Blood vessels in vertebrates form a dense closed network. The vessel wall consists of three layers:

The inner layer very thin, it is formed by one row of endothelial cells that impart smoothness inner surface vessels.
The middle layer is the thickest, it contains a lot of muscle, elastic and collagen fibers. This layer provides vascular strength.
The outer layer is connective tissue, it separates the vessels from the surrounding tissues.

According to the circles of blood circulation, blood vessels can be divided into:

Arteries of the systemic circulation [show]
- The largest arterial vessel in the human body is the aorta, which leaves the left ventricle and gives rise to all the arteries that form the systemic circulation. The aorta is divided into the ascending aorta, the aortic arch, and the descending aorta. The aortic arch divides in turn into a thoracic aorta and an abdominal aorta.
- Arteries of the neck and head
  Common carotid artery (right and left), which divides into the external carotid artery and the internal carotid artery at the level of the upper edge of the thyroid cartilage.
  - The external carotid artery gives a number of branches, which, according to their topographic features, are divided into four groups - anterior, posterior, medial and a group of terminal branches that supply blood thyroid gland, muscles of the hyoid bone, sternocleidomastoid muscle, muscles of the larynx mucosa, epiglottis, tongue, palate, tonsils, face, lips, ear (external and internal), nose, occiput, dura mater.
  - The internal carotid artery along its course is a continuation of both carotid artery... It distinguishes between the cervical and intracranial (head) parts. In the cervical part, the internal carotid artery usually does not give branches. In the cranial cavity, branches extend from the internal carotid artery to big brain and the orbital artery, which supplies the brain and eyes.
  Subclavian artery - steam room, begin at anterior mediastinum: right - from the shoulder-head trunk, left - directly from the aortic arch (therefore, the left artery is longer than the right). V subclavian artery three divisions are topographically distinguished, each of which gives its own branches:
  - Branches of the first section - vertebral artery, internal thoracic artery, thyroid-cervical trunk, - each of which gives its own branches that supply blood to the brain, cerebellum, neck muscles, thyroid gland, etc.
  - Branches of the second section - here only one branch departs from the subclavian artery - the costal-cervical trunk, which gives rise to arteries that supply blood to the deep muscles of the occiput, spinal cord, back muscles, intercostal spaces
  - Branches of the third section - one branch also departs here - the transverse artery of the neck, which supplies blood to the muscles of the back
- Arteries of the upper limb, forearm and hand
- Trunk arteries
- Pelvic arteries
- Arteries lower limbs
Veins of the systemic circulation [show]
- Superior vena cava system
  - Veins of the trunk
  - Veins of the head and neck
  - Veins of the upper limb
- Inferior vena cava system
  - Veins of the trunk
- Pelvic veins
  - Veins of the lower extremities
Vessels of a small circle of blood circulation [show]
The vessels of the small, pulmonary, circle of blood circulation include:
- pulmonary trunk
- pulmonary veins in the amount of two pairs, right and left
Pulmonary trunk is divided into two branches: the right pulmonary artery and the left pulmonary artery, each of which is directed to the gate of the corresponding lung, bringing venous blood to it from the right ventricle.
The right artery is somewhat longer and wider than the left. Having entered the root of the lung, it is divided into three main branches, each of which enters the gate of the corresponding lobe of the right lung.
The left artery at the root of the lung is divided into two main branches that enter the gate of the corresponding lobe of the left lung.
From the pulmonary trunk to the aortic arch there is a fibromuscular cord (arterial ligament). In the period of intrauterine development, this ligament is the ductus arteriosus, along which most of blood from the pulmonary trunk of the fetus passes into the aorta. After birth, this duct is obliterated and turns into the specified ligament.
Pulmonary veins, right and left, - remove arterial blood from the lungs. They leave the gate of the lungs, usually two from each lung (although the number of pulmonary veins can reach 3-5 or even more), the right veins are longer than the left ones, and flow into the left atrium.

According to the structural features and functions, blood vessels can be divided into:

Groups of vessels according to the structural features of the wall

Arteries

The blood vessels that go from the heart to the organs and carry blood to them are called arteries (aer - air, tereo - I contain; on corpses, arteries are empty, which is why in the old days they were considered air tubes). Blood from the heart flows through the arteries under great pressure, so the arteries have thick elastic walls.

According to the structure of the walls, arteries are divided into two groups:

Elastic-type arteries - the arteries closest to the heart (the aorta and its large branches) perform mainly the function of conducting blood. In them, the counteraction to stretching by a mass of blood, which is thrown out by a heart impulse, comes to the fore. Therefore, structures of a mechanical nature are relatively more developed in their wall, i.e. elastic fibers and membranes. The elastic elements of the arterial wall form a single elastic frame, which works like a spring and determines the elasticity of the arteries.
Elastic fibers give elastic properties to the arteries, which cause a continuous flow of blood throughout the vascular system. The left ventricle, during contraction, pushes under high pressure more blood than it flows from the aorta into the artery. In this case, the walls of the aorta are stretched, and it contains all the blood ejected by the ventricle. When the ventricle relaxes, the pressure in the aorta drops, and its walls, due to the elastic properties, collapse slightly. The excess blood contained in the distended aorta is pushed from the aorta into the artery, although no blood is drawn from the heart at this time. So, the periodic expulsion of blood by the ventricle, due to the elasticity of the arteries, turns into a continuous movement of blood through the vessels.
The elasticity of the arteries provides another physiological phenomenon. It is known that in any elastic system, a mechanical shock causes vibrations that propagate throughout the system. V circulatory system such a push is the blow of blood ejected by the heart against the walls of the aorta. The vibrations arising in this case propagate along the walls of the aorta and arteries at a speed of 5-10 m / s, which significantly exceeds the speed of blood movement in the vessels. In areas of the body where large arteries come close to the skin - on the wrist, temples, neck - you can feel the vibrations of the walls of the arteries with your fingers. This is the arterial pulse.
Muscular arteries are medium and small arteries in which the inertia of the heart impulse weakens and its own contraction of the vascular wall is required for further blood flow, which is ensured by the relatively large development of smooth muscle tissue in the vascular wall. Smooth muscle fibers contract and relax, narrowing and widening the arteries and thus regulating blood flow in them.

Individual arteries supply blood to whole organs or parts of them. In relation to the organ, arteries are distinguished that go outside the organ, before entering it - extraorganic arteries - and their extensions branching inside it - intraorgan or intraorganic arteries. Lateral branches of the same trunk or branches of different trunks can be connected to each other. Such a connection of vessels before their disintegration into capillaries is called anastomosis or anastomosis. The arteries that form anastomoses are called anastomosing (most of them). Arteries that do not have anastomoses with neighboring trunks before their transition to capillaries (see below) are called terminal arteries (for example, in the spleen). The terminal, or terminal, arteries are more easily clogged with a blood plug (thrombus) and predispose to the formation of a heart attack (local organ necrosis).

The last branches of the arteries become thin and small and are therefore secreted under the name of arterioles. They pass directly into the capillaries, and due to the presence of contractile elements in them, they perform a regulatory function.

The arteriole differs from the artery in that its wall has only one layer of smooth muscle, thanks to which it carries out a regulatory function. The arteriole continues directly into the precapillary, in which the muscle cells are scattered and do not form a continuous layer. The precapillary differs from the arteriole also in that it is not accompanied by a venule, as is the case with the arteriole. Numerous capillaries extend from the precapillary.

Capillaries - the smallest blood vessels located in all tissues between arteries and veins; their diameter is 5-10 microns. The main function of capillaries is to ensure the exchange of gases and nutrients between blood and tissues. In this regard, the capillary wall is formed by only one layer of flat endothelial cells, which is permeable to substances and gases dissolved in a liquid. Through it, oxygen and nutrients easily penetrate from the blood to the tissues, and carbon dioxide and waste products in the opposite direction.

At any given moment, only part of the capillaries is functioning (open capillaries), while the other remains in reserve (closed capillaries). On an area of 1 mm 2 of the cross-section of skeletal muscle at rest, there are 100-300 open capillaries. In a working muscle, where the need for oxygen and nutrients increases, the number of open capillaries reaches 2 thousand per 1 mm 2.

Widely anastomosed with each other, the capillaries form networks (capillary networks), which include 5 links:

arterioles as the most distal links of the arterial system;
precapillaries, which are intermediate between arterioles and true capillaries;
capillaries;
postcapillaries
venules, which are the roots of the veins and pass into the veins

All these links are equipped with mechanisms that ensure the permeability of the vascular wall and the regulation of blood flow at the microscopic level. Microcirculation of blood is regulated by the work of the muscles of the arteries and arterioles, as well as special muscle sphincters, which are located in the pre- and postcapillaries. Some vessels of the microvasculature (arterioles) perform predominantly a distribution function, while the rest (precapillaries, capillaries, postcapillaries, and venules) are predominantly trophic (exchange).

Veins

Unlike arteries, veins (Latin vena, Greek phlebs; hence phlebitis - inflammation of the veins) do not carry, but collect blood from the organs and carry it in the opposite direction to the arteries: from the organs to the heart. The walls of the veins are arranged according to the same plan as the walls of the arteries, however, the blood pressure in the veins is very low, therefore the walls of the veins are thin, they have less elastic and muscle tissue, due to which the empty veins collapse. Veins widely anastomose with each other, forming venous plexus. Merging with each other, small veins form large venous trunks - veins that flow into the heart.

The movement of blood through the veins is carried out due to the suction action of the heart and chest cavity, in which negative pressure is created during inhalation due to the pressure difference in the cavities, the contraction of the striated and smooth muscles of the organs and other factors. The contraction of the muscular sheath of the veins, which in the veins of the lower half of the body, where conditions for venous outflow is more difficult, is also important, is more developed than in the veins of the upper body.

The reverse flow of venous blood is impeded by the special devices of the veins - the valves that make up the features of the venous wall. Venous valves are composed of an endothelial fold containing a layer of connective tissue. They are directed with their free edge towards the heart and therefore do not interfere with the flow of blood in this direction, but keep it from returning back.

Arteries and veins usually go together, with the small and medium arteries accompanied by two veins, and the large ones accompanied by one. From this rule, in addition to some deep veins, the exception is mainly superficial veins, which run in the subcutaneous tissue and almost never accompany the arteries.

The walls of blood vessels have their own thin arteries and veins serving them, vasa vasorum. They depart either from the same trunk, the wall of which is supplied with blood, or from an adjacent one and pass in the connective tissue layer surrounding the blood vessels and more or less closely associated with their adventitia; this layer is called the vascular vagina, vagina vasorum.

Numerous nerve endings (receptors and effectors) associated with the central nervous system are embedded in the wall of arteries and veins, due to which, by the mechanism of reflexes, the nervous regulation of blood circulation is carried out. The blood vessels represent extensive reflexogenic zones that play an important role in the neurohumoral regulation of metabolism.

Functional groups of vessels

All vessels, depending on the function they perform, can be divided into six groups:

shock-absorbing vessels (vessels of the elastic type)
resistive vessels
sphincter vessels
exchange vessels
capacitive vessels
bypass vessels

Shock-absorbing vessels. These vessels include elastic-type arteries with a relatively high content of elastic fibers, such as the aorta, pulmonary artery, and adjacent areas of large arteries. The pronounced elastic properties of such vessels, in particular the aorta, determine the shock-absorbing effect, or the so-called Windkessel-effect (Windkessel in German means "compression chamber"). This effect consists in amortization (smoothing) of periodic systolic waves of blood flow.

The windkessel effect for leveling the movement of the liquid can be explained by the following experience: water is released from the tank in an intermittent stream simultaneously through two tubes - rubber and glass, which end in thin capillaries. At the same time, water flows out of the glass tube in jerks, while from the rubber tube it flows evenly and in greater quantities than from the glass tube. The ability of the elastic tube to align and increase the fluid flow depends on the fact that at the moment when its walls are stretched by a portion of the fluid, the elastic stress energy of the tube arises, that is, a part of the kinetic energy of the fluid pressure transforms into the potential energy of elastic stress.

In the cardiovascular system, part of the kinetic energy developed by the heart during systole is spent on stretching the aorta and large arteries extending from it. The latter form an elastic, or compression, chamber, into which a significant volume of blood enters, stretching it; in this case, the kinetic energy developed by the heart is converted into the energy of elastic tension of the arterial walls. When the systole ends, this elastic tension of the vascular walls created by the heart maintains blood flow during diastole.

More distally located arteries have more smooth muscle fibers, so they are referred to as muscle-type arteries. Arteries of one type smoothly pass into vessels of another type. Obviously, in large arteries, smooth muscles mainly affect the elastic properties of the vessel, without actually changing its lumen and, therefore, hydrodynamic resistance.

Resistive vessels. Resistive vessels include terminal arteries, arterioles and, to a lesser extent, capillaries and venules. It is the terminal arteries and arterioles, that is, the precapillary vessels with a relatively small lumen and thick walls with developed smooth muscles, that offer the greatest resistance to blood flow. Changes in the degree of contraction of the muscle fibers of these vessels lead to distinct changes in their diameter and, consequently, total area cross-section (especially when it comes to numerous arterioles). Considering that the hydrodynamic resistance largely depends on the cross-sectional area, it is not surprising that it is precisely the contractions of the smooth muscles of the precapillary vessels that serve as the main mechanism for regulating the volumetric blood flow rate in various vascular regions, as well as the distribution of cardiac output (systemic blood flow) over different organs. ...

The resistance of the postcapillary bed depends on the state of the venules and veins. The relationship between precapillary and postcapillary resistance is of great importance for hydrostatic pressure in capillaries and therefore for filtration and reabsorption.

Sphincter vessels. The number of functioning capillaries, that is, the area of the exchange surface of capillaries, depends on the narrowing or expansion of the sphincters - the last sections of the precapillary arterioles (see Fig.).

Exchange vessels. These vessels include capillaries. It is in them that such important processes as diffusion and filtration take place. The capillaries are incapable of contraction; their diameter changes passively following pressure fluctuations in pre- and postcapillary resistive vessels and sphincter vessels. Diffusion and filtration also occur in venules, which should therefore be referred to as exchange vessels.

Capacitive vessels. Capacitive vessels are mainly veins. Due to their high extensibility, veins are able to accommodate or eject large volumes of blood without significantly affecting other blood flow parameters. In this regard, they can play the role of blood reservoirs.

At low intravascular pressure, some veins are flattened (i.e., have an oval lumen) and therefore can accommodate some additional volume without stretching, but only acquiring a more cylindrical shape.

Some veins have a particularly high capacity as blood reservoirs, due to their anatomical structure. These veins include primarily 1) the veins of the liver; 2) large veins of the celiac region; 3) veins of the papillary plexus of the skin. Together, these veins can hold more than 1000 ml of blood, which is expelled when needed. Short-term deposition and release of sufficiently large amounts of blood can also be carried out by the pulmonary veins, connected in parallel with the systemic circulation. This changes the venous return to the right heart and / or the ejection of the left heart [show]

Intrathoracic vessels as a blood depot

Due to the great extensibility of the pulmonary vessels, the volume of blood circulating in them may temporarily increase or decrease, and these fluctuations can reach 50% of the average total volume equal to 440 ml (arteries - 130 ml, veins - 200 ml, capillaries - 110 ml). The transmural pressure in the vessels of the lungs and their extensibility change insignificantly.

The volume of blood in the pulmonary circulation together with the end-diastolic volume of the left ventricle of the heart constitutes the so-called central reserve of blood (600-650 ml) - a rapidly mobilized depot.

So, if it is necessary to increase the ejection of the left ventricle within a short time, then about 300 ml of blood can come from this depot. As a result, the balance between the ejections of the left and right ventricles will be maintained until another mechanism for maintaining this balance is activated - an increase in venous return.

A man, unlike animals, does not have a true depot in which blood could be retained in special education and discarded as needed (an example of such a depot is the spleen of a dog).

In a closed vascular system, changes in the capacity of any department are necessarily accompanied by a redistribution of blood volume. Therefore, changes in the capacity of the veins that occur during smooth muscle contractions affect the distribution of blood throughout the circulatory system and thus directly or indirectly on the overall function of the circulatory system.

Shunt vessels are arteriovenous anastomoses present in some tissues. When these vessels are open, blood flow through the capillaries either decreases or stops completely (see the figure above).

According to the function and structure of various departments and the characteristics of innervation, all blood vessels in Lately began to be divided into 3 groups:

near cardiac vessels, beginning and ending both circles of blood circulation - aorta and pulmonary trunk (i.e. elastic type arteries), hollow and pulmonary veins;
great vessels serving for the distribution of blood throughout the body. These are large and medium extraorganic arteries of muscle type and extraorganic veins;
organ vessels that provide metabolic reactions between blood and organ parenchyma. These are intraorgan arteries and veins, as well as capillaries.

Blood vessels are elastic, resilient tubes through which blood flows. The total length of all human vessels is more than 100 thousand kilometers in length, this is enough for 2.5 turns around the earth's equator. During sleep and wakefulness, work and rest - every moment of life, blood moves through the vessels by the force of a rhythmically contracting heart.

Human circulatory system

The circulatory system of the human body divided into lymphatic and circulatory... The main function of the vascular (vascular) system is to deliver blood to all parts of the body. Constant circulation is necessary for gas exchange in the lungs, protection against harmful bacteria and viruses, and metabolism. Thanks to blood circulation, heat exchange processes are carried out, as well as humoral regulation internal organs. Large and small vessels connect all parts of the body into a single well-coordinated mechanism.

Vessels are present in all tissues of the human body with one exception. They do not exist in the transparent tissue of the iris.

Blood transport vessels

Blood circulation is carried out through the vascular system, which are divided into 2 types: human arteries and veins. The layout of which can be represented in the form of two interconnected circles.

Arteries- these are rather thick vessels with a three-layer structure. From above they are covered with a fibrous membrane, in the middle is a layer of muscle tissue, and from the inside they are lined with epithelial scales. Through them, oxygenated blood is distributed under high pressure throughout the body. The main and thickest artery in the body is called the aorta. As you move away from the heart, the arteries become thinner and pass into arterioles, which, depending on the need, can contract or be in a relaxed state. Arterial blood is bright red.

Veins are similar in structure to arteries, they also have a three-layer structure, but these vessels have thinner walls and a larger internal lumen. Through them, the blood returns back to the heart, for which the venous vessels are equipped with a system of valves that pass only in one direction. The pressure in the veins is always lower than in the arteries, and the fluid has a dark tint - this is their feature.

Capillaries are a branched network of small vessels, covering all corners of the body. The structure of the capillaries is very thin, they are permeable, due to which metabolism occurs between the blood and cells.

Device and principle of operation

The vital activity of the body is ensured by the constant well-coordinated work of all elements of the human circulatory system. The structure and functions of the heart, blood cells, veins and arteries, as well as human capillaries ensure his health and normal functioning the whole organism.

Blood belongs to fluid connective tissue. It consists of plasma in which three types of cells move, as well as nutrients and minerals.

With the help of the heart, blood moves in two interconnected circles of blood circulation:

large (bodily), which carries blood enriched with oxygen throughout the body;
small (lung), it passes through the lungs, which enrich the blood with oxygen.

The heart is the main engine of the circulatory system that works throughout human life. During the year, this organ makes about 36.5 million contractions and passes more than 2 million liters through itself.

The heart is a muscular organ made up of four chambers:

right atrium and ventricle;
left atrium and ventricle.

The right side of the heart receives blood with a lower oxygen content, which flows through the veins, is pushed by the right ventricle into the pulmonary artery and is sent to the lungs to saturate them with oxygen. From the capillary system of the lungs, it enters the left atrium and is pushed by the left ventricle into the aorta and further throughout the body.

The arterial blood fills the system of small capillaries, where it gives oxygen and nutrients to the cells and is saturated with carbon dioxide, after which it becomes venous and goes to the right atrium, from where it is sent back to the lungs. Thus, the anatomy of the blood vessel network is a closed system.

Atherosclerosis is a dangerous pathology

There are many diseases and pathological changes in the structure of the human circulatory system, for example, narrowing of the lumen of blood vessels... Due to violations protein-fat metabolism this often develops serious illness as atherosclerosis - narrowing in the form of plaques caused by the deposition of cholesterol on the walls of arterial vessels.

Progressive atherosclerosis can significantly reduce the inner diameter of the arteries up to complete blockage and can lead to ischemic disease hearts. In severe cases, surgical intervention is inevitable - the clogged vessels have to be shunted. Over the years, the risk of getting sick increases significantly.

/ 12.11.2017

What is the name of the middle layer of the vessel wall. Vessels, types. The structure of the walls of blood vessels.

Anatomy of the heart.

2. Types of blood vessels, features of their structure and function.

3. The structure of the heart.

4. Topography of the heart.

1. General characteristics of cardiovascular vascular system and its meaning.

CCC includes two systems: circulatory (circulatory system) and lymphatic (lymph circulation system). The circulatory system connects the heart and blood vessels. The lymphatic system includes lymphatic capillaries, branched in organs and tissues, lymphatic vessels, lymphatic trunks and lymphatic ducts, through which lymph flows towards large venous vessels. The doctrine of CVS is called angiocardiology.

The circulatory system is one of the main body systems. It provides delivery of nutrient, regulatory, protective substances, oxygen to tissues, removal of metabolic products, heat exchange. It is a closed vascular network that permeates all organs and tissues, and has a centrally located pumping device - the heart.

Types of blood vessels, features of their structure and function.

Anatomically, blood vessels are divided into arteries, arterioles, precapillaries, capillaries, postcapillaries, venules and veins.

Arteries - these are blood vessels that carry blood from the heart, no matter what kind of blood: arterial or venous in them. They are cylindrical tubes, the walls of which consist of 3 shells: outer, middle and inner. Outdoor(adventitia) membrane is represented by connective tissue, average- smooth muscle, internal- endothelial (intima). In addition to the endothelial lining, the inner lining of most arteries also has an inner elastic membrane. An outer elastic membrane is located between the outer and middle membranes. Elastic membranes give the walls of the arteries additional strength and elasticity. The thinnest arterial vessels are called arterioles... They go into precapillaries, and the latter - in capillaries, the walls of which are highly permeable, due to which there is an exchange of substances between blood and tissues.

Capillaries - these are microscopic vessels that are located in tissues and connect arterioles with venules through the precapillaries and postcapillaries. Postcapillaries formed from the fusion of two or more capillaries. As the postcapillaries merge, venules- the smallest venous vessels. They flow into the veins.

Veins Are the blood vessels that carry blood to the heart. The walls of the veins are much thinner and weaker than the arterial ones, but they consist of the same three membranes. However, the elastic and muscle elements in the veins are less developed, so the walls of the veins are more pliable and may collapse. Unlike arteries, many veins have valves. The valves are semi-lunar folds of the inner lining that prevent blood from flowing back into them. There are especially many valves in the veins of the lower extremities, in which the movement of blood occurs against the force of gravity and the possibility of stagnation and reverse blood flow is created. Many valves in the veins upper limbs, less - in the veins of the trunk and neck. Only both vena cava, veins of the head, renal veins, portal and pulmonary veins do not have valves.

The branching arteries are connected to each other, forming arterial fistulas - anastomoses. The same anastomoses connect the veins. If the inflow or outflow of blood through the main vessels is disturbed, anastomoses promote the movement of blood in different directions. Vessels that provide blood flow bypassing the main path are called collateral (roundabout).

The blood vessels of the body are combined into big and small circles of blood circulation... In addition, they additionally allocate coronary circulation.

Systemic circulation (corporal) starts from the left ventricle of the heart, from which blood enters the aorta. From the aorta, through the arterial system, blood is carried away to the capillaries of organs and tissues of the whole body. Through the walls of the capillaries of the body, an exchange of substances occurs between blood and tissues. Arterial blood gives oxygen to tissues and, saturated with carbon dioxide, turns into venous blood. The systemic circulation ends with two vena cava flowing into the right atrium.

Small circle of blood circulation (pulmonary) begins with the pulmonary trunk, which departs from the right ventricle. Through it, blood is delivered to the pulmonary capillary system. In the capillaries of the lungs, venous blood, enriched with oxygen and freed from carbon dioxide, turns into arterial. From the lungs, arterial blood flows through 4 pulmonary veins into the left atrium. Here the small circle of blood circulation ends.

Thus, the blood moves through a closed circulatory system. The rate of blood circulation in a large circle is 22 seconds, in a small circle - 5 seconds.

Coronal circle of blood circulation (cardiac) includes the vessels of the heart itself for the blood supply to the heart muscle. It begins with the left and right coronary arteries, which branch off from the initial section of the aorta - the aortic bulb. Flowing through the capillaries, the blood gives oxygen and nutrients to the heart muscle, receives decay products, and turns into venous. Almost all the veins of the heart flow into a common venous vessel - the coronary sinus, which opens into the right atrium.

The structure of the heart.

Heart(cor; Greek cardia) - a hollow muscular organ in the shape of a cone, the top of which is facing down, left and forward, and the base - up, right and back. The heart is located in the chest cavity between the lungs, behind the sternum, in the region of the anterior mediastinum. Approximately 2/3 of the heart is in the left side of the chest and 1/3 in the right.

The heart has 3 surfaces. Front surface the heart is adjacent to the sternum and costal cartilage, back- to the esophagus and thoracic part of the aorta, bottom- to the diaphragm.

On the heart, the edges (right and left) and grooves are also distinguished: coronal and 2 interventricular (anterior and posterior). The coronary sulcus separates the atria from the ventricles, the interventricular sulcus separates the ventricles. Vessels and nerves are located in the grooves.

The size of the heart is individually different. Usually, the size of the heart is compared with the size of the fist of a given person (length 10-15 cm, transverse size - 9-11 cm, anteroposterior size - 6-8 cm). The average heart mass of an adult is 250-350 g.

The wall of the heart consists of 3 layers:

- inner layer (endocardium) lines the cavity of the heart from the inside, its outgrowths form the valves of the heart. It consists of a layer of flattened thin, smooth endothelial cells. The endocardium forms the atrioventricular valves, the valves of the aorta, the pulmonary trunk, as well as the valves of the inferior vena cava and coronary sinus;

- middle layer (myocardium) is the contractile apparatus of the heart. The myocardium is formed by striated cardiac muscle tissue and is the thickest and most functionally powerful part of the heart wall. The thickness of the myocardium is not the same: the largest is in the left ventricle, the smallest is in the atria.

The ventricular myocardium consists of three muscle layers - external, middle and internal; atrial myocardium - from two layers of muscles - superficial and deep. The muscle fibers of the atria and ventricles originate from the fibrous rings that separate the atria from the ventricles. fibrous rings are located around the right and left atrioventricular openings and form a kind of skeleton of the heart, which includes thin rings of connective tissue around the openings of the aorta, pulmonary trunk and adjacent right and left fibrous triangles.

- outer layer (epicardium) covers the outer surface of the heart and the areas of the aorta, pulmonary trunk and vena cava closest to the heart. It is formed by a layer of cells epithelial type and is an inner layer of the pericardial serous membrane - pericardium. The pericardium insulates the heart from the surrounding organs, protects the heart from excessive stretching, and the fluid between its plates reduces friction during heart contractions.

The human heart is divided by a longitudinal septum into 2 non-communicating halves (right and left). At the top of each half is atrium(atrium) right and left, at the bottom - ventricle(ventriculus) right and left. Thus, the human heart has 4 chambers: 2 atria and 2 ventricles.

The right atrium receives blood from all parts of the body through the superior and inferior vena cava. 4 pulmonary veins that carry arterial blood from the lungs flow into the left atrium. The pulmonary trunk leaves the right ventricle, through which venous blood enters the lungs. From the left ventricle leaves the aorta, which carries arterial blood into the vessels of the systemic circulation.

Each atrium communicates with its corresponding ventricle through atrioventricular opening, furnished flap valve... The valve between the left atrium and the ventricle is bicuspid (mitral), between the right atrium and ventricle - tricuspid... The valves open towards the ventricles and allow blood to flow only in that direction.

The pulmonary trunk and the aorta at their origin have semilunar valves , consisting of three semilunar valves and opening in the direction of blood flow in these vessels. Special protrusions of the atria form right and left auricular... On the inner surface of the right and left ventricles there are papillary muscles- these are outgrowths of the myocardium.

Heart topography.

Upper bound corresponds to the upper edge of the cartilage of the III pair of ribs.

Left border goes along an arcuate line from the cartilage of the III rib to the projection of the apex of the heart.

Top the heart is defined in the left V intercostal space 1–2 cm medial to the left midclavicular line.

Right border runs 2 cm to the right of the right edge of the sternum

Bottom line- from the upper edge of the cartilage V of the right rib to the projection of the apex of the heart.

There are age groups, constitutional features location (in newborns, the heart lies entirely in the left half of the chest horizontally).

The main hemodynamic parameters is an volumetric blood flow velocity, pressure in various parts of the vascular bed.

Volumetric velocity Is the amount of blood flowing through the cross-section of the vessel per unit of time and depends on the pressure difference at the beginning and end of the vascular system and on the resistance.

Arterial pressure depends on the work of the heart. Blood pressure fluctuates in the vessels with each systole and diastole. During the period of systole, blood pressure rises - systolic pressure. At the end of diastole, it decreases - diastolic. The difference between systolic and diastolic is the pulse pressure.

Vessels are tubular formations that run throughout the human body. Blood moves along them. The pressure in the circulatory system is quite high, since the system is closed. Blood circulates through such a system very quickly.

After a long period of time, plaques form on the vessels, which obstruct the movement of blood. They are formed on inside vessels. To overcome obstacles in the vessels, the heart must pump blood with greater intensity, as a result of which the working process of the heart is disrupted. At the moment, the heart is no longer capable of delivering blood to the organs of the body. It does not cope with the work. At this stage, there is still a possibility of recovery. The vessels are cleaned from cholesterol deposits and salts.

After cleansing the vessels, their flexibility and elasticity are restored. Most vascular diseases disappear, for example, headaches, paralysis, sclerosis, a tendency to heart attack. There is a restoration of vision and hearing, decreases, the state of the nasopharynx is normalized.

Types of blood vessels

There are three types of vessels in the human body: arteries, veins, and blood capillaries. The artery performs the function of delivering blood to a variety of tissues and organs from the heart. They form arterioles strongly and branch. Veins, on the contrary, return blood from tissues and organs to the heart. Blood capillaries are the thinnest vessels. When they merge, the smallest veins are formed - venules.

Arteries

Blood travels through the arteries from the heart to various human organs. At the farthest distance from the heart, the arteries are divided into fairly small branches. Such branches are called arterioles.

The artery consists of an inner, outer and middle membrane. The inner membrane is a squamous epithelium with smooth

The inner membrane consists of a flat epithelium, the surface of which is very smooth, it adjoins, and also rests on the basal elastic membrane. The middle shell consists of smooth muscle tissue and developed elastic tissue. Thanks to the muscle fibers, the arterial lumen is changed. Elastic fibers provide strength, elasticity and elasticity to the walls of the arteries.

Thanks to the fibrous loose connective tissue present in the outer sheath, the arteries are in the necessary anchored state, while they are perfectly protected.

The middle arterial layer does not have muscle tissue; it consists of elastic tissues, which make it possible for them to exist at a sufficiently high blood pressure. Such arteries include the aorta, the pulmonary trunk. The small arteries in the middle layer have practically no elastic fibers, but they are equipped with a muscle layer that is very developed.

Blood capillaries

Capillaries are located in the intercellular space. They are the thinnest of all vessels. They are located close to arterioles - in places of strong branching of small arteries, they are also further from the rest of the vessels from the heart. The length of the capillaries is in the range of 0.1 - 0.5 mm, the lumen is 4-8 microns. A huge number of capillaries in the heart muscle. And in the muscles of skeletal capillaries, on the contrary, there are very few. There are more capillaries in the human head in gray than in white matter. This is due to the fact that the number of capillaries increases in tissues that have a high degree of metabolism. The capillaries form the smallest venules when they merge.

Veins

These vessels are designed to return blood back to the heart from human organs. The venous wall also consists of an inner, outer and middle layer. But since the middle layer is thin enough in comparison with the arterial middle layer, the venous wall is much thinner.

Since the veins do not need to withstand high blood pressures, there are much less muscle and elastic fibers in these vessels than in the arteries. The veins also have significantly more venous valves on the inner wall. There are no such valves in the hollow superior vein, veins of the brain, head and heart, in the pulmonary veins. Venous valves prevent back movement in the veins of the blood in the working process of skeletal muscles.

VIDEO

Traditional methods of treating vascular diseases

Garlic treatment

It is necessary to crush one head of garlic with a garlic maker. Then the chopped garlic is laid out in a jar and poured into a glass of unrefined sunflower oil. If possible, it is better to use fresh flaxseed oil. Let the composition brew in a cold place for one day.

After that, you need to add one squeezed lemon to this tincture on a juicer along with the peel. The resulting mixture is intensively mixed and taken 30 minutes before a meal, a teaspoon three times throughout the day.

The course of treatment must be continued for one to three months. After a month, the treatment is repeated.

Tincture for heart attack and stroke

In folk medicine, there is a huge variety of remedies intended for the treatment of blood vessels, prevention of blood clot formation, as well as for the prevention and heart attack. Datura tincture is one such remedy.

Datura fruit resembles a chestnut. It also has thorns. Datura has five centimeter white pipes. The plant can grow up to one meter in height. The fruit cracks after ripening. During this period, its seeds ripen. Datura is sown in spring or autumn. In autumn, the plant attacks the Colorado potato beetle. To get rid of beetles, it is recommended to lubricate the trunk of the plant two centimeters from the ground with petroleum jelly or fat. After drying, the seeds are stored for three years.

Recipe: 85 g dry (100 g of ordinary seeds) is poured with moonshine in an amount of 0.5 liters (moonshine can be replaced rubbing alcohol diluted with water in a 1: 1 ratio). The agent must be allowed to brew for fifteen days, and it must be shaken every day. You do not need to filter the tincture. It must be stored in a dark bottle when room temperature, protect from sun rays.

Method of application: every morning, 30 minutes before a meal, 25 drops each, always on an empty stomach. The tincture is diluted in 50-100 ml of cool, but boiled water. The treatment course is one month. The process of treatment must be constantly monitored, it is recommended to draw up a schedule. A second course of treatment after six months, and then after two. After taking the tincture, you are very thirsty. Therefore, you need to consume a lot of water.

Blue iodine for the treatment of blood vessels

People say a lot about blue iodine. In addition to its use for the treatment of vascular diseases, it is used in a number of other diseases.

Cooking method: you need to dilute one teaspoon of potato starch in 50 ml of warm water, stir, add one teaspoon of sugar, citric acid on the tip of a knife. Then this solution is poured into 150 ml of boiled water. The mixture must be allowed to cool completely, and then pour into it 5% tincture of iodine in the amount of one teaspoon.

Recommendations for use: the mixture is stored in a closed jar at room temperature for several months. You need to take after meals once a day for five days, 6 teaspoons. Then a five-day break is taken. The medicine can be taken every other day. If you have an allergy, you need to drink two tablets of activated charcoal on an empty stomach.

It must be remembered that if citric acid and sugar are not added to the solution, then its shelf life is reduced to ten days. It is also not recommended to abuse blue iodine, because when it is consumed in excess, the amount of mucus increases, signs of a cold appear or. In such cases, you need to stop consuming blue iodine.

Special balm for blood vessels

There are two ways of treating blood vessels with the use of balms that can help with deep atherosclerosis, hypertension, coronary heart disease, spasms cerebral vessels, stroke.

Cooking recipe 1: 100 ml alcohol tinctures of blue cyanosis root, thorny hawthorn flowers, white mistletoe leaves, medicinal lemon balm herb, dog nettle, leaves big plantain, peppermint herbs.

Cooking Recipe 2: 100 ml of alcohol tinctures of Baikal skullcap root, hop cones, root are mixed medicinal valerian, dog nettle, May lily of the valley herb.

Method of using the balm: a spoonful of tablespoon 3 rubles per day 15 minutes before meals.

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Blood vessels develop from the mesenchyme. First, the primary wall is laid, which subsequently turns into the inner lining of the vessels. The cells of the mesenchyme, connecting, form the cavity of the future vessels. The wall of the primary vessel consists of flat mesenchymal cells that form the inner layer of future vessels. This layer of flat cells belongs to the endothelium. Later, the final, more complex vessel wall is formed from the surrounding mesenchyme. It is characteristic that all vessels in the embryonic period are laid and built like capillaries, and only in the process of their further development a simple capillary wall is gradually surrounded by various structural elements, and the capillary vessel turns into either an artery, or a vein, or a lymphatic vessel.

The finally formed walls of vessels of both arteries and veins are not the same throughout their entire length, but both of them consist of three main layers (Fig. 231). Common to all vessels is a thin inner membrane, or intima (tunica intima), lined from the side of the vascular cavity with the thinnest, very elastic and flat polygonal endothelial cells. Intima is a direct continuation of the endothelium of the endocardium. This smooth and smooth inner lining protects the blood from clotting. If the endothelium of the vessel is damaged by injury, infection, inflammatory or dystrophic process, etc., then at the site of damage small blood clots form (clots - thrombi), which can increase in size and cause blockage of the vessel. Sometimes they break away from the place of formation, are carried away by the blood stream and, as so-called emboli, clog the vessel in some other place. The effect of such a thrombus or embolus depends on where the vessel is blocked. Thus, a blockage of a vessel in the brain can cause paralysis; a blockage of the coronary artery of the heart deprives the heart muscle of blood flow, which is expressed in a severe heart attack and often leads to death. Blockage of a vessel suitable for any part of the body or an internal organ deprives it of nutrition and can lead to necrosis (gangrene) of the supplied part of the organ.

Outside of the inner layer is the middle shell (media), consisting of circular smooth muscle fibers with an admixture of elastic connective tissue.

The outer shell of the vessels (adventitia) wraps around the middle one. In all vessels, it is built of fibrous fibrous connective tissue, containing mainly longitudinally located elastic fibers and connective tissue cells.

On the border of the middle and inner, middle and outer shell of the vessels, elastic fibers form, as it were, a thin plate (membrana elastica interna, membrana elastica externa).

In the outer and middle membranes of blood vessels, the vessels branch out, feeding their wall (vasa vasorum).

The walls of the capillary vessels are extremely thin (about 2 μ) and consist mainly of a layer of endothelial cells that form a capillary tube. This endothelial tube is braided from the outside with a thinnest network of filaments on which it is suspended, due to which it can be displaced very easily and without damage. Fibers depart from a thin, basic film, to which special cells are also associated - pericytes, covering capillaries. The capillary wall is easily permeable to leukocytes and blood; it is at the level of the capillaries through their wall that an exchange takes place between blood and tissue fluids, as well as between blood and external environment(in the excretory organs).

Arteries and veins are usually divided into large, medium and small. The smallest arteries and veins passing into capillaries are called arterioles and venules. The arteriole wall consists of all three sheaths. The innermost endothelial, and the next middle one, is built of circularly located smooth muscle cells. When the arteriole passes into the capillary, only single smooth muscle cells are noted in its wall. With the enlargement of the arteries, the number of muscle cells gradually increases to a continuous annular layer - muscle-type arteries.

The structure of small and medium arteries is also distinguished by some peculiarity. A layer of elongated and stellate cells, which in the larger arteries form a layer that plays the role of a cambium (growth layer) for the vessels. This layer is involved in the processes of regeneration of the vessel wall, that is, it has the ability to restore the muscle and endothelial layers of the vessel. In arteries of medium caliber or mixed type, the cambial (germ) layer is more developed.

Large-caliber arteries (aorta, its large branches) are called elastic-type arteries. Elastic elements predominate in their walls; in the middle shell, strong elastic membranes are concentrically laid, between which there is a significantly smaller number of smooth muscle cells. The cambial layer of cells, well expressed in small and medium-sized arteries, in large arteries turns into a layer of subendothelial loose connective tissue rich in cells.

Due to the elasticity of the walls of the arteries, like rubber tubes, under the pressure of blood, they can easily stretch and do not collapse, even if the blood is released from them. All the elastic elements of the vessels together form a single elastic framework, which works like a spring, each time returning the vessel wall to its original state as soon as the smooth muscle fibers relax. Since arteries, especially large ones, have to withstand a fairly high blood pressure, their walls are very strong. Observations and experiments show that the arterial walls can withstand even this strong pressure, which happens in a steam boiler of a conventional steam locomotive (15 atm.).

The walls of the veins are usually thinner than the walls of the arteries, especially the middle lining. There is also much less elastic tissue in the venous wall, so the veins collapse very easily. The outer sheath is constructed of fibrous connective tissue dominated by collagen fibers.

A feature of the veins is the presence of valves in them in the form of semilunar pockets (Fig. 232), formed from the duplication of the inner membrane (intima). However, valves are not found in all veins in our body; they are deprived of the veins of the brain and its membranes, the veins of the bones, as well as a significant part of the veins of the viscera. The valves are more often found in the veins of the limbs and neck, they are open towards the heart, that is, in the direction of blood flow. By blocking backflow, which can occur due to low blood pressure and due to the law of gravity (hydrostatic pressure), the valves facilitate blood flow.

If there were no valves in the veins, the entire weight of the blood column more than 1 m high would press on the blood entering the lower extremity and this would greatly impede blood circulation. Further, if the veins were rigid tubes, some valves could not provide blood circulation, since all the same the entire column of liquid would press on underlying departments... The veins are located among the large skeletal muscles, which, by contracting and relaxing, periodically compress the venous vessels. When the contracting muscle compresses the vein, the valves below the clamping point close, and the valves above open; when the muscle relaxes and the vein is again free from compression, the upper valves in it close and retard the higher blood column, while the lower ones open and allow the vessel to re-fill with blood coming from below. This pumping action of the muscles (or "muscle pump") greatly aids in blood circulation; standing for many hours in one place, in which the muscles do not help much blood flow, is more tiring than walking.

The distribution of blood throughout the human body is carried out due to the work of the cardiovascular system. Its main organ is the heart. His every blow contributes to the fact that the blood moves and nourishes all organs and tissues.

System structure

The body produces different types of blood vessels. Each of them has its own purpose. So, the system includes arteries, veins and lymphatic vessels. The first of them are designed to ensure that blood, enriched with nutrients, flows to tissues and organs. It is saturated with carbon dioxide and various products released during the vital activity of cells, and returns through the veins back to the heart. But before entering this muscular organ, the blood is filtered in the lymphatic vessels.

The total length of the system, consisting of blood and lymph vessels, in the body of an adult is about 100 thousand km. And the heart is responsible for its normal functioning. It is it that pumps about 9.5 thousand liters of blood every day.

Principle of operation

The circulatory system is designed to support the entire body. If there are no problems, then it functions as follows. Oxygenated blood comes out of the left side of the heart through the largest arteries. It spreads throughout the body to all cells through wide vessels and tiny capillaries, which can only be seen under a microscope. It is the blood that enters the tissues and organs.

The place where the arterial and venous systems meet is called the “capillary bed”. The walls of the blood vessels in it are thin, and they themselves are very small. This allows you to fully release oxygen and various nutrients through them. The spent blood enters the veins and returns through them to the right side of the heart. From there, it enters the lungs, where it is re-enriched with oxygen. Going through lymphatic system, the blood is purified.

Veins are divided into superficial and deep. The former are close to the surface of the skin. Through them, blood enters deep veins, which return it to the heart.

The regulation of blood vessels, the work of the heart and general blood flow is carried out by the central nervous system and local chemicals secreted in the tissues. It helps to control the flow of blood through the arteries and veins, increasing or decreasing its intensity depending on the processes taking place in the body. For example, it increases with exercise and decreases with injury.

How does blood flow

The spent "depleted" blood flows through the veins into the right atrium, from where it flows into the right ventricle of the heart. With powerful movements, this muscle pushes the incoming fluid into the pulmonary trunk. It is split into two parts. The blood vessels of the lungs are designed to enrich the blood with oxygen and return them to the left ventricle of the heart. In every person, this part of him is more developed. After all, it is the left ventricle that is responsible for how the entire body will be supplied with blood. It is estimated that the load that falls on him is 6 times more than that which the right ventricle is subjected to.

The circulatory system includes two circles: small and large. The first of them is designed to saturate the blood with oxygen, and the second - to transport it throughout the orgasm, delivery to every cell.

Requirements for the circulatory system

In order for the human body to function normally, a number of conditions must be met. First of all, attention is paid to the condition of the heart muscle. After all, it is she who is the pump that drives the necessary biological fluid through the arteries. If the work of the heart and blood vessels is impaired, the muscle is weakened, then this can cause peripheral edema.

It is important that the difference between the areas of low and high pressure is observed. This is necessary for normal blood flow. So, for example, in the area of the heart, the pressure is lower than at the level of the capillary bed. This allows you to comply with the laws of physics. Blood moves from the area of higher pressure to the area where it is lower. If a number of diseases occur, due to which the established balance is disturbed, then this is fraught with stagnation in the veins, edema.

The release of blood from the lower extremities is carried out thanks to the so-called muscle-venous pumps. This is the name of the gastrocnemius muscles. With each step, they contract and push the blood against the natural force of gravity towards the right atrium. If this function is impaired, for example, as a result of trauma and temporary immobilization of the legs, then edema occurs due to a decrease in venous return.

Another important link responsible for the functioning of the blood vessels of a person is the venous valves. They are designed to keep fluid going through them until it enters the right atrium. If this mechanism is disrupted, and this is possible as a result of injury or due to wear of the valves, abnormal blood collection will be observed. As a result, this leads to an increase in pressure in the veins and the squeezing of the liquid part of the blood into the tissues around it. A prime example violation of this function is the veins in the legs.

Classification of vessels

To understand how the circulatory system works, it is necessary to understand how each of its components functions. So, the pulmonary and hollow veins, the pulmonary trunk and the aorta are the main pathways for the movement of the necessary biological fluid. And all the rest are able to regulate the intensity of the inflow and outflow of blood to the tissues due to the ability to change their lumen.

All vessels in the body are divided into arteries, arterioles, capillaries, venules, veins. All of them form a closed connecting system and serve a single purpose. Moreover, each blood vessel has its own purpose.

Arteries

The areas along which blood moves are divided depending on the direction in which it moves in them. So, all arteries are designed to carry blood from the heart through the body. They are of elastic, muscular and muscular-elastic types.

The first type includes those vessels that are directly connected with the heart and leave its ventricles. These are the pulmonary trunk, pulmonary and carotid arteries, aorta.

All of these vessels of the circulatory system are composed of elastic fibers that stretch. This happens with every heartbeat. As soon as the contraction of the ventricle has passed, the walls return to their original form. Due to this, it is supported normal pressure throughout the period until the heart is again filled with blood.

To all tissues of the body, blood enters through the arteries that depart from the aorta and pulmonary trunk. Wherein various bodies need different amounts of blood. This means that the arteries must be able to narrow or expand their lumen so that the liquid passes through them only in the necessary doses. This is achieved due to the fact that smooth muscle cells work in them. Such human blood vessels are called distribution vessels. Their lumen is regulated by the sympathetic nervous system. Muscle arteries include the artery of the brain, radial, brachial, popliteal, vertebral and others.

Other types of blood vessels are also distinguished. These include muscular-elastic or mixed arteries. They can shrink very well, but they are also highly elastic. This type includes the subclavian, femoral, iliac, mesenteric arteries, celiac trunk. They contain both elastic fibers and muscle cells.

Arterioles and capillaries

As the blood moves along the arteries, their lumen decreases, and the walls become thinner. Gradually they pass into the smallest capillaries. The area where the arteries end are called arterioles. Their walls consist of three layers, but they are poorly expressed.

The thinnest vessels are capillaries. Together, they represent the longest part of the entire blood supply system. They are the ones that connect the venous and arterial beds.

A true capillary is a blood vessel that forms as a result of the branching of arterioles. They can form loops, nets, which are located in the skin or bursae, or vascular glomeruli, which are located in the kidneys. The size of their lumen, the speed of blood flow in them and the shape of the networks formed depend on the tissues and organs in which they are located. For example, the thinnest vessels are located in skeletal muscles, lungs and nerve sheaths - their thickness does not exceed 6 microns. They form only flat networks. In mucous membranes and skin, they can reach 11 microns. In them, the vessels form a three-dimensional network. The widest capillaries are located in the hematopoietic organs, the endocrine glands. Their diameter in them reaches 30 microns.

The density of their placement is also not the same. The highest concentration of capillaries is noted in the myocardium and brain, for every 1 mm 3 there are up to 3,000 of them. Moreover, in skeletal muscle there are only up to 1,000 of them, and even less in bone tissue. It is also important to know that in an active state, under normal conditions, blood does not circulate through all capillaries. About 50% of them are in an inactive state, their lumen is compressed to a minimum, only plasma passes through them.

Venules and veins

Capillaries, into which blood comes from arterioles, unite and form larger vessels. They are called postcapillary venules. The diameter of each such vessel does not exceed 30 microns. At the transition points, folds are formed that perform the same functions as the valves in the veins. Elements of blood and plasma can pass through their walls. Postcapillary venules unite and flow into the collective. Their thickness is up to 50 microns. Smooth muscle cells begin to appear in their walls, but often they do not even surround the lumen of the vessel, but their outer shell is already clearly expressed. The collecting venules become muscular. The diameter of the latter often reaches 100 microns. They already have up to 2 layers of muscle cells.

The circulatory system is designed in such a way that the number of vessels that drain blood is usually twice the number of those through which it enters the capillary bed. In this case, the liquid is distributed as follows. The arteries contain up to 15% of the total amount of blood in the body, in the capillaries up to 12%, and in the venous system 70-80%.

By the way, fluid can flow from arterioles to venules without entering the capillary bed through special anastomoses, into the walls of which muscle cells enter. They are found in almost all organs and are designed so that blood can be discharged into the venous bed. With their help, pressure is controlled, the transition of tissue fluid and blood flow through the organ is regulated.

Veins are formed after venules fusion. Their structure directly depends on the location and diameter. The number of muscle cells is affected by the place of their localization and by what factors the fluid moves in them. Veins are divided into muscle and fibrous. The latter include the vessels of the retina, spleen, bones, placenta, soft and hard membranes of the brain. The blood circulating in the upper part of the body moves mainly under the force of gravity, as well as under the influence of the suction action during inhalation of the chest cavity.

The veins of the lower extremities are different. Each blood vessel in the legs must withstand the pressure created by the liquid column. And if the deep veins are able to maintain their structure due to the pressure of the surrounding muscles, then the superficial ones are more difficult. They have a well-developed muscle layer, and their walls are much thicker.

Also, a characteristic difference of veins is the presence of valves that prevent the backflow of blood under the influence of gravity. True, they are not in those vessels that are in the head, brain, neck and internal organs. They are also absent in the hollow and small veins.

The functions of blood vessels differ depending on their purpose. So, veins, for example, serve not only to move fluid to the heart area. They are also designed to reserve it in separate areas. The veins are activated when the body is working hard and needs to increase the volume of circulating blood.

Arterial wall structure

Each blood vessel is made up of several layers. Their thickness and density depend solely on what type of veins or arteries they belong to. It also affects their composition.

For example, elastic arteries contain a large number of fibers that provide stretching and elasticity of the walls. The inner lining of each such blood vessel, which is called the intima, is about 20% of the total thickness. It is lined with endothelium, and underneath is loose connective tissue, intercellular substance, macrophages, muscle cells. The outer layer of the intima is limited by an internal elastic membrane.

The middle layer of such arteries consists of elastic membranes; with age, they thicken, their number increases. Between them are smooth muscle cells that produce intercellular substance, collagen, elastin.

The outer sheath of elastic arteries is formed by fibrous and loose connective tissue, longitudinally in it elastic and collagen fibers are located. It also contains small vessels and nerve trunks. They are responsible for feeding the outer and middle membranes. It is the outer part that protects the arteries from rupture and overstretching.

The structure of blood vessels, which are called muscle arteries, is not much different. They also have three layers. The inner shell is lined with endothelium; it contains the inner membrane and loose connective tissue. In small arteries, this layer is poorly developed. Connective tissue contains elastic and collagen fibers, they are located longitudinally in it.

The middle layer is formed by smooth muscle cells. They are responsible for the contraction of the entire vessel and for pushing the blood into the capillaries. Smooth muscle cells connect with the extracellular substance and elastic fibers. The layer is surrounded by a kind of elastic membrane. The fibers located in the muscle layer are connected to the outer and inner layers of the layer. They seem to form an elastic frame that prevents the artery from sticking together. And muscle cells are responsible for regulating the thickness of the lumen of the vessel.

The outer layer consists of loose connective tissue, in which collagen and elastic fibers are located, they are located obliquely and longitudinally in it. Nerves, lymphatic and blood vessels pass through it.

The structure of the mixed blood vessels is an intermediate link between the muscular and elastic arteries.

Arterioles also have three layers. But they are rather weakly expressed. The inner lining is the endothelium, the layer of connective tissue and elastic membrane. The middle layer consists of 1 or 2 layers of muscle cells, which are arranged in a spiral.

Vein structure

In order for the heart and blood vessels, called arteries, to function, it is necessary that the blood can rise back up, bypassing the force of gravity. For these purposes, venules and veins with a special structure are intended. These vessels consist of three layers, as do the arteries, although they are much thinner.

The inner lining of the veins contains the endothelium, it also has a poorly developed elastic membrane and connective tissue. The middle layer is muscular, it is poorly developed, elastic fibers are practically absent in it. By the way, it is because of this that the cut vein always collapses. The thickest is the outer shell. It consists of connective tissue and contains a large number of collagen cells. It also contains smooth muscle cells in some veins. It is they who help push the blood towards the heart and prevent it from flowing back. The outer layer also contains lymphatic capillaries.

Blood vessels in vertebrates form a dense closed network. The vessel wall consists of three layers:

The inner layer is very thin, it is formed by one row of endothelial cells that smooth the inner surface of the vessels.
The middle layer is the thickest, it contains a lot of muscle, elastic and collagen fibers. This layer provides vascular strength.
The outer layer is connective tissue, it separates the vessels from the surrounding tissues.

According to the circles of blood circulation, blood vessels can be divided into:

Arteries of the systemic circulation [show]
- The largest arterial vessel in the human body is the aorta, which leaves the left ventricle and gives rise to all the arteries that form the systemic circulation. The aorta is divided into the ascending aorta, the aortic arch, and the descending aorta. The aortic arch divides in turn into a thoracic aorta and an abdominal aorta.
- Arteries of the neck and head
  Common carotid artery (right and left), which divides into the external carotid artery and the internal carotid artery at the level of the upper edge of the thyroid cartilage.
  - The external carotid artery gives a number of branches, which, according to their topographic features, are divided into four groups - anterior, posterior, medial and a group of terminal branches that supply blood to the thyroid gland, muscles of the hyoid bone, sternocleidomastoid muscle, muscles of the mucous membrane of the larynx, epiglottis, tongue, palate, tonsils, face, lips, ear (external and internal), nose, occiput, dura mater.
  - The internal carotid artery in its course is a continuation of both carotid artery. It distinguishes between the cervical and intracranial (head) parts. In the cervical part, the internal carotid artery usually does not give branches. In the cranial cavity from the internal carotid artery, branches branch off to the cerebrum and the orbital artery, which supply blood to the brain and eyes.
  The subclavian artery is a steam room, it begins in the anterior mediastinum: the right one - from the shoulder-head trunk, the left one - directly from the aortic arch (therefore, the left artery is longer than the right one). In the subclavian artery, three sections are topographically distinguished, each of which gives its own branches:
  - The branches of the first section - the vertebral artery, the internal thoracic artery, the thyroid-cervical trunk - each of which gives its own branches that supply blood to the brain, cerebellum, neck muscles, thyroid gland, etc.
  - Branches of the second section - here only one branch departs from the subclavian artery - the costal-cervical trunk, which gives rise to arteries that supply blood to the deep muscles of the occiput, spinal cord, back muscles, intercostal spaces
  - Branches of the third section - one branch also departs here - the transverse artery of the neck, which supplies blood to the muscles of the back
- Arteries of the upper limb, forearm and hand
- Trunk arteries
- Pelvic arteries
- Lower limb arteries
Veins of the systemic circulation [show]
- Superior vena cava system
  - Veins of the trunk
  - Veins of the head and neck
  - Veins of the upper limb
- Inferior vena cava system
  - Veins of the trunk
- Pelvic veins
  - Veins of the lower extremities
Vessels of a small circle of blood circulation [show]
The vessels of the small, pulmonary, circle of blood circulation include:
- pulmonary trunk
- pulmonary veins in the amount of two pairs, right and left
Pulmonary trunk is divided into two branches: the right pulmonary artery and the left pulmonary artery, each of which goes to the gate of the corresponding lung, bringing venous blood to it from the right ventricle.
The right artery is somewhat longer and wider than the left. Having entered the root of the lung, it is divided into three main branches, each of which enters the gate of the corresponding lobe of the right lung.
The left artery at the root of the lung is divided into two main branches that enter the gate of the corresponding lobe of the left lung.
From the pulmonary trunk to the aortic arch there is a fibromuscular cord (arterial ligament). In the period of intrauterine development, this ligament is the ductus arteriosus, through which most of the blood from the pulmonary trunk of the fetus passes into the aorta. After birth, this duct is obliterated and turns into the specified ligament.
Pulmonary veins, right and left, - remove arterial blood from the lungs. They leave the gate of the lungs, usually two from each lung (although the number of pulmonary veins can reach 3-5 or even more), the right veins are longer than the left ones, and flow into the left atrium.

According to the structural features and functions, blood vessels can be divided into:

Groups of vessels according to the structural features of the wall

Arteries

The blood vessels that go from the heart to the organs and carry blood to them are called arteries (aer - air, tereo - I contain; on corpses, arteries are empty, which is why in the old days they were considered air tubes). Through the arteries, blood flows from the heart underneath, so the arteries have thick elastic walls.

According to the structure of the walls, arteries are divided into two groups:

Elastic-type arteries - the arteries closest to the heart (the aorta and its large branches) perform mainly the function of conducting blood. In them, the counteraction to stretching by a mass of blood, which is thrown out by a heart impulse, comes to the fore. Therefore, structures of a mechanical nature are relatively more developed in their wall, i.e. elastic fibers and membranes. The elastic elements of the arterial wall form a single elastic frame, which works like a spring and determines the elasticity of the arteries.
Elastic fibers give elastic properties to the arteries, which cause a continuous flow of blood throughout the vascular system. The left ventricle, during contraction, pushes out more blood under high pressure than it flows from the aorta into the artery. In this case, the walls of the aorta are stretched, and it contains all the blood ejected by the ventricle. When the ventricle relaxes, the pressure in the aorta drops, and its walls, due to the elastic properties, collapse slightly. The excess blood contained in the distended aorta is pushed from the aorta into the artery, although no blood is drawn from the heart at this time. So, the periodic expulsion of blood by the ventricle, due to the elasticity of the arteries, turns into a continuous movement of blood through the vessels.
The elasticity of the arteries provides another physiological phenomenon. It is known that in any elastic system, a mechanical shock causes vibrations that propagate throughout the system. In the circulatory system, such a push is the blow of the blood ejected by the heart against the walls of the aorta. The vibrations arising in this case propagate along the walls of the aorta and arteries at a speed of 5-10 m / s, which significantly exceeds the speed of blood movement in the vessels. In areas of the body where large arteries come close to the skin - on the wrist, temples, neck - you can feel the vibrations of the walls of the arteries with your fingers. This is the arterial pulse.
Muscular arteries are medium and small arteries in which the inertia of the heart impulse weakens and its own contraction of the vascular wall is required for further blood flow, which is ensured by the relatively large development of smooth muscle tissue in the vascular wall. Smooth muscle fibers contract and relax, narrowing and widening the arteries and thus regulating blood flow in them.

Widely anastomosed with each other, the capillaries form networks (capillary networks), which include 5 links:

arterioles as the most distal links of the arterial system;
precapillaries, which are intermediate between arterioles and true capillaries;
capillaries;
postcapillaries
venules, which are the roots of the veins and pass into the veins

Veins

The movement of blood through the veins is carried out due to the suction action of the heart and chest cavity, in which negative pressure is created during inhalation due to the pressure difference in the cavities, contraction of the striated and smooth muscles of organs and other factors. The contraction of the muscular sheath of the veins, which in the veins of the lower half of the body, where conditions for venous outflow is more difficult, is also important, is more developed than in the veins of the upper body.

Functional groups of vessels

All vessels, depending on the function they perform, can be divided into six groups:

shock-absorbing vessels (vessels of the elastic type)
resistive vessels
sphincter vessels
exchange vessels
capacitive vessels
bypass vessels

Resistive vessels. Resistive vessels include terminal arteries, arterioles and, to a lesser extent, capillaries and venules. It is the terminal arteries and arterioles, that is, the precapillary vessels with a relatively small lumen and thick walls with developed smooth muscles, that offer the greatest resistance to blood flow. Changes in the degree of contraction of the muscle fibers of these vessels lead to distinct changes in their diameter and, consequently, in the total cross-sectional area (especially when it comes to numerous arterioles). Considering that the hydrodynamic resistance largely depends on the cross-sectional area, it is not surprising that it is precisely the contractions of the smooth muscles of the precapillary vessels that serve as the main mechanism for regulating the volumetric blood flow rate in various vascular regions, as well as the distribution of cardiac output (systemic blood flow) over different organs. ...

Intrathoracic vessels as a blood depot

In humans, unlike animals, there is no true depot, in which blood could be retained in special formations and, as necessary, thrown away (an example of such a depot is the spleen of a dog).

Shunt vessels are arteriovenous anastomoses present in some tissues. When these vessels are open, blood flow through the capillaries either decreases or stops completely (see the figure above).

According to the function and structure of various departments and the peculiarities of innervation, all blood vessels have recently been divided into 3 groups:

near cardiac vessels, beginning and ending both circles of blood circulation - aorta and pulmonary trunk (i.e. elastic type arteries), hollow and pulmonary veins;
great vessels serving for the distribution of blood throughout the body. These are large and medium extraorganic arteries of muscle type and extraorganic veins;
organ vessels that provide metabolic reactions between blood and organ parenchyma. These are intraorgan arteries and veins, as well as capillaries.

Details

The structure of the vessel wall. The vascular wall has three membranes - intima with endothelium, media, consisting of smooth muscle cells, and connective tissue adventitia. Each vessel wall shell has a characteristic structure.

Intima (functional group: blood - plasma - endothelium).

The endothelium consists of one layer of endothelial cells located on the basement membrane, facing the lumen of the vessel.
Endothelium lining inner surface of the vessel and is in close contact with blood and plasma. These components (blood, plasma and endothelium) form a functional group (community) both physiologically and pharmacologically.

From the circulating blood, the endothelium receives signals that it integrates and transmits to the blood or smooth muscles located below.

The middle shell is a media (functional group: smooth muscle cells - intercellular matrix - interstitial fluid).

Mainly formed circularly arranged smooth muscle fibers , as well as collagen and elastic elements and proteoglycans.
The middle lining of the artery attaches to the arterial wall shape responsible for capacitive and vasomotor functions... The latter depends on tonic contractions of smooth muscle cells. The intercellular matrix prevents blood from leaving the vascular bed. In addition to vasomotor activity, smooth muscle cells synthesize collagen and elastin for the extracellular matrix. Moreover, once activated, these cells potentially become hypertrophied, proliferated, and capable of migration. The middle membrane is located in the interstitial fluid, most of which comes from blood plasma.
Under physiological conditions, the complex of smooth muscle cells, extracellular matrix and interstitial fluid is indirectly associated with a complex that includes the endothelium, blood and plasma. In pathological conditions, the described complexes interact directly.

Outer sheath (adventitia).

Formed loose connective tissue composed of perivascular fibroblasts and collagen.
The outer shell consists of adventitia, which, in addition to collagen and fibroblasts, also contains capillaries and endings of neurons of the autonomic nervous system. In organs, perivascular fibrous tissue also acts as a dividing surface between the arterial wall and the surrounding organ-specific tissue (for example, the heart muscle, renal epithelium, etc.).

Perivascular fibrous tissue transmits signals both towards and from the vessel, as well as nerve impulses, signals coming from the surrounding tissues and directed to the middle lining of the artery.
The degree of innervation of arteries, capillaries and veins is not the same. Arteries with more developed muscle elements in the tunica media receive more abundant innervation, veins less abundant; v. cava inferior and v. portae are in between.

Innervation of blood vessels.

Larger vessels located inside the body cavities receive innervation from the branches of the sympathetic trunk, the nearest plexuses of the autonomic nervous system and adjacent spinal nerves; the peripheral vessels of the walls of the cavities and the vessels of the extremities receive innervation from the nerves passing nearby. The nerves approaching the vessels go segmental and form perivascular plexuses, from which fibers extend into the wall and are distributed in the adventitia (tunica externa) and between the latter and the tunica media. The fibers innervate the muscular formations of the wall, having different endings. Currently, the presence of receptors has been proven in all blood and lymphatic vessels.

First neuron afferent pathway the vascular system lies in the spinal nodes or nodes of the autonomic nerves (nn. splanchnici, n. vagus); then it goes as part of the conductor of the interoceptive analyzer (see "Interoceptive analyzer"). The vasomotor center lies in medulla oblongata... The globus pallidus, thalamus, and gray tubercle are related to the regulation of blood circulation. Higher centers of blood circulation, like everyone else vegetative functions, are embedded in the cortex of the motor area of the brain (frontal lobe), as well as in front and behind it. The cortical end of the analyzer of vascular functions is located, apparently, in all parts of the cortex. Descending connections of the brain with the stem and spinal centers are carried out, apparently, by the pyramidal and extrapyramidal tracts.

Closure reflex arc can occur at all levels of the central nervous system, as well as in the nodes of the autonomic plexus (autonomic reflex arc).
The efferent pathway causes a vasomotor effect - vasodilation or vasoconstriction. The vasoconstrictor fibers are part of the sympathetic nerves, the vasodilator fibers are part of all the parasympathetic nerves of the cranial part of the autonomic nervous system (III, VII, IX, X), as part of the anterior roots of the spinal nerves (not recognized by all) and parasympathetic nerves of the sacral part (nn. splanchnici pelvini).

AFO of the cardiovascular system.

Anatomy and physiology of the heart.

The structure of the circulatory system. Features of the structure in different age periods. The essence of the circulatory process. Structures that carry out the process of blood circulation. The main indicators of blood circulation (number of heartbeats, blood pressure, electrocardiogram indicators). Factors affecting blood circulation (physical and nutritional stress, stress, lifestyle, bad habits, etc.). Circles of blood circulation. Vessels, types. The structure of the walls of blood vessels. Heart - location, external structure, anatomical axis, projection onto the surface of the chest at different age periods. Heart chambers, openings and heart valves. How heart valves work. The structure of the heart wall - endocardium, myocardium, epicardium, location, physiological properties. Conductive system of the heart. Physiological properties... The structure of the pericardium. Vessels and nerves of the heart. Phases and duration cardiac cycle... Physiological properties of the heart muscle.

Circulatory system

The functions of the blood are performed thanks to continuous work circulatory system. Blood circulation - this is the movement of blood through the vessels, ensuring the exchange of substances between all tissues of the body and the external environment. The circulatory system includes the heart and blood vessels. The circulation of blood in the human body through a closed cardiovascular system is provided by rhythmic contractions hearts- its central organ. The vessels that carry blood from the heart to tissues and organs are called arteries and those through which blood is delivered to the heart - veins. In tissues and organs, thin arteries (arterioles) and veins (venules) are interconnected by a dense network blood capillaries.

Features of the structure in different age periods.

The heart of a newborn has a rounded shape. Its transverse diameter is 2.7-3.9 cm, the average length of the heart is 3.0-3.5 cm. Anterior-posterior size- 1.7-2.6 cm. The atria are large compared to the ventricles, and the right one is much larger than the left one. The heart grows especially rapidly during the year of a child's life, and its length increases more than its width. Individual parts of the heart change in different age periods differently: during the 1st year of life, the atria grow stronger than the ventricles. At the age of 2 to 6 years, the growth of the atria and ventricles is equally intense. After 10 years, the ventricles enlarge faster than the atria. The total weight of the heart in a newborn is 24 g, at the end of the 1st year of life it increases approximately 2 times, by 4-5 years - 3 times, at 9-10 years - 5 times and by 15-16 years - 10 once. The heart mass up to 5-6 years old is greater in boys than in girls, at 9-13 years old, on the contrary, it is higher in girls, and at 15 years old, the heart mass is again greater in boys than in girls. In newborns and children infancy the heart is high and lies transversely. The transition of the heart from a transverse position to an oblique one begins at the end of the 1st year of a child's life.

Factors affecting blood circulation (physical and nutritional stress, stress, lifestyle, bad habits, etc.).

Circles of blood circulation.

Large and small circles of blood circulation. V the human body, blood moves in two circles of blood circulation - large (trunk) and small (pulmonary).

A large circle of blood circulation begins in the left ventricle, from which arterial blood is ejected into the largest artery in diameter - aorta. The aorta makes an arc to the left and then runs along the spine, branching into smaller arteries that carry blood to the organs. In the organs, the arteries branch into smaller vessels - arterioles, who go online capillaries, penetrating tissues and delivering oxygen and nutrients to them. Venous blood is collected through the veins in two large vessels - upper and inferior vena cava, which pour it into the right atrium.

Small circle of blood circulation begins in the right ventricle, from where the arterial pulmonary trunk exits, which is divided into flowering arteries, carrying blood to the lungs. In the lungs, large arteries branch into smaller arterioles, passing into a network of capillaries, densely encircling the walls of the alveoli, where gases are exchanged. Oxygenated arterial blood flows through the pulmonary veins into the left atrium. Thus, venous blood flows in the arteries of the pulmonary circulation, and arterial blood flows in the veins.

Not all blood volume in the body circulates evenly. Much of the blood is in blood depots- liver, spleen, lungs, subcutaneous vascular plexuses. The importance of blood depots lies in the ability to quickly provide oxygen to tissues and organs in emergency situations.

Vessels, types. The structure of the walls of blood vessels.

The vessel wall consists of three layers:

1. The inner layer is very thin, it is formed by one row of endothelial cells that smooth the inner surface of the vessels.

2. The middle layer is the thickest, it contains a lot of muscle, elastic and collagen fibers. This layer provides vascular strength.

3. The outer layer is connective tissue, it separates the vessels from the surrounding tissues.

Arteries The blood vessels that run from the heart to the organs and carry blood to them are called arteries. Blood from the heart flows through the arteries under great pressure, so the arteries have thick elastic walls.

According to the structure of the walls, arteries are divided into two groups:

· Arteries of the elastic type - the arteries closest to the heart (the aorta and its large branches) perform mainly the function of conducting blood.

Muscular arteries - medium and small arteries, in which the inertia of the heart impulse weakens and its own contraction of the vascular wall is required for further blood flow

In relation to the organ, arteries are distinguished that go outside the organ, before entering it - extraorganic arteries - and their extensions branching inside it - intraorgan or intraorganic arteries. Lateral branches of the same trunk or branches of different trunks can be connected to each other. Such a connection of vessels before their disintegration into capillaries is called anastomosis or anastomosis (most of them). Arteries that do not have anastomoses with neighboring trunks before they go into capillaries are called terminal arteries (for example, in the spleen). The terminal, or terminal, arteries are more easily clogged with a blood plug (thrombus) and predispose to the formation of a heart attack (local organ necrosis).

Capillaries- the smallest blood vessels located in all tissues between arteries and veins. The main function of capillaries is to ensure the exchange of gases and nutrients between blood and tissues. In this regard, the capillary wall is formed by only one layer of flat endothelial cells, which is permeable to substances and gases dissolved in a liquid. Through it, oxygen and nutrients easily penetrate from the blood to the tissues, and carbon dioxide and waste products in the opposite direction.

At any given moment, only part of the capillaries is functioning (open capillaries), while the other remains in reserve (closed capillaries).

Veins- blood vessels carrying venous blood from organs and tissues to the heart. The exception is the pulmonary veins, which carry arterial blood from the lungs to the left atrium. The collection of veins forms the venous system, which is part of the cardiovascular system. The network of capillaries in the organs goes into small postcapillaries, or venules. At a considerable distance they still retain a structure similar to the structure of capillaries, but have a wider lumen. Venules merge into larger veins, which are connected by anastomoses, and form venous plexuses in or near organs. Veins are collected from the plexuses that carry blood out of the organ. Distinguish between superficial and deep veins. Superficial veins are located in the subcutaneous fatty tissue, starting from the superficial venous networks; their number, size and position vary greatly. Deep veins starting at the periphery from shallow deep veins accompany the arteries; often one artery is accompanied by two veins ("companion veins"). As a result of the fusion of superficial and deep veins, two large venous trunks are formed - the superior and inferior hollow veins, which flow into the right atrium, where the common drainage of the heart veins - the coronary sinus - also flows. The portal vein carries blood from the unpaired abdominal organs.
Low pressure and low blood flow velocity cause poor development of elastic fibers and membranes in the venous wall. The need to overcome the gravity of blood in the veins of the lower extremities led to the development of muscle elements in their wall, in contrast to the veins of the upper extremities and the upper half of the body. On the inner lining of the vein there are valves that open with the blood flow and facilitate the movement of blood in the veins towards the heart. A feature of venous vessels is the presence of valves in them, which are necessary to ensure unidirectional blood flow. The walls of the veins are arranged according to the same plan as the walls of the arteries, however, the blood pressure in the veins is very low, therefore the walls of the veins are thin, they have less elastic and muscle tissue, due to which the empty veins collapse.

Heart- a hollow fibromuscular organ, which, functioning as a pump, ensures the movement of blood in the circulatory system. The heart is located in the anterior mediastinum in the pericardium between the leaves of the mediastinal pleura. It has the shape of an irregular cone with a base at the top and a top facing downward, to the left and anteriorly. S. sizes are individually different. S.'s length of an adult varies from 10 to 15 cm (more often 12-13 cm), width at the base 8-11 cm (more often 9-10 cm) and anteroposterior size 6-8.5 cm (more often 6, 5-7 cm ). The average weight of S. in men is 332 g (from 274 to 385 g), in women - 253 g (from 203 to 302 g).
In relation to the midline of the body, the heart is located asymmetrically - about 2/3 to the left of it and about 1/3 to the right. Depending on the direction of the projection of the longitudinal axis (from the middle of its base to the apex) on the anterior chest wall, a transverse, oblique and vertical position of the heart is distinguished. The upright position is more common in people with a narrow and long chest, transverse - in people with a wide and short chest.

The heart consists of four chambers: two (right and left) atria and two (right and left) ventricles. The atria are located at the base of the heart. The aorta and the pulmonary trunk emerge from the heart in front, the superior vena cava flows into the right side, the inferior vena cava flows into the posterior inferior, the left pulmonary veins are behind and left, and the right pulmonary veins are somewhat to the right.

The function of the heart consists in the rhythmic pumping of blood in the artery, coming to it through the veins. The heart beats about 70-75 times per minute at rest of the body (1 time per 0.8 s). More than half of this time it rests - relaxes. The continuous activity of the heart consists of cycles, each of which consists of contraction (systole) and relaxation (diastole).

There are three phases of cardiac activity:

Atrial contraction - atrial systole - takes 0.1 s

Ventricular contraction - ventricular systole - takes 0.3 s

General pause - diastole (simultaneous relaxation of the atria and ventricles) - takes 0.4 s

Thus, during the entire cycle, the atria work 0.1 s and rest 0.7 s, the ventricles work 0.3 s and rest 0.5 s. This explains the ability of the heart muscle to work without fatigue throughout life. The high performance of the heart muscle is due to the increased blood supply to the heart. About 10% of the blood that is expelled by the left ventricle into the aorta goes into the arteries that branch out from it, which feed the heart.