How does blood circulation occur? Circulatory system Scientist who discovered two circles of blood circulation

Opening of blood circulation

William Harvey came to the conclusion that a snake bite is dangerous only because the venom spreads through the vein from the site of the bite throughout the body. For English doctors, this insight became the starting point for reflection that led to the development of intravenous injections. It is possible, the doctors reasoned, to inject this or that medicine into a vein and thereby introduce it into the entire body. But next step German doctors did this in this direction by using a new surgical enema on humans (as intravenous injection was then called). The first injection experience was carried out by one of the most prominent surgeons, the second half XVII century Mateus Gottfried Purman from Silesia. Czech scientist Pravac proposed an injection syringe. Before this, syringes were primitive, made from pig bladders, with wooden or copper spouts embedded in them. The first injection was performed in 1853 by English doctors.

After arriving from Padua, along with his practical medical activities, Harvey carried out systematic experimental studies structure and function of the heart and blood movement in animals. He first presented his thoughts in another Lumley lecture, which he gave in London on April 16, 1618, when he already had a large amount of observational and experimental material. Harvey briefly formulated his views by saying that blood moves in a circle. More precisely - in two circles: small - through the lungs and large - through the whole body. His theory was incomprehensible to listeners, it was so revolutionary, unusual and alien to traditional ideas. " Anatomical study on the movement of the heart and blood in animals" by Harvey was published in 1628, the edition was published in Frankfurt am Main. In this study, Harvey refuted Galen's teaching about the movement of blood in the body, which had prevailed for 1500 years, and formulated new ideas about blood circulation.

Of great importance for Harvey's research was detailed description venous valves that direct the movement of blood to the heart, first given by his teacher Fabricius in 1574. The simplest and at the same time the most convincing proof of the existence of blood circulation, proposed by Harvey, was to calculate the amount of blood passing through the heart. Harvey showed that in half an hour the heart ejects an amount of blood equal to the weight of the animal. This a large number of moving blood can only be explained based on the concept of a closed circulatory system. Obviously, Galen's assumption about the continuous destruction of blood flowing to the periphery of the body could not be reconciled with this fact. Harvey received another proof of the fallacy of his views about the destruction of blood on the periphery of the body in his experiments of applying a bandage to the upper limbs of a person. These experiments showed that blood flows from arteries to veins. Harvey's research revealed the importance of the pulmonary circulation and established that the heart is a muscular sac equipped with valves, the contractions of which act as a pump forcing blood into the circulatory system.

History of the discovery of the role of the heart and circulatory system

This drop of blood that appeared
then disappearing again, it seemed,
hesitated between existence and the abyss,
and this was the source of life.
She's red! She is beating. This is the heart!

W. Harvey

A look into the past

Doctors and anatomists of ancient times were interested in the work of the heart and its structure. This is confirmed by information about heart structure given in ancient manuscripts.

In the Ebers papyrus* “The Secret Book of the Physician” there are sections “Heart” and “Vessels of the Heart”.

Hippocrates (460–377 BC), the great Greek physician, who is called the father of medicine, wrote about muscle structure hearts.

Greek scientist Aristotle(384–322 BC) argued that the most important organ of the human body is the heart, which is formed in the fetus before other organs. Based on observations of death occurring after cardiac arrest, he concluded that the heart is the thinking center. He pointed out that the heart contains air (the so-called “pneuma” - a mysterious carrier of mental processes that penetrates matter and animates it), spreading through the arteries. Aristotle assigned the brain a secondary role as an organ designed to produce fluid that cools the heart.

The theories and teachings of Aristotle found followers among representatives of the Alexandrian school, from which many famous doctors emerged Ancient Greece, in particular Erasistratus, who described the heart valves, their purpose, as well as the contraction of the heart muscle.

Ancient Roman doctor Claudius Galen(131–201 BC) proved that blood flows in arteries, not air. But Galen found blood in the arteries only in living animals. The dead's arteries were always empty. Based on these observations, he created a theory according to which blood originates in the liver and is distributed through the vena cava to the lower part of the body. Blood moves through the vessels in tides: back and forth. The upper parts of the body receive blood from the right atrium. There is a communication between the right and left ventricles through the walls: in the book “On the Purpose of Parts human body“He provided information about an oval hole in the heart. Galen made his “mite to the treasury of prejudices” in the doctrine of blood circulation. Like Aristotle, he believed that the blood is endowed with “pneuma.”

According to Galen's theory, arteries do not play any role in the work of the heart. However, his undoubted merit was the discovery of the fundamentals of the structure and functioning of the nervous system. He was the first to indicate that the brain and spinal column are the sources of activity of the nervous system. Contrary to the statement of Aristotle and representatives of his school, he argued that “ human brain is the abode of thought and the refuge of the soul."

The authority of ancient scientists was undeniable. To encroach on the laws they established was considered sacrilege. If Galen argued that blood flows from the right side of the heart to the left, then this was accepted as true, although there was no evidence for this. However, progress in science cannot be stopped. The flourishing of sciences and arts during the Renaissance led to a revision of established truths.

An outstanding scientist and artist also made an important contribution to the study of the structure of the heart. Leonardo da Vinci(1452–1519). He was interested in the anatomy of the human body and was going to write a multi-volume illustrated work on its structure, but, unfortunately, he did not finish it. However, Leonardo left behind records of many years of systematic research, providing them with 800 anatomical sketches with detailed explanations. In particular, he identified four chambers in the heart, described the atrioventricular valves (atrioventricular), their chordae tendineae and papillary muscles.

Of the many outstanding scientists of the Renaissance, it is necessary to highlight Andreas Vesalius(1514–1564), a talented anatomist and fighter for progressive ideas in science. Studying the internal structure of the human body, Vesalius established many new facts, boldly contrasting them with erroneous views that were rooted in science and had a centuries-old tradition. He outlined his discoveries in the book “On the Structure of the Human Body” (1543), which contains a thorough description of the anatomical sections performed, the structure of the heart, as well as his lectures. Vesalius refuted the views of Galen and his other predecessors on the structure of the human heart and the mechanism of blood circulation. He was interested not only in the structure of human organs, but also in their functions, and paid most attention to the work of the heart and brain.

Vesalius's great merit lies in the liberation of anatomy from the religious prejudices that bound it, medieval scholasticism - a religious philosophy according to which all scientific research must obey religion and blindly follow the works of Aristotle and other ancient scientists.

Renaldo Colombo(1509(1511)–1553) - a student of Vesalius - believed that blood from the right atrium of the heart enters the left.

Andrea Cesalpino(1519–1603) – also one of the outstanding scientists Renaissance, doctor, botanist, philosopher, proposed his own theory of human blood circulation. In his book “Peripathic Discourses” (1571), he gave a correct description of the pulmonary circulation. It can be said that he, and not William Harvey (1578–1657), the outstanding English scientist and physician who made the greatest contribution to the study of the work of the heart, should have the glory of discovering blood circulation, and Harvey’s merit lies in the development of Cesalpino’s theory and its proof by relevant experiments.

By the time Harvey appeared on the “arena,” the famous professor at the University of Padua Fabricius Acquapendente I found special valves in the veins. However, he did not answer the question of what they are needed for. Harvey set about solving this mystery of nature.

The young doctor performed his first experiment on himself. He bandaged his own hand and waited. Only a few minutes passed, and the hand began to swell, the veins swollen and turned blue, and the skin began to darken.

Harvey guessed that the bandage was holding back the blood. But which one? There has been no answer yet. He decided to conduct experiments on a dog. Having lured a street dog into the house with a piece of pie, he deftly threw the string around his paw, wrapped it around it and pulled it off. The paw began to swell and swell below the bandaged area. Having again lured the trusting dog, Harvey grabbed his other paw, which also turned out to be tightened in a tight noose. A few minutes later Harvey called the dog again. The unfortunate animal, hoping for help, hobbled for the third time to its tormentor, who made a deep cut on his paw.

The swollen vein below the bandage was cut and thick, dark blood dripped from it. On the second paw, the doctor made an incision just above the bandage, and not a single drop of blood flowed out. With these experiments, Harvey proved that blood in the veins moves in one direction.

Over time, Harvey drew up a blood circulation diagram based on the results of sections performed at 40 various types animals. He came to the conclusion that the heart is a muscular sac that acts as a pump, forcing blood into blood vessels. Valves allow blood to flow in only one direction. Heart beats are successive contractions of the muscles of its parts, i.e. external signs of the “pump” operation.

Harvey came to a completely new conclusion that the blood flow passes through the arteries and returns to the heart through the veins, i.e. In the body, blood moves in a vicious circle. In a large circle it moves from the center (heart) to the head, to the surface of the body and to all its organs. In the small circle, blood moves between the heart and lungs. In the lungs, the composition of the blood changes. But how? Harvey didn't know. There is no air in the vessels. The microscope had not yet been invented, so he could not trace the path of blood in the capillaries, just as he could not figure out how the arteries and veins were connected to each other.

Thus, Harvey is responsible for the proof that the blood in the human body continuously circulates (circulates) always in the same direction and that the central point of blood circulation is the heart. Consequently, Harvey refuted Galen's theory that the center of blood circulation was the liver.

In 1628, Harvey published a treatise “An Anatomical Study of the Movement of the Heart and Blood in Animals,” in the preface of which he wrote: “What I present is so new that I fear that people will not be my enemies, for once accepted prejudices and teachings are deeply rooted in everyone.”

In his book, Harvey accurately described the work of the heart, as well as the small and large circles of blood circulation, and indicated that during the contraction of the heart, blood from the left ventricle enters the aorta, and from there, through vessels of smaller and smaller cross-sections, it reaches all corners of the body. Harvey proved that “the heart beats rhythmically as long as there is life in the body.” After each contraction of the heart, there is a pause in the work, during which this important organ rests. True, Harvey could not determine why blood circulation is needed: for nutrition or for cooling the body?

William Harvey tells Charles I
about blood circulation in animals

The scientist dedicated his work to the king, comparing it to the heart: “The king is the heart of the country.” But this little trick did not save Harvey from the attacks of scientists. Only later was the scientist’s work appreciated. Harvey's merit also lies in the fact that he guessed about the coexistence of capillaries and, having collected scattered information, created a holistic, truly scientific theory of blood circulation.

In the 17th century V natural sciences events occurred that radically changed many previous ideas. One of them was the invention of the microscope by Antoni van Leeuwenhoek. The microscope allowed scientists to see the microcosm and the subtle structure of the organs of plants and animals. Leeuwenhoek himself, using a microscope, discovered microorganisms and the cell nucleus in the red blood cells of the frog (1680).

The last point in solving the mystery of the circulatory system was put by an Italian doctor Marcello Malpighi(1628–1694). It all started with his participation in meetings of anatomists in the house of Professor Borely, at which not only scientific debates and readings of reports took place, but also animal dissections were performed. At one of these meetings, Malpighi opened up a dog and showed the structure of the heart to the ladies of the court and gentlemen who attended these meetings.

Duke Ferdinand, interested in these questions, asked to dissect a living dog to see how the heart worked. The request was fulfilled. In the open chest of the Italian greyhound, the heart was beating rhythmically. The atrium contracted and a sharp wave ran through the ventricle, lifting its blunt end. Contractions were also visible in the thick aorta. Malpighi accompanied the autopsy with explanations: from the left atrium blood enters left ventricle..., from it passes into the aorta..., from the aorta - into the body. One of the ladies asked: “How does blood get into the veins?” There was no answer.

Malpighi was destined to be solved the last secret circles of blood circulation. And he did it! The scientist began research, starting with the lungs. He took a glass tube, attached it to the cat’s bronchi and began to blow into it. But no matter how much Malpighi blew, the air did not leave his lungs. How does it get from the lungs into the blood? The issue remained unresolved.

The scientist pours mercury into the lung, hoping that with its heaviness it will break into the blood vessels. The mercury stretched the lung, a crack appeared on it, and shiny droplets rolled down the table. “There is no communication between the respiratory tubes and blood vessels,” Malpighi concluded.

Now he began to study arteries and veins using a microscope. Malpighi was the first to use a microscope in studies of blood circulation. At 180x magnification, he saw what Harvey could not see. Examining a specimen of a frog's lungs under a microscope, he noticed air bubbles surrounded by a film and small blood vessels, an extensive network of capillary vessels connecting arteries to veins.

Malpighi not only answered the lady of the court's question, but completed the work begun by Harvey. The scientist categorically rejected Galen’s theory of blood cooling, but he himself made the wrong conclusion about the mixing of blood in the lungs. In 1661, Malpighi published the results of observations of lung structure, was the first to describe capillary vessels.

The last point in the doctrine of capillaries was put by our compatriot, anatomist Alexander Mikhailovich Shumlyansky(1748–1795). He proved that arterial capillaries directly pass into certain “intermediate spaces,” as Malpighi believed, and that the vessels are closed along their entire length.

An Italian researcher was the first to report on lymphatic vessels and their connection with blood vessels. Gaspard Azeli (1581–1626).

In subsequent years, anatomists discovered a number of formations. Eustachius discovered a special valve at the mouth of the inferior vena cava, L.Bartello– duct connecting the left pulmonary artery with the aortic arch in the prenatal period, Lower- fibrous rings and intervenous tubercle in the right atrium, Tebesius - the smallest veins and the valve of the coronary sinus, Vyusan wrote a valuable work on the structure of the heart.

In 1845 Purkinje published research on specific muscle fibers that conduct excitation through the heart (Purkinje fibers), which laid the foundation for the study of its conduction system. V.Gis in 1893 he described the atrioventricular bundle, L.Ashof in 1906 together with Tawaroi– atrioventricular (atrioventricular) node, A.Kis in 1907 together with Flex described the sinoatrial node, Yu. Tandmer At the beginning of the 20th century, he conducted research on the anatomy of the heart.

Domestic scientists have made a great contribution to the study of heart innervation. F.T. Bider in 1852 he discovered clusters in the heart of a frog nerve cells(Bider's knot). A.S. Dogel in 1897–1890 published the results of studies of the structure of the nerve ganglia of the heart and the nerve endings in it. V.P. Vorobiev in 1923 conducted classic research nerve plexuses hearts. B.I. Lavrentiev studied the sensitivity of the innervation of the heart.

Serious research into the physiology of the heart began two centuries after W. Harvey's discovery of the pumping function of the heart. The most important role was played by the creation K. Ludwig kymograph and his development of a method for graphically recording physiological processes.

Important discovery the influence of the vagus nerve on the heart was done by the brothers Webers in 1848. This was followed by the discoveries of the brothers Tsionami sympathetic nerve and study of its effect on the heart I.P. Pavlov, identification of the humoral mechanism of transmission of nerve impulses to the heart O. Levi in 1921

All these discoveries made it possible to create modern theory structure of the heart and blood circulation.

Heart

Heart is powerful muscular organ, located in the chest between the lungs and the sternum. The walls of the heart are formed by a muscle unique to the heart. The heart muscle contracts and is innervated autonomously and is not subject to fatigue. The heart is surrounded by the pericardium - the pericardial sac (cone-shaped sac). The outer layer of the pericardium consists of inextensible white fibrous tissue, the inner layer consists of two layers: visceral (from lat. viscera– internals, i.e. related to internal organs) and parietal (from lat. parietalis- wall, wall).

The visceral layer is fused with the heart, the parietal layer is fused with fibrous tissue. Pericardial fluid is released into the gap between the layers, reducing friction between the walls of the heart and surrounding tissues. It should be noted that the generally inelastic pericardium prevents excessive stretching of the heart and its overflow with blood.

The heart consists of four chambers: two upper ones - thin-walled atria - and two lower ones - thick-walled ventricles. The right half of the heart is completely separated from the left.

The function of the atria is to collect and retain blood a short time until it passes into the ventricles. The distance from the atria to the ventricles is very short, therefore the atria do not need to contract with great force.

The right atrium receives deoxygenated (oxygen-poor) blood from the systemic circulation, and the left atrium receives oxygenated blood from the lungs.

The muscular walls of the left ventricle are approximately three times thicker than the walls of the right ventricle. This difference is explained by the fact that the right ventricle supplies blood only to the pulmonary (lesser) circulation, while the left ventricle pumps blood through the systemic (large) circle, which supplies blood to the entire body. Accordingly, the blood entering the aorta from the left ventricle is under significantly higher pressure (~105 mm Hg) than the blood entering the pulmonary artery (16 mm Hg).

When the atria contract, blood is pushed into the ventricles. There is a contraction of the circular muscles located at the confluence of the pulmonary and vena cava into the atria and blocking the mouths of the veins. As a result, blood cannot flow back into the veins.

The left atrium is separated from the left ventricle by the bicuspid valve, and the right atrium from the right ventricle by the tricuspid valve.

Strong tendon threads are attached to the valve flaps from the ventricles, the other end is attached to the cone-shaped papillary (papillary) muscles - outgrowths of the inner wall of the ventricles. When the atria contract, the valves open. When the ventricles contract, the valve leaflets close tightly, preventing blood from returning to the atria. At the same time, the papillary muscles contract, stretching the tendon threads, preventing the valves from everting towards the atria.

At the bases of the pulmonary artery and aorta there are connective tissue pockets - semilunar valves, which allow blood to pass into these vessels and prevent it from returning to the heart.

To be continued

* Found and published in 1873 by German Egyptologist and writer Georg Maurice Ebers. Contains about 700 magical formulas and folk recipes for treating various diseases, as well as getting rid of flies, rats, scorpions, etc. The papyrus describes the circulatory system with amazing accuracy.

The circulatory system (Fig. 4) moves blood and lymph (tissue fluid), which makes it possible to transport not only oxygen and nutrients, but also biologically active substances that are involved in regulating the functioning of various organs and systems. Together with the nervous system (due to the expansion or, conversely, constriction of blood vessels), the function of regulating body temperature is carried out.

The central authority in this system is heart - a muscle that self-governs and, at the same time, self-regulates, self-adapts to the activities of the body and, if necessary, self-corrects. The better developed a person's skeletal muscles are, the larger his heart is. U normal person The size of the heart is approximately comparable to the size of the hand clenched into a fist. A person with large weight also has a large heart and mass. The heart is a hollow muscular organ enclosed in the pericardium (pericardium). It has 4 chambers (2 atria and 2 ventricles) (Fig. 5). The organ is divided into left and right halves, each of which has an atrium and a ventricle. Between the atria and ventricles, as well as at the exit from the ventricles, there are valves that prevent the backflow of blood. The main impulse for the heartbeat occurs in the heart muscle itself, since it has the ability to contract automatically. Contractions of the heart occur rhythmically and synchronously - the right and left atrium, then the right and left ventricles. With its correct rhythmic activity, the heart maintains a certain and constant pressure difference and establishes a certain balance in the movement of blood. Normally, per unit of time, the right and left parts of the heart pass the same amount of blood.

The heart is connected to the nervous system by two nerves that act opposite to each other. If necessary for the body's needs, one nerve can speed up the heart rate and the other can slow down. It should be remembered that sharply pronounced violations frequency (very frequent (tachycardia) or, conversely, rare (bradycardia)) and rhythm (arrhythmia) of heartbeats are dangerous to human life.

The main function of the heart is pumping. It may be violated for the following reasons:

a small or, conversely, a very large amount of blood entering it;

disease (damage) to the heart muscle;

compression of the heart from the outside.

Although the heart is very resilient, situations may arise in life when the degree of impairment as a result of the above reasons is excessive. This, as a rule, leads to the cessation of cardiac activity and, as a consequence, the death of the body.

The muscular activity of the heart is closely related to the work of blood and lymphatic vessels. They are the second key element of the circulatory system.

Blood vessels divided into arteries through which blood flows from the heart; the veins through which it flows to the heart; capillaries (very small vessels connecting arteries and veins). Arteries, capillaries and veins form two circles of blood circulation (large and small) (Fig. 6).

The great circle begins with the largest arterial vessel, the aorta, which arises from the left ventricle of the heart. From the aorta, oxygen-rich blood is delivered through the arteries to organs and tissues, in which the diameter of the arteries becomes smaller, turning into capillaries. In the capillaries, arterial blood releases oxygen and, saturated with carbon dioxide, enters the veins. If arterial blood is scarlet, then venous blood is dark cherry. Veins that arise from organs and tissues are collected into larger venous vessels and, ultimately, into the two largest - the superior and inferior vena cava. This ends the large circle of blood circulation. From the vena cava, blood enters the right atrium and is then released through the right ventricle into the pulmonary trunk, from which the pulmonary circulation begins. Through the pulmonary arteries extending from the pulmonary trunk, venous blood enters the lungs, in the capillary bed of which it releases carbon dioxide, and, enriched with oxygen, moves through the pulmonary veins into the left atrium. This ends the pulmonary circulation. From the left atrium through the left ventricle, oxygen-rich blood is again ejected into the aorta (great circle). In the greater circle, the aorta and large arteries have a fairly thick but elastic wall. In medium and small arteries the wall is thick due to the pronounced muscle layer. The muscles of the arteries must constantly be in a state of some contraction (tension), since this so-called “tone” of the arteries is a necessary condition for normal blood circulation. In this case, blood is pumped to the area where the tone has disappeared. Vascular tone is maintained by the activity of the vasomotor center, which is located in the brain stem.

In capillaries, the wall is thin and does not contain muscle elements, so the lumen of the capillary cannot actively change. But through thin wall capillaries exchange substances with surrounding tissues. In the venous vessels of the systemic circle, the wall is quite thin, which allows it to easily stretch if necessary. These venous vessels have valves that prevent blood from flowing back.

In arteries, blood flows under high pressure, in capillaries and veins - under low pressure. That is why, when bleeding occurs from an artery, scarlet (oxygen-rich) blood flows very intensely, even gushing. With venous or capillary bleeding the rate of receipt is low.

The left ventricle, from which blood is ejected into the aorta, is a very strong muscle. Its contractions make a major contribution to maintaining blood pressure in the systemic circulation. Conditions can be considered life-threatening when a significant portion of the left ventricular muscle is disabled. This can happen, for example, with infarction (death) of the myocardium (heart muscle) of the left ventricle of the heart. You should know that almost any lung disease leads to a decrease in the lumen of the blood vessels of the lungs. This immediately leads to an increase in the load on the right ventricle of the heart, which is functionally very weak and can lead to cardiac arrest.

The movement of blood through the vessels is accompanied by fluctuations in the tension of the vascular walls (especially arteries) resulting from heart contractions. These fluctuations are called pulse. It can be identified in places where the artery lies close to the skin. Such places are the anterolateral surface of the neck (carotid artery), the middle third of the shoulder on the inner surface (brachial artery), the upper and middle third of the thigh (femoral artery), etc. (Fig. 7).

Usually the pulse can be felt on the forearm above the base of the thumb on the palm side above the wrist joint. It is convenient to feel it not with one finger, but with two (index and middle) (Fig. 8).

Typically, the pulse rate in an adult is 60 - 80 beats per minute, in children - 80 - 100 beats per minute. In athletes, the heart rate in everyday life can decrease to 40 - 50 beats per minute. The second indicator of the pulse, which is quite easy to determine, is its rhythm. Normally, the time interval between pulse impulses should be the same. Various heart diseases can cause heart rhythm disturbances. An extreme form of rhythm disturbances is fibrillation - sudden, uncoordinated contractions. muscle fibers heart, which instantly lead to a drop in the pumping function of the heart and the disappearance of the pulse.

The amount of blood in an adult is about 5 liters. It consists of a liquid part - plasma and various cells (red - erythrocytes, white - leukocytes, etc.). The blood also contains platelets - platelets, which, together with other substances contained in the blood, participate in its coagulation. Blood clotting is an important protective process during blood loss. With minor external bleeding, the duration of blood clotting is usually up to 5 minutes.

The color of the skin largely depends on the content of hemoglobin (an iron-containing substance that carries oxygen) in the blood (in erythrocytes - red blood cells). So, if the blood contains a lot of oxygen-free hemoglobin, the skin becomes bluish in color (cyanosis). When combined with oxygen, hemoglobin has a bright red color. Therefore, normally, a person’s skin color is pink tint. In some cases, for example, with carbon monoxide poisoning ( carbon monoxide) a compound called carboxyhemoglobin accumulates in the blood, which gives the skin a bright pink color.

The release of blood from the vessels is called hemorrhage. The color of the hemorrhage depends on the depth, location and duration of the injury. A fresh bleed in the skin is usually light red, but over time it changes color, becoming bluish, then greenish and finally yellow. Only hemorrhages in the white of the eye have a bright red color, regardless of their age.

Circulation circles represent a structural system of vessels and components of the heart, within which blood constantly moves.

Circulation plays one of the essential functions human body, it carries blood flows enriched with oxygen and nutrients necessary for tissues, removing metabolic decay products, as well as carbon dioxide, from the tissues.

Transportation of blood through vessels is a critical process, so its deviations lead to the most serious complications.

The circulation of blood flows is divided into a small and large circle of blood circulation. They are also called systemic and pulmonary, respectively. Initially, the systemic circle comes from the left ventricle, through the aorta, and entering the cavity of the right atrium, it ends its journey.

The pulmonary circulation of blood starts from the right ventricle, and enters the left atrium and ends its journey.

Who first identified the circles of blood circulation?

Due to the fact that in the past there were no devices for hardware research organism, studying the physiological characteristics of a living organism was not possible.

The studies were carried out on corpses, in which doctors of that time studied only anatomical features, since the corpse’s heart was no longer beating, and circulatory processes remained a mystery to specialists and scientists of past times.

Some physiological processes they simply had to speculate or use their imagination.

The first assumptions were the theories of Claudius Galen, back in the 2nd century. He was trained in the science of Hippocrates, and put forward the theory that the arteries inside themselves carry air cells, and not masses of blood. As a result, for many centuries they tried to prove this physiologically.

All scientists were aware of what the structural system of blood circulation looks like, but could not understand on what principle it functions.

A big step in organizing data on the functioning of the heart was made by Miguel Servet and William Harvey already in the 16th century.

The latter, for the first time in history, described the existence of systemic and pulmonary circulation circles, back in one thousand six hundred and sixteen, but was never able to explain in his works how they are connected to each other.

Already in the 17th century, Marcello Malpighi, the one who began to use a microscope for practical purposes, one of the first people in the world, discovered and described that there are small capillaries that are not visible to the naked eye, they connect two circles of blood circulation.

This discovery was disputed by the geniuses of those times.

How did blood circulation circles evolve?

As the class “vertebrates” developed more and more both anatomically and physiologically, an increasingly developed structure of the cardiovascular system was formed.

The formation of a vicious circle of blood movement occurred to increase the speed of movement of blood flows in the body.

When compared with other classes of animal beings (let’s take arthropods), chordates show the initial formation of blood movement in a vicious circle. The class of lancelets (a genus of primitive marine animals) does not have a heart, but has an abdominal and dorsal aorta.

The formation of two circulation circles is the evolution of the cardiovascular system, which adapted to its environment.

Types of vessels

The entire blood circulation system consists of the heart, which is responsible for pumping blood and its constant movement in the body, and the vessels inside which the pumped blood is distributed.

Many arteries, veins, as well as small capillaries form a closed circle of blood circulation with their multiple structure.

Mostly large vessels, which have the shape of a cylinder and are responsible for moving blood from the heart to the feeding organs, make up the systemic circulatory system.

All arteries have elastic walls that contract, resulting in blood moving evenly and in a timely manner.

The vessels have their own structure:

• Inner endothelial membrane. It is strong and elastic, it interacts directly with the blood;
• Smooth muscle elastic tissue. They make up the middle layer of the vessel, are more durable and protect the vessel from external damage;
• Connective tissue membrane. It is the outermost layer of the vessel, covering them along the entire length, protects the vessels from external influence on them.

The veins of the systemic circle help blood flow from small capillaries directly to the tissues of the heart. They have the same structure as arteries, but are more fragile, since their middle layer contains less tissue and is less elastic.

In view of this, the speed of blood movement through the veins is influenced by the tissues located in close proximity to the veins, and especially the skeletal muscles. Almost all veins contain valves that prevent blood from moving through reverse direction. The only exception is the vena cava.

The smallest components of the structure of the vascular system are capillaries, the covering of which is a single-layer endothelium. They are the smallest and shortest types of vessels.

It is they who enrich the tissues with useful elements and oxygen, removing from them the remnants of metabolic decay, as well as processed carbon dioxide.

Blood circulation in them occurs more slowly, in the arterial part of the vessel water is transported to the intercellular zone, and in the venous part the pressure drops and water rushes back into the capillaries.

On what principle are arteries located?

The placement of vessels on the way to the organs occurs along the shortest path to them. The vessels located in our limbs pass from the inside, since from the outside, their path would be longer.

Also, the pattern of vessel formation is definitely related to the structure human skeleton. An example is that the brachial artery runs along the upper limbs, which is called according to the bone near which it passes - the brachial artery.

Other arteries are also called according to this principle: the radial artery - directly next to the radius bone, the ulnar artery - in the vicinity of the elbow, etc.

With the help of connections between nerves and muscles, networks of vessels are formed in the joints, in the systemic blood circulation. That is why when the joints move, they constantly support blood circulation.

The functional activity of an organ affects the size of the vessel leading to it; in this case, the size of the organ does not play a role. The more important and functional the organs, the more arteries leading to them.

Their placement around the organ itself is influenced solely by the structure of the organ.

System circle

The main task great circle blood circulation is gas exchange in any organs except the lungs. It starts from the left ventricle, blood from it enters the aorta, spreading further throughout the body.

Components of the systemic circulatory system from the aorta, with all its branches, arteries of the liver, kidneys, brain, skeletal muscles and other organs. After the large vessels, it continues with small vessels and the beds of the veins of the above organs.

The right atrium is its final point.

Directly from the left ventricle, arterial blood enters the vessels through the aorta, it contains the majority of oxygen and a small proportion of carbon. The blood in it is taken from the pulmonary circulation, where it is enriched oxygen to the lungs.

The aorta is the largest vessel in the body, and consists of a main canal and many branching, smaller arteries leading to the organs for their saturation.

Arteries leading to organs are also divided into branches and deliver oxygen directly to the tissues of certain organs.

With further branches, the vessels become smaller and smaller, eventually forming a great many capillaries, which are the smallest vessels in the human body. Capillaries do not have a muscular layer, but are represented only by the inner lining of the vessel.

Many capillaries form a capillary network. They are all covered with endothelial cells, which are located at a sufficient distance from each other for nutrients to penetrate into the tissues.

This promotes gas exchange between small vessels and the area between cells.

They supply oxygen and take away carbon dioxide. The entire exchange of gases occurs constantly; after each contraction of the heart muscle in some part of the body, oxygen is delivered to tissue cells and hydrocarbons flow out of them.

The vessels that collect hydrocarbons are called venules. They subsequently join into larger veins and form one large vein. Large veins form the superior and inferior vena cava, ending in the right atrium.

Features of the systemic circulation

A special difference between the systemic circulatory system is that in the liver there is not only a hepatic vein, which removes venous blood from it, but also a portal vein, which in turn supplies blood to it, where blood purification is performed.

After this, the blood enters the hepatic vein and is transported to the systemic circle. The blood in the portal vein comes from the intestines and stomach, which is why harmful products nutrition has such a detrimental effect on the liver - they undergo cleansing in it.

The tissues of the kidneys and pituitary gland also have their own characteristics. Directly in the pituitary gland there is its own capillary network, which involves the division of arteries into capillaries and their subsequent connection into venules.

After this, the venules again divide into capillaries, then a vein is formed, which drains blood from the pituitary gland. Regarding the kidneys, the arterial network is divided according to a similar pattern.

How does blood circulation occur in the head?

One of the most complex structures of the body is blood circulation in the cerebral vessels. The sections of the head are fed by the carotid artery, which is divided into two branches (read). More details about

The arterial vessel enriches the face, temporal zone, mouth, nasal cavity, thyroid gland and other parts of the face.

This is how most of the systemic circle is formed, which ends in the cerebral artery.

The main arteries supplying the brain are the subclavian and carotid arteries, which are connected together.

Supported by vascular network the brain functions with minor disruptions in blood flow.

Small circle

The main purpose of the pulmonary circulation is the exchange of gases in the tissues, saturating the entire area of ​​the lungs in order to enrich the already exhausted blood with oxygen.

The pulmonary circle of blood circulation starts from the right ventricle, where blood enters from the right atrium, with a low concentration of oxygen and a high concentration of hydrocarbons.

From there, the blood enters the pulmonary trunk, bypassing the valve. Next, the blood moves through a network of capillaries located throughout the lungs. Similar to the capillaries of the systemic circle, small vessels of the pulmonary tissues carry out gas exchange.

The only difference is that oxygen enters the lumen of small vessels, and not carbon dioxide, which here penetrates the cells of the alveoli. The alveoli, in turn, are enriched with oxygen with each inhalation of a person, and remove hydrocarbons from the body with exhalation.

Oxygen saturates the blood, making it arterial. After which it is transported through the venules and reaches the pulmonary veins, which end in the left atrium. This explains that the left atrium contains arterial blood, and the right atrium contains venous blood, and in a healthy heart they do not mix.

Lung tissue contains a double-level capillary network. The first is responsible for gas exchange for oxygen enrichment venous blood(connection with the pulmonary blood circulation), and the second supports the saturation of the lung tissues themselves (connection with the systemic blood circulation).

This is an additional protection for the brain from lack of oxygen. Its components are the following vessels: internal carotid arteries, the initial part of the anterior and posterior cerebral arteries, as well as the anterior and posterior communicating arteries.

Also, in pregnant women, an additional circle of blood circulation is formed, called the placental. Its main task is to maintain the child’s breathing. Its formation occurs at 1-2 months of gestation.

It begins to work in full force after the twelfth week. Since the fetal lungs are not yet functioning, oxygen enters the blood through the umbilical vein of the fetus with the arterial blood flow.

Special transport system, which supplies cells with the substances necessary for life, develops already in animals with an open circulatory system (most invertebrates, as well as lower chordates); The movement of fluid (hemolymph) in these organisms is carried out due to contractions of the muscles of the body or blood vessels. Mollusks and arthropods develop a heart. In animals with a closed circulatory system (some invertebrates, all vertebrates and humans), the further evolution of blood circulation is mainly the evolution . In fish it is two-chambered. When one of the chambers, the ventricle, contracts, blood flows into the abdominal aorta, then into the vessels of the gills, then into the dorsal aorta, and from there to all organs and tissues.

Rice. 1. Diagram of the blood circulation of fish: 1 - vessels of the gills, 2 - vessels of the body, 3 - atrium, 4 - ventricle of the heart.

In amphibians, blood pumped by the ventricle of the heart into the aorta directly flows to the organs and tissues. With the transition to In addition to the main, large circle of K., a special small, or pulmonary, circle of K. appears.

Rice. 2. Diagram of the blood circulation of an amphibian: A - small circle, B - large circle; 1 - pulmonary vessels, 2 - right atrium, 3 - left atrium, 4 - ventricle of the heart, 5 - body vessels.

In birds, mammals and humans, the principle of blood circulation is the same. The blood ejected by the left ventricle into the main artery, the aorta, flows further into the arteries, then into the arterioles and capillaries of organs and tissues, where the exchange of substances between blood and tissues occurs. From tissue capillaries, venous blood flows through venules and veins to the heart, entering the right atrium. The sections of the vascular system located between the left ventricle and the right atrium make up the so-called systemic circulation.

Rice. 3. Diagram of human blood circulation: 1 - vessels of the head and neck, 2 - upper limb, 3 - aorta, 4 - pulmonary vein, 5 - vessels of the lung, 6 - stomach, 7 - spleen, 8 - intestines, 9 - lower extremities, 10 - kidneys, 11 - liver, 12 - inferior vena cava, 13 - left ventricle of the heart, 14 - right ventricle of the heart, 15 - right atrium, 16 - left atrium, 17 - pulmonary artery, 18 - superior vena cava.

From the right atrium, blood enters the right ventricle, which, when contracted, is ejected into the pulmonary artery. Then, through the arterioles, it enters the capillaries of the alveoli, where it releases carbon dioxide and is enriched with oxygen, turning from venous to arterial. Arterial blood from the lungs it returns through the pulmonary veins to the heart - to its left atrium. , through which blood flows from the right ventricle to the left atrium, make up the pulmonary circulation. From the left atrium, blood flows into the left ventricle and again into the aorta.

Rice. 4. Blood circulation. Pronounced asymmetry large arteries, appearing during the development of the human embryo: 1 - right subclavian artery, 2 - pulmonary duct, 3 - ascending aorta, 4 and 8 - right and left pulmonary artery, 5 and 6 - right and left carotid artery, 7 - aortic arch, 9 - descending aorta.

The movement of blood through the vessels occurs due to the pumping function of the heart. The amount of blood ejected by the heart in 1 minute is called minute volume (MV).

Rice. 5. Blood circulation. Symmetrical formation of large arteries in the human embryo: 1 - dorsal aorta, 2 - ductus arteriosus, 3 - 8 - aortic arches.

MO can be measured directly using special flow meters. In humans, MO is determined by indirect methods. By measuring, for example, the difference in the CO 2 content in 100 ml of arterial and venous blood [(A - B) CO 2 ], as well as the amount of CO 2 released by the lungs in 1 minute (I' CO 2), the volume of blood flowing through the lungs is calculated in 1 min, - MO according to the Fick formula:

Instead of CO 2, you can determine the content of O 2 or harmless dyes, gases or other indicators specially introduced into the blood. A person’s MO at rest is 4-5 liters, and during physical or emotional stress it increases 3-5 times. Its magnitude, like the linear speed of blood flow, blood circulation time, etc., is an important indicator of the state of blood circulation. Basic data characterizing the laws of blood movement through the vessels and the state of blood in various parts of the vascular system:

Characteristics of the vascular bed and blood movement in various parts of the cardiovascular system

Notes:

* Blood volume in the cavities of the heart - 15%; blood volume in the pulmonary circle is 18%.

** Including arteries of the great circle.

The aorta and arteries of the body are a pressure reservoir in which blood is kept under high pressure(for humans, the normal level is about 120/70 mmHg). The heart pumps blood into the arteries in separate portions. At the same time, the elastic walls of the arteries are stretched. Thus, during diastole, the energy accumulated by them maintains the blood in the arteries at a certain level, which ensures the continuity of blood flow in the capillaries. The level of blood pressure in the arteries is determined by the relationship between MO and peripheral vascular resistance. The latter, in turn, depends on the tone of the arterioles, which are, in the words of the Russian scientist and materialist thinker, creator of the physiological school Ivan Mikhailovich Sechenov, “the taps of the circulatory system.” Increased arteriolar tone impedes the outflow of blood from the arteries and increases blood pressure; a decrease in their tone causes the opposite effect. In different parts of the body, arteriolar tone may change differently. With a decrease in tone in any area, the amount of blood flowing increases. In other areas, this may simultaneously result in an increase in arteriolar tone, leading to a decrease in blood flow. The total resistance of all arterioles of the body and, therefore, the value of the so-called average blood pressure however, they may not change. Thus, in addition to regulating the average level of blood pressure, the tone of the arterioles determines the amount of blood flow through the capillaries various organs and fabrics.

The hydrostatic pressure of blood in the capillaries promotes the filtration of fluid from the capillaries into the tissue; this process is prevented by the oncotic pressure of the blood plasma.

Moving along the capillary, the blood experiences resistance, which requires energy to overcome. As a result, the blood pressure along the capillary drops. This leads to the flow of fluid from the intercellular spaces into the capillary cavity. Part of the fluid flows from the intercellular gaps through the lymphatic vessels ( click on the picture to enlarge):

Rice. 6. The pressure ratio that ensures the movement of fluid in capillaries, intercellular space and lymphatic vessels. * Negative pressure in the intercellular space, resulting from the suction of fluid by lymphatic vessels; ** the resulting pressure ensuring the movement of fluid from the capillary to the tissue; *** the resulting pressure that ensures the movement of fluid from the tissues into the capillary.

Direct measurement of fluid pressure in the intercellular spaces of tissues by introducing microcannulas connected to sensitive electromanometers showed that this pressure is not equal to atmospheric pressure, but is 5 - 10 mm Hg lower than it. Art. This seemingly paradoxical fact is explained by the fact that active pumping of fluid occurs in the tissues. Periodic compression of tissue by pulsating arteries and arterioles and contracting muscles leads to the pushing of tissue fluid into the lymphatic vessels, the valves of which prevent its return to the tissue. This creates a pump that maintains negative (relative to atmospheric) pressure in the intercellular spaces. Pumps that pump out fluid from the intercellular spaces create a constant vacuum, facilitating the continuous flow of fluid into the tissue even with significant fluctuations in capillary pressure. This ensures greater reliability of the main function of blood circulation - metabolism between blood and tissues. These same pumps simultaneously guarantee sufficient fluid outflow through lymphatic system in cases sharp fall oncotic pressure of blood plasma (and the resulting decrease in reabsorption of tissue fluid into the blood). Thus, these pumps represent a true “peripheral heart”, the function of which depends on the degree of elasticity of the arteries and on the periodic activity of the muscles.

Blood flows from tissues through venules and veins. The veins of the systemic circulation contain more than half of the body's total blood. Skeletal muscle contractions and respiratory movements facilitate blood flow into the right atrium. The muscles compress the veins located between them, squeezing blood towards the heart (reverse blood flow is impossible due to the presence of valves in the veins:

Rice. 7. The action of skeletal muscles, helping the movement of blood through the veins: A - muscle at rest; B - when it contracts, blood is pushed upward through the vein - to the heart; the lower valve prevents the reverse flow of blood; B - after the muscle relaxes, the vein expands, filling with a new portion of blood; the upper valve prevents its reverse flow; 1 - muscle; 2 - valves; 3 - vein.

The increase in negative pressure in the chest during each breath helps draw blood to the heart. The blood circulation of individual organs - the heart, lungs, brain, spleen - differs in a number of features due to the specific functions of these organs.

Coronary circulation also has significant features.

Rice. 8. Diagram of the blood circulation of a human embryo: 1 - umbilical cord, 2 - umbilical vein, 3 - heart, 4 - aorta, 5 - superior vena cava, 6 - cerebral veins, 7 - cerebral arteries, 8 - aortic arch, 9 - ductus arteriosus , 10 - pulmonary artery, 11 - inferior vena cava, 12 - descending aorta, 13 - umbilical arteries.

Regulation of blood circulation

The intensity of activity of various organs and tissues is constantly changing, and therefore their need for various substances. At a constant level of blood flow, the delivery of oxygen and glucose to tissues can triple due to more complete utilization of these substances from the flowing blood. Under the same conditions delivery fatty acids can increase by 28 times, amino acids by 36 times, carbon dioxide by 25 times, products of protein metabolism by 480 times, etc. Consequently, the most “bottleneck” of the circulatory system is the transport of oxygen and glucose. Therefore, if the amount of blood flow is sufficient to provide tissues with oxygen and glucose, it is more than sufficient for the transport of all other substances. In tissues, as a rule, there are significant reserves of glucose deposited in the form of glycogen; oxygen reserves are practically absent (with the exception of only very small amounts of oxygen bound to muscle myoglobin). Therefore, the main factor determining the intensity of blood flow in tissues is their need for oxygen. The work of the mechanisms regulating K. is aimed primarily at satisfying precisely this need.

In the complex system of blood circulation regulation, only general principles have so far been studied and only some links have been studied in detail. Significant progress in this area has been achieved, in particular, thanks to the study of the regulation of the main function of the cardiovascular system - blood circulation - using methods of mathematical and electrical modeling. K. is regulated by reflex and humoral mechanisms that provide organs and tissues at any given moment with the amount of oxygen they need, as well as the simultaneous maintenance of the basic parameters of hemodynamics - blood pressure, MO, peripheral resistance, etc. - at the required level.

The processes of blood regulation are carried out by changes in the tone of arterioles and the value of MO. The tone of the arterioles is regulated by the vasomotor center located in the medulla oblongata. This center sends impulses to smooth muscles vascular wall through the centers of the autonomic nervous system. The required blood pressure in the arterial system is maintained only under the condition of constant tonic contraction of the muscles of the arterioles, which requires the continuous supply of nerve impulses to these muscles through the vasoconstrictor fibers of the sympathetic nervous system. These pulses follow at a frequency of 1-2 pulses per 1 second. An increase in frequency leads to an increase in arteriolar tone and an increase in blood pressure; a decrease in impulses causes the opposite effect. The activity of the vasomotor center is regulated by signals coming from baroreceptors or mechanoreceptors of the vascular reflexogenic zones(the most important of them is the carotid sinus). An increase in pressure in these areas causes an increase in the frequency of impulses arising in the baroreceptors. which leads to a decrease in the tone of the vasomotor center, and consequently to a decrease in response impulses coming from it to the smooth muscles of the arterioles. This leads to a decrease in the tone of the muscle wall of the arterioles, a decrease in heart rate (decreased MO) and, as a consequence, a drop in blood pressure. A drop in pressure in these areas causes the opposite reaction:

Rice. 9. Diagram of one of the links in the mechanism of blood pressure regulation.

Thus, the entire system is a servomechanism operating on the principle feedback and maintaining blood pressure at a relatively constant level (see depressor reflexes, carotid reflexes). Similar reactions occur when baroreceptors in the pulmonary circulation are stimulated. The tone of the vasomotor center also depends on impulses arising in the chemoreceptors of the vascular bed and tissues, as well as under the influence of biologically active substances in the blood. In addition, the state of the vasomotor center is also determined by signals coming from other parts of the central nervous system. Thanks to this, adequate changes in blood circulation occur with changes functional state any organ, system or the whole organism.

In addition to the tone of the arterioles, there is also a value of MO, which depends on the amount of blood flowing to the heart and on the energy of heart contractions. The amount of blood flowing to the heart depends on the tone of the smooth muscles of the venous wall, which determines the capacity of the venous system, on the contractile activity of skeletal muscles, which facilitates the return of blood to the heart, as well as on the total volume of blood and tissue fluid in the body. The tone of the veins and the contractile activity of skeletal muscles are determined by impulses arriving to these organs, respectively, from the vasomotor center and the centers that control body movement. The total volume of blood and tissue fluid is regulated by reflexes that occur in the stretch receptors of the right and left atria. An increase in blood flow to the right atrium excites these receptors, causing a reflex inhibition of the adrenal glands' production of the hormone Aldosterone. A deficiency in aldosterone leads to increased excretion of Na and Cl ions in the urine and, as a result, to a decrease in the total amount of water in the blood and tissue fluid, and consequently to a decrease in the volume of circulating blood. Increased stretching of the left atrium by blood also causes a decrease in the volume of circulating blood and tissue fluid. However, in this case, another mechanism is activated: signals from stretch receptors inhibit the release of the hormone vasopressin by the pituitary gland, which leads to increased release of water. The magnitude of MO also depends on the strength of contractions of the heart muscle, which is regulated by a number of intracardiac mechanisms, the action of humoral agents, and the central nervous system.

In addition to the described central mechanisms of blood circulation regulation, there are also peripheral mechanisms. One of them is changes in the “basal tone” of the vascular wall, which occur even after the complete shutdown of all central vasomotor influences. Stretching of the vascular walls excessive quantity blood causes, after a short period of time, a decrease in the tone of the smooth muscles of the vascular wall and an increase in the volume of the vascular bed. Decreasing blood volume has the opposite effect. Thus, a change in the “basal tone” of blood vessels ensures, within certain limits, the automatic maintenance of the so-called average pressure in cardiovascular system what's playing important role in the regulation of minute volume. The reasons for direct changes in the “basal tone” of blood vessels have not yet been sufficiently studied.

So, the general regulation of blood is ensured by complex and diverse mechanisms, often duplicating each other, which determines the high reliability of regulation general condition this vital system for the body.

Along with the general mechanisms of blood circulation, there are central and local mechanisms that control local blood circulation, that is, blood circulation in individual organs and tissues. Research using microelectrode technology, studying vascular tone individual areas of the body (resistography) and other works have shown that the vasomotor center selectively turns on neurons that regulate the tone of certain vascular areas. This allows you to reduce the tone of some vascular areas, while simultaneously increasing the tone of others. Local dilation of blood vessels occurs not only as a result of a decrease in the frequency of vasoconstrictor impulses, but in some cases as a result of signals arriving through special vasodilator fibers. A number of organs are supplied with vasodilator fibers of the parasympathetic nervous system, and skeletal muscles are innervated by vasodilator fibers sympathetic system. Vasodilation of any organ or tissue occurs when the working activity of this organ increases and is not always accompanied general changes K. Peripheral mechanisms of blood circulation regulation ensure an increase in blood flow through an organ or tissue with an increase in their working activity. It is believed that main reason These reactions are the accumulation in tissues of metabolic products that have a local vasodilating effect (this opinion is not shared by all researchers). Biologically play a significant role in the general and local regulation of blood cells. active substances. These include hormones - adrenaline, renin and, possibly, vasopressin and the so-called local, or tissue, hormones - serotonin, bradykinin and other kinins, prostaglandins and other substances. Their role in the regulation of K. is being studied.

The circulatory regulation system is not closed. It continuously receives information from other parts of the central nervous system and, in particular, from the centers that regulate body movements, the centers that determine the occurrence of emotional stress, and from the cerebral cortex. Thanks to this, changes in K. occur with any changes in the state and activity of the body, with emotions, etc. These changes in K. are adaptive, adaptive in nature. Restructuring of K.'s function often precedes the body's transition to new mode, as if preparing him in advance for the upcoming activity.

Circulatory disorders

Circulatory disorders can be local and general in nature. Local - manifested by arterial and venous hyperemia or caused by disorders nervous regulation K., embolism, as well as exposure to external damaging factors on blood vessels; local violations of K. underlie endarteritis obliterans and others.

General disorders are manifested by circulatory failure - a condition in which the circulatory system does not deliver the required amount of blood to organs and tissues. A distinction is made between cardiac insufficiency of cardiac (central) origin if its cause is a dysfunction of the heart; vascular (peripheral) - if the cause is associated with primary disorders of vascular tone; general With K. it is noted venous stasis, because it throws out less blood into the arteries than flows to it through the veins. Vascular insufficiency characterized by a decrease in venous and blood pressure: the venous flow to the heart decreases due to a discrepancy between the capacity of the vascular bed and the volume of blood circulating in it. Its causes may be those causing the development of heart failure: hypoxia and tissue metabolic disorders. Congestive failure is characterized by myocardial hypertrophy, increased venous pressure, increased mass of circulating blood, edema, and slowed blood circulation. In case of deficiency associated with primary , 1927;