Where does the blood of the great circle flow? Circulation circles

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

In goblin animals and humans, which have a four-chambered heart, the greater, lesser, and cardiac circles of blood circulation are distinguished (Fig. 367). The heart occupies a central place in blood circulation.

367. Blood circulation diagram (according to Kishsh, Sentagotai).

1 - general carotid artery;
2 - aortic arch;
3 - pulmonary artery;
4 - pulmonary vein;
5 - left ventricle;
6 - right ventricle;
7 - celiac trunk;
8 - top 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.

Pulmonary circulation (pulmonary)

Venous blood from the right atrium passes through the right atrioventricular orifice into the right ventricle, which contracts and pushes 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 surrounding each alveolus. After red blood cells release carbon dioxide and enrich them with oxygen, venous blood turns into arterial blood. Arterial blood flows through four pulmonary veins (there are two veins in each lung) into the left atrium, then passes through the left atrioventricular orifice into the left ventricle. The systemic circulation begins from the left ventricle.

Systemic circulation

Arterial blood from the left ventricle is ejected into the aorta during its contraction. The aorta splits into arteries that supply blood to the limbs and torso. All internal organs and ending with capillaries. Nutrients, water, salts and oxygen are released from the blood capillaries into the tissues, metabolic products and carbon dioxide are resorbed. The capillaries gather into venules, where the venous system of vessels begins, representing the roots of the superior and inferior vena cava. Venous blood through these veins enters 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 collects through small veins into the venous coronary sinus. This vessel opens with a wide mouth into the right atrium. Some of the small veins of the heart wall directly open into the cavity of the right atrium and ventricle of the heart.

Nutrition of tissues with oxygen, important elements, as well as the removal of carbon dioxide and metabolic products from the cells in the body - blood functions. The process is a closed vascular path - circles of human blood circulation, through which a continuous flow of vital life passes important fluid, its sequence of movement is ensured by special valves.

There are several circles of blood circulation in the human body

How many circles of blood circulation does a person have?

Human blood circulation or hemodynamics is a continuous flow of plasma fluid through the vessels of the body. This is a closed path of a closed type, that is, it does not come into contact with external factors.

Hemodynamics has:

• main circles – large and small;
• additional loops - placental, coronal and Willis.

The circulation cycle is always complete, which means that mixing of arterial and venous blood does not occur.

The heart, the main organ of hemodynamics, is responsible for plasma circulation. It is divided into 2 halves (right and left), where they are located internal departments- ventricles and atria.

Heart - main body in the human circulatory system

The direction of flow of liquid movable connective tissue is determined by cardiac bridges or valves. They control the flow of plasma from the atria (cusps) and prevent the return arterial blood back into the ventricle (lunate).

The blood moves in circles in a certain order - first the plasma circulates in a small loop (5-10 seconds), and then in big ring. Specific regulators control the functioning of the circulatory system - humoral and nervous.

Big circle

The large circle of hemodynamics has 2 functions:

• saturate the entire body with oxygen, distribute it to tissues necessary elements;
• remove gas dioxide and toxic substances.

Here pass the superior and inferior vena cava, venules, arteries and artioles, as well as the largest artery, the aorta, which emerges from the left ventricle of the heart.

The systemic circulation saturates organs with oxygen and removes toxic substances

In a large ring, the flow of blood fluid begins in the left ventricle. Purified plasma exits through the aorta and is distributed to all organs through movement through arteries, arterioles, reaching the smallest vessels - the capillary network, where it gives oxygen and useful components. In return, harmful waste and carbon dioxide are removed. The return path of plasma to the heart lies through venules, which smoothly flow into the vena cava - this is venous blood. Circulation along the large loop ends in the right atrium. Duration full circle– 20–25 seconds.

Small circle (pulmonary)

The primary role of the pulmonary ring is to carry out gas exchange in the alveoli of the lungs and produce heat transfer. During the cycle, venous blood is saturated with oxygen, cleared of carbon dioxide. The small circle has additional features. It blocks the further advancement of emboli and blood clots that have penetrated from great circle. And if the volume of blood changes, then it accumulates in separate vascular reservoirs, which in normal conditions do not participate in circulation.

The pulmonary circle has the following structure:

• pulmonary vein;
• capillaries;
• pulmonary artery;
• arterioles.

Venous blood, due to ejection from the atrium of the right side of the heart, passes into the large pulmonary trunk and enters the central organ of the small ring - the lungs. IN capillary network There is a process of plasma enrichment with oxygen and release of carbon dioxide. Arterial blood flows into the pulmonary veins, the ultimate goal of which is to reach the left heart (atrium). This completes the circulation around the small ring.

The peculiarity of the small ring is that the movement of plasma along it has the reverse sequence. Here, blood rich in carbon dioxide and cellular waste flows through the arteries, and oxygen-rich fluid moves through the veins.

Additional circles

Based on the characteristics of human physiology, in addition to the 2 main ones, there are 3 more auxiliary hemodynamic rings - placental, cardiac or coronary and Willisian.

Placental

The period of development in the uterus of the fetus implies the presence of a blood circulation in the embryo. Its main task is to saturate with oxygen and useful elements all tissues of the body of the unborn child. Liquid connective tissue enters the fetal organ system through the mother's placenta through the capillary network of the umbilical vein.

The movement sequence is as follows:

• the mother’s arterial blood, entering the fetus’s body, mixes with its venous blood from the lower part of the body;
• fluid moves to the right atrium through the inferior vena cava;
• a larger volume of plasma enters the left side of the heart through interatrial septum(the small circle is passed, since it does not yet function in the embryo) and passes into the aorta;
• the remaining amount of undistributed blood flows into the right ventricle, where through the superior vena cava, collecting all venous blood from the head, goes to right side heart, and from there into the pulmonary trunk and aorta;
• From the aorta, blood spreads into all tissues of the embryo.

After the birth of the child, the need for the placental circle disappears, and the connecting veins are empty and do not function.

The placental circulation saturates the baby’s organs with oxygen and necessary elements

Heart circle

Due to the fact that the heart continuously pumps blood, it needs increased blood supply. Therefore, an integral part of the great circle is the coronal circle. It begins with the coronary arteries, which surround the main organ like a crown (hence the name of the additional ring).

The cardiac circle supplies the muscular organ with blood

The role of the heart circle is increased nutrition hollow muscular organ blood. A feature of the coronary ring is that the contraction of the coronary vessels is affected by vagus nerve, while on contractility other arteries and veins are affected by the sympathetic nerve.

The circle of Willis is responsible for the complete supply of blood to the brain. The purpose of such a loop is to compensate for the lack of blood circulation in case of blockage of blood vessels. in such a situation, blood from other arterial basins will be used.

The structure of the arterial ring of the brain includes such arteries as:

• anterior and posterior brain;
• front and back connecting.

The circle of Willis circulation supplies the brain with blood

IN in good condition the Willis ring is always closed.

The human circulatory system has 5 circles, of which 2 are main and 3 are additional, thanks to which the body is supplied with blood. The small ring carries out gas exchange, and the large one is responsible for transporting oxygen and nutrients to all tissues and cells. Additional circles are performed important role during pregnancy, reduce the load on the heart and compensate for the lack of blood supply to the brain.

Pulmonary circulation

Circulation circles - this concept conditionally, since only in fish the blood circulation is completely closed. In all other animals, the end of the systemic circulation is the beginning of the small one and vice versa, which makes it impossible to talk about their complete isolation. In fact, both circles of blood circulation form a single whole bloodstream, in two sections of which (the right and left heart), kinetic energy is imparted to the blood.

Circulation is a vascular pathway that has its beginning and end in the heart.

Systemic (systemic) circulation

Structure

It begins with the left ventricle, which ejects blood into the aorta during systole. Numerous arteries depart from the aorta, as a result the blood flow is distributed over several parallel regional vascular networks, each of which supplies blood separate body. Further division of the arteries occurs into arterioles and capillaries. The total area of ​​all capillaries in the human body is approximately 1000 m².

After passing through the organ, the process of capillaries merging into venules begins, which in turn gather into veins. Two vena cavae approach the heart: superior and inferior, which, when fused, form part of the right atrium of the heart, which is the end of the systemic circulation. The circulation of blood in the systemic circulation occurs in 24 seconds.

Exceptions in the structure

• Blood circulation of the spleen and intestines. IN general structure The blood circulation in the intestines and spleen does not enter, since after the formation of the splenic and intestinal veins, they merge to form the portal vein. The portal vein re-disintegrates in the liver into a capillary network, and only after that the blood flows to the heart.
• Kidney circulation. In the kidney, there are also two capillary networks- the arteries break up into afferent arterioles, Shumlyansky-Bowman capsules, each of which breaks up into capillaries and gathers into an efferent arteriole. The efferent arteriole reaches the convoluted tubule of the nephron and re-disintegrates into a capillary network.

Functions

Blood supply to all organs of the human body, including the lungs.

Lesser (pulmonary) circulation

Structure

It begins in the right ventricle, which ejects blood into the pulmonary trunk. The pulmonary trunk is divided into right and left pulmonary artery. Arteries are dichotomously divided into lobar, segmental and subsegmental arteries. Subsegmental arteries are divided into arterioles, which break up into capillaries. Outflow there's blood coming out through the veins that gather in reverse order, which in the amount of 4 pieces flow into the left atrium. Blood circulation in the pulmonary circulation occurs in 4 seconds.

The pulmonary circulation was first described by Miguel Servetus in the 16th century in his book “The Restoration of Christianity.”

Functions

• Heat dissipation

Small circle function is not nutrition of lung tissue.

“Additional” circulation circles

Depending on physiological state body, as well as practical expediency, sometimes additional circles of blood circulation are distinguished:

• placental,
• cordial.

Placental circulation

Exists in the fetus located in the uterus.

Blood that is not fully oxygenated leaves through umbilical vein, passing in the umbilical cord. From here, most of the blood flows through the ductus venosus into the inferior vena cava, mixing with unoxygenated blood from the lower body. A smaller portion of the blood enters left branch portal vein, passes through the liver and hepatic veins and enters the inferior vena cava.

Mixed blood flows through the inferior vena cava, the oxygen saturation of which is about 60%. Almost all of this blood flows through the foramen ovale in the wall of the right atrium into the left atrium. From the left ventricle, blood is ejected into the systemic circulation.

Blood from the superior vena cava first enters the right ventricle and pulmonary trunk. Since the lungs are in a collapsed state, the pressure in the pulmonary arteries is greater than in the aorta, and almost all the blood passes through the ductus arteriosus into the aorta. Ductus arteriosus flows into the aorta after the arteries of the head and upper extremities depart from it, which provides them with more enriched blood. A very small part of the blood enters the lungs, which subsequently enters the left atrium.

Part of the blood (~60%) from the systemic circulation enters the placenta through two umbilical arteries; the rest goes to the organs of the lower body.

Cardiac circulatory system or coronary circulatory system

Structurally, it is part of the greater circulatory system, but due to the importance of the organ and its blood supply, you can sometimes find mention of this circle in the literature.

Arterial blood flows to the heart through the right and left coronary artery. They begin at the aorta above its semilunar valves. Smaller branches extend from them, enter the muscle wall and branch to the capillaries. The outflow of venous blood occurs in 3 veins: large, middle, small, and cardiac vein. Merging they form the coronary sinus and it opens into the right atrium.

Wikimedia Foundation. 2010.

What is the pulmonary circulation?

From the right ventricle, blood is pumped into the capillaries of the lungs. Here she "gives" carbon dioxide and “takes” oxygen, after which it goes back to the heart, namely to the left atrium.

moves along a closed circuit which consists of the large and small circles of blood circulation. The path in the pulmonary circulation is from the heart to the lungs and back. In the pulmonary circulation, venous blood from the right ventricle of the heart enters pulmonary lungs, where it gets rid of carbon dioxide and is saturated with oxygen and flows through the pulmonary veins into the left atrium. After this, the blood is pumped into the systemic circulation and flows to all organs of the body.

Why is the pulmonary circulation needed?

Dividing the human circulatory system into two circulation circles has one significant advantage: oxygen-enriched blood is separated from “used” blood, saturated with carbon dioxide. Thus, it is subjected to significantly less load than if, in general, it pumped both oxygen-saturated and carbon dioxide-saturated. This structure of the pulmonary circulation is due to the presence of a closed arterial and venous system connecting the heart and lungs. In addition, precisely due to the presence of the pulmonary circulation, it consists of four chambers: two atria and two ventricles.

How does the pulmonary circulation function?

Blood enters the right atrium through two venous trunks: the superior vena cava, which brings blood from upper parts body, and the inferior vena cava, which brings blood from its lower parts. From the right atrium, blood enters the right ventricle, from where it is pumped through the pulmonary artery into the lungs.

Heart valves:

In the heart there are: one between the atria and the ventricles, the second between the ventricles and the arteries emerging from them. prevent backflow of blood and provide direction of blood flow.

Positive and negative pressure:

Alveoli are located on branches of the bronchial tree (bronchioles).

Under high pressure Blood is pumped into the lungs, and at negative pressure it enters the left atrium. Therefore, blood moves through the capillaries of the lungs at the same speed all the time. Thanks to the slow flow of blood in the capillaries, oxygen has time to penetrate the cells and carbon dioxide enters the blood. When oxygen demand increases, for example during intense or severe physical activity, the pressure created by the heart increases and blood flow accelerates. Due to the fact that blood enters the lungs at a lower pressure than into the systemic circulation, the pulmonary circulation is also called the low-pressure system. : Its left half, which does the heavier work, is usually somewhat thicker than the right.

How is blood flow regulated in the pulmonary circulation?

Nerve cells, acting as a kind of sensors, constantly monitor various indicators, for example, acidity (pH), concentration of liquids, oxygen and carbon dioxide, content, etc. All information is processed in the brain. From it, corresponding impulses are sent to the heart and blood vessels. In addition, each artery has its own internal lumen, ensuring a constant blood flow rate. When the heartbeat speeds up, the arteries widen; when the heartbeat slows down, they narrow.

What is the systemic circulation?

Circulatory system: through the arteries, oxygenated blood is carried from the heart and supplied to the organs; Through the veins, blood saturated with carbon dioxide returns to the heart.

Oxygenated blood travels through the blood vessels of the systemic circulation to all human organs. The diameter of the largest artery, the aorta, is 2.5 cm. The diameter of the smallest blood vessels, capillaries, is 0.008 mm. The systemic circulation begins from, from here arterial blood enters the arteries, arterioles and capillaries. Through the walls of the capillaries, the blood releases nutrients and oxygen to tissue fluid. And the waste products of cells enter the blood. From the capillaries, blood flows into small veins, which form more large veins and drain into the superior and inferior vena cava. The veins bring venous blood to the right atrium, where the systemic circulation ends.

100,000 km of blood vessels:

If we take all the arteries and veins of an adult of average height and connect them into one, then its length would be 100,000 km, and its area would be 6000-7000 m2. This large number in the human body is necessary for the normal implementation of metabolic processes.

How does the systemic circulation work?

From the lungs, oxygenated blood flows into the left atrium and then into the left ventricle. When the left ventricle contracts, blood is ejected into the aorta. The aorta divides into two large iliac arteries, which run down and supply blood to the limbs. Blood vessels branch off from the aorta and its arch, supplying blood to the head, chest wall, arms and torso.

Where are the blood vessels located?

Blood vessels of the extremities are visible in the folds, for example, veins can be seen in the elbow bends. The arteries are located somewhat deeper, so they are not visible. Some blood vessels are quite elastic, so when you bend an arm or leg they are not pinched.

Main blood vessels:

The heart is supplied with blood by the coronary vessels belonging to the systemic circulation. The aorta branches into large number arteries, and as a result, blood flow is distributed over several parallel vascular networks, each of which supplies blood to a separate organ. The aorta, rushing down, enters abdominal cavity. Arteries that supply the digestive tract and spleen depart from the aorta. Thus, organs actively involved in metabolism are directly “connected” to the circulatory system. In the area of ​​the lumbar spine, just above the pelvis, the aorta branches: one of its branches supplies blood to the genitals, and the other to the lower extremities. Veins carry oxygen-depleted blood to the heart. From lower limbs venous blood collects in the femoral veins, which unite into iliac vein giving rise to the inferior vena cava. Venous blood flows from the head through the jugular veins, one on each side, and from the upper extremities through the subclavian veins; the latter, merging with the jugular veins, form the innominate veins on each side, which unite to form the superior vena cava.

Portal vein:

The portal vein system is a circulatory system that receives oxygen-depleted blood from the blood vessels of the digestive tract. Before entering the inferior vena cava and the heart, this blood passes through the capillary network

Connections:

In the fingers and toes, intestines and anus there are anastomoses - connections between the afferent and efferent vessels. Rapid heat transfer is possible through such connections.

Air embolism:

If at intravenous administration When taking medications, air enters the bloodstream, which can cause an air embolism and lead to death. Air bubbles clog the capillaries of the lungs.

NOTE:

The opinion that arteries carry only oxygenated blood, and veins carry blood containing carbon dioxide, is not entirely correct. The fact is that in the pulmonary circulation the opposite is true - used blood is carried by arteries, and fresh blood is carried by veins.

And the pulmonary circulation so that the liquid tissue successfully copes with its duties: transports substances necessary for their development to the cells and carries away decay products. Despite the fact that such concepts as “large and small circle” are rather arbitrary, since they are not completely closed systems(the first goes into the second and vice versa), each of them has its own task and purpose in the work of the cardiovascular system.

The human body contains from three to five liters of blood (women have less, men have more), which continuously moves through the vessels. It is a liquid tissue that contains huge amount various substances: hormones, proteins, enzymes, amino acids, blood cells and other components (their number is in the billions). Such a high content of them in plasma is necessary for the development, growth and successful functioning of cells.

Blood transmits nutrients and oxygen to tissues through capillary walls. Then it takes carbon dioxide and decay products from the cells and carries them to the liver, kidneys, and lungs, which neutralize them and remove them outside. If for some reason the blood flow is stopped, the person will die within the first ten minutes: this time is enough for the brain cells deprived of nutrition to die, and the body to be poisoned by toxins.

The substance moves through the vessels, which is vicious circle, consisting of two loops, each of which originates in one of the, ends in the atrium. Each circle has veins and arteries, and the composition of the substance that is in them is one of the differences between the circulatory circles.

The arteries of the large loop contain tissue enriched with oxygen, while the veins contain tissue saturated with carbon dioxide. In the small loop, the opposite picture is observed: blood that needs purification is in the arteries, while fresh blood is in the veins.

The small and large circles perform two different tasks in the functioning of the cardiovascular system. In a large loop, human plasma flows through the vessels, transfers the necessary elements to the cells and takes away waste. In a small circle, the substance is cleared of carbon dioxide and saturated with oxygen. In this case, the plasma flows through the vessels only forward: the valves prevent the reverse movement of the liquid tissue. This system, consisting of two loops, allows different types blood do not mix with each other, which greatly facilitates the task of the lungs and heart.

How is blood purified?

The functioning of the cardiovascular system depends on the work of the heart: contracting rhythmically, it forces blood to move through the vessels. Consists of four hollow chambers located one after another according to the following scheme:

• right atrium;
• right ventricle;
• left atrium;
• left ventricle

Both ventricles are significantly larger than the atria. This is due to the fact that the atria simply collect and send the substance that enters them into the ventricles, and therefore do less work (the right one collects blood with carbon dioxide, the left one – saturated with oxygen).

According to the diagram, right side the heart muscle does not come into contact with the left one. The small circle originates inside the right ventricle. From here, blood with carbon dioxide is sent to the pulmonary trunk, which subsequently diverges in two: one artery goes to the right, the second to left lung. Here the vessels are divided into a huge number of capillaries, which lead to the pulmonary vesicles (alveoli).

Further through thin walls capillaries, gas exchange takes place: red blood cells, which are responsible for transporting gas through the plasma, detach carbon dioxide molecules from themselves and combine with oxygen (blood is transformed into arterial blood). Then the substance leaves the lungs through four veins and ends up in the left atrium, where the pulmonary circulation ends.

It takes the blood four to five seconds to complete the small circle. If the body is at rest, this time is quite enough to ensure it the right amount oxygen. For physical or emotional stress The pressure on the human cardiovascular system increases, which causes blood circulation to accelerate.

Features of blood flow in a large circle

Purified blood enters the left atrium from the lungs, then goes into the cavity of the left ventricle (this is where it originates). This chamber has the thickest walls, due to which, when contracted, it is able to eject blood with a force sufficient for it to reach the farthest parts of the body in a few seconds.

During contraction, the ventricle releases liquid tissue into the aorta (this vessel is the largest in the body). Then the aorta diverges into smaller branches (arteries). Some of them go up to the brain, neck, upper limbs, part - down, and serves the organs that are located below the heart.

In the systemic circulation, the purified substance moves through the arteries. Their distinctive feature are elastic but thick walls. The substance then flows into more small vessels- arterioles, from them - into capillaries, whose walls are so thin that gases and nutrients easily pass through them.

When the exchange ends, the blood, due to the added carbon dioxide and breakdown products, acquires more dark color, is transformed into venous blood and sent through the veins to the heart muscle. The walls of veins are thinner than arterial ones, but are characterized by a large lumen, so they can accommodate significantly more more blood: About 70% of the liquid tissue is in the veins.

If the movement of arterial blood is mainly influenced by the heart, then venous blood moves forward due to the contraction of skeletal muscles, which pushes it forward, as well as breathing. Since most of the plasma that is in the veins moves upward to prevent it from flowing into reverse side, the vessels are equipped with valves that hold it. At the same time, the blood that flows to the heart muscle from the brain moves through veins that do not have valves: this is necessary to avoid blood stagnation.

Approaching the heart muscle, the veins gradually converge with each other. Therefore, only two enter the right atrium large vessels: superior and inferior vena cava. A large circle is completed in this chamber: from here the liquid tissue flows into the cavity of the right ventricle, then gets rid of carbon dioxide.

The average speed of blood flow in a large circle when a person is in calm state, a little less than thirty seconds. At physical exercise, stress, and other factors that excite the body, blood flow can accelerate, since the cells need oxygen and nutrients during this period increases significantly.

Any diseases of the cardiovascular system negatively affect blood circulation, blocking blood flow, destroying vascular walls, which leads to starvation and cell death. Therefore, you need to be very careful about your health. If you experience pain in the heart, tumors in the limbs, arrhythmia and other health problems, be sure to consult a doctor so that he can determine the cause of circulatory problems or malfunctions cardiovascular system and prescribed a treatment regimen.