Through which vessels the darker blood moves and how the circulatory system works. What vessels carry venous blood

Veins are vessels that carry blood to the heart. In the large circle, venous blood flows through the veins, and in the small circle, arterial blood flows.

The heart is four-chambered, consists of two atria and two ventricles.

Two circles of blood circulation:

Large circle: from the left ventricle, arterial blood, first through the aorta, and then through the arteries, goes to all organs of the body. In the capillaries of the great circle, gas exchange occurs: oxygen passes from the blood to the tissues, and carbon dioxide from the tissues into the blood. The blood becomes venous, through the veins enters the right atrium, and from there - into the right ventricle.
Small circle: from the right ventricle, venous blood goes through the pulmonary arteries to the lungs. In the capillaries of the lungs, gas exchange occurs: carbon dioxide passes from the blood into the air, and oxygen from the air into the blood, the blood becomes arterial and enters the left atrium through the pulmonary veins, and from there into the left ventricle.

Tests

27-01. In what chamber of the heart does the pulmonary circulation conditionally begin?

A) in the right ventricle

B) in the left atrium

B) in the left ventricle

D) in the right atrium

27-02. Which statement correctly describes the movement of blood in the pulmonary circulation?

A) begins in the right ventricle and ends in the right atrium

B) begins in the left ventricle and ends in the right atrium

B) begins in the right ventricle and ends in the left atrium

D) begins in the left ventricle and ends in the left atrium

27-03. Which chamber of the heart receives blood from the veins of the systemic circulation?

A) left atrium

B) left ventricle

B) right atrium

D) right ventricle

27-04. Which letter in the figure indicates the chamber of the heart, in which the pulmonary circulation ends?

27-05. The figure shows the human heart and large blood vessels. What letter indicates the inferior vena cava?

27-06. What numbers indicate the vessels through which venous blood flows?

27-07. Which of the following statements correctly describes the movement of blood in the systemic circulation?

A) begins in the left ventricle and ends in the right atrium

B) begins in the right ventricle and ends in the left atrium

B) begins in the left ventricle and ends in the left atrium

D) begins in the right ventricle and ends in the right atrium

27-08. Blood in the human body changes from venous to arterial after leaving

A) capillaries of the lungs

B) left atrium

B) liver capillaries

D) right ventricle

27-09. Which vessel carries venous blood?

B) brachial artery

B) pulmonary vein

D) pulmonary artery

27-10. From the left ventricle of the heart, blood enters

A) pulmonary vein

B) pulmonary artery

27-11. In mammals, the blood is enriched with oxygen in

What color is venous blood and why is it darker than arterial blood?

What kind of blood is in the pulmonary vein?

What is saturated in venous blood?

Why are tests taken from a vein?

This is due to the fact that the blood in the veins is saturated with metabolic products and the vital activity of organs. If a person is sick, it contains certain groups of substances, the remains of bacteria and other pathogenic cells. In a healthy person, these impurities are not found. By the nature of impurities, as well as by the level of concentration of carbon dioxide and other gases, it is possible to determine the nature of the pathogenic process.

Deoxygenated blood

arterial blood

Small circle of blood circulation

Systemic circulation

Blood flow disorder

Determination of glucose level

What color is venous blood and why is it darker than arterial blood. Through which vessels the darker blood moves and how the circulatory system works.

Blood is a liquid tissue circulating in the circulatory system of vertebrates and humans.

Thanks to the blood, the metabolism in the cells is maintained: the blood brings the necessary nutrients and oxygen and takes away the decay products. Carrying biologically active substances (for example, hormones), blood carries out the relationship between various organs and systems and plays a major role in maintaining the constancy of the internal environment of the body. The connection of tissues with blood occurs through lymph - a fluid that is located in the interstitial and intercellular space.

Blood consists of plasma and formed elements - erythrocytes (red blood cells), leukocytes (white blood cells) and platelets. Blood is about 20% dry matter and 80% water. Plasma contains sugar, minerals and proteins - albumin, globulin, fibrinogen. Red blood cells are essential for the process of respiration. They supply the body with oxygen thanks to the hemoglobin they contain. Leukocytes protect the body from microbes and accumulate where inflammation occurs. Platelets, together with fibrinogen, take part in blood clotting during cuts and bleeding.

The blood in the body is constantly updated. It circulates in a closed system - the circulatory system. Its movement is provided by the work of the heart and a certain tone of the blood vessels. Vessels that carry blood to organs are called arteries. From the organs, blood flows through the veins (the liver and heart are an exception). The color of arterial blood is bright scarlet, and venous blood is dark red.

The heart is a kind of pump that continuously pumps blood through the blood vessels. The longitudinal septum divides it into right and left halves, each of which consists of two cavities - the atrium and the ventricle. Blood enters the atria through the veins, and exits through the arteries from the ventricles, which have thick muscular walls. The passage of blood from the atria to the ventricles, and from them to the arteries, is regulated by connective tissue formations - valves. They close automatically and do not allow blood to flow in the opposite direction.

The work of the heart depends on a number of factors. If physical activity is increased, then the walls of the atria and ventricles contract more often. The same thing happens with mental influence (for example, fright). The frequency of contractions of the heart in individual species of animals is different. At rest in cattle, sheep, pigs, it is 60-80 times per minute, in horses - 32-42, in chickens - up to 300 times. You can determine the heart rate by the pulse - the periodic expansion of blood vessels.

There are two circles of blood circulation - large and small. Venous blood from the internal organs is collected in two large veins - the left and right. They flow into the right atrium, from which venous blood in portions enters the right ventricle, and from it passes through the pulmonary artery to the lungs, where it is saturated with oxygen through the lung tissue, giving off carbon dioxide. The oxygenated blood then flows through the pulmonary veins into the left atrium. The path along which blood moves from the right ventricle through the lungs to the left atrium is called the small or respiratory circle. The main purpose of the pulmonary circulation is to saturate the blood with oxygen and remove carbon dioxide from it.

From the left atrium, blood enters the left ventricle, and from there into the aorta. Arteries depart from it, branching into smaller ones. Organs and tissues are supplied with blood through the smallest blood vessels - arterial capillaries, which penetrate all tissues of the animal's body. From the left ventricle, blood moves through the arterial vessels, and then through the venous vessels and enters the right atrium, passing through the systemic circulation. It supplies blood enriched with oxygen and nutrients to all organs and tissues of the body.

In order to notice any violations in the body in time, at least elementary knowledge of the anatomy of the human body is necessary. It is not worth going deep into this issue, but having an idea of the simplest processes is very important. Today, let's find out how venous blood differs from arterial blood, how it moves and through which vessels.

The main function of blood is to transport nutrients to organs and tissues, in particular, the supply of oxygen from the lungs and the reverse movement of carbon dioxide to them. This process can be called gas exchange.

Blood circulation is carried out in a closed system of vessels (arteries, veins and capillaries) and is divided into two circles of blood circulation: small and large. This feature allows you to divide it into venous and arterial. As a result, the load on the heart is significantly reduced.

Let's look at what kind of blood is called venous and how it differs from arterial. This type of blood is primarily dark red in color, sometimes it is also said to have a bluish tint. This feature is explained by the fact that it carries carbon dioxide and other metabolic products.

The acidity of venous blood, in contrast to arterial blood, is slightly lower, and it is also warmer. It flows slowly through the vessels and close enough to the surface of the skin. This is due to the structural features of the veins, in which there are valves that help to reduce the speed of blood flow. It also has extremely low levels of nutrients, including reduced sugar.

In the vast majority of cases, it is this type of blood that is used for testing during any medical examinations.

Venous blood goes to the heart through the veins, has a dark red color, carries metabolic products

With venous bleeding, it is much easier to deal with the problem than with a similar process from the arteries.

The number of veins in the human body is several times greater than the number of arteries; these vessels provide blood flow from the periphery to the main organ - the heart.

arterial blood

Based on the foregoing, we will characterize the arterial blood type. It ensures the outflow of blood from the heart and carries it to all systems and organs. Her color is bright red.

Arterial blood is saturated with many nutrients, it delivers oxygen to the tissues. Compared to venous, it has a higher level of glucose, acidity. It flows through the vessels according to the type of pulsation, this can be determined on the arteries located close to the surface (wrist, neck).

With arterial bleeding, it is much more difficult to cope with the problem, since the blood flows out very quickly, which poses a threat to the patient's life. Such vessels are located both deep in the tissues and close to the surface of the skin.

Now let's talk about the ways in which arterial and venous blood moves.

Small circle of blood circulation

This path is characterized by the flow of blood from the heart to the lungs, as well as in the opposite direction. Biological fluid from the right ventricle travels through the pulmonary arteries to the lungs. At this time, it gives off carbon dioxide and absorbs oxygen. At this stage, the venous turns into an arterial one and flows through the four pulmonary veins to the left side of the heart, namely, to the atrium. After these processes, it enters the organs and systems, we can talk about the beginning of a large circle of blood circulation.

Systemic circulation

Oxygenated blood from the lungs enters the left atrium and then into the left ventricle, from which it is pushed into the aorta. This vessel, in turn, is divided into two branches: descending and ascending. The first supplies blood to the lower limbs, the organs of the abdomen and pelvis, the lower part of the chest. The latter nourishes the arms, organs of the neck, upper chest, and brain.

Blood flow disorder

In some cases, there is a poor outflow of venous blood. Such a process can be localized in any organ or part of the body, which will lead to a violation of its functions and the development of appropriate symptoms.

To prevent such a pathological condition, it is necessary to eat right, provide the body with at least minimal physical activity. And if you have any disorders, immediately consult a doctor.

Determination of glucose level

In some cases, doctors prescribe a blood test for sugar, but not capillary (from a finger), but venous. In this case, biological material for research is obtained by venipuncture. The preparation rules are no different.

But the rate of glucose in venous blood is somewhat different from capillary blood and should not exceed 6.1 mmol / l. As a rule, such an analysis is prescribed for the purpose of early detection of diabetes mellitus.

Venous and arterial blood has fundamental differences. Now you are unlikely to be able to confuse them, but it will not be difficult to identify some disorders using the above material.

Venous circulation occurs as a result of the circulation of blood towards the heart, and in general, through the veins. It is deprived of oxygen, as it is completely dependent on carbon dioxide, which is necessary for tissue gas exchange.

As for human venous blood, in contrast to arterial, then it is several times warmer and has a lower pH. In its composition, doctors note the low content of most nutrients, including glucose. It is characterized by the presence of metabolic end products.

In order to receive venous blood, you must undergo a procedure called venipuncture! Basically, all medical research in the laboratory is based on venous blood. Unlike arterial, it has a characteristic color with a red-bluish, deep tint.

About 300 years ago the explorer Van Horn made a sensational discovery: it turns out that the entire human body is permeated by capillaries! The doctor begins to make various experiments with medicines, as a result he observes the behavior of capillaries filled with red liquid. Modern doctors know that capillaries play a key role in the human body. With their help, blood flow is gradually provided. Thanks to them, oxygen is supplied to all organs and tissues.

Human arterial and venous blood, difference

From time to time, one asks the question: is venous blood different from arterial blood? The entire human body is divided into numerous veins, arteries, large and small vessels. Arteries contribute to the so-called outflow of blood from the heart. Purified blood moves throughout the human body and thus provides timely nutrition.

In this system, the heart is a kind of pump that gradually distills blood throughout the body. Arteries can be located both deep and close under the skin. You can feel the pulse not only on the wrist, but also on the neck! Arterial blood has a characteristic bright red hue, which, when bleeding, acquires a somewhat poisonous color.

Human venous blood, unlike arterial blood, is located very close to the surface of the skin. On the entire surface of its length, venous blood is accompanied by special valves that contribute to a calm and even passage of blood. Dark blue blood nourishes the tissues and gradually moves into the veins.

In the human body, there are several times more veins than arteries. In case of any damage, venous blood flows slowly and stops very quickly. Venous blood is very different from arterial blood, and all because of the structure of individual veins and arteries.

The walls of the veins are unusually thin, unlike the arteries. They can withstand high pressure, as powerful shocks can be observed during the ejection of blood from the heart.

In addition, elasticity plays a key role, due to which the movement of blood through the vessels occurs quickly. Veins and arteries provide normal blood circulation, which does not stop even for a minute in the human body. Even if you are not a doctor, it is very important to know a minimum of information about venous and arterial blood that will help you quickly provide first aid in case of open bleeding. The World Wide Web will help to replenish the stock of knowledge regarding venous and arterial circulation. You just need to enter the word of interest in the search box and in a few minutes you will receive answers to all your questions.

This video shows the process of converting arterial blood into venous blood:

Blood constantly circulates throughout the body, providing the transport of various substances. It consists of plasma and suspension of various cells (the main ones are erythrocytes, leukocytes and platelets) and moves along a strict route - the system of blood vessels.

Venous blood - what is it?

Venous - blood that returns to the heart and lungs from organs and tissues. It circulates through the pulmonary circulation. The veins through which it flows lie close to the surface of the skin, so the venous pattern is clearly visible.

This is partly due to a number of factors:

It is thicker, saturated with platelets, and if damaged, venous bleeding is easier to stop.
The pressure in the veins is lower, so when the vessel is damaged, the volume of blood loss is lower.
Its temperature is higher, so in addition it prevents the rapid loss of heat through the skin.

The same blood flows in both arteries and veins. But its composition is changing. From the heart, it enters the lungs, where it is enriched with oxygen, which it transfers to the internal organs, providing them with nutrition. The veins that carry arterial blood are called arteries. They are more elastic, the blood moves through them in jerks.

Arterial and venous blood do not mix in the heart. The first passes on the left side of the heart, the second - on the right. They are mixed only with serious pathologies of the heart, which entails a significant deterioration in well-being.

What is the systemic and pulmonary circulation?

From the left ventricle, the contents are pushed out and enter the pulmonary artery, where they are saturated with oxygen. Then, through the arteries and capillaries, it spreads throughout the body, carrying oxygen and nutrients.

The aorta is the largest artery, which then divides into superior and inferior. Each of them supplies blood to the upper and lower parts of the body, respectively. Since the arterial “flows around” absolutely all organs, is supplied to them with the help of an extensive system of capillaries, this circle of blood circulation is called large. But the volume of the arterial at the same time is about 1/3 of the total.

Blood flows through the pulmonary circulation, which gave up all the oxygen, and "took" metabolic products from the organs. It flows through the veins. The pressure in them is lower, the blood flows evenly. Through the veins, it returns to the heart, from where it is then pumped to the lungs.

How are veins different from arteries?

Arteries are more elastic. This is due to the fact that they need to maintain a certain rate of blood flow in order to deliver oxygen to the organs as quickly as possible. The walls of the veins are thinner, more elastic. This is due to a lower blood flow rate, as well as a large volume (venous is about 2/3 of the total volume).

What kind of blood is in the pulmonary vein?

The pulmonary arteries provide oxygenated blood to the aorta and its further circulation through the systemic circulation. The pulmonary vein returns some of the oxygenated blood to the heart to feed the heart muscle. It is called a vein because it brings blood to the heart.

What is saturated in venous blood?

Coming to the organs, the blood gives them oxygen, in return it is saturated with metabolic products and carbon dioxide, and acquires a dark red hue.

A large amount of carbon dioxide is the answer to the question why venous blood is darker than arterial blood and why veins are blue. It also contains nutrients that are absorbed in the digestive tract, hormones and other substances synthesized by the body.

Venous blood flow depends on its saturation and density. The closer to the heart, the thicker it is.

Why are tests taken from a vein?

The second reason is that venous bleeding during a vessel puncture is much easier to stop. But there are times when bleeding from a vein does not stop for a long time. This is a sign of hemophilia, a low platelet count. In this case, even a small injury can be very dangerous for a person.

How to distinguish venous bleeding from arterial:

Assess the volume and nature of the flowing blood. The venous one flows out in a uniform stream, the arterial one is thrown out in portions and even "fountains".
Assess what color the blood is. Bright scarlet indicates arterial bleeding, dark burgundy indicates venous bleeding.
Arterial is more liquid, venous is thicker.

Why does the venous fold faster?

It is thicker, contains a large number of platelets. A low blood flow rate allows the formation of a fibrin network at the site of damage to the vessel, for which platelets “cling”.

How to stop venous bleeding?

With a slight damage to the veins of the limbs, it is enough to create an artificial outflow of blood by raising an arm or leg above the level of the heart. A tight bandage should be applied to the wound itself to minimize blood loss.

If the injury is deep, a tourniquet should be applied to the area above the injured vein to limit the amount of blood flowing to the injury site. In summer it can be kept for about 2 hours, in winter - for an hour, a maximum of one and a half. During this time, you need to have time to deliver the victim to the hospital. If you keep the tourniquet longer than the specified time, tissue nutrition will be disturbed, which threatens with necrosis.

It is advisable to apply ice to the area around the wound. This will help slow down the circulation.

Video

Blood in the human body circulates in a closed system. The main function of the biological fluid is to provide cells with oxygen and nutrients and remove carbon dioxide and metabolic products.

A little about the circulatory system

The human circulatory system has a complex structure, the biological fluid circulates in the pulmonary and systemic circulation.

The heart, acting as a pump, consists of four sections - two ventricles and two atria (left and right). Vessels that carry blood away from the heart are called arteries, and those that carry blood to the heart are called veins. Arterial is enriched with oxygen, venous - with carbon dioxide.

Thanks to the interventricular septum, venous blood, which is located in the right side of the heart, does not mix with arterial blood, which is in the right section. Valves located between the ventricles and atria and between the ventricles and arteries prevent it from flowing in the opposite direction, that is, from the largest artery (aorta) to the ventricle, and from the ventricle to the atrium.

With the contraction of the left ventricle, the walls of which are the thickest, maximum pressure is created, oxygen-rich blood is pushed into the systemic circulation and carried through the arteries throughout the body. In the capillary system, gases are exchanged: oxygen enters the tissue cells, carbon dioxide from the cells enters the bloodstream. Thus, the arterial becomes venous and flows through the veins into the right atrium, then into the right ventricle. This is a large circle of blood circulation.

Further, the venous through the pulmonary arteries enters the pulmonary capillaries, where it releases carbon dioxide into the air and is enriched with oxygen, again becoming arterial. Now it flows through the pulmonary veins into the left atrium, then into the left ventricle. This closes the pulmonary circulation.

Venous blood is in the right side of the heart

Characteristics

Venous blood differs in a number of parameters, ranging from its appearance to its functions.

Many people know what color it is. Due to the saturation of carbon dioxide, its color is dark, with a bluish tint.
It is poor in oxygen and nutrients, while it contains a lot of metabolic products.
Its viscosity is higher than that of oxygen-rich blood. This is due to an increase in the size of red blood cells due to the intake of carbon dioxide in them.
It has a higher temperature and a lower pH.
Blood flows slowly through the veins. This is due to the presence of valves in them, which slow down its speed.
There are more veins in the human body than arteries, and venous blood as a whole makes up about two-thirds of the total volume.
Due to the location of the veins, it flows close to the surface.

Compound

Laboratory studies make it easy to distinguish venous blood from arterial blood in composition.

In the venous, the oxygen tension is normally equal to the mercury column (in the arterial - from 80 to 100).
Carbon dioxide - about 60 mm Hg. Art. (in the arterial - about 35).
The pH level remains 7.35 (arterial - 7.4).

Functions

The veins carry out the outflow of blood, which carries metabolic products and carbon dioxide. It receives nutrients that are absorbed by the walls of the digestive tract, and hormones produced by the endocrine glands.

Movement through the veins

Venous blood, in its movement, overcomes gravity and experiences hydrostatic pressure, therefore, when a vein is damaged, it flows calmly in a stream, and when an artery is damaged, it spurts.

Its speed is much less than that of the arterial. The heart ejects arterial blood at a pressure of 120 mmHg, and after it passes through the capillaries and becomes venous, the pressure gradually drops and reaches 10 mmHg. pillar.

Why is material taken from a vein for analysis?

Venous blood contains decay products formed during metabolism. In diseases, substances enter it that should not be in the normal state. Their presence makes it possible to suspect the development of pathological processes.

How to determine the type of bleeding

Visually, this is quite easy to do: the blood from the vein is dark, thicker and flows out in a stream, while the arterial blood is more liquid, has a bright scarlet hue and flows out in a fountain.

Venous bleeding is easier to stop, in some cases, when a blood clot forms, it may stop on its own. A pressure bandage applied below the wound is usually required. If a vein in the arm is damaged, it may be enough to raise the arm up.

As for arterial bleeding, it is very dangerous because it will not stop on its own, blood loss is significant, and death can occur within an hour.

Conclusion

The circulatory system is closed, so the blood in the course of its movement becomes either arterial or venous. Enriched with oxygen, when passing through the capillary system, it gives it to the tissues, takes away decay products and carbon dioxide, and thus becomes venous. After that, it rushes to the lungs, where it loses carbon dioxide and metabolic products and is enriched with oxygen and nutrients, becoming arterial again.

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This is the continuous movement of blood through a closed cardiovascular system, which ensures the exchange of gases in the lungs and body tissues.

In addition to providing tissues and organs with oxygen and removing carbon dioxide from them, blood circulation delivers nutrients, water, salts, vitamins, hormones to cells and removes metabolic end products, and also maintains a constant body temperature, ensures humoral regulation and the interconnection of organs and organ systems in body.

The circulatory system consists of the heart and blood vessels that permeate all organs and tissues of the body.

Blood circulation begins in the tissues, where metabolism takes place through the walls of the capillaries. The blood that has given oxygen to organs and tissues enters the right half of the heart and is sent to the pulmonary (pulmonary) circulation, where the blood is saturated with oxygen, returns to the heart, entering its left half, and again spreads throughout the body (large circulation) .

Heart- the main organ of the circulatory system. It is a hollow muscular organ consisting of four chambers: two atria (right and left), separated by an interatrial septum, and two ventricles (right and left), separated by an interventricular septum. The right atrium communicates with the right ventricle through the tricuspid valve, and the left atrium communicates with the left ventricle through the bicuspid valve. The mass of the heart of an adult is on average about 250 g in women and about 330 g in men. The length of the heart is 10-15 cm, the transverse size is 8-11 cm and the anteroposterior is 6-8.5 cm. The volume of the heart in men is on average 700-900 cm 3, and in women - 500-600 cm 3.

The outer walls of the heart are formed by the cardiac muscle, which is similar in structure to the striated muscles. However, the heart muscle is distinguished by the ability to automatically contract rhythmically due to impulses that occur in the heart itself, regardless of external influences (cardiac automaticity).

The function of the heart is to rhythmically pump blood into the arteries, which comes to it through the veins. The heart contracts about 70-75 times per minute at rest (1 time per 0.8 s). More than half of this time it rests - relaxes. The continuous activity of the heart consists of cycles, each of which consists of contraction (systole) and relaxation (diastole).

There are three phases of cardiac activity:

atrial contraction - atrial systole - takes 0.1 s
ventricular contraction - ventricular systole - takes 0.3 s
total pause - diastole (simultaneous relaxation of the atria and ventricles) - takes 0.4 s

Thus, during the entire cycle, the atria work 0.1 s and rest 0.7 s, the ventricles work 0.3 s and rest 0.5 s. This explains the ability of the heart muscle to work without fatigue throughout life. The high efficiency of the heart muscle is due to the increased blood supply to the heart. Approximately 10% of the blood ejected from the left ventricle into the aorta enters the arteries departing from it, which feed the heart.

arteries- blood vessels that carry oxygenated blood from the heart to organs and tissues (only the pulmonary artery carries venous blood).

The wall of the artery is represented by three layers: the outer connective tissue membrane; middle, consisting of elastic fibers and smooth muscles; internal, formed by the endothelium and connective tissue.

In humans, the diameter of the arteries ranges from 0.4 to 2.5 cm. The total volume of blood in the arterial system averages 950 ml. Arteries gradually branch into smaller and smaller vessels - arterioles, which pass into capillaries.

capillaries(from Latin "capillus" - hair) - the smallest vessels (the average diameter does not exceed 0.005 mm, or 5 microns), penetrating the organs and tissues of animals and humans with a closed circulatory system. They connect small arteries - arterioles with small veins - venules. Through the walls of the capillaries, consisting of endothelial cells, there is an exchange of gases and other substances between the blood and various tissues.

Vienna- blood vessels that carry blood saturated with carbon dioxide, metabolic products, hormones and other substances from tissues and organs to the heart (with the exception of pulmonary veins that carry arterial blood). The wall of the vein is much thinner and more elastic than the wall of the artery. Small and medium-sized veins are equipped with valves that prevent the reverse flow of blood in these vessels. In humans, the volume of blood in the venous system averages 3200 ml.

Circles of blood circulation

The movement of blood through the vessels was first described in 1628 by the English physician W. Harvey.

In humans and mammals, blood moves through a closed cardiovascular system, consisting of a large and small circles of blood circulation (Fig.).

The large circle starts from the left ventricle, carries blood throughout the body through the aorta, gives oxygen to the tissues in the capillaries, takes carbon dioxide, turns from arterial to venous and returns to the right atrium through the superior and inferior vena cava.

The pulmonary circulation starts from the right ventricle, carries blood through the pulmonary artery to the pulmonary capillaries. Here the blood gives off carbon dioxide, is saturated with oxygen and flows through the pulmonary veins to the left atrium. From the left atrium through the left ventricle, blood again enters the systemic circulation.

Small circle of blood circulation- pulmonary circle - serves to enrich the blood with oxygen in the lungs. It starts from the right ventricle and ends at the left atrium.

From the right ventricle of the heart, venous blood enters the pulmonary trunk (common pulmonary artery), which soon divides into two branches that carry blood to the right and left lungs.

In the lungs, arteries branch into capillaries. In the capillary networks braiding the pulmonary vesicles, the blood gives off carbon dioxide and receives a new supply of oxygen in return (pulmonary respiration). Oxygenated blood acquires a scarlet color, becomes arterial and flows from the capillaries into the veins, which, having merged into four pulmonary veins (two on each side), flow into the left atrium of the heart. In the left atrium, the small (pulmonary) circle of blood circulation ends, and the arterial blood that enters the atrium passes through the left atrioventricular opening into the left ventricle, where the systemic circulation begins. Consequently, venous blood flows in the arteries of the pulmonary circulation, and arterial blood flows in its veins.

Systemic circulation- bodily - collects venous blood from the upper and lower half of the body and similarly distributes arterial blood; starts from the left ventricle and ends with the right atrium.

From the left ventricle of the heart, blood enters the largest arterial vessel - the aorta. Arterial blood contains nutrients and oxygen necessary for the life of the body and has a bright scarlet color.

The aorta branches into arteries that go to all organs and tissues of the body and pass in their thickness into arterioles and further into capillaries. Capillaries, in turn, are collected in venules and further into veins. Through the wall of the capillaries there is a metabolism and gas exchange between the blood and body tissues. Arterial blood flowing in the capillaries gives off nutrients and oxygen and in return receives metabolic products and carbon dioxide (tissue respiration). As a result, the blood entering the venous bed is poor in oxygen and rich in carbon dioxide and therefore has a dark color - venous blood; when bleeding, the color of the blood can determine which vessel is damaged - an artery or a vein. The veins merge into two large trunks - the superior and inferior vena cava, which flow into the right atrium of the heart. This part of the heart ends with a large (corporeal) circle of blood circulation.

The addition to the great circle is third (cardiac) circulation serving the heart itself. It begins with the coronary arteries of the heart emerging from the aorta and ends with the veins of the heart. The latter merge into the coronary sinus, which flows into the right atrium, and the remaining veins open directly into the atrial cavity.

The movement of blood through the vessels

Any fluid flows from a place where the pressure is higher to where it is lower. The greater the pressure difference, the higher the flow rate. The blood in the vessels of the systemic and pulmonary circulation also moves due to the pressure difference that the heart creates with its contractions.

In the left ventricle and aorta, blood pressure is higher than in the vena cava (negative pressure) and in the right atrium. The pressure difference in these areas ensures the movement of blood in the systemic circulation. High pressure in the right ventricle and pulmonary artery and low pressure in the pulmonary veins and left atrium ensure the movement of blood in the pulmonary circulation.

The highest pressure is in the aorta and large arteries (blood pressure). Arterial blood pressure is not a constant value [show]

Blood pressure- this is the blood pressure on the walls of the blood vessels and chambers of the heart, resulting from the contraction of the heart, which pumps blood into the vascular system, and the resistance of the vessels. The most important medical and physiological indicator of the state of the circulatory system is the pressure in the aorta and large arteries - blood pressure.

Arterial blood pressure is not a constant value. In healthy people at rest, the maximum, or systolic, blood pressure is distinguished - the level of pressure in the arteries during the systole of the heart is about 120 mm Hg, and the minimum, or diastolic - the pressure level in the arteries during the diastole of the heart is about 80 mm Hg. Those. arterial blood pressure pulsates in time with the contractions of the heart: at the time of systole, it rises to 120-130 mm Hg. Art., and during diastole decreases to 80-90 mm Hg. Art. These pulse pressure oscillations occur simultaneously with the pulse oscillations of the arterial wall.

As blood moves through the arteries, part of the pressure energy is used to overcome the friction of the blood against the walls of the vessels, so the pressure gradually drops. A particularly significant drop in pressure occurs in the smallest arteries and capillaries - they provide the greatest resistance to the movement of blood. In the veins, blood pressure continues to gradually decrease, and in the vena cava it is equal to or even lower than atmospheric pressure. The indicators of blood circulation in different parts of the circulatory system are given in Table. one.

The speed of blood movement depends not only on the pressure difference, but also on the width of the bloodstream. Although the aorta is the widest vessel, it is the only one in the body and all the blood flows through it, which is pushed out by the left ventricle. Therefore, the maximum speed here is 500 mm/s (see Table 1). As the arteries branch, their diameter decreases, but the total cross-sectional area of all arteries increases and the blood flow rate decreases, reaching 0.5 mm/s in the capillaries. Due to such a low rate of blood flow in the capillaries, the blood has time to give oxygen and nutrients to the tissues and take their waste products.

The slowing down of blood flow in the capillaries is explained by their huge number (about 40 billion) and the large total lumen (800 times the lumen of the aorta). The movement of blood in the capillaries is carried out by changing the lumen of the supply small arteries: their expansion increases the blood flow in the capillaries, and their narrowing decreases it.

The veins on the way from the capillaries, as they approach the heart, enlarge, merge, their number and the total lumen of the bloodstream decrease, and the speed of blood movement increases compared to the capillaries. From Table. 1 also shows that 3/4 of all blood is in the veins. This is due to the fact that the thin walls of the veins can easily stretch, so they can contain much more blood than the corresponding arteries.

The main reason for the movement of blood through the veins is the pressure difference at the beginning and end of the venous system, so the movement of blood through the veins occurs in the direction of the heart. This is facilitated by the suction action of the chest ("respiratory pump") and the contraction of skeletal muscles ("muscle pump"). During inhalation, the pressure in the chest decreases. In this case, the pressure difference at the beginning and at the end of the venous system increases, and the blood through the veins is sent to the heart. Skeletal muscles, contracting, compress the veins, which also contributes to the movement of blood to the heart.

The relationship between the speed of blood flow, the width of the bloodstream and blood pressure is illustrated in Fig. 3. The amount of blood flowing per unit of time through the vessels is equal to the product of the speed of blood movement by the cross-sectional area of the vessels. This value is the same for all parts of the circulatory system: how much blood pushes the heart into the aorta, how much it flows through the arteries, capillaries and veins, and the same amount returns back to the heart, and is equal to the minute volume of blood.

Redistribution of blood in the body

If the artery extending from the aorta to any organ, due to the relaxation of its smooth muscles, expands, then the organ will receive more blood. At the same time, other organs will receive less blood due to this. This is how blood is redistributed in the body. As a result of redistribution, more blood flows to the working organs at the expense of the organs that are currently at rest.

The redistribution of blood is regulated by the nervous system: simultaneously with the expansion of blood vessels in the working organs, the blood vessels of the non-working organs narrow and blood pressure remains unchanged. But if all the arteries dilate, this will lead to a drop in blood pressure and to a decrease in the speed of blood movement in the vessels.

Blood circulation time

Circulation time is the time it takes for blood to travel through the entire circulation. A number of methods are used to measure blood circulation time. [show]

The principle of measuring the time of the blood circulation is that some substance that is not usually found in the body is injected into the vein, and it is determined after what period of time it appears in the vein of the same name on the other side or causes an action characteristic of it. For example, a solution of the alkaloid lobeline, which acts through the blood on the respiratory center of the medulla oblongata, is injected into the cubital vein, and the time is determined from the moment the substance is injected until the moment when a short-term breath holding or cough occurs. This happens when the lobelin molecules, having made a circuit in the circulatory system, act on the respiratory center and cause a change in breathing or coughing.

In recent years, the rate of blood circulation in both circles of blood circulation (or only in a small, or only in a large circle) is determined using a radioactive isotope of sodium and an electron counter. To do this, several of these counters are placed on different parts of the body near large vessels and in the region of the heart. After the introduction of a radioactive isotope of sodium into the cubital vein, the time of appearance of radioactive radiation in the region of the heart and the studied vessels is determined.

The circulation time of the blood in humans is on average about 27 systoles of the heart. At 70-80 heartbeats per minute, a complete blood circulation occurs in about 20-23 seconds. We must not forget, however, that the speed of blood flow along the axis of the vessel is greater than that of its walls, and also that not all vascular regions have the same length. Therefore, not all blood circulates so quickly, and the time indicated above is the shortest.

Studies on dogs have shown that 1/5 of the time of a complete blood circulation occurs in the pulmonary circulation and 4/5 in the systemic circulation.

Regulation of blood circulation

Innervation of the heart. The heart, like other internal organs, is innervated by the autonomic nervous system and receives dual innervation. Sympathetic nerves approach the heart, which strengthen and accelerate its contractions. The second group of nerves - parasympathetic - acts on the heart in the opposite way: it slows down and weakens heart contractions. These nerves regulate the heart.

In addition, the work of the heart is affected by the hormone of the adrenal glands - adrenaline, which enters the heart with blood and increases its contractions. The regulation of the work of organs with the help of substances carried by the blood is called humoral.

Nervous and humoral regulation of the heart in the body act in concert and provide an accurate adaptation of the activity of the cardiovascular system to the needs of the body and environmental conditions.

Innervation of blood vessels. Blood vessels are innervated by sympathetic nerves. Excitation propagating through them causes contraction of smooth muscles in the walls of blood vessels and constricts blood vessels. If you cut the sympathetic nerves going to a certain part of the body, the corresponding vessels will expand. Consequently, through the sympathetic nerves to the blood vessels, excitation is constantly supplied, which keeps these vessels in a state of some narrowing - vascular tone. When excitation increases, the frequency of nerve impulses increases and the vessels narrow more strongly - vascular tone increases. On the contrary, with a decrease in the frequency of nerve impulses due to inhibition of sympathetic neurons, vascular tone decreases and blood vessels dilate. To the vessels of some organs (skeletal muscles, salivary glands), in addition to vasoconstrictor, vasodilating nerves are also suitable. These nerves become excited and dilate the blood vessels of the organs as they work. Substances that are carried by the blood also affect the lumen of the vessels. Adrenaline constricts blood vessels. Another substance - acetylcholine - secreted by the endings of some nerves, expands them.

Regulation of the activity of the cardiovascular system. The blood supply of the organs varies depending on their needs due to the described redistribution of blood. But this redistribution can only be effective if the pressure in the arteries does not change. One of the main functions of the nervous regulation of blood circulation is to maintain a constant blood pressure. This function is carried out reflexively.

There are receptors in the wall of the aorta and carotid arteries that are more irritated if blood pressure exceeds normal levels. Excitation from these receptors goes to the vasomotor center located in the medulla oblongata and inhibits its work. From the center along the sympathetic nerves to the vessels and the heart, a weaker excitation begins to flow than before, and the blood vessels dilate, and the heart weakens its work. As a result of these changes, blood pressure decreases. And if the pressure for some reason fell below the norm, then the irritation of the receptors stops completely and the vasomotor center, without receiving inhibitory influences from the receptors, intensifies its activity: it sends more nerve impulses per second to the heart and blood vessels, the vessels constrict, the heart contracts, more often and stronger, blood pressure rises.

Hygiene of cardiac activity

The normal activity of the human body is possible only in the presence of a well-developed cardiovascular system. The rate of blood flow will determine the degree of blood supply to organs and tissues and the rate of removal of waste products. During physical work, the need of organs for oxygen increases simultaneously with the increase and increase in heart rate. Only a strong heart muscle can provide such work. To be enduring for a variety of work activities, it is important to train the heart, increase the strength of its muscles.

Physical labor, physical education develop the heart muscle. To ensure the normal function of the cardiovascular system, a person should start his day with morning exercises, especially people whose professions are not related to physical labor. To enrich the blood with oxygen, physical exercises are best done in the fresh air.

It must be remembered that excessive physical and mental stress can cause disruption of the normal functioning of the heart, its diseases. Alcohol, nicotine, drugs have a particularly harmful effect on the cardiovascular system. Alcohol and nicotine poison the heart muscle and nervous system, causing sharp disturbances in the regulation of vascular tone and heart activity. They lead to the development of severe diseases of the cardiovascular system and can cause sudden death. Young people who smoke and drink alcohol are more likely than others to develop spasms of the heart vessels, causing severe heart attacks and sometimes death.

First aid for wounds and bleeding

Injuries are often accompanied by bleeding. There are capillary, venous and arterial bleeding.

Capillary bleeding occurs even with a minor injury and is accompanied by a slow flow of blood from the wound. Such a wound should be treated with a solution of brilliant green (brilliant green) for disinfection and a clean gauze bandage should be applied. The bandage stops bleeding, promotes the formation of a blood clot and prevents microbes from entering the wound.

Venous bleeding is characterized by a significantly higher rate of blood flow. The escaping blood is dark in color. To stop bleeding, it is necessary to apply a tight bandage below the wound, that is, further from the heart. After stopping the bleeding, the wound is treated with a disinfectant (3% solution of hydrogen peroxide, vodka), bandaged with a sterile pressure bandage.

With arterial bleeding, scarlet blood gushes from the wound. This is the most dangerous bleeding. If the artery of the limb is damaged, it is necessary to raise the limb as high as possible, bend it and press the wounded artery with your finger in the place where it comes close to the surface of the body. It is also necessary to apply a rubber tourniquet above the wound site, i.e. closer to the heart (you can use a bandage, a rope for this) and tighten it tightly to completely stop the bleeding. The tourniquet must not be kept tightened for more than 2 hours. When it is applied, a note must be attached in which the time of applying the tourniquet should be indicated.

It should be remembered that venous, and even more arterial bleeding can lead to significant blood loss and even death. Therefore, when injured, it is necessary to stop the bleeding as soon as possible, and then take the victim to the hospital. Severe pain or fright can cause the person to lose consciousness. Loss of consciousness (fainting) is a consequence of inhibition of the vasomotor center, a drop in blood pressure and insufficient supply of blood to the brain. The unconscious person should be allowed to sniff some non-toxic substance with a strong odor (for example, ammonia), moisten his face with cold water, or lightly pat his cheeks. When olfactory or skin receptors are stimulated, excitation from them enters the brain and relieves inhibition of the vasomotor center. Blood pressure rises, the brain receives sufficient nutrition, and consciousness returns.

Vessels are tubular formations that extend throughout the human body and through which blood moves. The pressure in the circulatory system is very high because the system is closed. According to this system, the blood circulates quite quickly.

When the vessels are cleansed, their elasticity and flexibility return. Many diseases associated with blood vessels go away. These include sclerosis, headaches, a tendency to a heart attack, paralysis. Hearing and vision are restored, varicose veins are reduced. The state of the nasopharynx returns to normal.

Blood circulates through the vessels that make up the systemic and pulmonary circulation.

All blood vessels are made up of three layers:

The inner layer of the vascular wall is formed by endothelial cells, the surface of the vessels inside is smooth, which facilitates the movement of blood through them.

The middle layer of the walls provides strength to blood vessels, consists of muscle fibers, elastin and collagen.

The upper layer of the vascular walls is made up of connective tissues, it separates the vessels from nearby tissues.

arteries

The walls of the arteries are stronger and thicker than those of the veins, as the blood moves through them with greater pressure. Arteries carry oxygenated blood from the heart to the internal organs. In the dead, the arteries are empty, which is found at autopsy, so it was previously believed that the arteries are air tubes. This was reflected in the name: the word "artery" consists of two parts, translated from Latin, the first part aer means air, and tereo means to contain.

Depending on the structure of the walls, two groups of arteries are distinguished:

Elastic type of arteries- these are vessels located closer to the heart, these include the aorta and its large branches. The elastic framework of the arteries must be strong enough to withstand the pressure with which blood is ejected into the vessel from heart contractions. The fibers of elastin and collagen, which make up the frame of the middle wall of the vessel, help to resist mechanical stress and stretching.

Due to the elasticity and strength of the walls of the elastic arteries, blood continuously enters the vessels and its constant circulation is ensured to nourish organs and tissues, supplying them with oxygen. The left ventricle of the heart contracts and forcefully ejects a large volume of blood into the aorta, its walls stretch, containing the contents of the ventricle. After relaxation of the left ventricle, blood does not enter the aorta, the pressure is weakened, and blood from the aorta enters other arteries, into which it branches. The walls of the aorta regain their former shape, as the elastin-collagen framework provides them with elasticity and resistance to stretching. Blood moves continuously through the vessels, coming in small portions from the aorta after each heartbeat.

The elastic properties of the arteries also ensure the transmission of vibrations along the walls of the vessels - this is a property of any elastic system under mechanical influences, which is played by a cardiac impulse. The blood hits the elastic walls of the aorta, and they transmit vibrations along the walls of all the vessels of the body. Where the vessels come close to the skin, these vibrations can be felt as a weak pulsation. Based on this phenomenon, methods for measuring the pulse are based.

Muscular type arteries in the middle layer of the walls contain a large number of smooth muscle fibers. This is necessary to ensure blood circulation and the continuity of its movement through the vessels. Muscular-type vessels are located farther from the heart than elastic-type arteries, so the force of the cardiac impulse in them weakens, in order to ensure further movement of blood, it is necessary to contract the muscle fibers. When the smooth muscles of the inner layer of the arteries contract, they narrow, and when they relax, they expand. As a result, blood moves through the vessels at a constant speed and enters the organs and tissues in a timely manner, providing them with nutrition.

Another classification of arteries determines their location in relation to the organ whose blood supply they provide. Arteries that pass inside the organ, forming a branching network, are called intraorgan. Vessels located around the organ, before entering it, are called extraorganic. Lateral branches that originate from the same or different arterial trunks may reconnect or branch into capillaries. At the point of their connection, before branching into capillaries, these vessels are called anastomosis or fistula.

Arteries that do not anastomose with neighboring vascular trunks are called terminal. These include, for example, the arteries of the spleen. The arteries that form fistulas are called anastomizing, most of the arteries belong to this type. The terminal arteries have a greater risk of blockage by a thrombus and a high susceptibility to a heart attack, as a result of which part of the organ may die.

In the last branches, the arteries become very thin, such vessels are called arterioles, and the arterioles already pass directly into the capillaries. Arterioles contain muscle fibers that perform a contractile function and regulate the flow of blood into the capillaries. The layer of smooth muscle fibers in the walls of arterioles is very thin compared to the artery. The branching point of the arteriole into capillaries is called the precapillary, here the muscle fibers do not form a continuous layer, but are located diffusely. Another difference between a precapillary and an arteriole is the absence of a venule. The precapillary gives rise to numerous branches into the smallest vessels - capillaries.

capillaries

Capillaries are the smallest vessels, the diameter of which varies from 5 to 10 microns, they are present in all tissues, being a continuation of the arteries. Capillaries provide tissue metabolism and nutrition, supplying all body structures with oxygen. In order to ensure the transfer of oxygen and nutrients from the blood to the tissues, the capillary wall is so thin that it consists of only one layer of endothelial cells. These cells are highly permeable, so through them the substances dissolved in the liquid enter the tissues, and the metabolic products return to the blood.

The number of working capillaries in different parts of the body varies - in large numbers they are concentrated in the working muscles, which need a constant blood supply. For example, in the myocardium (the muscular layer of the heart), up to two thousand open capillaries are found per square millimeter, and in skeletal muscles there are several hundred capillaries per square millimeter. Not all capillaries function at the same time - many of them are in reserve, in a closed state, to start working when necessary (for example, during stress or increased physical activity).

Capillaries anastomize and, branching out, make up a complex network, the main links of which are:

Arterioles - branch into precapillaries;

Precapillaries - transitional vessels between arterioles and capillaries proper;

True capillaries;

Postcapillaries;

Venules are places where capillaries pass into veins.

Each type of vessel that makes up this network has its own mechanism for the transfer of nutrients and metabolites between the blood they contain and nearby tissues. The musculature of larger arteries and arterioles is responsible for the promotion of blood and its entry into the smallest vessels. In addition, the regulation of blood flow is also carried out by the muscular sphincters of pre- and post-capillaries. The function of these vessels is mainly distributive, while true capillaries perform a trophic (nutritional) function.

Veins are another group of vessels, the function of which, unlike arteries, is not to deliver blood to tissues and organs, but to ensure its entry into the heart. To do this, the movement of blood through the veins occurs in the opposite direction - from tissues and organs to the heart muscle. Due to the difference in functions, the structure of the veins is somewhat different from the structure of the arteries. The factor of strong pressure that blood exerts on the walls of blood vessels is much less manifested in veins than in arteries, therefore, the elastin-collagen framework in the walls of these vessels is weaker, and muscle fibers are also represented in a smaller amount. That is why veins that do not receive blood collapse.

Like arteries, veins branch widely to form networks. Many microscopic veins merge into single venous trunks that lead to the largest vessels that flow into the heart.

The movement of blood through the veins is possible due to the action of negative pressure on it in the chest cavity. Blood moves in the direction of the suction force into the heart and chest cavity, in addition, its timely outflow provides a smooth muscle layer in the walls of blood vessels. The movement of blood from the lower extremities upwards is difficult, therefore, in the vessels of the lower body, the muscles of the walls are more developed.

In order for the blood to move towards the heart, and not in the opposite direction, valves are located in the walls of the venous vessels, represented by a fold of the endothelium with a connective tissue layer. The free end of the valve freely directs blood towards the heart, and the outflow is blocked back.

Most veins run next to one or more arteries: small arteries usually have two veins, and larger ones have one. Veins that do not accompany any arteries occur in the connective tissue under the skin.

The walls of larger vessels are nourished by smaller arteries and veins that originate from the same trunk or from neighboring vascular trunks. The entire complex is located in the connective tissue layer surrounding the vessel. This structure is called the vascular sheath.

The venous and arterial walls are well innervated, contain a variety of receptors and effectors, well connected with the leading nerve centers, due to which the automatic regulation of blood circulation is carried out. Thanks to the work of the reflexogenic sections of blood vessels, the nervous and humoral regulation of metabolism in tissues is ensured.

Functional groups of vessels

According to the functional load, the entire circulatory system is divided into six different groups of vessels. Thus, in the human anatomy, shock-absorbing, exchange, resistive, capacitive, shunting and sphincter vessels can be distinguished.

Cushioning Vessels

This group mainly includes arteries in which a layer of elastin and collagen fibers is well represented. It includes the largest vessels - the aorta and the pulmonary artery, as well as the areas adjacent to these arteries. The elasticity and resilience of their walls provides the necessary shock-absorbing properties, due to which the systolic waves that occur during heart contractions are smoothed out.

The cushioning effect in question is also called the Windkessel effect, which in German means "compression chamber effect".

To demonstrate this effect, the following experiment is used. Two tubes are attached to a container filled with water, one of an elastic material (rubber) and the other of glass. From a hard glass tube, water splashes out in sharp intermittent shocks, and from a soft rubber one it flows evenly and constantly. This effect is explained by the physical properties of the tube materials. The walls of an elastic tube are stretched under the action of fluid pressure, which leads to the emergence of the so-called elastic stress energy. Thus, the kinetic energy that appears due to pressure is converted into potential energy, which increases the voltage.

The kinetic energy of cardiac contraction acts on the walls of the aorta and large vessels that depart from it, causing them to stretch. These vessels form a compression chamber: the blood entering them under the pressure of the systole of the heart stretches their walls, the kinetic energy is converted into the energy of elastic tension, which contributes to the uniform movement of blood through the vessels during the diastole.

The arteries located farther from the heart are of the muscular type, their elastic layer is less pronounced, they have more muscle fibers. The transition from one type of vessel to another occurs gradually. Further blood flow is provided by the contraction of the smooth muscles of the muscular arteries. At the same time, the smooth muscle layer of large elastic type arteries practically does not affect the diameter of the vessel, which ensures the stability of hydrodynamic properties.

Resistive vessels

Resistive properties are found in arterioles and terminal arteries. The same properties, but to a lesser extent, are characteristic of venules and capillaries. The resistance of the vessels depends on their cross-sectional area, and the terminal arteries have a well-developed muscle layer that regulates the lumen of the vessels. Vessels with a small lumen and thick, strong walls provide mechanical resistance to blood flow. The developed smooth muscles of resistive vessels provide regulation of the volumetric blood velocity, controls the blood supply to organs and systems due to cardiac output.

Vessels-sphincters

Sphincters are located in the terminal sections of the precapillaries; when they narrow or expand, the number of working capillaries that provide tissue trophism changes. With the expansion of the sphincter, the capillary goes into a functioning state, in non-working capillaries, the sphincters are narrowed.

exchange vessels

Capillaries are vessels that perform an exchange function, carry out diffusion, filtration and trophism of tissues. Capillaries cannot independently regulate their diameter, changes in the lumen of the vessels occur in response to changes in the sphincters of the precapillaries. The processes of diffusion and filtration occur not only in capillaries, but also in venules, so this group of vessels also belongs to the exchange ones.

capacitive vessels

Vessels that act as reservoirs for large volumes of blood. Most often, capacitive vessels include veins - the peculiarities of their structure allow them to hold more than 1000 ml of blood and throw it out as needed, ensuring the stability of blood circulation, uniform blood flow and full blood supply to organs and tissues.

In humans, unlike most other warm-blooded animals, there are no special reservoirs for depositing blood from which it could be ejected as needed (in dogs, for example, this function is performed by the spleen). Veins can accumulate blood to regulate the redistribution of its volumes throughout the body, which is facilitated by their shape. Flattened veins contain large volumes of blood, while not stretching, but acquiring an oval lumen shape.

Capacitive vessels include large veins in the womb, veins in the subpapillary plexus of the skin, and liver veins. The function of depositing large volumes of blood can also be performed by the pulmonary veins.

Shunt vessels

Shunt vessels are an anastomosis of arteries and veins, when they are open, blood circulation in the capillaries is significantly reduced. Shunt vessels are divided into several groups according to their function and structural features:

Cardiac vessels - these include the elastic type arteries, vena cava, pulmonary arterial trunk and pulmonary vein. They begin and end with a large and small circle of blood circulation.

Main vessels- large and medium-sized vessels, veins and arteries of the muscular type, located outside the organs. With their help, blood is distributed to all parts of the body.

Organ vessels - intraorgan arteries, veins, capillaries that provide trophism to the tissues of internal organs.

The most dangerous vascular diseases life-threatening: aneurysm of the abdominal and thoracic aorta, arterial hypertension, ischemic disease, stroke, renal vascular disease, atherosclerosis of the carotid arteries.

Diseases of the vessels of the legs- a group of diseases that lead to impaired blood circulation through the vessels, pathologies of the valves of the veins, impaired blood clotting.

Atherosclerosis of the lower extremities- the pathological process affects large and medium-sized vessels (aorta, iliac, popliteal, femoral arteries), causing their narrowing. As a result, the blood supply to the limbs is disturbed, severe pain appears, and the patient's performance is impaired.

Which doctor should I contact with vessels?

Vascular diseases, their conservative and surgical treatment and prevention are dealt with by phlebologists and angiosurgeons. After all the necessary diagnostic procedures, the doctor draws up a course of treatment, which combines conservative methods and surgery. Drug therapy of vascular diseases is aimed at improving blood rheology, lipid metabolism in order to prevent atherosclerosis and other vascular diseases caused by elevated blood cholesterol levels. (Read also:) Your doctor may prescribe vasodilators, medicines to treat underlying conditions, such as hypertension. In addition, the patient is prescribed vitamin and mineral complexes, antioxidants.

The course of treatment may include physiotherapy procedures - barotherapy of the lower extremities, magnetic and ozone therapy.

Education: Moscow State University of Medicine and Dentistry (1996). In 2003 he received a diploma from the educational and scientific medical center for the administration of the President of the Russian Federation.

Venous blood - what is it?

This is partly due to a number of factors:

It is thicker, saturated with platelets, and if damaged, venous bleeding is easier to stop.
The pressure in the veins is lower, so when the vessel is damaged, the volume of blood loss is lower.
Its temperature is higher, so in addition it prevents the rapid loss of heat through the skin.

The same blood flows in both arteries and veins. But its composition is changing. From the heart, it enters the lungs, where it is enriched with oxygen, which it transfers to the internal organs, providing them with nutrition. The veins that carry arterial blood are called arteries. They are more elastic, the blood moves through them in jerks.

What is the systemic and pulmonary circulation?

The aorta is the largest artery, which then divides into superior and inferior. Each of them supplies blood to the upper and lower parts of the body, respectively. Since the arterial “flows around” absolutely all organs, is supplied to them with the help of an extensive system of capillaries, this circle of blood circulation is called large. But the volume of the arterial at the same time is about 1/3 of the total.

How are veins different from arteries?

Arteries are more elastic. This is due to the fact that they need to maintain a certain rate of blood flow in order to deliver oxygen to the organs as quickly as possible. The walls of the veins are thinner, more elastic. This is due to a lower blood flow rate, as well as a large volume (venous is about 2/3 of the total volume).

What kind of blood is in the pulmonary vein?

What is saturated in venous blood?

Coming to the organs, the blood gives them oxygen, in return it is saturated with metabolic products and carbon dioxide, and acquires a dark red hue.

A large amount of carbon dioxide is the answer to the question why venous blood is darker than arterial blood and why veins are blue. It also contains nutrients that are absorbed in the digestive tract, hormones and other substances synthesized by the body.

Venous blood flow depends on its saturation and density. The closer to the heart, the thicker it is.

Why are tests taken from a vein?

How to distinguish venous bleeding from arterial:

Assess the volume and nature of the flowing blood. The venous one flows out in a uniform stream, the arterial one is thrown out in portions and even "fountains".
Assess what color the blood is. Bright scarlet indicates arterial bleeding, dark burgundy indicates venous bleeding.
Arterial is more liquid, venous is thicker.

Why does the venous fold faster?

It is thicker, contains a large number of platelets. A low blood flow rate allows the formation of a fibrin network at the site of damage to the vessel, for which platelets “cling”.

How to stop venous bleeding?

It is advisable to apply ice to the area around the wound. This will help slow down the circulation.

Video

The circulatory system includes:

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

The structure of the heart

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

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

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

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

Functions of the arteries

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

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

Functions of capillaries

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

Functions of the veins

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

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

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

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

The movement of blood through the vessels

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

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

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

Small circle of blood circulation

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

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

Systemic circulation

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

3. Art - arteries of the trunk and limbs.

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

6. PP - right atrium.

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

Personal circulation of the heart

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

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

Placental circulation

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

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

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

Circulatory pathologies

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

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

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

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

Regulation of blood circulation

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

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

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

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

The cardiovascular system

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

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

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

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What vessels carry blood away from the heart

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Circulation is the continuous movement of blood through a closed cardiovascular system, which ensures the exchange of gases in the lungs and body tissues.

The circulatory system consists of the heart and blood vessels that permeate all organs and tissues of the body.

The heart is the main organ of the circulatory system. It is a hollow muscular organ consisting of four chambers: two atria (right and left), separated by an interatrial septum, and two ventricles (right and left), separated by an interventricular septum. The right atrium communicates with the right ventricle through the tricuspid valve, and the left atrium communicates with the left ventricle through the bicuspid valve. The mass of the heart of an adult is on average about 250 g in women and about 330 g in men. The length of the heart is cm, the transverse size is 8-11 cm and the anteroposterior is 6-8.5 cm. The volume of the heart in men is on average cm 3, and in women cm 3.

The function of the heart is to rhythmically pump blood into the arteries, which comes to it through the veins. The heart contracts about once per minute at rest (1 time per 0.8 s). More than half of this time it rests - relaxes. The continuous activity of the heart consists of cycles, each of which consists of contraction (systole) and relaxation (diastole).

There are three phases of cardiac activity:

atrial contraction - atrial systole - takes 0.1 s
ventricular contraction - ventricular systole - takes 0.3 s
total pause - diastole (simultaneous relaxation of the atria and ventricles) - takes 0.4 s

Arteries are blood vessels that carry oxygenated blood from the heart to organs and tissues (only the pulmonary artery carries venous blood).

In humans, the diameter of the arteries ranges from 0.4 to 2.5 cm. The total volume of blood in the arterial system averages 950 ml. Arteries gradually branch into smaller and smaller vessels - arterioles, which pass into capillaries.

Capillaries (from the Latin “capillus” - hair) are the smallest vessels (the average diameter does not exceed 0.005 mm, or 5 microns), penetrating the organs and tissues of animals and humans that have a closed circulatory system. They connect small arteries - arterioles with small veins - venules. Through the walls of the capillaries, consisting of endothelial cells, there is an exchange of gases and other substances between the blood and various tissues.

Veins are blood vessels that carry blood saturated with carbon dioxide, metabolic products, hormones and other substances from tissues and organs to the heart (with the exception of pulmonary veins that carry arterial blood). The wall of the vein is much thinner and more elastic than the wall of the artery. Small and medium-sized veins are equipped with valves that prevent the reverse flow of blood in these vessels. In humans, the volume of blood in the venous system averages 3200 ml.

The movement of blood through the vessels was first described in 1628 by the English physician W. Harvey.

Harvey William () - English physician and naturalist. He created and introduced into the practice of scientific research the first experimental method - vivisection (live cutting).

In 1628 he published the book "Anatomical Studies on the Movement of the Heart and Blood in Animals", in which he described the large and small circles of blood circulation, formulated the basic principles of blood movement. The date of publication of this work is considered the year of the birth of physiology as an independent science.

In humans and mammals, blood moves through a closed cardiovascular system, consisting of a large and small circles of blood circulation (Fig.).

Small circle of blood circulation- pulmonary circle - serves to enrich the blood with oxygen in the lungs. It starts from the right ventricle and ends at the left atrium.

From the right ventricle of the heart, venous blood enters the pulmonary trunk (common pulmonary artery), which soon divides into two branches that carry blood to the right and left lungs.

In the systemic circulation, arterial blood flows through the arteries, and venous blood flows through the veins.

In a small circle, on the contrary, venous blood flows from the heart through the arteries, and arterial blood returns to the heart through the veins.

The movement of blood through the vessels

The highest pressure is in the aorta and large arteries (blood pressure). Arterial blood pressure is not a constant value [show]

Arterial blood pressure is not a constant value. In healthy people at rest, the maximum, or systolic, blood pressure is distinguished - the level of pressure in the arteries during the systole of the heart is about 120 mm Hg, and the minimum, or diastolic - the pressure level in the arteries during the diastole of the heart is about 80 mm Hg. Those. arterial blood pressure pulsates in time with the contractions of the heart: at the time of systole, it rises to damm Hg. Art., and during diastole decreases domm Hg. Art. These pulse pressure oscillations occur simultaneously with the pulse oscillations of the arterial wall.

Pulse- periodic jerky expansion of the walls of the arteries, synchronous with the contraction of the heart. The pulse is used to determine the number of heartbeats per minute. In an adult, the average heart rate is beats per minute. During physical exertion, the heart rate may increase up to beats. In places where the arteries are located on the bone and lie directly under the skin (radial, temporal), the pulse is easily felt. The propagation speed of the pulse wave is about 10 m/s.

Blood pressure is affected by:

work of the heart and force of cardiac contraction;
the size of the lumen of the vessels and the tone of their walls;
the amount of blood circulating in the vessels;
blood viscosity.

A person's blood pressure is measured in the brachial artery, comparing it with atmospheric pressure. For this, a rubber cuff connected to a pressure gauge is put on the shoulder. The cuff is inflated with air until the pulse at the wrist disappears. This means that the brachial artery is compressed by a lot of pressure, and blood does not flow through it. Then, gradually releasing air from the cuff, monitor the appearance of a pulse. At this moment, the pressure in the artery becomes slightly higher than the pressure in the cuff, and the blood, and with it the pulse wave, begins to reach the wrist. The readings of the pressure gauge at this time characterize the blood pressure in the brachial artery.

A persistent increase in blood pressure above the indicated figures at rest is called hypertension, and its decrease is called hypotension.

The level of blood pressure is regulated by nervous and humoral factors (see table).

(diastolic)

The speed of blood movement depends not only on the pressure difference, but also on the width of the bloodstream. Although the aorta is the widest vessel, it is the only one in the body and all the blood flows through it, which is pushed out by the left ventricle. Therefore, the speed here is maximum mm/s (see Table 1). As the arteries branch, their diameter decreases, but the total cross-sectional area of all arteries increases and the blood flow rate decreases, reaching 0.5 mm/s in the capillaries. Due to such a low rate of blood flow in the capillaries, the blood has time to give oxygen and nutrients to the tissues and take their waste products.

Redistribution of blood in the body

Blood circulation time

Circulation time is the time it takes for blood to travel through the entire circulation. A number of methods are used to measure blood circulation time. [show]

The circulation time of the blood in humans is on average about 27 systoles of the heart. With heartbeats per minute, the complete circulation of blood occurs in about a second. We must not forget, however, that the speed of blood flow along the axis of the vessel is greater than that of its walls, and also that not all vascular regions have the same length. Therefore, not all blood circulates so quickly, and the time indicated above is the shortest.

Studies on dogs have shown that 1/5 of the time of a complete blood circulation occurs in the pulmonary circulation and 4/5 in the systemic circulation.

Innervation of the heart. The heart, like other internal organs, is innervated by the autonomic nervous system and receives dual innervation. Sympathetic nerves approach the heart, which strengthen and accelerate its contractions. The second group of nerves - parasympathetic - acts on the heart in the opposite way: it slows down and weakens heart contractions. These nerves regulate the heart.

Innervation of blood vessels. Blood vessels are innervated by sympathetic nerves. Excitation propagating through them causes contraction of smooth muscles in the walls of blood vessels and constricts blood vessels. If you cut the sympathetic nerves going to a certain part of the body, the corresponding vessels will expand. Consequently, through the sympathetic nerves to the blood vessels, excitation is constantly supplied, which keeps these vessels in a state of some narrowing - vascular tone. When excitation increases, the frequency of nerve impulses increases and the vessels narrow more strongly - vascular tone increases. On the contrary, with a decrease in the frequency of nerve impulses due to inhibition of sympathetic neurons, vascular tone decreases and blood vessels dilate. To the vessels of some organs (skeletal muscles, salivary glands), in addition to vasoconstrictor, vasodilating nerves are also suitable. These nerves become excited and dilate the blood vessels of the organs as they work. Substances that are carried by the blood also affect the lumen of the vessels. Adrenaline constricts blood vessels. Another substance - acetylcholine - secreted by the endings of some nerves, expands them.

Regulation of the activity of the cardiovascular system. The blood supply of the organs varies depending on their needs due to the described redistribution of blood. But this redistribution can only be effective if the pressure in the arteries does not change. One of the main functions of the nervous regulation of blood circulation is to maintain a constant blood pressure. This function is carried out reflexively.

Hygiene of cardiac activity

First aid for wounds and bleeding

Injuries are often accompanied by bleeding. There are capillary, venous and arterial bleeding.

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