Structure of the cardiovascular system

The heart and blood vessels belong to the cardiovascular system. The cardiovascular system performs the functions of blood transport, and, together with it, nutrient and activating substances to organs and tissues (oxygen, glucose, proteins, hormones, vitamins, etc.). From organs and tissues through the blood vessels (veins) are transferred the products of metabolism. Blood vessels are absent only in the epithelial cover of the skin and mucous membranes, in hair, nails, the cornea of the eyeball and in the articular cartilage.

The main organ of blood circulation is the heart, the rhythmic contractions of which determine the movement of blood. Vessels, through which blood is carried out from the heart and enters the organs, are called arteries, which bring blood to the heart vessels - veins.

The heart is a four-chambered muscular organ located in the thoracic cavity. The right half of the heart (right atrium and right ventricle) is completely separated from the left half (left atrium and left ventricle). Venous blood enters the right atrium along the upper and lower hollow veins, and also through the veins of the heart.

Passing through the right atrioventricular orifice, along the edges of which the right atrioventricular (tricuspid) valve is strengthened, the blood enters the right ventricle. From the right ventricle, the blood enters the pulmonary trunk, then through the pulmonary arteries into the lungs. In the capillaries of the lungs, closely adjacent to the walls of the alveoli, there is a gas exchange between the air and blood entering the lungs. Enriched oxygen arterial blood through the pulmonary veins is sent to the left atrium. After passing through the left atrioventricular aperture, which has a left atrioventricular (mitral, bivalve) valve, the blood enters the left ventricle, and from it into the largest artery - the aorta. Given the features of the structure and function of the heart and blood vessels, two circles of blood circulation are distinguished in the human body - large and small.

A large circle of blood circulation begins in the left ventricle, from where the aorta comes out, and ends in the right atrium, into which the upper and lower hollow veins flow. On the aorta and its branches, arterial blood containing oxygen and other substances is directed to all parts of the body. One or more arteries fit each organ. From the veins go out, which, merging with each other, eventually form the largest vessels of the human body - the upper and lower hollow veins flowing into the right atrium. Between the arteries and veins is the distal part of the cardiovascular system - the microcirculatory bed, where the interaction of blood and tissues is ensured. To the capillary network of the microvasculature, a vessel of the arterial type (arteriola) is suitable , but comes out more than a vein. Some organs (kidney, liver) have a deviation from this rule. So, to the glomerulus (capillary) of the renal corpuscle is an artery - bringing the glomerular arteriol. Leaves from the glomerulus also artery - enduring glomerular arterioles. A capillary network inserted between two similar vessels (arterioles) is called the arterial miraculous network (rete mirabile arteriosum). By the type of a wonderful network, a capillary network is built between the interlobium and the central vein in the lobule of the liver, the venous wonderful network (rete mirabile venosum).

The small circle of blood circulation begins in the right ventricle, from which the pulmonary trunk leaves, and ends in the left atrium, where four pulmonary veins flow. From the heart to the lungs (pulmonary trunk, divided into two pulmonary arteries) comes venous blood, and to the heart (pulmonary veins) arterial blood flows. Therefore, a small circle of blood circulation is also called pulmonary.

[1], [2], [3]