The heart of man is a romantic organ. At us it is considered a receptacle of the soul. “I feel my heart,” people say. In African Aborigines, it is considered an organ of the mind.

Anatomically, the heart is a muscular organ. Its size is small, about the size of a clenched fist. The heart works throughout the life of a person. It pumps about 5-6 liters of blood per minute. This volume increases when a person moves, physically strains, and decreases during rest.

It can be said that the heart is a muscular pump that provides continuous movement of blood through the vessels. Together, the heart and blood vessels form the cardiovascular system. This system consists of large and small circles of blood circulation. From the left parts of the heart, blood first moves along the aorta, then along the large and small arteries, arterioles, capillaries. In the capillaries, oxygen and other substances necessary for the body enter organs and tissues, and from there carbon dioxide and metabolic products are released. After that, the blood from the arterial becomes venous and again starts moving towards the heart. First by the venules, then by the smaller and larger veins. Through the lower and upper hollow veins, blood again enters the heart, only in the right atrium. A large circle of blood circulation is formed.

Venous blood from the right parts of the heart through the pulmonary arteries is sent to the lungs, where it is enriched with oxygen and again returns to the heart.

Inside, the heart is divided by partitions into four chambers. The two atriums are separated by an interatrial septum into the left and right atriums. The left and right ventricles of the heart are divided by the interventricular septum. Normally, the left and right parts of the heart are absolutely separate. Atrial and ventricles have different functions. In the atria accumulates blood flowing into the heart. When the volume of this blood is sufficient, it is pushed into the ventricles. A ventricle pushes blood into the arteries, along which it moves throughout the body. The ventricles have to perform more difficult work, so the muscle layer in the ventricles is much thicker than in the atria. The atria and ventricles on each side of the heart are connected by the atrioventricular opening. Blood through the heart moves only in one direction.valvular heart apparatus :

aortic valves.
They open at the right time and close, preventing the blood flow in the opposite direction.
Three-leaf valve.

It is located between the right atrium and the right ventricle. It consists of three leaves. If the valve is open, the blood passes from the right atrium to the right ventricle. When the ventricle becomes full, the muscle contracts and the blood pressure closes the valve, preventing the back flow of blood into the atrium.

Pulmonary valve.

With the tricuspid valve closed, the outlet of blood in the right ventricle is possible only through the pulmonary trunk into the pulmonary arteries. The pulmonary valve is located at the entrance to the pulmonary trunk. It opens under the pressure of blood with a contraction of the right ventricle, blood enters the pulmonary arteries, then under the action of the reverse blood flow during relaxation of the right ventricle, it closes, preventing the return of blood from the pulmonary trunk to the right ventricle.

Bivalve or mitral valve.

It is located between the left atrium and the left ventricle. It consists of two leaflets. If it is open, the blood flows from the left atrium into the left ventricle, when it closes the left ventricle it closes, preventing the back flow of blood.

Aortic valve.

Closes the entrance to the aorta. It also consists of three leaves, which look like a half moon. It opens with a contraction of the left ventricle. In this case, blood enters the aorta. When the left ventricle relaxes, it closes. Thus, the venous blood (poor in oxygen) from the upper and lower hollow veins enters the right atrium. When the right atrium contractes through the tricuspid valve, it progresses to the right ventricle. Cutting, the right ventricle ejects blood through the pulmonary valve into the pulmonary arteries (small circle of blood circulation). Enriched with oxygen in the lungs, the blood turns into the arterial and through the pulmonary veins advances into the left atrium, then into the left ventricle. With the contraction of the left ventricle, arterial blood flows through the aortic valve under great pressure into the aorta and spreads throughout the body (a large circle of blood circulation).

The heart muscle is called the myocardium.

Allocate a contractile and conductive myocardium. The contractile myocardium is actually the muscle that contracts and produces the work of the heart. In order for the heart to contract in a certain rhythm, it has a unique conducting system. An electrical impulse to contract the heart muscle arises in the sinoatrial node, which is in the upper part of the right atrium and spreads through the conduction system of the heart, reaching each muscle fiber.