Capillary

Capillaries are microscopic blood vessels that play an important role in the blood supply to body tissues. They are thin tubes with a diameter of only a few micrometers (millionths of a meter). Capillaries are found in various organs and tissues such as the skin, lungs, kidneys, liver and heart.

The main function of capillaries is the delivery of oxygen and nutrients to tissue cells. In capillaries, exchange occurs between blood and tissues: oxygen and nutrients from the blood enter the tissues, and carbon dioxide and metabolic products are released back into the blood.

Capillaries have a very thin wall, consisting of three layers: inner endothelial, middle muscular and outer connective tissue. Thanks to this, capillaries can change their diameter depending on the tissue’s need for oxygen and nutrients.

An important property of capillaries is their high permeability to various substances, which allows them to perform their function in the exchange of substances between blood and tissues. However, in some diseases, for example, atherosclerosis, capillaries may become less permeable, which leads to impaired blood supply to tissues and the development of various diseases.

Thus, capillaries play a key role in the functioning of the body, ensuring the exchange of substances between blood and tissues and ensuring sufficient blood supply to all organs and tissues.

Vessel capillaries

A capillary is the smallest blood vessel.

The central organs of the capillary network are the heart and carotid arteries. But throughout the body they penetrate tissues, right down to the surfaces of cells: **capillaries consist of small blood vessels**, similar to large ones - arteries and veins. However, these latter are much larger than their “giants” of capillaries, which distinguish the area of ​​functional activity of the body and the structurally functional unit of blood circulation - the capillary. In this regard, it is customary to speak of capillarogenic zones, which contribute to the development of many pathological processes in the human body, and are divided into two zones in relation to the metabolic process in the tissue cells of the central venous system. The capillary network not only serves as a feeding medium for cells, but also performs many other functions. At the same time, some capillaries are deprived of the metabolic process for tissue cells. All capillaries are divided into pulmonary and capillary. The role of capillaries can be limited to the exchange of gases between tissue cells and tissues with the external environment (this is 80 - 90% of the volume of capillaries), and the functions of the lungs can be transport (up to 18% of the total number of vessels). The venous part is represented by the large and small circle of blood circulation. They connect the veins of all organs and ensure the return of blood to the heart. The circulatory circle completely follows the shape of the heart, which is why they are called closed, excluding another large one - the pulmonary circulatory circle. It includes the superficial veins of the lungs, through which gases are exchanged between the respiratory tissue and the lungs. The small circle forms a venous vessel - the vena cava, which unites all other vena cava.