006 to 1.009, a daily secretion of 1.5 to 2.5 liters, and a solid content of about 0.3 to 0.5%. The inorganic substances are mainly Na +, K +, H +, and Cl -. The ion concentration varies with the secretion rate of gastric juice. When the secretion rate increases, the concentration of Na + decreases, and H + rises rapidly, up to 150 mg equivalent / liter, Cl- also increases slightly, and K + is basically stable. H + and Cl- combine to form hydrochloric acid. Organics include pepsinogen, mucin, and "internal factors." These components are secreted by various epithelial cells of the gastric mucosa, parietal cells secrete HCl and internal factors, and main cells secrete pepsinogen.

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(Gastric juice) A general term for gastric secretions. Including water, electrolytes, lipids, proteins and

Mucus is spread by epithelial cells on the surface of the gastric mucosa

Amount: The residual amount of gastric juice in normal fasting 12h is about 50ml. After the successful intubation, the total amount of gastric juice obtained by continuous negative pressure suction for 1 hour is called the basal gastric fluid volume, and the normal basal gastric fluid volume is 10 to 100 ml. If it is greater than 100ml, it is increased, which is commonly seen in: increased gastric secretion, such as duodenal ulcers, gastrinoma, etc .; gastric emptying disorders, such as pyloric obstruction, reduced gastric motility, etc .; duodenal reflux. If the amount of gastric fluid is less than 10ml, it is mainly reduced in atrophic gastritis and hypergastric motility.

Color: Normal gastric juice is colorless and transparent liquid, without bile, blood, and no food residue. Cloudy off-white, mixed with a large amount of mucus; bright red bloodshot, mostly due to damage during gastric tube insertion

In order to understand the secretory function and emptying status of the stomach, and whether there is bleeding in the stomach and bacterial reproduction, the gastric tube can be taken through the nose or the mouth to extract the gastric juice for examination.

Patients with gastric disease should understand the correct method of gastric juice collection: fasting, drug prohibition, and smoking cessation should be performed for more than an hour before collecting gastric juice. In the morning, a physician inserts a sterilized (cooked) gastric tube into the stomach through the nose or mouth. -55 cm depth can reach the gastric crooked mucus pool; then use a 50 ml syringe connected to the outer end of the gastric tube to aspirate gastric juice (or continue to be suctioned by a negative pressure pump), fill it into the container after pumping, and then take the tube to continue suction; During the collection process, patients can change their positions (upward, lateral, prone, and sitting), and try to suck the gastric fluid clean as much as possible; after extubation, record the amount of gastric juice extracted, label it on a container for inspection, and check the gastric juice by yourself. The thick mucus was filtered out with gauze, and then gastric juice analysis was performed according to the required items.

Through the analysis of gastric juice, various components in gastric juice can be analyzed, and the basic gastric acid secretion and the maximum gastric acid secretion after stimulation can be measured at the same time, which has a guiding role for further treatment. Based on the analysis of gastric juice, we can understand the gastric motor function and assist Diagnose stomach problems and other diseases related to changes in the composition of the gastric juices. Such as duodenal ulcer, stomach, pancreatic disease, various anemia and so on.

Pure gastric juice is a colorless and transparent acidic liquid with a pH of about 0.9 to 1.5. Normal adults have a daily gastric secretion of about 1.5 to 2.5L. Important components in the solids contained in gastric juice are hydrochloric acid, pepsinogen, mucus, and "internal factors".

Regulation of gastric juice secretion includes factors that stimulate gastric juice secretion and factors that inhibit gastric juice secretion. Normal gastric juice secretion is the result of the interaction of two factors, excitement and inhibition.

Factors that stimulate gastric secretion

Food is a physiological stimulant that causes gastric juice secretion. Generally, food is divided into three periods according to the part that feels the food stimulus: the head, stomach, and intestine. There are some differences in the quality and quantity of gastric fluid secretion in each period. But in time, the secretions of each phase overlap, and in terms of the regulatory mechanism, they include both neural and humoral factors.

(1) First stage: The afferent impulses that cause gastric secretion mainly come from the receptors located on the head, so it is called the first stage. With a dog with a gastric fistula, it can be observed that when it sees and smells food, gastric juice flows out, which is a conditioned reflex secretion that requires the involvement of the cerebral cortex. The sham feeding method (Figure 8-5) proves that, when chewing and swallowing food, although the food fails to enter the stomach, it still causes gastric secretion. This is an unconditioned reflex secretion caused by food stimulating chemical and mechanoreceptors in the mouth, pharynx, and esophagus. The basic center is located in the medulla oblongata, but is affected by the higher parts of the brain. The vagus parasympathetic fibers are these reflected efferent nerves. When the vagus efferent nerve is excited, in addition to directly causing the secretion of glandular cells, it can also cause the "G" cells of the pyloric mucosa to release gastrin, which is stimulated by blood circulation Stomach glands. Therefore, the secretion of gastric juice in the first stage includes two regulatory mechanisms, neurological and neuro-humoral.

The characteristics of gastric juice secreted in the first stage: high secretion, high acidity, high pepsin content, and strong digestion.

(2) Gastric phase: After food enters the stomach, it continues to stimulate gastric juice secretion. The mechanism is mainly as follows: The stimulus of expansion of the stomach on the stomach can act on the receptors in the gastric wall, through the long reflection of vagus-vagus nerve, and the short reflection of inner plexus And the release of gastrin by the "G" cells of the gastric pylorus caused by the intramural plexus causes the gastric glands to secrete; The chemical components of the food (mainly the digestion products of proteins) directly act on the "G" cells and cause gastritis release.

Characteristics of gastric secretion in the gastric phase: acidity is also high, but digestion is weaker than in the first phase.

(3) Intestinal phase: After food is partially digested in the stomach and becomes chyme and enters the small intestine, it can also cause a small amount of gastric juice secretion, which is the result of the mechanical and chemical stimulation of the chyme in the small intestine. Its mechanism of action is not as clear as in the first and gastric stages. It is known that there are also "G" cells that produce gastrin in the duodenal mucosa. After the chyme enters the intestine, it may stimulate the release of gastrin and cause the secretion of acidic gastric juice. Cholecystokinin produced by the duodenal mucosa also has the function of stimulating gastric secretion, but it has a weaker effect than gastrin.

Characteristics of gastric juice secreted in the intestine: less secretion, accounting for about 10% of the total secretion of gastric juice after eating, and less zymogen content.

Factors that inhibit gastric secretion

Harsh stimuli of spirit, mood, and eating-related conditions can reduce gastric acid secretion through reflexes in the central nervous system. Hydrochloric acid, fat and hypertonic solution are three important factors that inhibit gastric secretion in the gastrointestinal tract.

Hydrochloric acid is secreted by the gastric glands, but when the gastrointestinal hydrochloric acid reaches a certain concentration (such as the pH of the stomach pylorus is 1.2 to 1.5 and the pH in the duodenum is 2.5), the secretory activity of the gastric glands is suppressed. A negative feedback regulation mechanism of secretion is of great significance for regulating gastric acid levels.

The role of fat and its metabolites in inhibiting the secretion of gastric glands occurs when fat passes through the pylorus and enters the duodenum. As early as the 1930s, Chinese physiologist Lin Kesheng and others discovered that a substance that weakens gastric secretion and gastric movement can be extracted from the small intestinal mucosa. This substance is considered to be a hormone produced by the action of fat on the small intestinal mucosa and is named enterostatin, but this substance has not been purified so far. In recent years, it is believed that enterostatin is not necessarily a single hormone It may be a general term for a class of hormones. For example, gastrostatin can be released from the small intestine by fat stimulation, but whether it is a component of gastrostatin remains to be further studied.

The hypertonic solution in duodenum also inhibits gastric secretion, and its mechanism of action is unclear.

There is also a large amount of prostaglandins (PGs) in the gastric mucosa. Stimulation of the vagus nerve or injection of gastrin can cause an increase in prostaglandin release, which in turn inhibits gastric acid secretion after prostaglandin release. Therefore, it may be a negative feedback inhibitor of gastric secretion.

Effects of drugs on gastric juice

Histamine is a strong stimulator of gastric acid secretion. Under normal circumstances, the gastric mucosa constantly releases a small amount of histamine, which reaches the adjacent parietal cells through local diffusion to play a role. It is commonly used clinically to check the secretory function of the gastric glands. In recent years, it is believed that histamine not only has the effect of stimulating gastric acid secretion, but also can increase the sensitivity of parietal cells to gastrin and acetylcholine.

Parasympathomimetic drugs such as acetylcholine, methacholine and pilocarpine are all drugs that promote gastric secretion. Atropine cholinergic blockers inhibit gastric secretion.

Adrenal cortex hormones can enhance the response of gastric glands to stimuli such as vagus nerve impulses and gastrin, but it can also inhibit gastric mucus secretion. Therefore, caution should be used when using these hormones in patients with peptic ulcer.