Intestinal villi: structure, function, blood supply and features

For the normal functioning of the human body you need food intake. Absorption of substances necessary for life and the products of their cleavage takes place precisely in the small intestine. Located in it intestinal villi and carry out this function. On their anatomy, placement, cytology and will go further.

The structure of the small intestine, its functions

In human anatomy, 3 departments are distinguished: duodenum, lean and iliac. The first is about 30 cm long. Special enzymes from the intestinal epithelium, bile and enzymes of the pancreas come here. In the same section, the suction process begins. Water and salts, amino acids and vitamins, fatty acids are actively sucked out with the help of villi.

Between the lean and iliac there is no clear outer border, and the total length is 4.5-5.5 m. But the internal differences, of course, exist. Skin :

• Has a large wall thickness;
• Intestinal villi it is longer and smaller diameter, and their number is larger;
• It is better supplied with blood.

Still, the main function of duodenum is digestion of food. Not only in the intestinal cavity this process is carried out, but also near the walls (parietal digestion), and also inside cells (intracellular).

To implement the latter in the mucosa there are special transport systems, their own for each ingredient. An additional function of this department of the small intestine is absorption. In the rest - this is the main function.

Placement of villi and their anatomy

Intestinal villi in the digestive canal are located in all three sections of the small intestine and give them a velvety appearance. The length of each of the villi is approximately 1 mm, and the placement is very dense. They are formed from protrusions of the mucosa. On one square millimeter of the surface of the first and second sections of the small intestine, there may be 22 to 40 of them, on the ileum - up to 30.

Outside, all intestinal villi are covered with epithelium. Each cell has many outgrowths, called microvilli. Their number can reach 4 thousand per epitheliocyte, which significantly increases the surface of the epithelium, and, as a consequence, the intestinal absorption surface.

All intestinal villi in the human digestive channel are along the axis of the lymphatic capillary, originating at the top of the villi and a number of blood capillaries located in the stroma.

Cell structure of villi

It is the presence of a certain type of cells responsible for how the intestinal villi functions. But first things first:

Each villus, regardless of location, is lined with a layer of epithelium consisting of 3 cell types: columnar epitheliocyte, goblet exocrine cytoplasm and endocrinocyte.

Enterocytes

This is the type of cells most often found in the epithelium of the villi. The second name is columnar epitheliocyte. The cells are prismatic. And the main function of intestinal villi is performed by them. Enterocytes provide a transfer from the gastrointestinal tract to the blood and lymph needed for the body of substances that come during eating.

In epithelial cells on the surface there is a special border formed by microvilli. These microvilli on 1 micron ² are located from 60 to 90 pieces. It is they that increase the suction surface of each cell 30-40 times. Located on the surface of microvilli glycocalyx produces digestive enzymes.

One of the varieties of epithelial cells are cells with microfolds or so-called M-cells. Their location - the surface of lymphatic follicles, both group and single. They are distinguished by a more flattened shape and a small amount of microvilli. But the surface is covered with micro-folds, with which the cell is able to capture macromolecules and intestinal lumen.

Goblet exocrine cells and endocrinocytes

Single cells, the number of which increases from duodenum to iliac. These are typical mucous cells that accumulate, and then secrete their secret on the surface of the mucous membrane. It is mucus that promotes food along the intestine and simultaneously participates in the process of parietal digestion.

The appearance of the cell depends on the degree of accumulation in it of a secret, and the formation of mucus itself takes place in the area of placement of the Golgi apparatus. An empty cell that completely isolated its secret is narrow and with a reduced core.

It is the endocrinocytes that synthesize and release biologically active substances that not only play a digestive function, but also play an important role in the overall metabolism. The main location of these cells is the duodenum.

Functions

From the structure it becomes immediately clear what function the intestinal villi perform in the digestive process, therefore, we list them only briefly:

1. Absorption of carbohydrates, proteins, amino acids, as well as the products of their decomposition. They are transmitted through the villi to the capillaries and, together with the blood, are transferred to the portal system of the liver.
2. Absorption of lipids, more precisely, chylomicrons, particles derived from lipids. They are transmitted by villi to the lymphatic and then to the circulatory system, bypassing the liver.
3. Another function of the intestinal villi is the secretion, secreting mucus for easier food movement through the intestines.
4. Endocrine, because some cells of villi produce histamine and serotonin, secretin and many other hormones and BAS.

Embryo bookmark and regeneration after lesions

What cells are made up and how the intestinal villus functions, we have figured out, but when is it laid in the human body and from which cells? We will deal with this issue.

At the end of the second month or the beginning of the third intrauterine development of a person, the intestinal endoderm begins to form in the small intestine and its functional components - folds, villi, crypts.

At first, epithelial cells do not have strict differentiation, only by the end of the third month their division occurs. Glycocalix on the microvilli, which covered epithelial cells, is laid on the fourth month of development of the baby.

In the fifth week, with the correct course of pregnancy, the serous membrane of the intestine is laid, and on the eighth - the muscular and connective tissue envelope of the intestine. All shells are laid from the mesoderm (visceral leaf) and connective tissue mesenchyme.

Although all the cells and tissues of the digestive system are still embedded in the prenatal development, intestinal villi can be damaged during the performance of their functions. How is the restoration of the sites where the cells died? By the mitotic division of healthy cells located side by side. They simply take the place of dead brothers and begin to fulfill their function.