The human stomach is the body's main food storage reservoir. If the body did not have such a capacity as the stomach, we would eat constantly, and not just several times a day. It also releases a mixture of acid, mucus and digestive enzymes that help digest and sanitize our food while it is being stored.
Macroscopic Anatomy
What kind of stomach does a person have? It is a round, hollow organ. Where is the human stomach? It is located below the diaphragm on the left side of the abdomen.
The structure of human organs is such that the stomach is located between the esophagus and the duodenum.
The stomach is an enlarged part of the gastrointestinal tract, having the shape of a crescent. Its inner layer is full of wrinkles, known to us as wrinkles (or folds). It is these folds that allow it to stretch to fit large portions of food, which subsequently moves smoothly during digestion.
According to form and function, the human stomach can be divided intofour parts:
1. The esophagus connects to the stomach at a small area called the cardia. This is a narrow, tube-like part that passes into a wider cavity - the body of the stomach. The cardia is made up of the lower esophageal sphincter, as well as a group of muscle tissue that contracts to keep food and acid in the stomach.
2. The cardial section passes into the body of the stomach, which forms the central and largest part of it.
3. Slightly above the body is a domed area known as its floor.
4. Below the body is the pylorus. This part connects the stomach to the duodenum and contains the pyloric sphincter, which controls the flow of partially digested food (chyme) from the stomach and into the duodenum.
Microscopic anatomy of the stomach
Microscopic analysis of the structure of the stomach reveals that it is made up of several distinct layers of tissue: mucosal, submucosal, muscular, and serous.
Mucous membrane
The inner layer of the stomach consists entirely of mucous membrane, which is a simple epithelial tissue with many exocrine cells. Small pores called gastric pits contain many exocrine cells that produce digestive enzymes and hydrochloric acid into the stomach. Mucous cells located throughout the mucosa and gastric pits secrete mucus to protect the stomach from its own digestive secretions. Due to the depth of the gastric pits, the mucous membrane can thicken, which cannot be said aboutmucosa of other organs of the gastrointestinal tract.
In the depths of the mucous membrane there is a thin layer of smooth muscles - the muscular plate. It is she who forms the folds and increases the contact of the mucosa with the contents of the stomach.
There is another layer around the mucous membrane - the submucosa. It is made up of connective tissue, blood vessels and nerves. Connective tissues support the structure of the mucosa and connect it to the muscle layer. The blood supply of the submucosa ensures the supply of nutrients to the walls of the stomach. Nervous tissue in the submucosa controls the contents of the stomach and governs smooth muscle and the secretion of digestive substances.
Muscle layer
The muscular layer of the stomach surrounds the submucosa and makes up most of the mass of the stomach. The muscular lamina consists of 3 layers of smooth muscle tissue. These layers of smooth muscle allow the stomach to contract to mix food and move it through the digestive tract.
Serosa
The outer layer of the stomach, surrounding the muscle tissue, is called the serosa, which is made of simple squamous epithelial and loose connective tissue. The serous layer has a smooth, slippery surface and secretes a thin, watery secretion known as serous fluid. The smooth, wet surface of the serosa helps protect the stomach from friction as it expands and contracts.
The anatomy of the human stomach is now more or less clear. Everything that is described above, we will consider a little later on the diagrams. But first, let's see what arefunctions of the human stomach.
Storage
In the mouth, we chew and moisten solid food until it becomes a homogeneous mass shaped like a small ball. As we swallow each pellet, it slowly passes through the esophagus to the stomach, where it is stored along with the rest of the food.
The volume of a person's stomach can vary, but on average it is able to hold 1-2 liters of food and liquid to help digestion. When the stomach is stretched with a lot of food, it can store up to 3-4 liters. A distended stomach makes digestion difficult. Since the cavity cannot easily contract to mix the food properly, this results in a feeling of discomfort. The volume of a person's stomach also depends on the age and condition of the body.
After the stomach cavity has been filled with food, it remains for another 1-2 hours. At this time, the stomach continues the digestive process that began in the mouth and allows the intestines, pancreas, gallbladder and liver to prepare to finish the process.
At the end of the stomach, the pyloric sphincter controls the movement of food into the intestines. As a general rule, it usually closes to keep food and stomach secretions out. Once the chyme is ready to leave the stomach, the pyloric sphincter opens to allow a small amount of digested food to pass into the duodenum. Within 1-2 hours, this process is slowly repeated until all the digested food leaves the stomach. The slow release rate of chyme helps break it down and maximizedigestion and absorption of nutrients in the intestines.
Secretion
The stomach produces and stores several important substances to manage the digestion of food. Each is produced by exocrine or endocrine cells found in the mucosa.
The main exocrine product of the stomach is gastric juice - a mixture of mucus, hydrochloric acid and digestive enzymes. Gastric juices mix with food in the stomach to aid digestion.
Specialized exocrine mucosal cells - mucous cells that store mucus in the folds and pits of the stomach. This mucus spreads across the mucosal surface to coat the lining of the abdomen with a thick, acid- and enzyme-resistant barrier. Gastric mucus is also rich in bicarbonate ions, which neutralize the pH of stomach acid.
The parietal cells located in the pits of the stomach produce 2 important substances: the internal factor of Castle and hydrochloric acid. Intrinsic factor is a glycoprotein that binds to vitamin B12 in the stomach and helps it be absorbed by the small intestine. Vitamin B12 is an essential nutrient for the formation of red blood cells.
The acid in the human stomach protects our body by killing pathogenic bacteria that are present in food. It also helps digest proteins, turning them into an unfolded form that is easier for enzymes to process. Pepsin, a protein-digesting enzyme, is only activated by hydrochloric acid in the stomach.
Main cells, alsolocated in the pits of the stomach, produce two digestive enzymes: pepsinogen and gastric lipase. Pepsinogen is the precursor molecule to a very powerful protein-digesting enzyme, pepsin. Since pepsin would destroy the master cells that make it, it has been hidden in the form of pepsinogen where it is harmless. When pepsinogen comes into contact with the acidic pH found in stomach acid, it changes shape and becomes the active enzyme pepsin, which converts proteins into amino acids.
Gastric lipase is an enzyme that digests fats by removing the fatty acid from the triglyceride molecule.
G-cells of the stomach - endocrine cells located at the base of the pits of the stomach. G-cells synthesize the hormone gastrin into the bloodstream in response to many stimuli, such as signals from the vagus nerve, the presence of amino acids in the stomach from digested proteins, or stretching of the stomach walls while eating. Gastrin passes through the blood to various receptor cells throughout the stomach, and its main task is to stimulate the gland and muscles of the stomach. The effect of gastrin on the glands leads to an increase in the secretion of gastric juice, which improves digestion. Stimulation of smooth muscle by gastrin promotes stronger contractions of the stomach and the opening of the pyloric sphincter to move food into the duodenum. Gastrin can also stimulate cells in the pancreas and gallbladder, where it increases the secretion of juice and bile.
As you can see, human stomach enzymes perform very important functions in digestion.
Digestion
Digestion in the stomach can be divided into two classes: mechanical and chemical digestion. Mechanical digestion is nothing more than the physical division of a mass of food into smaller portions, while chemical digestion is nothing more than the transformation of larger molecules into smaller molecules.
• Mechanical digestion occurs due to the mixing action of the walls of the stomach. Its smooth muscles contract, causing portions of food to mix with gastric juice, which leads to the formation of a thick liquid - chyme.
• While food is physically mixed with gastric juice, the enzymes present in it chemically break down large molecules into their smaller subunits. Gastric lipase breaks down triglyceride fats into fatty acids and diglycerides. Pepsin breaks down proteins into smaller amino acids. The chemical decomposition, begun in the stomach, is not completed until the chyme enters the intestines.
But the functions of the human stomach are not limited to digestion.
Hormones
The activity of the stomach is controlled by a number of hormones that regulate the production of stomach acid and the release of food into the duodenum.
• Gastrin, produced by the G-cells of the stomach itself, increases its activity by stimulating an increase in the amount of gastric juice produced, muscle contraction and gastric emptying through the pyloric sphincter.
• Cholecystokinin (CCK) is produced by the lining of the duodenum. Is a hormone that slows down gastric emptying by contracting the sphinctergatekeeper. CCK is released in response to eating foods rich in proteins and fats, which are very difficult for our body to digest. CCK allows food to be stored in the stomach longer for more thorough digestion and gives time for the pancreas and gallbladder to release enzymes and bile to improve digestion in the duodenum.
• Secretin, another hormone produced by the duodenal mucosa, responds to the acidity of the chyme entering the intestine from the stomach. Secretin passes through the blood to the stomach, where it slows down the production of gastric juice by the exocrine mucosal glands. Secretin also stimulates the production of pancreatic juice and bile, which contain acid-neutralizing bicarbonate ions. The purpose of secretin is to protect the intestines from the harmful effects of chyme acid.
Human stomach: structure
Formally, we have already familiarized ourselves with the anatomy and functions of the human stomach. Let's use illustrations to look at where the human stomach is located and what it consists of.
Pattern 1:
This figure shows the human stomach, the structure of which can be considered in more detail. Marked here:
1 - esophagus; 2 - lower esophageal sphincter; 3 - cardia; 4- body of the stomach; 5 - bottom of the stomach; 6 - serous membrane; 7 - longitudinal layer; 8 - circular layer; 9 - oblique layer; 10 - large curvature; 11 - folds of the mucous membrane; 12 - cavity of the pylorus of the stomach; 13 - channel of the pylorus of the stomach; 14 - pyloric sphincterstomach; 15 - duodenum; 16 - gatekeeper; 17 – small curvature.
Picture 2:
This image clearly shows the anatomy of the stomach. The numbers are marked:
1 - esophagus; 2 - the bottom of the stomach; 3 - the body of the stomach; 4 - large curvature; 5 - cavity; 6 - gatekeeper; 7 - duodenum; 8 - small curvature; 9 - cardia; 10 - gastroesophageal junction.
Pattern 3:
This shows the anatomy of the stomach and the location of its lymph nodes. Numbers match:
1 - upper group of lymph nodes; 2 - pancreatic group of nodes; 3 - pyloric group; 4 - the lower group of pyloric nodes.
Pattern 4:
This image shows the structure of the stomach wall. Marked here:
1 - serous membrane; 2 - longitudinal muscle layer; 3 - circular muscle layer; 4 - mucous membrane; 5 - longitudinal muscular layer of the mucous membrane; 6 - circular muscle layer of the mucous membrane; 7 - glandular epithelium of the mucous membrane; 8 - blood vessels; 9 - gastric gland.
Pattern 5:
Of course, the structure of human organs in the last picture is not visible, but the approximate position of the stomach in the body can be seen.
This image is quite interesting. It does not depict the anatomy of the human stomach or anything like that, although some parts of it can still be seen. On theThis picture shows what heartburn is and what happens when it occurs.
1 - esophagus; 2 - lower esophageal sphincter; 3 - contractions of the stomach; 4 - stomach acid, together with its contents, rises into the esophagus; 5 - Burning feeling in chest and throat.
In principle, the picture clearly shows what happens with heartburn and no further explanation is required.
The stomach of the person whose pictures were presented above is a very important organ in our body. You can live without it, but this life is unlikely to replace a full one. Fortunately, in our time, many problems can be avoided simply by periodically visiting a gastroenterologist. Timely diagnosis of the disease will help to get rid of it faster. The main thing is not to delay going to the doctor, and if something hurts, then you should immediately contact a specialist with this problem.
