Coronary circle of blood circulation diagram. Let's analyze in detail the arteries of the systemic circulation

The regularity of the movement of blood in the circles of blood circulation was discovered by Harvey (1628). Subsequently, the doctrine of the physiology and anatomy of blood vessels was enriched with numerous data that revealed the mechanism of general and regional blood supply to organs.

In goblin animals and humans with a four-chambered heart, there are large, small and cardiac circles of blood circulation (Fig. 367). The heart plays a central role in circulation.

367. Scheme of blood circulation (according to Kishsh, Sentagotai).

1 - common carotid artery;
2 - aortic arch;
3 - pulmonary artery;
4 - pulmonary vein;
5 - left ventricle;
6 - right ventricle;
7 - celiac trunk;
8 - superior mesenteric artery;
9 - inferior mesenteric artery;
10 - inferior vena cava;
11 - aorta;
12 - common iliac artery;
13 - common iliac vein;
14 - femoral vein. 15 - portal vein;
16 - hepatic veins;
17 - subclavian vein;
18 - superior vena cava;
19 - internal jugular vein.

Small circle of blood circulation (pulmonary)

Venous blood from the right atrium through the right atrioventricular opening passes into the right ventricle, which, contracting, pushes the blood into the pulmonary trunk. It divides into the right and left pulmonary arteries, which enter the lungs. In lung tissue, the pulmonary arteries divide into capillaries that surround each alveolus. After the erythrocytes release carbon dioxide and enrich them with oxygen, venous blood turns into arterial blood. Arterial blood flows through four pulmonary veins (two veins in each lung) into the left atrium, then through the left atrioventricular opening passes into the left ventricle. The systemic circulation begins from the left ventricle.

Systemic circulation

Arterial blood from the left ventricle during its contraction is ejected into the aorta. The aorta splits into arteries that supply blood to the limbs, torso, and. all internal organs and ending in capillaries. Nutrients, water, salts and oxygen are released from the blood of capillaries into the tissues, metabolic products and carbon dioxide are resorbed. Capillaries gather into venules, where the venous vascular system begins, representing the roots of the superior and inferior vena cava. Venous blood through these veins enters the right atrium, where the systemic circulation ends.

Cardiac circulation

This circle of blood circulation begins from the aorta with two coronary cardiac arteries, through which blood enters all layers and parts of the heart, and then is collected through small veins into the venous coronary sinus. This vessel with a wide mouth opens into the right atrium. Part of the small veins of the heart wall directly opens into the cavity of the right atrium and ventricle of the heart.

The work of all body systems does not stop even during rest and sleep of a person. Cell regeneration, metabolism, brain activity at normal rates continue regardless of human activity.

The most active organ in this process is the heart. Its constant and uninterrupted work ensures sufficient blood circulation to maintain all human cells, organs, and systems.

Muscular work, the structure of the heart, as well as the mechanism of blood movement through the body, its distribution in various parts of the human body is a rather extensive and complex topic in medicine. As a rule, such articles are filled with terminology that is not understandable to a person without a medical education.

This edition describes the circles of blood circulation concisely and clearly, which will allow many readers to replenish their knowledge in matters of health.

Note. This topic is interesting not just for general development, knowledge of the principles of blood circulation, the mechanisms of the heart can be useful if you need first aid for bleeding, injuries, heart attacks and other incidents before the arrival of doctors.

Many of us underestimate the importance, complexity, high accuracy, coordination of the heart vessels, as well as human organs and tissues. Day and night without stopping, all elements of the system in one way or another communicate with each other providing the human body with nutrition and oxygen. A number of factors can disturb the balance of blood circulation, after which all areas of the body that are directly and indirectly dependent on it will be affected by a chain reaction.

The study of the circulatory system is impossible without basic knowledge of the structure of the heart and human anatomy. Given the complexity of the terminology, the vastness of the topic at the first acquaintance with it for many becomes a discovery that the human blood circulation goes through two whole circles.

A full-fledged circulatory message of the body is based on the synchronization of the work of the muscle tissues of the heart, the difference in blood pressure created by its work, as well as the elasticity, patency of arteries and veins. Pathological manifestations affecting each of the above factors worsen the distribution of blood throughout the body.

It is its circulation that is responsible for the delivery of oxygen, useful substances to the organs, as well as the removal of harmful carbon dioxide, metabolic products harmful to their functioning.

The heart is a human muscular organ, divided into four parts by partitions that form cavities. Through the contraction of the heart muscle, different blood pressures are created inside these cavities, which ensure the operation of valves that prevent accidental backflow of blood into the vein, as well as the outflow of blood from the artery into the cavity of the ventricle.

At the top of the heart are two atria, named according to their location:

1. Right atrium. Dark blood comes from the superior vena cava, after which, due to the contraction of muscle tissue, it splashes under pressure into the right ventricle. The contraction begins at the point where the vein joins the atrium, which provides protection against backflow of blood into the vein.
2. Left atrium. The cavity is filled with blood through the pulmonary veins. By analogy with the above-described mechanism of the myocardium, the blood squeezed out by the contraction of the atrial muscle enters the ventricle.

The valve between the atrium and the ventricle opens under blood pressure and allows it to freely pass into the cavity, after which it closes, limiting its ability to return.

At the bottom of the heart are its ventricles:

1. Right ventricle. The blood expelled from the atrium enters the ventricle. Then there is its contraction, the closure of the three leaflet valves and the opening of the pulmonary artery valve under blood pressure.
2. left ventricle. The muscle tissue of this ventricle is significantly thicker than the right ventricle, and therefore, when contracted, it can create stronger pressure. This is necessary to ensure the force of ejection of blood into a large circulation cycle. As in the first case, the pressure force closes the atrial valve (mitral) and opens the aortic valve.

Important. The full work of the heart depends on the synchrony, as well as the rhythm of contractions. The division of the heart into four separate cavities, the inlets and outlets of which are fenced off by valves, ensures the movement of blood from the veins into the arteries without the risk of mixing. Anomalies in the development of the structure of the heart, its components violate the mechanics of the heart, and therefore the blood circulation itself.

The structure of the circulatory system of the human body

In addition to the rather complex structure of the heart, the structure of the circulatory system itself has its own characteristics. Blood is distributed throughout the body through a system of hollow interconnected vessels of various sizes, wall structure, and purpose.

The structure of the vascular system of the human body includes the following types of vessels:

1. arteries. Vessels that do not contain smooth muscles in the structure have a strong shell with elastic properties. When extra blood is ejected from the heart, the walls of the artery expand, allowing the blood pressure in the system to be controlled. During a pause, the walls stretch, narrow, reducing the lumen of the inner part. This prevents the pressure from dropping to critical levels. The function of the arteries is to carry blood from the heart to the organs and tissues of the human body.
2. Vienna. The blood flow of venous blood is provided by its contractions, the pressure of the skeletal muscles on its membrane, and the pressure difference in the pulmonary vena cava during the work of the lungs. A feature of the functioning is the return of the used blood to the heart, for further gas exchange.
3. capillaries. The structure of the wall of the thinnest vessels consists of only one layer of cells. This makes them vulnerable, but at the same time highly permeable, which predetermines their function. The exchange between tissue cells and the plasma that they provide saturates the body with oxygen, nutrition, cleanses of metabolic products through filtration in the network of capillaries of the corresponding organs.

Each type of vessel forms its own so-called system, which can be considered in more detail in the presented diagram.

Capillaries are the thinnest of vessels, they dot all parts of the body so densely that they form so-called networks.

The pressure in the vessels created by the muscular tissue of the ventricles varies, it depends on their diameter and distance from the heart.

Types of circulatory circles, functions, characteristics

The circulatory system is divided into two closed systems that communicate thanks to the heart, but perform different tasks. We are talking about the presence of two circles of blood circulation. Experts in medicine call them circles because of the closed nature of the system, highlighting their two main types: large and small.

These circles have cardinal differences both in structure, size, number of vessels involved, and functionality. The table below will help you learn more about their main functional differences.

Table number 1. Functional characteristics, other features of the large and small circles of blood circulation:

As can be seen from the table, the circles perform completely different functions, but have the same significance for blood circulation. While the blood makes a cycle in a large circle once, 5 cycles are made inside a small circle for the same period of time.

In medical terminology, there is sometimes also such a term as additional circles of blood circulation:

• cardiac - passes from the coronary arteries of the aorta, returns through the veins to the right atrium;
• placental - circulates in the fetus developing in the uterus;
• willisium - located at the base of the human brain, acts as a backup blood supply in case of blockage of blood vessels.

One way or another, all additional circles are part of a large one or are directly dependent on it.

Important. Both circles of blood circulation maintain a balance in the work of the cardiovascular system. Violation of blood circulation due to the occurrence of various pathologies in one of them leads to an inevitable effect on the other.

big circle

From the name itself, one can understand that this circle differs in size, and, accordingly, in the number of vessels involved. All circles begin with the contraction of the corresponding ventricle and end with the return of blood to the atrium.

The large circle originates from the contraction of the strongest left ventricle, pushing blood into the aorta. Passing along its arc, thoracic, abdominal segment, it is redistributed along the network of vessels through arterioles and capillaries to the corresponding organs, parts of the body.

It is through the capillaries that oxygen, nutrients, and hormones are released. When outflowing into the venules, it takes with it carbon dioxide, harmful substances formed by metabolic processes in the body.

Further, through the two largest veins (hollow upper and lower), the blood returns to the right atrium, closing the cycle. You can visualize the scheme of blood circulating in a large circle in the figure below.

As can be seen in the diagram, the outflow of venous blood from unpaired organs of the human body does not occur directly to the inferior vena cava, but bypasses it. Having saturated the organs of the abdominal cavity with oxygen and nutrition, the spleen rushes to the liver, where it is cleansed through the capillaries. Only after that the filtered blood enters the inferior vena cava.

The kidneys also have filtering properties, a double capillary network allows venous blood to directly enter the vena cava.

Of great importance, despite the rather short cycle, is the coronary circulation. The coronary arteries leaving the aorta branch into smaller ones and go around the heart.

Entering his muscle tissues, they are divided into capillaries that feed the heart, and the outflow of blood is provided by three cardiac veins: small, medium, large, as well as thebesius and anterior cardiac veins.

Important. The constant work of heart tissue cells requires a large amount of energy. About 20% of the total amount of blood, enriched with oxygen and nutrients, pushed out of the organ into the body passes through the coronary circle.

small circle

The structure of the small circle includes much fewer involved vessels and organs. In medical literature, it is often called pulmonary and not without reason. It is this body that is the main one in this chain.

Carried out by means of blood capillaries, braiding the pulmonary vesicles, gas exchange is of paramount importance for the body. It is the small circle that subsequently makes it possible for the large circle to saturate the entire human body with enriched blood.

The blood flow in a small circle is carried out in the following order:

1. By contraction of the right atrium, venous blood, darkened due to excess carbon dioxide in it, is pushed into the cavity of the right ventricle of the heart. The atriogastric septum is closed at this point to prevent the return of blood into it.
2. Under pressure from the muscle tissue of the ventricle, it is pushed into the pulmonary trunk, while the tricuspid valve separating the cavity from the atrium is closed.
3. After blood enters the pulmonary artery, its valve closes, which excludes the possibility of its return to the ventricular cavity.
4. Passing through a large artery, blood enters the site of its branching into capillaries, where carbon dioxide is removed, as well as oxygen saturation.
5. Scarlet, purified, enriched blood through the pulmonary veins finishes its cycle at the left atrium.

As you can see when comparing two blood flow patterns in a large circle, dark venous blood flows through the veins to the heart, and scarlet purified blood in a small circle and vice versa. The arteries of the pulmonary circle are filled with venous blood, while enriched scarlet flows through the arteries of the large circle.

Circulatory disorders

In 24 hours, the heart pumps more than 7000 liters through the vessels of a person. blood. However, this figure is relevant only with the stable operation of the entire cardiovascular system.

Only a few can boast of excellent health. In real life conditions, due to many factors, almost 60% of the population has health problems, the cardiovascular system is no exception.

Her work is characterized by the following indicators:

• the efficiency of the heart;
• vascular tone;
• condition, properties, mass of blood.

The presence of deviations of even one of the indicators leads to a violation of the blood flow of two circles of blood circulation, not to mention the detection of their whole complex. Specialists in the field of cardiology distinguish between general and local disorders that impede the movement of blood through the circulation circles, a table with their list is presented below.

Table number 2. List of disorders of the circulatory system:

The above violations are also divided into types, depending on the system, the circulation of which it affects:

1. Violations of the work of the central circulation. This system includes the heart, aorta, vena cava, pulmonary trunk, and veins. Pathologies of these elements of the system affect its other components, which threatens with a lack of oxygen in the tissues, intoxication of the body.
2. Violation of the peripheral circulation. It implies a pathology of microcirculation, manifested by problems with blood filling (complete / anemia arterial, venous), rheological characteristics of blood (thrombosis, stasis, embolism, DIC), vascular permeability (blood loss, plasmorrhagia).

The main risk group for the manifestation of such disorders in the first place are genetically predisposed people. If parents have problems with blood circulation or heart function, there is always a chance to pass on a similar diagnosis by inheritance.

However, even without genetics, many people expose their body to the risk of developing pathologies both in the large and in the pulmonary circulation:

• bad habits;
• passive lifestyle;
• harmful working conditions;
• constant stress;
• the predominance of junk food in the diet;
• uncontrolled intake of drugs.

All this gradually affects not only the state of the heart, blood vessels, blood, but also the entire body. The result is a decrease in the protective functions of the body, immunity weakens, which makes it possible for the development of various diseases.

Important. Changes in the structure of the walls of blood vessels, muscle tissue of the heart, and other pathologies can be caused by infectious diseases, some of which are sexually transmitted.

The world medical practice considers atherosclerosis, hypertension, ischemia to be the most common diseases of the cardiovascular system.

Atherosclerosis is usually chronic and progresses quite rapidly. Violation of protein-fat metabolism leads to structural changes, mainly large and medium-sized arteries. The proliferation of connective tissue is provoked by lipid-protein deposits on the walls of blood vessels. Atherosclerotic plaque closes the lumen of the artery, preventing the flow of blood.

Hypertension is dangerous with a constant load on the vessels, accompanied by its oxygen starvation. As a result, dystrophic changes occur in the walls of the vessel, the permeability of their walls increases. Plasma seeps through the structurally altered wall, forming edema.

Coronary heart disease (ischemic) is caused by a violation of the cardiac circulation. Occurs when there is a lack of oxygen sufficient for the full functioning of the myocardium or a complete stop of blood flow. It is characterized by dystrophy of the heart muscle.

Prevention of circulatory problems, treatment

The best option for preventing diseases, maintaining proper blood circulation in the large and small circles is prevention. Compliance with simple, but quite effective rules will help a person not only strengthen the heart and blood vessels, but also prolong the youth of the body.

Key steps to prevent cardiovascular disease:

• quitting smoking, alcohol;
• maintaining a balanced diet;
• sports, hardening;
• compliance with the regime of work and rest;
• healthy sleep;
• regular preventive check-ups.

An annual check-up with a healthcare professional will help with early detection of signs of circulatory problems. In case of detection of a disease of the initial stage of development, experts recommend drug treatment, drugs of the appropriate groups. Following the doctor's instructions increases the chances of a positive result.

Important. Quite often, diseases are asymptomatic for a long time, which makes it possible for him to progress. In such cases, surgery may be needed.

Quite often, for the prevention, as well as the treatment of the pathologies described by the editors, patients use alternative methods of treatment and recipes. Such methods require prior consultation with your doctor. Based on the patient's medical history, the individual characteristics of his condition, the specialist will give detailed recommendations.

The human body is permeated with vessels through which blood circulates continuously. This is an important condition for the life of tissues and organs. The movement of blood through the vessels depends on nervous regulation and is provided by the heart, which acts as a pump.

The structure of the circulatory system

The circulatory system includes:

• veins;
• arteries;
• capillaries.

The liquid constantly circulates in two closed circles. Small supplies the vascular tubes of the brain, neck, upper body. Large - vessels of the lower body, legs. In addition, there are placental (available during fetal development) and coronary circulation.

The structure of the heart

The heart is a hollow cone made up of muscle tissue. In all people, the body is slightly different in shape, sometimes in structure.. It has 4 departments - the right ventricle (RV), the left ventricle (LV), the right atrium (RA) and the left atrium (LA), which communicate with each other by openings.

The holes are covered with valves. Between the left sections - the mitral valve, between the right - tricuspid.

The pancreas pushes fluid into the pulmonary circulation - through the pulmonary valve to the pulmonary trunk. The LV has denser walls, as it pushes blood to the systemic circulation, through the aortic valve, that is, it must create sufficient pressure.

After a portion of the liquid is ejected from the department, the valve is closed, which ensures the movement of the liquid in one direction.

Functions of the arteries

The arteries supply oxygenated blood. Through them, it is transported to all tissues and internal organs. The walls of the vessels are thick and highly elastic. Fluid is ejected into the artery under high pressure - 110 mm Hg. Art., and elasticity is a vital quality that keeps the vascular tubes intact.

The artery has three sheaths that ensure its ability to perform its functions. The middle shell consists of smooth muscle tissue, which allows the walls to change the lumen depending on body temperature, the needs of individual tissues, or under high pressure. Penetrating into the tissues, the arteries narrow, passing into the capillaries.

Functions of capillaries

Capillaries penetrate all tissues of the body, except for the cornea and epidermis, carry oxygen and nutrients to them. The exchange is possible due to the very thin wall of the vessels. Their diameter does not exceed the thickness of the hair. Gradually, the arterial capillaries pass into the venous ones.

Functions of the veins

Veins carry blood to the heart. They are larger than arteries and contain about 70% of the total blood volume. Along the course of the venous system there are valves that work on the principle of the heart. They allow blood to pass through and close behind it to prevent its outflow. Veins are divided into superficial, located directly under the skin, and deep - passing in the muscles.

The main task of the veins is to transport blood to the heart, in which there is no longer oxygen and decay products are present. Only the pulmonary veins carry oxygenated blood to the heart. There is an upward movement. In case of violation of the normal operation of the valves, the blood stagnates in the vessels, stretching them and deforming the walls.

What are the reasons for the movement of blood in the vessels:

• myocardial contraction;
• contraction of the smooth muscle layer of blood vessels;
• difference in blood pressure between arteries and veins.

The movement of blood through the vessels

Blood moves through the vessels continuously. Somewhere faster, somewhere slower, it depends on the diameter of the vessel and the pressure under which blood is ejected from the heart. The speed of movement through the capillaries is very low, due to which metabolic processes are possible.

The blood moves in a vortex, bringing oxygen along the entire diameter of the vessel wall. Due to such movements, oxygen bubbles seem to be pushed out of the boundaries of the vascular tube.

The blood of a healthy person flows in one direction, the outflow volume is always equal to the inflow volume. The reason for the continuous movement is due to the elasticity of the vascular tubes and the resistance that the fluid has to overcome. When blood enters, the aorta with the artery stretches, then narrows, gradually passing fluid further. Thus, it does not move in jerks, as the heart contracts.

Small circle of blood circulation

The small circle diagram is shown below. Where, RV — right ventricle, LS — pulmonary trunk, RLA — right pulmonary artery, LLA — left pulmonary artery, LV — pulmonary veins, LA — left atrium.

Through the pulmonary circulation, the fluid passes to the pulmonary capillaries, where it receives oxygen bubbles. The oxygenated fluid is called arterial. From the LP, it passes to the LV, where the bodily circulation originates.

Systemic circulation

Scheme of the corporal circle of blood circulation, where: 1. Left - left ventricle.

2. Ao - aorta.

3. Art - arteries of the trunk and limbs.

4. B - veins.

5. PV - vena cava (right and left).

6. PP - right atrium.

The bodily circle is aimed at spreading a liquid full of oxygen bubbles throughout the body. It carries O 2 , nutrients to the tissues, collecting decay products and CO 2 along the way. After that, there is a movement along the route: PZH - LP. And then it starts again through the pulmonary circulation.

Personal circulation of the heart

The heart is an "autonomous republic" of the body. It has its own system of innervation, which sets the muscles of the organ in motion. And its own circle of blood circulation, which is made up of coronary arteries with veins. The coronary arteries independently regulate the blood supply to the heart tissues, which is important for the continuous functioning of the organ.

The structure of the vascular tubes is not identical. Most people have two coronary arteries, but there is a third. The heart can be fed from the right or left coronary artery. Because of this, it is difficult to establish the norms of cardiac circulation. depends on the load, physical fitness, age of the person.

Placental circulation

Placental circulation is inherent in every person at the stage of fetal development. The fetus receives blood from the mother through the placenta, which forms after conception. From the placenta, it moves to the umbilical vein of the child, from where it goes to the liver. This explains the large size of the latter.

The arterial fluid enters the vena cava, where it mixes with the venous fluid, then goes to the left atrium. From it, blood flows to the left ventricle through a special hole, after which it goes directly to the aorta.

The movement of blood in the human body in a small circle begins only after birth. With the first breath, the vessels of the lungs expand, and they develop for a couple of days. The oval hole in the heart can persist for a year.

Circulatory pathologies

Blood circulation is carried out in a closed system. Changes and pathologies in the capillaries can adversely affect the functioning of the heart. Gradually, the problem will worsen and develop into a serious disease. Factors affecting the movement of blood:

1. Pathologies of the heart and large vessels lead to the fact that the blood flows to the periphery in insufficient volume. Toxins stagnate in the tissues, they do not receive proper oxygen supply and gradually begin to break down.
2. Blood pathologies such as thrombosis, stasis, embolism lead to blockage of blood vessels. Movement through the arteries and veins becomes difficult, which deforms the walls of blood vessels and slows down the flow of blood.
3. vascular deformity. The walls can become thinner, stretch, change their permeability and lose elasticity.
4. Hormonal pathologies. Hormones are able to increase blood flow, which leads to a strong filling of blood vessels.
5. Compression of blood vessels. When the blood vessels are compressed, the blood supply to the tissues stops, which leads to cell death.
6. Violations of the innervation of organs and injuries can lead to the destruction of the walls of arterioles and provoke bleeding. Also, a violation of normal innervation leads to a disorder of the entire circulatory system.
7. Infectious diseases of the heart. For example, endocarditis, in which the valves of the heart are affected. The valves do not close tightly, which contributes to the backflow of blood.
8. Damage to the vessels of the brain.
9. Diseases of the veins in which the valves are affected.

Also, the way of life of a person affects the movement of blood. Athletes have a more stable circulatory system, so they are more enduring and even fast running will not immediately speed up the heart rate.

The average person can undergo changes in blood circulation even from smoking a cigarette. With injuries and ruptures of blood vessels, the circulatory system is able to create new anastomoses in order to provide blood to the "lost" areas.

Regulation of blood circulation

Any process in the body is controlled. There is also regulation of blood circulation. The activity of the heart is activated by two pairs of nerves - sympathetic and vagus. The first excite the heart, the second slow down, as if controlling each other. Severe stimulation of the vagus nerve can stop the heart.

A change in the diameter of the vessels also occurs due to nerve impulses from the medulla oblongata. The heart rate increases or decreases depending on signals received from external irritation, such as pain, temperature changes, etc.

In addition, the regulation of cardiac work occurs due to substances contained in the blood. For example, adrenaline increases the frequency of myocardial contractions and at the same time constricts blood vessels. Acetylcholine has the opposite effect.

All these mechanisms are needed to maintain constant uninterrupted work in the body, regardless of changes in the external environment.

The cardiovascular system

The above is only a brief description of the human circulatory system. The body contains a huge number of blood vessels. The movement of blood in a large circle passes throughout the body, providing blood to every organ.

The cardiovascular system also includes the organs of the lymphatic system. This mechanism works in concert, under the control of neuro-reflex regulation. The type of movement in the vessels can be direct, which excludes the possibility of metabolic processes, or vortex.

The movement of blood depends on the work of each system in the human body and cannot be described by a constant value. It varies depending on many external and internal factors. For different organisms that exist in different conditions, there are their own norms of blood circulation, under which normal life will not be in danger.

In mammals and humans, the circulatory system is the most complex. It is a closed system consisting of two circles of blood circulation. Providing warm-bloodedness, it is more energetically favorable and allows a person to occupy the habitat niche in which he is currently located.

The circulatory system is a group of hollow muscular organs responsible for the circulation of blood through the vessels of the body. It is represented by the heart and vessels of different calibers. These are muscular organs that form circles of blood circulation. Their scheme is offered in all textbooks on anatomy and is described in this publication.

The concept of circulatory circles

The circulatory system consists of two circles - bodily (large) and pulmonary (small). The circulatory system is called the system of vessels of the arterial, capillary, lymphatic and venous type, which supplies blood from the heart to the vessels and its movement in the opposite direction. The heart is central, since two circles of blood circulation cross in it without mixing arterial and venous blood.

Systemic circulation

The system of supplying peripheral tissues with arterial blood and its return to the heart is called the systemic circulation. It starts from where the blood exits into the aorta through the aortic orifice. From the aorta, the blood goes to the smaller bodily arteries and reaches the capillaries. This is a set of organs that form the leading link.

Here, oxygen enters the tissues, and carbon dioxide is captured from them by red blood cells. Also, blood transports amino acids, lipoproteins, glucose into the tissues, the metabolic products of which are carried out of the capillaries into venules and further into larger veins. They drain into the vena cava, which return blood directly to the heart in the right atrium.

The right atrium ends the systemic circulation. The scheme looks like this (in the course of blood circulation): left ventricle, aorta, elastic arteries, musculo-elastic arteries, muscular arteries, arterioles, capillaries, venules, veins and vena cava, returning blood to the heart in the right atrium. From a large circle of blood circulation, the brain, all skin, and bones are fed. In general, all human tissues are fed from the vessels of the systemic circulation, and the small one is only a place of blood oxygenation.

Small circle of blood circulation

The pulmonary (small) circulation, the scheme of which is presented below, originates from the right ventricle. Blood enters it from the right atrium through the atrioventricular orifice. From the cavity of the right ventricle, oxygen-depleted (venous) blood enters the pulmonary trunk through the output (pulmonary) tract. This artery is thinner than the aorta. It divides into two branches that go to both lungs.

The lungs are the central organ that forms the pulmonary circulation. The human diagram described in anatomy textbooks explains that pulmonary blood flow is needed for blood oxygenation. Here it gives off carbon dioxide and takes in oxygen. In the sinusoidal capillaries of the lungs with a diameter atypical for the body of about 30 microns, gas exchange takes place.

Subsequently, oxygenated blood is sent through the system of intrapulmonary veins and collected in 4 pulmonary veins. All of them are attached to the left atrium and carry oxygen-rich blood there. This is where circulation circles end. The scheme of the small pulmonary circle looks like this (in the direction of blood flow): right ventricle, pulmonary artery, intrapulmonary arteries, pulmonary arterioles, pulmonary sinusoids, venules, left atrium.

Features of the circulatory system

A key feature of the circulatory system, which consists of two circles, is the need for a heart with two or more chambers. Fish have only one circulation, because they do not have lungs, and all gas exchange takes place in the vessels of the gills. As a result, the fish heart is single-chamber - it is a pump that pushes blood in only one direction.

Amphibians and reptiles have respiratory organs and, accordingly, circulatory circles. The scheme of their work is simple: from the ventricle, blood is directed to the vessels of the large circle, from the arteries to the capillaries and veins. Venous return to the heart is also implemented, however, from the right atrium, blood enters the common ventricle for the two circulations. Since the heart of these animals is three-chambered, the blood from both circles (venous and arterial) is mixed.

In humans (and mammals), the heart has a 4-chamber structure. In it, two ventricles and two atria are separated by partitions. The lack of mixing of two types of blood (arterial and venous) was a giant evolutionary invention that ensured that mammals were warm-blooded.

and hearts

In the circulatory system, which consists of two circles, nutrition of the lung and heart is of particular importance. These are the most important organs that ensure the closure of the bloodstream and the integrity of the respiratory and circulatory systems. So, the lungs have two circles of blood circulation in their thickness. But their tissue is fed by the vessels of a large circle: bronchial and pulmonary vessels branch off from the aorta and intrathoracic arteries, carrying blood to the lung parenchyma. And the organ cannot be fed from the right parts, although part of the oxygen diffuses from there as well. This means that the large and small circles of blood circulation, the scheme of which is described above, perform different functions (one enriches the blood with oxygen, and the second sends it to the organs, taking deoxygenated blood from them).

The heart is also fed from the vessels of the large circle, but the blood in its cavities is able to provide oxygen to the endocardium. At the same time, part of the myocardial veins, mostly small ones, flows directly into it. It is noteworthy that the pulse wave to the coronary arteries propagates into cardiac diastole. Therefore, the organ is supplied with blood only when it "rests".

Human circulation circles, the scheme of which is presented above in the relevant sections, provide both warm-bloodedness and high endurance. Although man is not the animal that often uses his strength to survive, it has allowed the rest of the mammals to populate certain habitats. Previously, they were inaccessible to amphibians and reptiles, and even more so to fish.

In phylogenesis, a large circle appeared earlier and was characteristic of fish. And the small circle supplemented it only in those animals that completely or completely went out onto land and settled it. Since its inception, the respiratory and circulatory systems have been considered together. They are functionally and structurally related.

This is an important and already indestructible evolutionary mechanism for leaving the aquatic habitat and settling on land. Therefore, the continuing complication of mammalian organisms will now go not along the path of complication of the respiratory and circulatory systems, but in the direction of strengthening the oxygen-binding and increasing the area of ​​​​the lungs.

The life and health of a person largely depend on the normal functioning of his heart. It pumps blood through the vessels of the body, maintaining the viability of all organs and tissues. The evolutionary structure of the human heart - the scheme, circles of blood circulation, the automatism of the cycles of contractions and relaxation of the muscle cells of the walls, the operation of the valves - everything is subordinated to the fulfillment of the main task of uniform and sufficient blood circulation.

The structure of the human heart - anatomy

The organ, thanks to which the body is saturated with oxygen and nutrients, is an anatomical formation of a cone-shaped shape, located in the chest, mostly on the left. Inside the organ, a cavity divided into four unequal parts by partitions is two atria and two ventricles. The former collect blood from the veins flowing into them, while the latter push it into the arteries emanating from them. Normally, in the right side of the heart (atrium and ventricle) there is oxygen-poor blood, and in the left - oxygenated.

atrium

Right (PP). It has a smooth surface, the volume is 100-180 ml, including an additional formation - the right ear. Wall thickness 2-3 mm. Vessels flow into the PP:

• superior vena cava,
• cardiac veins - through the coronary sinus and pinholes of small veins,
• inferior vena cava.

Left (LP). The total volume, including the ear, is 100-130 ml, the walls are also 2-3 mm thick. The LP receives blood from four pulmonary veins.

The atria are separated by the interatrial septum (IAS), which normally does not have any openings in adults. They communicate with the cavities of the corresponding ventricles through openings equipped with valves. On the right - tricuspid tricuspid, on the left - bicuspid mitral.

Ventricles

Right (RV) cone-shaped, base facing upwards. Wall thickness up to 5 mm. The inner surface in the upper part is smoother, closer to the top of the cone it has a large number of muscle cords-trabeculae. In the middle part of the ventricle, there are three separate papillary (papillary) muscles, which, by means of tendinous filaments-chords, keep the cusps of the tricuspid valve from deflecting them into the atrial cavity. The chords also depart directly from the muscular layer of the wall. At the base of the ventricle are two openings with valves:

• serving as an outlet for blood into the pulmonary trunk,
• connecting the ventricle to the atrium.

Left (LV). This section of the heart is surrounded by the most impressive wall, the thickness of which is 11-14 mm. The LV cavity is also cone-shaped and has two openings:

• atrioventricular with bicuspid mitral valve,
• outlet to the aorta with a tricuspid aortic.

The muscle cords in the region of the apex of the heart and the papillary muscles supporting the leaflets of the mitral valve are more powerful here than similar structures in the pancreas.

shells of the heart

To protect and ensure the movements of the heart in the chest cavity, it is surrounded by a heart shirt - the pericardium. Directly in the wall of the heart there are three layers - epicardium, endocardium, myocardium.

• The pericardium is called the heart bag, it is loosely adjacent to the heart, its outer leaf is in contact with neighboring organs, and the inner one is the outer layer of the heart wall - the epicardium. Composition: connective tissue. A small amount of fluid is normally present in the pericardial cavity for better glide of the heart.
• The epicardium also has a connective tissue base, accumulations of fat are observed in the region of the apex and along the coronal sulci, where the vessels are located. In other places, the epicardium is firmly connected with the muscle fibers of the main layer.
• The myocardium makes up the main thickness of the wall, especially in the most loaded zone - the region of the left ventricle. Muscle fibers located in several layers run both longitudinally and in a circle, ensuring uniform contraction. The myocardium forms trabeculae in the region of the apex of both ventricles and papillary muscles, from which tendon chords extend to the valve leaflets. The muscles of the atria and ventricles are separated by a dense fibrous layer, which also serves as a framework for the atrioventricular (atrioventricular) valves. The interventricular septum consists of 4/5 of the length of the myocardium. In the upper part, called membranous, its basis is connective tissue.
• Endocardium - a sheet that covers all the internal structures of the heart. It is three-layered, one of the layers is in contact with the blood and is similar in structure to the endothelium of the vessels that enter and exit the heart. Also in the endocardium there is connective tissue, collagen fibers, smooth muscle cells.

All heart valves are formed from the folds of the endocardium.

Human heart structure and functions

The pumping of blood by the heart into the vascular bed is provided by the features of its structure:

• the heart muscle is capable of automatic contraction,
• the conducting system guarantees the constancy of the cycles of excitation and relaxation.

How does the cardiac cycle work?

It consists of three consecutive phases: general diastole (relaxation), atrial systole (contraction), and ventricular systole.

• General diastole is a period of physiological pause in the work of the heart. At this time, the heart muscle is relaxed, and the valves between the ventricles and atria are open. From the venous vessels, blood freely fills the cavities of the heart. The valves of the pulmonary artery and aorta are closed.
• Atrial systole occurs when the pacemaker in the atrial sinus node is automatically excited. At the end of this phase, the valves between the ventricles and the atria close.
• The systole of the ventricles takes place in two stages - isometric tension and expulsion of blood into the vessels.
• The period of tension begins with an asynchronous contraction of the muscle fibers of the ventricles until the moment of complete closure of the mitral and tricuspid valves. Then, in the isolated ventricles, tension begins to grow, pressure rises.
• When it becomes higher than in the arterial vessels, the period of exile is initiated - the valves open, releasing blood into the arteries. At this time, the muscle fibers of the walls of the ventricles are intensively reduced.
• Then the pressure in the ventricles decreases, the arterial valves close, which corresponds to the beginning of diastole. During the period of complete relaxation, the atrioventricular valves open.

The conduction system, its structure and the work of the heart

The conduction system of the heart provides contraction of the myocardium. Its main feature is the automatism of cells. They are able to self-excite in a certain rhythm, depending on the electrical processes that accompany cardiac activity.

As part of the conduction system, the sinus and atrioventricular nodes, the underlying bundle and branchings of His, Purkinje fibers are interconnected.

• sinus node. Normally generates an initial impulse. It is located in the area of ​​the mouth of both hollow veins. From it, excitation passes to the atria and is transmitted to the atrioventricular (AV) node.
• The atrioventricular node propagates the impulse to the ventricles.
• The bundle of His is a conductive "bridge" located in the interventricular septum, where it is also divided into the right and left legs, which transmit excitation to the ventricles.
• Purkinje fibers are the terminal part of the conduction system. They are located near the endocardium and are in direct contact with the myocardium, causing it to contract.

The structure of the human heart: diagram, circles of blood circulation

The task of the circulatory system, the main center of which is the heart, is the delivery of oxygen, nutrients and bioactive components to the tissues of the body and the elimination of metabolic products. To do this, the system provides a special mechanism - the blood moves through the circles of blood circulation - small and large.

small circle

From the right ventricle at the time of systole, venous blood is pushed into the pulmonary trunk and enters the lungs, where it is saturated with oxygen in the microvessels of the alveoli, becoming arterial. It flows into the cavity of the left atrium and enters the system of a large circle of blood circulation.

big circle

From the left ventricle into systole, arterial blood through the aorta and further through vessels of different diameters enters various organs, giving them oxygen, transferring nutrients and bioactive elements. In small tissue capillaries, the blood turns into venous blood, as it is saturated with metabolic products and carbon dioxide. Through the system of veins, it flows to the heart, filling its right sections.

Nature has worked hard to create such a perfect mechanism, giving it a margin of safety for many years. Therefore, you should carefully treat it so as not to create problems with blood circulation and your own health.