What is the beginning of a large circle of human circulation. Circles of blood circulation in humans: evolution, structure and work of large and small, additional, features

After all, it is a shame for future doctors not to know the basis of the basics - the circulatory system. Without this information and understanding of how the blood moves through the body, it is impossible to understand the mechanism of development of vascular and heart diseases, to explain the pathological processes that occur in the heart with a particular lesion. Without knowing the circles of blood circulation, it is impossible to work as a doctor. This information will not interfere with a common man in the street, because knowledge about your own body is never superfluous.

1 Big trip

To better imagine how the systemic circulation is arranged, let's fantasize a little? Imagine that all the vessels of the body are rivers, and the heart is a bay, into the bay of which all the river channels fall. Let's go on a journey: our ship begins a long voyage. From the left ventricle we float into the aorta - the main vessel human body... It is here that the systemic circle of blood circulation begins.

Oxygenated blood flows in the aorta, because the aortic blood is distributed throughout the human body. The aorta gives off branches, like a river, tributaries that supply blood to the brain, all organs. Arteries branch to arterioles, which in turn give off capillaries. Bright, arterial blood gives oxygen to cells, nutrients, and takes away metabolic products of cellular life.

The capillaries are organized into venules, which carry dark, cherry-colored blood, because it has given oxygen to the cells. Venules collect in larger veins. Our ship completes its journey along the two largest "rivers" - the upper and lower hollow veins - falls into right atrium... The path is over. A large circle can be schematically represented as follows: the beginning is the left ventricle and aorta, the end is the hollow veins and the right atrium.

2 Small trip

What is the small circle of blood circulation? Let's go on a second trip! Our ship originates from the right ventricle, from which the pulmonary trunk departs. Remember that completing the systemic circulation, we moored in the right atrium? From it venous blood flows into the right ventricle, and then, with heart rate, is pushed into the vessel, the outgoing is the pulmonary trunk. This vessel is directed to the lungs, where it bifurcates into the pulmonary arteries, and then into the capillaries.

Capillaries envelop the bronchi and alveoli of the lungs, give off carbon dioxide and metabolic products and are enriched with life-giving oxygen. Capillaries organize into venules, exiting the lungs, and then into the larger pulmonary veins. We are accustomed to the fact that venous blood flows in the veins. Not in the lungs! These veins are rich in arterial, bright scarlet, O2-rich blood. Our ship sails through the pulmonary veins to the bay, where its journey ends - to the left atrium.

So, the beginning of the small circle is the right ventricle and pulmonary trunk, the end is the pulmonary veins and the left atrium. A more detailed description is as follows: the pulmonary trunk is divided into two pulmonary arteries, which in turn branch into a network of capillaries, like a cobweb enveloping the alveoli, where gas exchange takes place, then the capillaries collect into venules and pulmonary veins that flow into the left upper cardiac chamber of the heart.

3 Historical facts

Having dealt with the departments of blood circulation, it seems that there is nothing complicated in their structure. Everything is simple, logical, understandable. The blood leaves the heart, collects metabolic products and CO2 from the cells of the whole body, saturates them with oxygen, and venous blood returns to the heart again, which, passing through the body's natural "filters" - the lungs, becomes arterial again. But it took many centuries to study and understand the movement of blood flow in the body. Galen mistakenly assumed that the arteries did not contain blood, but air.

This position today can be explained by the fact that at that time the vessels were studied only on corpses, and in the dead body the arteries were drained of blood, and the veins, on the contrary, were full of blood. It was believed that blood is produced in the liver, and in the organs it is consumed. Miguel Servetus in the 16th century suggested that “the spirit of life originates in the left cardiac ventricle, facilitated by the lungs, where air and blood coming from the right cardiac ventricle mix”, thus the scientist recognized and described for the first time a small circle.

But Servetus's discovery was largely ignored. The father of the circulatory system is considered to be Harvey, who already in 1616 wrote in his writings that the blood "circulates through the body." For many years he studied the movement of blood, and in 1628 he published a work that became a classic, and crossed out all ideas about Galen's blood circulation, in this work the circles of blood circulation were outlined.

Harvey did not find only the capillaries discovered later by the scientist Malpighi, who supplemented the knowledge of the "circles of life" with a capillary link between arterioles and venules. The microscope helped open the capillaries to the scientist, which gave a magnification of up to 180 times. Harvey's discovery was met with criticism and challenge by the great minds of those times, many scientists did not agree with Harvey's discovery.

But even today, reading his works, one is surprised how accurately and in detail for that time the scientist described the work of the heart and the movement of blood through the vessels: “The heart, doing work, first makes movement, and then rests in all animals while they are still alive. At the moment of contraction, it squeezes out the blood from itself, the heart is emptied at the moment of contraction. " Circulatory circles were also described in detail, except that Harvey could not observe the capillaries, but did he accurately describe that blood collects from the organs and flows back to the heart?

But how does the transition from arteries to veins take place? This question haunted Harvey. Malpighi discovered this secret of the human body by discovering capillary circulation. It's a shame that Harvey did not live several years before this discovery, because the discovery of capillaries with 100% reliability confirmed the veracity of Harvey's teachings. The great scientist did not have a chance to feel the fullness of the triumph from his discovery, but we remember him and his enormous contribution to the development of anatomy and knowledge about the nature of the human body.

4 From largest to smallest

I would like to dwell on the main elements of the circulatory systems, which are their frame, along which blood moves - the vessels. Arteries are the vessels that carry blood from the heart. The aorta is the most important and important artery of the body, it is the largest - about 25 mm in diameter, it is through it that blood flows to other vessels departing from it and is delivered to organs, tissues, cells.

Exception: the pulmonary arteries do not carry oxygen-rich blood, but CO2-rich blood to the lungs.

Veins are vessels that carry blood to the heart, their walls are easily stretchable, the diameter of the vena cava is about 30 mm, and the diameter of the small ones is 4-5 mm. The blood in them is dark, the color of ripe cherries, saturated with metabolic products.

Exception: The pulmonary veins are the only ones in the body through which arterial blood flows.

Capillaries are the thinnest vessels, consisting of only one layer of cells. The single-layer structure allows gas exchange, the exchange of useful and harmful products between cells and directly capillaries.

The diameter of these vessels is only 0.006 mm on average, and the length is not more than 1 mm. How small they are! However, if we sum up the length of all the capillaries together, we get a very significant figure - 100 thousand km ... Our body is shrouded inside them like a spider web. And it is not surprising - after all, every cell of the body needs oxygen and nutrients, and capillaries can provide the supply of these substances. All vessels, and the largest and smallest capillaries, form a closed system, or rather two systems - the aforementioned circles of blood circulation.

5 Important features

What are the circulatory circles for? Their role cannot be overestimated. Just as life on Earth is impossible without water resources, so human life is impossible without the circulatory system. The main role of the large circle is:

1. Providing oxygen to every cell of the human body;
2. The release of nutrients from the digestive system into the blood;
3. Filtration from blood into excretory organs of waste products.

The role of the small circle is no less important than the ones described above: the removal of CO2 from the body and metabolic products.

Knowledge about the structure of one's own body is never superfluous, knowledge of how the blood circulation departments function leads to a better understanding of the body's work, and also forms an idea of \u200b\u200bthe unity and integrity of organs and systems, the connecting link of which is undoubtedly the bloodstream, organized in circles of blood circulation.

CIRCULATIONS OF CIRCULATION

Arterial and venous vessels are not isolated and independent, but are interconnected as a single system of blood vessels. The circulatory system forms two circles of blood circulation: LARGE and SMALL.

The movement of blood through the vessels is also possible due to the difference in pressure at the beginning (artery) and end (vein) of each circle of blood circulation, which creates the work of the heart. The pressure in the arteries is higher than in the veins. With contractions (systole), the ventricle ejects an average of 70-80 ml of blood each. Blood pressure rises and their walls stretch. During diastole (relaxation), the walls return to their original position, pushing the blood further, ensuring its uniform flow through the vessels.

Speaking about the circles of blood circulation, it is necessary to answer the questions: (WHERE? And WHAT?). For example: WHERE does it end ?, begins? - (in which ventricle or atrium).

WHAT does it end with?, Begins? - (with what vessels) ..

A SMALL CIRCULAR CIRCUIT carries out the delivery of blood to the lungs where gas exchange takes place.

It begins in the right ventricle of the heart with the pulmonary trunk, into which venous blood enters during ventricular systole. The pulmonary trunk is divided into right and left pulmonary arteries. Each artery enters the lung through its gate and, accompanying the structure of the "bronchial tree" reaches the structural - functional lung units - (acnus) - dividing up to the blood capillaries. Gas exchange occurs between the blood and the contents of the alveoli. Venous vessels form two pulmonary vessels in each lung

veins that carry arterial blood to the heart. The pulmonary circulation in the left atrium ends with four pulmonary veins.

right ventricle heart --- pulmonary trunk --- pulmonary arteries ---

division of intrapulmonary arteries --- arterioles --- blood capillaries ---

venules --- confluence of intrapulmonary veins --- pulmonary veins --- left atrium.

by what vessel and in which chamber of the heart the pulmonary circulation begins:

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,towith these vessels, the pulmonary circulation begins and endsi.

starts from the right ventricle with the pulmonary trunk

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vessels that form a small circle of blood circulation:

truncus pulmonalis

by what vessels and in which chamber of the heart the pulmonary circulation ends:

Atrium sinistrum

A LARGE CIRCLE of blood circulation delivers blood to all organs of the body.

From the left ventricle of the heart, arterial blood is sent to the aorta during systole. Arteries of elastic and muscular types depart from the aorta, intraorgan arteries, which divide up to arterioles and blood capillaries. Venous blood through the venule system, then intraorgan veins, extraorgan veins form the superior, inferior vena cava. They go to the heart and flow into the right atrium.

consistently it looks like this:

left ventricle of the heart --- aorta --- arteries (elastic and muscular) ---

intraorgan arteries --- arterioles --- blood capillaries --- venules ---

intraorgan veins --- veins --- superior and inferior vena cava ---

in which chamber of the heart begins systemic circulation and how

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v. cava superior

v. cava inferior

with which vessels and in which chamber of the heart the systemic circulation ends:

v. cava inferior

Small circle of blood circulation

Circles of blood circulation - this concept is conditional, since only in fish the circle of blood circulation is completely closed. In all other animals, the end of a large circle of blood circulation is the beginning of a small one and vice versa, which makes it impossible to talk about their complete isolation. In fact, both circles of blood circulation make up a single whole bloodstream, in two parts of which (right and left heart) kinetic energy is communicated to the blood.

Circle of blood circulation is a vascular pathway that has its beginning and end in the heart.

Large (systemic) circle of blood 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, blood flow is distributed over several parallel regional vascular networks, each of which supplies blood to a separate organ. Further division of arteries occurs into arterioles and capillaries. The total area of \u200b\u200ball capillaries in the human body is approximately 1000 m².

After the passage of the organ, the process of fusion of capillaries into venules begins, which in turn are collected in veins. Two hollow veins approach the heart: the upper and lower, which, when merged, form part of the right atrium of the heart, which is the end of the systemic circulation. The blood circulation in the systemic circulation occurs in 24 seconds.

Structure Exceptions

• Spleen and intestinal circulation... The general structure does not include blood circulation in the intestines and spleen, since after the formation of the splenic and intestinal veins, they merge to form the portal vein. The portal vein re-splits into a capillary network in the liver, and only then the blood flows to the heart.
• Renal circulation... In the kidney, there are also two capillary networks - the arteries disintegrate into the Shumlyansky-Bowman capsules bringing arterioles, each of which disintegrates into capillaries and collects into the outflowing arteriole. The efferent arteriole reaches the convoluted tubule of the nephron and again disintegrates into the capillary network.

Functions

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

Small (pulmonary) circle of blood circulation

Structure

It begins in the right ventricle, which pumps blood into the pulmonary trunk. The pulmonary trunk is divided into a right and left pulmonary artery. Arteries are dichotomously divided into lobar, segmental, and subsegmental arteries. Subsegmental arteries are divided into arterioles, which disintegrate into capillaries. Outflow blood goes through the veins, going in the opposite order, which in the amount of 4 pieces flow into the left atrium. The blood circulation in the pulmonary circulation occurs in 4 seconds.

The small circle of blood circulation was first described by Miguel Servetus in the 16th century in the book "The Restoration of Christianity".

Functions

• Heat dissipation

Small circle function is not nutrition of the lung tissue.

"Additional" circles of blood circulation

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

• placental,
• cordial.

Placental circulation

It exists in the fetus in the uterus.

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

Mixed blood flows through the inferior vena cava, the saturation of which with oxygen 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 released 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 arterial (Botall's) duct into the aorta. The arterial duct flows into the aorta after the arteries of the head leave it and upper limbs, which provides them with more enriched blood. A very small part of the blood enters the lungs, which then enters the left atrium.

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

Cardiac circulation or coronary circulatory system

Structurally, it is part of the large circle of blood circulation, but due to the importance of the organ and its blood supply, one 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 branch off from them, which enter the muscle wall and branch to capillaries. Outflow of venous blood occurs in 3 veins: large, medium, small, vein of the heart. Merging they form the coronary sinus and it opens into the right atrium.

Wikimedia Foundation. 2010.

Human life and health largely depend on the normal functioning of his heart. It pumps blood through the vessels of the body, maintaining the vitality of all organs and tissues. Evolutionarily, the structure of the human heart - the diagram, the circulation circles, the automatism of the cycles of contractions and relaxation of the muscle cells of the walls, the work of the valves - everything is subordinated to the fulfillment of the main task of uniform and sufficient blood circulation.

The structure of the human heart - anatomy

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

Atria

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

• superior vena cava,
• heart veins - through the coronary sinus and puncture holes of small veins,
• inferior vena cava.

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

The atrial septum (MPP) separates the atria, which normally does not have any holes in adults. They communicate with the cavities of the corresponding ventricles through holes equipped with valves. On the right - tricuspid tricuspid, on the left - bicuspid mitral.

Ventricles

The right (RV) is cone-shaped, the base facing up. Wall thickness up to 5 mm. The inner surface in the upper part is smoother; closer to the apex of the cone it has a large number of muscle cords, trabeculae. In the middle part of the ventricle there are three separate papillary (papillary) muscles, which, by means of tendon filaments-chords, keep the tricuspid valve leaflets from bending them into the atrial cavity. The chords also extend directly from the muscle layer of the wall. At the base of the ventricle there are two holes with valves:

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

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

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

Muscle cords in the apex of the heart and papillary muscles that support the leaflets of the mitral valve are more powerful here than similar structures in the pancreas.

Shell of the heart

To protect and support the movement of the heart in the chest cavity, it is surrounded by a heart shirt - the pericardium. There are three layers directly in the heart wall - epicardium, endocardium, myocardium.

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

All heart valves are formed from endocardial folds.

Human heart structure and function

The pumping of blood by the heart into the vascular bed is ensured by the peculiarities of its structure:

• the heart muscle is capable of automatic contraction,
• the conductive system guarantees a constant cycle of excitation and relaxation.

How is the heart cycle

It consists of three successive phases: total diastole (relaxation), atrial systole (contraction), ventricular systole.

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

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

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

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

• Sinus node. Normally generates an initial impulse. Located in the region of the mouth of both vena cava. From it, excitement goes to the atria and is transmitted to the atrioventricular (AV) node.
• The atrioventricular node distributes impulse to the ventricles.
• The bundle of His is a conducting "bridge" located in the interventricular septum, where it is divided into the right and left legs, which transmit excitation to the ventricles.
• Purkinje fibers are the final section of the conducting system. They are located at the endocardium and come in direct contact with the myocardium, causing it to contract.

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

The task of the circulatory system, the main center of which is the heart, is the delivery of oxygen, nutrient and bioactive components to the tissues of the body and the elimination of metabolic products. For this, a special mechanism is provided in the system - the blood moves in circles of blood circulation - small and large.

Small circle

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

Big circle

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

Nature has worked hard to create such a perfect mechanism, giving it reserves of strength for many years. Therefore, you should pay close attention to it, so as not to create problems with blood circulation and your own health.

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

The structure of the circulatory system

The circulatory system includes:

• veins;
• arteries;
• capillaries.

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

Heart structure

The heart is a hollow cone consisting of muscle tissue. In all people, the organ is slightly different in shape, sometimes in structure.... It has 4 sections - the right ventricle (RV), left ventricle (LV), right atrium (RA) and left atrium (LA), which are communicated with each other by holes.

The holes are closed by valves. Between the left sections there is a mitral valve, between the right ones there is a tricuspid valve.

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

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

Artery function

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

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

Capillary functions

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

Function of veins

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

The main task of veins is to transport blood to the heart, in which there is no longer oxygen and decay products are present. Only the pulmonary veins carry blood and oxygen to the heart. There is a movement from the bottom up. If the normal operation of the valves is disrupted, the blood stagnates in the vessels, stretching them and deforming the walls.

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

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

The movement of blood through the vessels

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

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

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

Small circle of blood circulation

The small circle diagram is shown below. Where, RV - right ventricle, LS - pulmonary trunk, PLA - right pulmonary artery, LLA - left pulmonary artery, LH - pulmonary veins, LA - left atrium.

Through the pulmonary circulation, the fluid passes to the pulmonary capillaries, where it receives oxygen bubbles. The oxygen-rich fluid is called arterial fluid. From the LP, it goes to the LV, where bodily circulation begins.

A large circle of blood circulation

The scheme of the bodily circle of blood circulation, where: 1. Lzh - left ventricle.

2. Ao - aorta.

3. Art - arteries of the trunk and limbs.

4. B - veins.

5. PV - hollow veins (right and left).

6. PP - right atrium.

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

Personal blood circulation of the heart

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

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

Placental circulation

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

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

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

Circulatory pathologies

Blood circulation is carried out in a closed system. Changes and abnormalities in the capillaries can negatively affect the work of the heart. Gradually, the problem will worsen and develop into a serious illness. Factors affecting the movement of blood:

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

Also, a person's lifestyle affects the movement of blood. Athletes have a more stable circulation system, so they are more enduring and even a fast run will not immediately accelerate the heart rate.

The average person can undergo changes in blood circulation even from a smoked cigarette. In case of trauma and rupture of blood vessels, the circulatory system is able to create new anastomoses to provide blood to the "lost" areas.

Regulation of blood circulation

Any process in the body is controlled. There is also a regulation of blood circulation. The activity of the heart is activated by two pairs of nerves - sympathetic and vagus. The former excite the heart, the latter inhibit, as if controlling each other. Severe irritation of the vagus nerve can stop the heart.

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

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

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

The cardiovascular system

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

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

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