The cardiovascular system combines the heart and blood vessels, forming two circles of blood circulation: large and small. The cardiovascular system transports blood throughout the human body, supplying oxygen and nutrients to cells, tissues and carrying away their waste products.
The heart has always, at all times been considered and is considered the main human organ. Emotions are considered a product of the heart: “heart story” – love; “the heart has sounded the alarm” alarm; “the heart of the Sparrow” – a puny human; – smells good and evil; “the heart is burning with love” is filled with passionate love; “the heart comes the blood”, “blood” on the mountain; “the heart of no place” – about the experiences. You can’t list everything. Although it is known that emotions are a function of the brain. A person lives while the heart is working. Cardiac arrest is death.
The heart is a hollow cone-shaped muscular organ located between the lungs; its apex is directed down, forward and left. The size of the heart does not exceed the size of a clenched fist. Its walls are formed mainly by striated cardiac muscle (myocardium), which is surrounded by the epicardium and lined with endocardium. The septum divides the heart into the right and left halves, each of which, in turn, is formed by the atrium located at the top and the ventricle under it.
Oxygen-depleted blood from the hollow veins enters the right atrium, from where through the right atrioventricular orifice, along the edges of which the atrioventricular tricuspid valve is located, enters the right ventricle. It cuts and pumps blood into the lungs through the opening of the pulmonary trunk, the hole is closed by a valve, which is formed by three semilunar valves that freely pass blood from the ventricle to the pulmonary trunk. Touching their ends, they, like filled pockets, close the hole and prevent the reverse flow of blood. This occurs after the emptying of the ventricle. Oxygen-enriched blood then returns through the pulmonary veins to the left atrium, and from it enters the left ventricle through the left atrioventricular orifice, equipped with a bicuspid valve. This causes a contraction of the left ventricle, resulting in blood being thrown into the aorta, equipped with a valve consisting of three semilunar valves having the same structure as the valve of the pulmonary trunk. From the aorta, blood travels throughout the body. The direction of blood flow inside the heart is controlled by valves (Fig. 17 per cent. insert.)
Pay attention! Today, in men after 35-40 years in the myocardium usually begins some increase in the amount of connective tissue, it appears fat cells. As you age, many muscle cells are replaced by connective tissue-the heart is sclerosed. These changes can be significantly slowed or even prevented by regular exercise and proper nutrition.
Systemic circulation. In a closed cardiovascular system, blood moves due to the contraction of the myocardium (heart muscle) and smooth muscles of the walls of blood vessels. Arteries carry blood from the heart to various organs, blood flows through the veins from organs to the heart. Arterial blood enriched with oxygen flows through the arteries, except the pulmonary artery and its branches (Fig. 18 na TSV. insert.) The aorta begins from the left ventricle of the heart (aortic bulb), the ascending aorta, bending to the left (aortic arch), descends downwards in front of the spine (descending aorta). On this path from the aorta departs many large and small branches. From the convex side of the arcs are the three major vessels: brachiocephalic trunk (right), the left common carotid and subclavian arteries. Brachiocephalic trunk depart right subclavian and right common carotid artery. Subclavian arteries supply blood to the neck and upper limbs, carotid arteries supply the head and contents of the skull. The site of the descending aorta from the aortic arch to the diaphragm is called the thoracic aorta, vessels, blood supply walls and organs of the chest cavity (bronchi, esophagus, lungs, etc.) depart from it. The area of the aorta located under the diaphragm-the abdominal aorta supplies the walls and organs of the abdominal cavity. At the level of the IV lumbar vertebra, it is divided into two common iliac arteries – the right and left each. The common iliac artery is divided into the external and internal iliac arteries. The external iliac artery feeds the lower limb, the internal – the walls and organs of the pelvis. Hollow veins collect blood from all other veins and carry it to the right atrium. The inferior Vena cava is formed by the connection of the right and left common iliac veins; it receives blood from all parts of the body that are below the diaphragm. The upper hollow vein is formed as a result of the connection of two unnamed veins, collects blood from the organs of the head, neck, chest and hands.
The portal vein collects blood from the unpaired organs of the abdominal cavity: the spleen, pancreas, large omentum, gall bladder and digestive tract, starting from the cardiac part of the stomach and ending with the upper part of the rectum. Unlike all other veins, portal vein, entering the gate of the liver, again breaks up into smaller branches, up to sinusoidal capillaries of the liver, which flow into the Central vein of the hepatic lobule. Veins, enlarging, gather in hepatic veins, flowing into the lower Vena cava. The portal vein carries digestive products to the liver, which are used by the liver, harmful substances are neutralized.
Blood supply to the heart. Two coronary arteries, right and left, whose branches are widely anastomosed, supply the heart with blood. They branch out to the capillaries in all three layers of the heart wall. The blood is collected in the heart veins, then – in the venous sinus, which is poured directly into the right atrium.
The small circle of blood circulation begins in the right ventricle. Oxygen-poor and carbon dioxide-rich blood from the right ventricle of the heart enters the pulmonary artery, from where it is transferred to all the capillary networks located in the lungs, entwining the alveoli. In them there is a gas exchange, during which carbon dioxide is removed from the blood, and the blood is enriched with oxygen. The oxygenated blood then flows into the veins, which, when combined into four pulmonary veins, return the blood to the left atrium.
Venous blood flows to the heart through all veins except the pulmonary vein, arterial blood enriched with oxygen is directed to the heart through the pulmonary veins.
The main events-the actual metabolism between blood and tissues-occur in the microcirculatory bed, represented by the smallest arteries-arterioles, capillaries and tiny venules (Fig. 19 in front wheel drive. insert.) The most important part of the circulatory system – is capillaries, they carry out metabolism and gas exchange. The common exchange surface of capillaries of an adult male reaches 1000 m2. Blood flows from the aorta in which the pressure is high (average 100 mm Hg. art.), through the capillaries, where the pressure is very low (15-25 mm Hg. art.), through a system of vessels in which the pressure decreases progressively. From the capillaries blood enters the venules (pressure 12-15 mm Hg. art.), then into the veins (pressure 3-5 mm Hg. art.). In the hollow veins through which venous blood flows into the right atrium, the pressure is only 1-3 mm Hg. art., and in the atrium about 0 mm Hg. accordingly, the rate of blood flow decreases from 50 cm/s in the aorta to 0.07 cm / s in the capillaries and venules.