After all, I am ashamed to future doctors not to know the basis of the foundations - circulation circles. Do not own this information and understanding how blood is moving in the body, it is impossible to understand the mechanism for the development of diseases of the vascular diseases and hearts, explain the pathological processes that flow into the heart at one or another defeat. Not knowing circles of blood circulation is impossible to work by a doctor. This information does not interfere with a simple man in half, because knowledge of its own organism is never superfluous.

1 Large trip

To better imagine how a big circle of blood circulation is arranged, will dream a little? Imagine that all organism vessels - rivers, and the heart - bay, in which all river ducts fall into the bay. We go on a trip: our ship begins great swimming. From the left ventricle we float in Aorta - the main vessel human organism. It is here that the big circle of blood circulation originates.

In the aorta flows blood saturated with oxygen, because the aortic blood is distributed throughout the human body. Aorta gives branches, as if the river is the tributary, which blood supply to the brain, all organs. The arteries are branched to the arteriole, and they in turn give the capillaries. Bright, arterial blood gives cells oxygen, nutrients, and takes the products of cell life exchange products.

Capillaries are organized in Venules who carry the blood of the dark, cherry blossom, because it gave oxygen cells. Venules are collected in larger veins. Our ship completes his journey through the two largest "rivers" - upper and lower hollow veins - enters the right atrium. The path is over. It is possible to schematically imagine a large circle: the beginning is the left ventricle and aorta, the end is hollow veins and the right atrium.

2 Small journey

What is a small circle of blood circulation? We go to the second journey! Our ship originates from the right ventricle, from which the pulmonary trunk leaves. Remember that by completing a large circle of blood circulation, we moored in the right of atrium? Out of him deoxygenated blood It follows in the right ventricle, and then, with a heart abbreviation, pushed into a vessel, from it from it - the pulmonary trunk. This vessel is sent to the light, where it is splitted on the pulmonary artery, and then on the capillaries.

Capillaries envelop bronons and lung alveoli, give carbon dioxide and exchanging products and are enriched with grooming oxygen. The capillaries are organized in Venuly, leaving the lungs, and then to larger pulmonary veins. We are accustomed to the fact that venous blood flows in veins. Only not in the pulmonary! These veins are rich in arterial, bright-scarlet, enriched o2, blood. According to the lung veins, our ship sails into the bay, where his journey ends - in the left atrium.

So, the beginning of a small circle is the right ventricle and the pulmonary trunk, the end is the pulmonary veins and the left atrium. More detailed description Next: The pulmonary trunk is divided into two pulmonary artery, which in turn branches the capillary network, as if the cobweb envelope of the alveoli, where gas exchange occurs, then the capillaries are collected in Vienules and pulmonary veins flowing into the left upper heart heart chamber.

3 Historical facts

Having understood with the departments of blood circulation, it seems that there is nothing complicated in their structure. Everything is simple, logical, understandable. Blood comes out of the heart, collects the products of exchange and CO2 from the cells of the whole body, saturates with oxygen, returns again to the heart already venous blood, which passing through the natural "filters" of the body - light, becomes again arterial. But to learn and understand the flow of blood flow in the body, it took a lot of centuries. Galen mistakenly assumed that the arteries do not contain blood, but the air.

This position today can be explained by the fact that in those days, the vessels were studied only on corpses, and in the dead body artery bleed, and veins, on the contrary, are full. It was believed that blood is made in the liver, and in the organs it is spent. Miguel Servet in the XVI century expressed the assumption that "the spirit of life originates in the left heart ventricle, promote the lungs, where the mixing of air and blood coming from the right heart ventricle," so the scientist recognized and described a small circle for the first time.

But on the opening of the servo, they practically did not pay any attention. The father of the circulatory system is considered to be Garvet, who already in 1616 wrote in his writings that the blood "circling in the body". For many years, he studied blood movement, and in 1628 he published work that became a classic, and crossed all the ideas about the blood circulation of Galen, in this work there were settled circles of blood circulation.

Not discovered Garvai only the capillaries, open later, a Malpigi scientist who supplemented knowledge of the "circles of life" with a binding capillary link between the arteriols and venules. He helped open the capillaries to a scientist microscope, which gave an increase of up to 180 times. The opening of Gareva was met with criticism and challenging the great minds of those times, many scientists did not agree with the opening of Garwa.

But even today, reading his works, wonder how exactly and in detail for that time the scientist described the work of the heart and the flow of blood along the vessels: "The heart, doing work, first produces a move, and then rests in all animals while those are still alive. At the moment of abbreviation, it squeezes blood, the heart is emptied at the moment of abbreviation. " The circles of blood circulation were also described in detail, as the exception that Gaveva could not observe the capillaries, but did he exactly describe that blood is going out of the organs and flows back to the heart?

But how does the transition from the arteries to the veins? This question did not give Garvey rest. Malpigi revealed this secret of the human body, discovering capillary blood circulation. It's a shame that Gaverway did not live a few years before the discovery, because the discovery of capillaries with 100% reliability confirmed the truthfulness of Groom's teachings. The great scientist did not happen to feel all the completeness of the celebration from his discovery, but we remember him and his huge contribution to the development of anatomy and knowledge about the nature of the human body.

4 from more to a smaller

I would like to dwell on the main elements of circles of circulation, which are their framework, for which blood is moving - vessels. Artery - vessels carrying blood from the heart. Aorta is the most important and important artery of the body, it is the largest - about 25 mm in diameter, it is its blood that goes to another vessels departing from it and is delivered to organs, tissues, cells.

Exception: pulmonary arteries carry not rich blood blood, and saturated CO2 to the easy.

Viennes are vessels carrying blood to heart, their walls are easily stretchable, the diameter of hollow veins is about 30 mm, and small - 4-5 mm. The blood is dark, the colors of ripe cherries saturated with the exchange products.

Exception: pulmonary veins are the only blood in the body by which arterial blood flows.

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

The diameter of the data of the vessels is only 0.006 mm on average, and the length is not more than 1 mm. That's what they are small! However, if you summarize the length of all capillaries together, we will get a very essential figure - 100 thousand km ... our body inside is shrouded with them like a cobweb. And no wonder - because each cell of the body needs oxygen and nutrients, and capillaries can ensure the flow 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 functions

Why do blood circulation circles need? Their role cannot be overestimated. How life on earth is impossible without water resourcesSo and human life is impossible without blood circulation system. Main role big Circle lies:

1. Ensuring oxygen of each cell of the human body;
2. Admission of nutrients from the digestion system in blood;
3. Filtering from the blood to the excretory organs of life products.

The role of a small circle is not less important than the above described: the excretion of C02 from the body and the exchange products.

Knowledge of the structure of your own body is never superfluous, knowledge of how the blood circulation departments function will lead to a better understanding of the body's work, and also forms an idea of \u200b\u200bthe unity and integrity of organs and systems that the link is undoubtedly the bloodstream organized into circles of blood circulation.

1. Install the correspondence between the blood vessels of the person and the direction of blood flow in them: 1-heart, 2-to heart
A) veins of a small circle of blood circulation
B) veins of a large circulation circle
C) arteries of a small circle of blood circulation
D) artery of a large circle of blood circulation

Answer

2. Human blood from the left ventricle hearts
A) when it is reduced in the aorta
B) when it is reduced, it falls into the left atrium
B) supplies body cells with oxygen
D) gets into the pulmonary artery
E) under great pressure enters the big cool blood circulation
E) under low pressure enters a small circle of blood circulation

Answer

3. Install in which sequence in the human body the blood moves along a large circulation of blood circulation
A) Vienna Big Circle
B) the artery of the head, arms and torso
C) Aorta
D) Capillaries of the Big Circle
D) left ventricle
E) right atria

Answer

4. Install, in what sequence in the human body the blood passes a small circle of blood circulation
A) left atrium
B) pulmonary capillaries
B) pulmonary veins
D) pulmonary arteries
E) right ventricle

Answer

5. According to the arteries of the small circle of blood circulation, the blood flows blood flow
A) from the heart
B) to heart

D) oxygen
E) faster than in the light capillaries
E) slower than in light capillaries

Answer

6. Vienna - these are blood vessels for which blood flows
A) from the heart
B) to heart
B) under greater pressure than in the arteries
D) under less pressure than in the arteries
E) faster than in capillaries
E) slower than in capillaries

Answer

7. According to the arteries of a large circle of blood circulation in humans, blood flows
A) from the heart
B) to heart
B) carbonic gas saturated
D) oxygen
E) faster than in other blood vessels
E) slower than in other blood vessels

Answer

8. Install the sequence of blood flow by a large circulation circle
A) left ventricle
B) capillaries
B) right atria
D) artery
E) Vienna
E) Aorta

Answer

9. Install in which sequence it is necessary to position the blood vessels in order to reduce blood pressure in them.
A) Vienna
B) Aorta
C) artery
D) Capillaries

Circulation - This is the movement of blood along the vascular system, providing gas exchange between the body and the external environment, the metabolism between organs and tissues and humoral regulation Different features of the body.

Circulatory system Includes both the aorta, arteries, arterioles, capillaries, venules, veins and. Blood moves along vessels due to the reduction of the heart muscle.

The blood circulation is performed on a closed system consisting of small and large circles:

• A large circle of blood circulation provides all organs and tissues with blood with nutrients contained in it.
• Small, or pulmonary, circulation circle is designed to enrich blood oxygen.

Circular circle circles were first described by the English scientist William Garvet in 1628 in labor "Anatomical research on the movement of the heart and vessels".

Small circle circulation Begins from the right ventricle, with a reduction in which the venous blood enters the pulmonary barrel and, passing through the lungs, gives carbon dioxide and is saturated with oxygen. Oxygen-enriched blood from the lungs by the pulmonary veins enters the left atrium, where the small circle ends.

Big circle circulation Begins from the left ventricle, with a reduction in which the blood enriched with oxygen is inserted into the aorta, arteries, arterioles and capillaries of all organs and tissues, and from there on venue and veins flow into the right atrium, where the big circle ends.

The largest vessel of a large circle of blood circulation is aorta that comes out of the left ventricle of the heart. Aorta forms an arc, from which arteries that carry blood to the head (carotid artery) and to the upper limbs (vertebral artery) are bred. Aorta passes down along the spine, where branches carrying blood to the abdominal organs, to the muscles of the body and lower limbs.

Arterial blood rich in oxygen is held throughout the body, delivering nutrients and oxygen to the tissues and oxygen necessary for their activities, and in the capillary system turns into venous blood. Venous blood saturated with carbon dioxide and cellular exchange products is returned to the heart and comes to the lungs for gas exchange. The largest veins of a large circle of blood circulation are the upper and lower hollow veins flowing into the right atrium.

Fig. Scheme of small and large circles of blood circulation

Attention should be paid to how the blood circulation systems of the liver and kidneys are included in a large circulation circle. All blood from the capillaries and veins of the stomach, the intestines, the pancreas and the spleen enters the portal vein and passes through the liver. In the liver, the portable vein branches into small veins and capillaries, which are then again connected to the common trunk of the hepatic vein flowing into the lower hollow vein. All the blood of the abdominal organs before entering a large circle of blood circulation flows through two capillary networks: the capillaries of these organs and the liver capillaries. The gorgeous liver system plays a big role. It provides neutralization poisonous substanceswhich are formed in a thick intestine when cleaving the unansitated in thin intestines Amino acids and absorbed the dysfoline mucosa into the blood. Liver, like all other organs, gets and blood arterial Through the hepatic artery, departing from the abdominal artery.

There are two capillary networks in the kidneys: there is a capillary network in every Malpigiyev Glomechka, then these capillaries are connected to the arterial vessel, which again disintegrates the capillaries that have soaked the convolves.

Fig. Circulatory scheme

A feature of blood circulation in the liver and kidneys is the slowdown of the blood flow due to the function of these organs.

Table 1. Difference of blood current in large and small circles of blood circulation

Time of blood circuit - The time of a single passage of blood particle over the large and small circles of the vascular system. Read more next section of the article.

Patterns of blood flow by vessels

Basic principles of hemodynamics

Hemodynamics - This is a section of physiology that studies patterns and mechanisms of blood flow through the vessels of the human body. With its study, terminology is used and the laws of hydrodynamics are taken into account - the science of the movement of liquids.

The speed with which blood moves but vessels depends on two factors:

• from the difference in blood pressure at the beginning and end of the vessel;
• from resistance, which meets fluid on its path.

Pressure difference contributes to the movement of the fluid: what it is more, the more intense is the movement. Resistance in a vascular system that reduces blood flow rate depends on a number of factors:

• the length of the vessel and its radius (the larger length and less radius, the more resistance);
• blood viscosity (it is 5 times more water viscosity);
• friction of blood particles about the wall of the vessels and among themselves.

Hemodynamic indicators

The rate of blood flow in vessels is carried out according to the laws of hemodynamics, common with the laws of hydrodynamics. The rate of blood flow is characterized by three indicators: the volumetric rate of blood flow, the linear speed of blood flow and the time of blood circuit.

Surrounding speed of blood flow - The amount of blood flowing through the cross section of all vessels of this caliber per unit of time.

Linear blood flow rate - The speed of movement of a separate blood particle along the vessel per unit of time. In the center of the vessel, the linear speed is maximum, and near the vessel wall is minimal due to increased friction.

Time of blood circuit - The time during which the blood passes through the large and small circles of blood circulation. It is the norm of 17-25 p. About 1/5 is spent on the passage through a small circle, and on the passage through large - 4/5 of this time

Driving force of blood flow but the system of vessels of each of the circles of blood circulation is the difference in blood pressure ( ΔР.) In the initial section of the arterial channel (aorta for a large circle) and the final section of the venous bed (hollow veins and right atrium). Blood pressure difference ( ΔР.) At the beginning of the vessel ( P1) and at the end of it ( P2.) It is the driving force of blood stream through any vessel of the circulatory system. The strength of blood pressure gradient is spent on overcoming resistance to blood flow ( R.) In the system of vessels and in each separate vessel. The higher the blood pressure gradient in the circle of blood circulation or in a separate vessel, the greater the bulk blood flow.

The most important indicator of blood flow by vessels is blood flow rate, or volumetric blood flow (Q.), under which they understand the volume of blood flowing through the total cross section of the vascular bed or section of a separate vessel per unit of time. The volumetric rate of blood flow is expressed in liters per minute (l / min) or milliliters per minute (ml / min). To estimate the bulk blood flow through the aorta or the total cross section of any other level of blood circulation vessels use the concept volumetric system blood flow. Since per unit of time (minute) through the aorta and other vessels of a large circle of blood circulation proceeds the entire amount of blood thrown by left ventricle during this time, synonymous with the concept of systemic volumetric blood flow is the concept (IOC). MOK adult man alone is 4-5 l / min.

There are also bulk blood flow in the organ. In this case, they mean the total blood flow, flowing per unit of time through all the brings arterial or submitting venous vessels of the organ.

Thus, bulk blood flow Q \u003d (P1 - P2) / R.

In this formula, the essence of the basic law of hemodynamics, claiming that the amount of blood flowing through the total cross section of the vascular system or a separate vessel per unit of time is directly proportional to the blood pressure difference at the beginning and at the end of the vascular system (or vessel) and inversely proportional to the current resistance blood.

The total (systemic) minute blood flow in a large circle is calculated taking into account the magnitudes of the average hydrodynamic blood pressure at the beginning of the aorta P1, and at the mouth of hollow veins P2. Since the blood pressure is close to 0 then in the expression for calculating Q. or IOC is substituted Requal to the average hydrodynamic arterial blood pressure at the beginning of the aorta: Q. (IOC) = P./ R..

One of the consequences of the basic law of hemodynamics is the driving force of the blood current in the vascular system - due to blood pressure generated by the work of the heart. Confirmation of the decisive value of blood pressure for blood flow is the pulsating nature of the blood current throughout the cardiac cycle. During the systole of the heart, when blood pressure reaches the maximum level, the bloodstream increases, and during diastole, when blood pressure is minimal, the blood flow is weakened.

As the blood progresses along the vessels from the aorta to the veins, the blood pressure decreases and the rate of its decrease is proportional to the resistance of blood flow in the vessels. The pressure in the arteriols and capillaries is particularly quickly reduced, as they have a large blood flow resistance, having a small radius, greater total length and numerous branches that create an additional obstacle to blood flow.

Resistance to blood flow, created in the entire vascular bed of a large circle of blood circulation, called common peripheral resistance (OPS). Consequently, in the formula for calculating the volume blood flow symbol R. It is possible to replace it with analogue - OPS:

Q \u003d P / OPS.

From this expression, a number of important consequences are derived to understand the processes of blood circulation in the body, assess the results of measuring blood pressure and its deviations. The factors affecting the resistance of the vessel for the fluid current are described by the Poiseil law, according to which

where R. - resistance; L. - length of the vessel; η - blood viscosity; Π - number 3.14; r. - Vessel radius.

From the above expression implies that since the numbers 8 and Π are constant L. In an adult, a little changes, the magnitude of the peripheral resistance of blood flow is determined by the changing values \u200b\u200bof the radius of the vessels r. and blood viscosity η ).

It has already been mentioned that the radius of the muscular type vessels can quickly change and have a significant effect on the amount of resistance to blood flow (hence their name is resistive vessels) and the value of blood flow through organs and tissues. Since resistance depends on the size of the radius in the 4th degree, even small fluctuations in the radius of the vessels strongly affect the values \u200b\u200bof blood flow and blood flow. So, for example, if the radius of the vessel decreases from 2 to 1 mm, then it will increase by 16 times and with a constant pressure gradient of blood flow in this vessel will also decrease 16 times. Reverse resistance changes will be observed by increasing the radius of the vessel 2 times. With a constant average hemodynamic pressure of blood flow in one body, it may increase in the other, depending on the reduction or relaxation of the smooth muscles of bringing arterial vessels and veins of this body.

Blood viscosity depends on the blood content of erythrocytes (hematocrit), protein, blood plasma lipoproteins, as well as from the aggregate state of the blood. Under normal conditions, blood viscosity does not change so quickly as the lumen of the vessels. After blood loss, with erythrogenation, hypoproteinemia blood viscosity decreases. With significant erythrocytosis, leukemia, increased aggregation of red blood cells and hypercoagulation, blood viscosity is capable of significantly increasing, which entails the increase in resistance to blood flow, an increase in the load on myocardium and may be accompanied by a bleeding violation in the microcirculatory vessels.

In the established blood circulation mode, the blood volume, exiled to the left ventricle and flowing through the cross section of the aorta is equal to the volume of blood flowing through the total cross-section of the vessels of any other section of a large circle of blood circulation. This blood volume returns to the right atrium and enters the right ventricle. From it, blood is expelled in a small circle of blood circulation and then through the pulmonary veins returns to left heart. Since the IOC of the left and right ventricles is the same, and large and small circulation circles are connected in series, then the volumetric rate of blood flow in the vascular system remains the same.

However, during the change of blood flow conditions, for example, when moving from horizontal in vertical positionWhen the strength of gravity causes a temporary accumulation of blood in the veins of the bottom of the body and legs, for a short time, the IOC left and right ventricles can become different. Soon the intracardiac and extracardial mechanisms of the regulation of the heart level the volume of blood flow through a small and large circulation circle.

With a sharp decrease in the venous blood return to the heart, which causes the decrease in the shock volume, may decrease arterial pressure blood. With a pronounced reduction, blood flow to the brain can decrease. This explains the feeling of dizziness, which may occur with a sharp transition of a person from horizontal to a vertical position.

Volume and linear speed of blood currents in vessels

The total blood volume in the vascular system is an important homeostatic indicator. The average value of it is 6-7% for women, for men 7-8% of the body weight and is in the range of 4-6 liters; 80-85% of blood from this volume - in the vessels of a large circle of blood circulation, about 10% - in the vessels of a small circle of blood circulation and about 7% - in the cavities of the heart.

The most blood is contained in the veins (about 75%) - this indicates their role in the deposition of blood both in large and in a small circulation of blood circulation.

Blood flow in vessels is characterized not only by volume, but also linear speed of blood flow. Under it understand the distance to which the blood particle moves per unit of time.

There is a relationship between the bulk and linear blood flow rate described by the following expression:

V \u003d Q / PR 2

where V. - linear speed of blood flow, mm / s, cm / s; Q. - The volumetric speed of blood flow; P - a number equal to 3.14; r. - Vessel radius. Value PR 2. Reflects the cross-sectional area of \u200b\u200bthe vessel.

Fig. 1. Changes in blood pressure, linear blood flow velocity and cross-sectional area in various sections of the vascular system

Fig. 2. Hydrodynamic characteristics of the vascular bed

From the expression of the dependence of the magnitude of the linear velocity from the volumetric system in the vessels of the circulatory system, it can be seen that the linear speed of blood flow (Fig. 1.) is proportional to the volumetric blood flow through the vessel (s) and inversely proportional to the cross-sectional area of \u200b\u200bthis vessel (s). For example, in aorta having the smallest cross-sectional area in a large circulation circle (3-4 cm 2), the linear speed of blood The greatest and is at rest about 20-30 cm / s. For exercise It may increase 4-5 times.

In the direction of the capillars, the total transverse lumen of the vessels increases and, therefore, the linear rate of blood flow in the arteries and arteriols is reduced. In capillary vessels, the total cross-sectional area of \u200b\u200bwhich is greater than in any other separation of the large circle vessels (500-600 times the cross section of the aorta), the linear blood flow rate becomes minimal (less than 1 mm / s). Slow blood flow in capillaries creates best conditions For leakage exchange processes Between blood and tissues. In veins, the linear rate of blood flow increases due to the decrease in the area of \u200b\u200btheir total cross-section as it approaches the heart. At the mouth of the hollow veins, it is 10-20 cm / s, and with loads increase to 50 cm / s.

The linear speed of the plasma movement and depends not only on the type of vessel, but also from their location in the blood flow. The laminar type of blood flow is distinguished, in which the blood notch can be divided into layers. In this case, the linear speed of the flow of blood layers (mainly plasma), close or adjacent to the vessel wall, is the smallest, and the layers in the center of the flow is the largest. Between the endothelium of blood vessels and the closed blood layers, friction forces arise, creating shear stresses on the endothelium. These stresses play a role in the development of the endothelium of vascular factors governing the clearance of vessels and the rate of blood flow.

Erythrocytes in vessels (with the exception of capillaries) are located mainly in the central part of the blood flow and move in it with a relatively high speed. Leukocytes, on the contrary, are located preferably in the interface layers of blood flow and perform rolled movements at low speed. This allows them to bind to adhesion receptors in places of mechanical or inflammatory damage to the endothelium, stick to the vessel wall and migrate to the tissue to perform protective functions.

With a significant increase in the linear velocity of blood flow in the narrowed part of the vessels, in places of departing from the vessel of its branches, the laminar nature of blood flow can be replaced by turbulent. At the same time, in the blood stream, the layering of the movement of its particles may be disturbed, large friction and shear stresses may occur between the vessel wall and blood than when laminar motion. The vortex blood flows are developing, the likelihood of damage to the endothelium and sediments of cholesterol and other substances in the interface of the vessel wall is developed. This is able to lead to a mechanical impairment of the structure of the vascular wall and initiating the development of trombic thromboms.

Time of complete blood circulation, i.e. The return of the blood particle into the left ventricle after its release and passing through the large and small circles circulation, is in the radiation of 20-25 s, or approximately after 27 stitties of the heart of the heart. Approximately a quarter of this time is spent on the movement of blood along the vessels of a small circle and three quarters - according to the vessels of a large circle of blood circulation.

A small circle of blood circulation enriches blood in light oxygen. It begins from the right ventricle (from where the blood feeds the light barrel, which divides two branches, feeding blood to the left and right light) and ends with the left atrium. The small circle of blood circulation serves oxygen into the blood feeding the lungs. It begins in the right ventricle of the heart, from where the venous blood is supplied to the general easy artery. (barrel), dividing into two branches leading to the left and right light. The end point of the small circle of blood circulation is the left atrium.

Anatomical features of a small circle of blood circulation

Blood in the body flows along a closed circulatory system connecting the heart and light, which consists of small and large circles of blood circulation. In the second of them, its path runs away from the heart to the lungs and then in the opposite direction. Blood from the veins of the right heart ventricle, entering the artery of the lungs and its branching - capillaries, gets rid of the excess carbon dioxide, and is also saturated with a new oxygen reserve (breathing), after which the lungs are flowing into the left atrium.

Alveola's light capillaries are so-called "Light bubbles". A blood vessel is attached to each tiny alveolum. Blood from atmospheric air separates only the finest porous wall of the capillary and light, so that oxygen and other gases can freely penetrate through it, falling into the vessels and alveoli. This is gas exchange. Its principle is the transition from greater concentration to the smaller. For example, if oxygen is lacking in venous blood, its admission to capillaries is carried out from atmospheric air. As for carbon dioxide, here, on the contrary, it enters the lightweight alveoli, because its concentration is lower.

Verynas blood, which is saturated with oxygen and delivered from excess carbon dioxide, acquiring Aluu painting, becomes arterial and from the Capillary system again enters four veins of lungs (two on the left and right), after which he flows into the left atrium. It is the end of the small circle of blood circulation. The blood fell in the atrium, flows into the left ventricle, in which it takes a large circle of blood circulation, feeding it to all organs.

Running into two circles, the blood system of the body acquires a significant advantage, since due to this oxygen-enriched blood separated from the spent, which is saturated with carbon dioxide and as a result, a significantly lower load turns out to be. It is because of the existence of a small circle of blood circulation, a human heart is four chambers in the form of two ventricles and two atrials.

Functioning of a small circulation circle

In the right atrium, blood is supplied to the two light veins - the upper floor, which pumps it from the upper half of the body and the lower empty vein, according to which blood comes from the lower part of it. Next, it flows into the right ventricle, after which it is transferred to lungs through a light artery.

The heart is equipped with two pairs of valves: one is located between ventricles and atrialists, and the second is between ventricles and arteries that are separated from them. Valves are not allowed to be carried out by the reverse current of blood, asking him the direction.

Any kind of liquid flows from there, where the pressure is higher in the place where it is lower and the more pressure varies, the speed of the flow is greater. The blood in the veins of both circles circulation also flows due to the pressure difference generated by heart abbreviations. Blood pressure in the left ventricle and in the aorta is higher than in the right atrium and in hollow veins. This pressure difference moves blood in a large circulation circle. In a small circle, its movement is provided by high pressure in the light artery and the right heart ventricle in combination with low pressure in the left atrium and lung veins. Most high pressure Aorta and large arteries are subject to (hence the name - "blood pressure"). It is not a permanent value.

The blood by means of a large pressure is injected into the lungs, and under the influence of negative pressure flows into the left atrium. Thus, it is constantly moving along the light vessels at the same speed. Due to the fact that the blood flow is slow, oxygen has time to get into the cells, while carbon dioxide enters the blood. When the need for oxygen is increased (for example, with severe physical exertion and intensive sports), heart pressure rises, accelerating blood flow. Due to the fact that in a small circle of blood circulation in light blood flows under less pressure than in a large circle, its other name is a low pressure system. The human heart is deprived of symmetry: his left part that performs the most severe work, as a rule, thicker than the right.

Adjusting the work of the small circle of blood circulation

Diverse blood indicators, such as: acidity, level of hormone content, degree of concentration of liquids, carbon dioxide, oxygen, etc. Controlled by nerve cells playing the role of sensors. All available information processes a brain, sending certain impulses to the heart and veins. Each artery has its own inner lumen providing a continuous blood flow rate. The vessels of a small circulation circle are expanding during the acceleration of heartbeat and narrow when it slows down.

In order not to have problems with blood circulation, fraught with dangerous complications, it is necessary to conduct a healthy, active lifestyle and regularly eat. After all, it is easier to warn any disease than to cure him.

The blood circulation is an unintended flow of blood, which moves along vessels and cavities of the heart. This system is responsible for metabolic processes in organs and tissues of the human body. Circulating blood transports oxygen and nutrients to cells, taking carbon dioxide from there, as well as metabolites. That is why any circulatory disorders threaten dangerous consequences.

The blood circulation consists of a large (systemic) and small (light) circle. Each round has a complex structure and functions. The system circle comes out of the left ventricle, and ends in the right of atrium, and lightly - originates from the right ventricle and ends in the left atrium.

Blood circulation is a complex system that consists of a heart and blood vessels. The heart is constantly declining, pushes blood according to the vessels to all organs, as well as tissues. Circulatory system Consists of arteries, veins, capillaries.

The circulatory system form arteries, veins and capillaries

The arteries of the large circle of blood circulation are the largest vessels, they have a cylindrical shape, transport blood from the heart to the organs.

Structure of walls of arterial vessels:

• outdoor connective tissue shell;
• the middle layer of smooth muscle fibers with elastic veins;
• durable elastic inner endothelial shell.

The arteries have elastic walls, constantly declining, due to which the blood is moving evenly.

With the help of a large circle of blood circulation, blood moves from the capillaries to the heart. Veins have the same structure as arteries, but they are less strong, since their average shell contains less smooth muscle and elastic fibers. That is why the speed of blood in venous vessels is more affected by nearby fabrics, especially skeletal muscles. All veins, except hollow, are equipped with valves that prevent the reverse blood flow.

Capillaries are small vessels, which consist of endothelium (single-layer plastic flat cells). They are thin (about 1 μm) and short (from 0.2 to 0.7 mm). Due to its structure, the microsudes are saturated with oxygen fabrics, useful substances, carrying carbon dioxide from them, as well as metabolic products. Blood moves slowly, in the arterial part of the capillaries, the water is displayed in the intercellular space. In the venous part, blood pressure decreases, and water goes back to the capillaries.

Structure of a large circulation circle

Aorta is the largest vessel of a large circle, the diameter of which is 2.5 cm. This is a kind of source from which all other artery overlook. The vessels branched themselves, their size decreases, they go to the periphery, where they give oxygen and tissues.

The largest vessel of the system circle of blood circulation is aorta

The aorta is divided into the following departments:

• ascending
• downward
• arc that connects them.

The upstream plot is the shortest, its length is no more than 6 cm. From it proceed coronary arterywhich supply blood rich blood to myocardial tissues. Sometimes for the name of the ascending department, the term "heart circle of blood circulation" is used. From the most convex surface of the arc of the aorta, arterial branches are deployed, which supply hands with blood, neck, head: on the right side it is a shoulder barrel, divided in half, and with left - general sleepy, subclavian artery.

Downward aorta to share for 2 groups of branches:

• Priest arteries that supply blood chest, vertebral pole, spinal cord.
• Visceral (domestic) arteries that transport blood and nutrients to bronchoms, light, esophagus, etc.

Under the diaphragm there is an abdominal aorta, the on-line branches of which nourish abdominal cavity, lower diaphragm surface, spine.

Internal branches of the abdominal aorta are divided into paired and unpaired. Vessels that depart from unpaired trunks transport oxygen to the liver, spleen, stomach, intestines, pancreas. Unparalleled branches include an enzyme trunk, as well as the upper and lower biketical artery.

Paired trunk only two: kidney, ovarian or testicular. These arterial vessels are adjacent to the organs of the same name.

The aorta is ends with the left and right iliac artery. Their branches depart to the organs of a small pelvis and legs.

Many are interested in the question of how the system circle of blood circulation operates. In the lungs, the blood is saturated with oxygen, after which it is transported to the left atrium, and then to the left ventricle. The iliac arterys are blood supply to the legs, and the remaining branches are saturated with blood chest, hands, organs of the top half of the body.

Viennes of a large circle of blood circulation are boring poor oxygen. The system circle ends with the upper and lower hollow vein.

The scheme of the veins of the system circle is quite understandable. The femoral veins on the legs are combined into a iliac venu, which goes into the lower hollow vein. In the head, venous blood is going to yarem ViennaAnd in your hands - in the connective. Jugs, and also connectory vessels are combined, forming a unnamed vein, which gives the beginning of the upper hollow vein.

Blood supply system head

The blood system of the head is the most difficult structure of the body. For the blood supply to the departments of the head corresponds to the carotid artery, which is divided into 2 branches. The outer sleepy arterial vessel saturates oxygen, as well as the useful substances face, temporal area, purph cavity, nose, thyroid, etc.

The main vessel is a bloodsinking head - this is a carotid artery

The inner branch of the carotid artery leaves Bolly deep, forming a valley circle that transports blood to the brain. In the cranial box, the inner carotid artery branches on the eye, front, middle brain, connective artery.

This is formed only ⅔ systemic circle, which ends with a rear brain arterial vessel. It has a different origin, the diagram of its formation is as follows: Connected artery - vertebrate - Basilar - rear brain. In this case, saturates blood brain with blood and plug-in arteries that are connected to each other. Thanks to the anastomosis (recesses of vessels), the brain survives with minor blood flow disorders.

Principle of placement arteries

The circulatory system of each body structure roughly resembles the above described. Arterial vessels are always suitable for organs on the shortest trajectory. The vessels in the limbs pass exactly along the side of bending, as the extensive part is longer. Each artery takes its origin at the site of the germinal laying of the body, and not its actual location. For example, an arterial vessel of eggs leaves the abdominal department of aorta. Thus, all vessels are connected to their organs from the inside.

Vascular placement scheme resembles a skeleton structure

The placement scheme of the arteries is also associated with the structure of the skeleton. For example, on the upper limb there is a shoulder branch that corresponds to shoulder bone, elbow and radiation artery also take place near the bones of the same name. And in the cranial box there are holes through which arterial vessels transport blood to the brain.

Arterial vessels of a large circle of blood circulation using anastomoses form networks in the joints of the joints. Thanks to this scheme, the joints during the movement continuously bustling. The size of the vessels and their number dependes not from the size of the organ, but on its functional activity. Authorities that work more intensive are saturated with a large number of arteries. Their placement around the organ depends on its structure. For example, the scheme of vessels of parenchymal organs (liver, kidneys, lungs, spleen) correspond to their shape.

Structure and functions of a small circle of blood circulation

The light circle of blood circulation comes from the right ventricle, from which several light arterial vessels come out. A small circle is closed in the left atrium, to which the light veins are adjacent.

The light circle of blood circulation is so called for the reason that it is responsible for gas exchanges between the light capillaries and the same alveolmi. It consists of a common light artery, the right, left branch with branches, vessels of lungs, which are combined into 2 right, 2 left veins and are included in the left atrium.

From the right ventricle, the general light artery (diameter from 26 to 30 mm) comes out, it passes diagonally (up and left), divided into 2 branches that are suitable for light. The right light arterial vessel is directed to the right to the medial surface of the easy, where it is divided into 3 branches, which also have branch. The left vessel is shorter and thin, it passes from the point of separation of the total light artery to the medial part of the left light in the transverse direction. Near the middle part of the lung left artery is divided into 2 branches, which in turn are divided into segmental branches.

Venules come from the capillary vessels of the lungs, which are moving to the village of a small circle. From each light, 2 veins (top and bottom) comes out of 2 veins. When connecting a common basal vein with the upper vein of the lower share, the right lower light vein is formed.

The upper lighting trunk has 3 branches: the top-end, front, bunch vein. It takes blood from the top of the left lung. The left upper trunk is larger, it collects blood from the lower share of the organ.

The upper and lower hollow veins transport blood from the top and bottom of the body to the right atrium. From there, blood goes into the right ventricle, and then through the light artery in the lungs.

Under the influence of large pressure, the blood rushes to a slight, and under negative - to the left atrium. For this reason, the blood on the capillary vessels of lungs always moves slowly. Due to this tempo, the cells have time to be saturated with oxygen, and carbon dioxide penetrates blood. When a person is engaged in sports or performs a hard job, then the need for oxygen increases, then the heart increases the pressure and the flow of blood is accelerated.

Based on the foregoing, blood circulation is a complex system that ensures the life activity of the whole organism. The heart is a muscular pump, and arteries, veins, capillaries are channel systems that transport oxygen and nutrients to all organs and tissues. It is important to monitor the condition of the cardiovascular system, since any violation threatens with dangerous consequences.