The human digestive system begins with the oral cavity. Here the food is crushed and moistened with saliva. Further food enters the esophagus, from it – into the stomach. Then she moves and enters the small intestine, and from there into the fat.
In the digestive tract, as in a conveyor, food gradually moves forward and under the influence of digestive juices, it turns into easily absorbed by the body simple chemicals, which are absorbed from the colon into the blood, and it distributes them to all systems and organs. After that, undigested remains, slags are thrown out through the rectum.
An important role in the digestive system is the stomach. In terms of its structure and appearance, the human stomach is oblong. The size of the stomach can be different and can hold 3–4 liters of fluid at the same time or more, some stomachs stretch to sizes that can already hold 5-6 liters.
Human digestive system: 1 – hypoglossal salivary gland, 2 – submandibular salivary gland, 3 – parotid salivary gland, 4 – esophagus, 5 – stomach, 6 – pancreas, 7 – rectum, 8 – small intestine, 9 – outfected intestine, 10 – duodenal ulcer , 11 – gallbladder, 12 — liver
The uppermost part of the stomach is the place where the esophagus passes into the stomach. There are powerful longitudinal folds of the walls and the esophagus in this passage.
Passing food into the stomach, these folds are straightened, and then closed again behind it, thus preventing the food from coming back.
The upper half of the stomach is called the antral region of the stomach (from the Greek word “antrum” – which means “input”). But doctors often use not the Latin term, but everyday, calling the antrum the upper, or input, and, accordingly, the pyloric – the lower, or output, of the stomach.
The stomach itself is slightly away from the top and from the bottom – called the body of the stomach.
The bends of the stomach correspond to the lesser curvature of the stomach and the curvature large. It is along the greater curvature that food flows down inside the stomach.
At the very bottom of the stomach, there is another gastric valve, called scientific sphincter. The sphincter consists of a double layer of muscles. This is necessary to enhance the retaining and locking properties, since the exit from the stomach must overlap with special force.
In the stomach there are three types of cells. Their functions are strictly delimited. Some of them secrete only acid, others only digestive enzymes, and still others – liquid and protective mucus. Mixing in the cavity of the stomach, these components and make up the gastric juice. The one that processes the food. The quality of digestion and the resistance of the stomach wall to aggressive environmental factors depend on the proper, balanced work of gastric cells.
The walls of the stomach consist of three main layers. The inner layer – the mucous membrane, consisting of a huge number of glands that produce gastric juice. The second layer is the submucosa, which includes many small blood vessels and nerve formations.
The outer layer of the stomach consists of muscle tissue. Muscles are located in a variety of directions – circular, longitudinal, diagonal. When the muscles contract in all these directions, the food in the stomach is mixed with gastric juice, crushed and turned into a homogeneous liquid gruel. Thus, physical processing of food is carried out. If the muscles contract, and in the stomach at this moment there is nothing, then there is a feeling of hunger.
Muscular, the very last layer of the stomach consists of two directions of fibers – longitudinal (located along the stomach) and circular (arranged in a circle). This layer provides shaking up, thoroughly mixing the food and, of course, its progress along the stomach to the duodenum.
Immediately after the stomach should be no less important for the process of food processing organ, its length equal to 12 fingers (folded across). Hence its name, more precisely, its name – the duodenum.
In this gut, the final digestion of food takes place: the task of this gut is to briefly hold in itself pieces of food in order to “chop” it up into even smaller particles than those that got into it from the stomach. The duodenum has an onion – a kind of folded thickening at the place of its transition into the stomach – and the body, that is, the intestine itself. This organ consists of the same layers as the stomach: mucous, submucous and muscular, performing the same functions as in the stomach (respectively: excretory, nourishing and motor).
It is in the duodenal bulb that the ducts of the liver and pancreas are opened. Mixing intestinal juice with pancreatic juice and bile allows you to split food pieces into such tiny particles that they will be easily absorbed in the future by the “food vacuum cleaner of the body” – the small intestine.
In addition to the physical processing of food, the stomach processes it chemically (with the help of gastric juice).