The structure of the cardiovascular system

The cardiovascular system includes the heart and blood vessels. The cardiovascular system performs the functions of transporting blood, and along with it, nutrients and activating substances to organs and tissues (oxygen, glucose, proteins, hormones, vitamins, etc.). Metabolic products are transported from organs and tissues through blood vessels (veins). Blood vessels are absent only in the epithelial covering of the skin and mucous membranes, in hair, nails, the cornea of the eyeball, and in articular cartilage.

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

The heart is a four-chambered muscular organ located in the chest cavity. The right half of the heart (the right atrium and the right ventricle) is completely separated from the left half (the left atrium and the left ventricle). Venous blood enters the right atrium through the superior and inferior vena cava, as well as through the heart's own veins.

After passing through the right atrioventricular orifice, along the edges of which the right atrioventricular (tricuspid) valve is fixed, 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, gas exchange between the air entering the lungs and the blood occurs. Oxygen-enriched arterial blood is directed through the pulmonary veins to the left atrium. Then passing through the left atrioventricular orifice, which has a left atrioventricular (mitral, bicuspid) valve, the blood enters the left ventricle, and from it - into the largest artery - the aorta. Given the structural features and functions of the heart and blood vessels, two circles of blood circulation are distinguished in the human body - large and small.

The systemic circulation begins in the left ventricle, where the aorta emerges, and ends in the right atrium, into which the superior and inferior vena cava flow. Arterial blood containing oxygen and other substances is directed to all parts of the body through the aorta and its branches. One or more arteries approach each organ. Veins emerge from the organs, which merge with each other and ultimately form the largest vessels of the human body - the superior and inferior vena cava, which flow 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. An arterial vessel (arteriole) approaches the capillary network of the microcirculatory bed, and a venule emerges from it. Some organs (kidney, liver) deviate from this rule. Thus, an artery - the afferent glomerular arteriole - approaches the glomerulus (capillary) of the renal corpuscle. An artery also leaves the glomerulus - the efferent glomerular arteriole. The capillary network inserted between two identical vessels (arterioles) is called the arterial marvelous network (rete mirabile arteriosum). The capillary network between the interlobular and central veins in the liver lobule is built according to the marvelous network type - the venous marvelous network (rete mirabile venosum).

The pulmonary circulation begins in the right ventricle, from which the pulmonary trunk emerges, and ends in the left atrium, where four pulmonary veins flow. Venous blood flows from the heart to the lungs (the pulmonary trunk, which divides into two pulmonary arteries), and arterial blood flows to the heart (the pulmonary veins). Therefore, the pulmonary circulation is also called pulmonary.

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