Vessels of the circulatory system. The main arteries of the small pelvis. Structure and classification

Blood vessels - essential part organism, which is part of the circulatory system and permeates almost the entire human body. They are absent only in the skin, hair, nails, cartilage and cornea of ​​​​the eyes. And if they are assembled and stretched into one straight line, then the total length will be about 100 thousand km.

These tubular elastic formations function continuously, transferring blood from the constantly contracting heart to all corners. human body, oxygenating them and nourishing them, and then bringing it back. By the way, the heart pushes more than 150 million liters of blood through the vessels in a lifetime.

The main types of blood vessels are: capillaries, arteries, and veins. Each type performs its specific functions. It is necessary to dwell on each of them in more detail.

Division into types and their characteristics

The classification of blood vessels is different. One of them involves division:

• on arteries and arterioles;
• precapillaries, capillaries, postcapillaries;
• veins and venules;
• arteriovenous anastomoses.

They represent a complex network, differing from each other in structure, size and their specific function, and form two closed systems connected to the heart - circles of blood circulation.

The following can be distinguished in the device: the walls of both arteries and veins have a three-layer structure:

• an inner layer that provides smoothness, built from the endothelium;
• medium, which is a guarantee of strength, consisting of muscle fibers, elastin and collagen;
• top layer of connective tissue.

Differences in the structure of their walls are only in the width of the middle layer and the predominance of either muscle fibers or elastic ones. And also in the fact that venous - contain valves.

arteries

They deliver blood rich beneficial substances and oxygen from the heart to all cells of the body. By structure, human arterial vessels are more durable than veins. Such a device (more dense and durable middle layer) allows them to withstand the stress of high internal blood pressure.

The names of arteries, as well as veins, depend on:

Once upon a time it was believed that the arteries carry air and therefore the name is translated from Latin as “containing air”.

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There are such types:

Arteries, leaving the heart, become thinner to small arterioles. This is the name of the thin branches of the arteries, passing into the precapillaries, which form the capillaries.

These are the thinnest vessels, with a diameter much thinner than a human hair. This is the longest part of the circulatory system, and their total in the human body ranges from 100 to 160 billion.

The density of their accumulation is different everywhere, but the highest in the brain and myocardium. They consist only of endothelial cells. They carry out very important activities: chemical exchange between bloodstream and fabrics.

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The capillaries are further connected to the post-capillaries, which become venules - small and thin venous vessels flowing into the veins.

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it blood vessels, according to which the oxygen-depleted blood is coming back to the heart.

The walls of the veins are thinner than the walls of the arteries, because there is no strong pressure. The layer of smooth muscles in the middle wall of the vessels of the legs is most developed, because moving up is not an easy job for the blood under the action of gravity.

Venous vessels (all but the superior and inferior vena cava, pulmonary, collar, renal veins and veins of the head) contain special valves that ensure the movement of blood to the heart. The valves block the return flow. Without them, the blood would drain to the feet.

Arteriovenous anastomoses are branches of arteries and veins connected by fistulas.

Separation by functional load

There is another classification that blood vessels undergo. It is based on the difference in the functions they perform.

There are six groups:

There is another very interesting fact concerning this unique system human body. In the presence of excess weight in the body, more than 10 km (per 1 kg of fat) of additional blood vessels are created. It all creates a very heavy load to the heart muscle.

heart disease and overweight and even worse, obesity is always very tightly linked. But the good thing is that the human body is capable of reverse process- removal of unnecessary vessels when getting rid of excess fat(precisely from him, and not just from extra pounds).

What role do blood vessels play in human life? In general, they perform a very serious and important work. They are the delivery vehicle. essential substances and oxygen to every cell of the human body. They also remove carbon dioxide and waste from organs and tissues. Their importance cannot be overestimated.

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Blood circulates throughout the body through a complex system of blood vessels. This transport system delivers blood to every cell in the body so that it "exchanges" oxygen and nutrients for waste products and carbon dioxide.

Some numbers

There are over 95,000 kilometers of blood vessels in the body of a healthy adult. More than seven thousand liters of blood are pumped through them daily.

The size of the blood vessels varies from 25 mm(aortic diameter) up to eight microns(capillary diameter).

What are the vessels?

All vessels in the human body can be divided into arteries, veins and capillaries. Despite the difference in size, all vessels are arranged approximately the same.

Inside their walls are lined flat cells- endothelium. With the exception of capillaries, all vessels contain tough and elastic collagen fibers and smooth muscle fibers that can contract and expand in response to chemical or neural stimuli.

arteries bear rich in oxygen blood from the heart to tissues and organs. This blood is bright red so all the arteries look red.

Blood moves through the arteries from great strength, so their walls are thick and elastic. They are made up of large amounts of collagen, which allows them to withstand blood pressure. The presence of muscle fibers helps turn the intermittent supply of blood from the heart into a continuous flow in the tissues.

As they move away from the heart, the arteries begin to branch, and their lumen becomes thinner and thinner.

The thinnest vessels that deliver blood to every corner of the body are capillaries. Unlike arteries, their walls are very thin, so oxygen and nutrients can pass through them into the cells of the body. This same mechanism allows waste products and carbon dioxide to pass from the cells into the bloodstream.

Capillaries, through which oxygen-poor blood flows, gather into thicker vessels - veins. Due to lack of oxygen venous blood is darker than arterial, and the veins themselves appear bluish. They carry blood to the heart and from there to the lungs for oxygenation.

The walls of the veins are thinner than arterial ones, since venous blood does not create such strong pressure as arterial blood.

What are the largest blood vessels in the human body?

The two largest veins in the human body are inferior and superior vena cava. They bring blood to right atrium: the superior vena cava - from the upper body, and the inferior vena cava - from the bottom.

Aorta is the largest artery in the body. It comes out of the left ventricle of the heart. Blood enters the aorta through the aortic canal. The aorta branches into large arteries that carry blood throughout the body.

What is blood pressure?

Blood pressure is the force with which blood presses against the walls of the arteries. It increases when the heart contracts and pumps out blood, and decreases when the heart muscle relaxes. Blood pressure is stronger in the arteries and weaker in the veins.

Blood pressure is measured special device – tonometer. Pressure indicators are usually written in two digits. So, normal pressure for an adult is considered score 120/80.

First number - systolic pressure is the pressure during heart contraction. Second - diastolic pressure- pressure during relaxation of the heart.

Pressure is measured in the arteries and is expressed in millimeters of mercury. In the capillaries, the pulsation of the heart becomes imperceptible and the pressure in them drops to about 30 mm Hg. Art.

A blood pressure reading can tell your doctor how your heart is working. If one or both numbers are above normal, this indicates high blood pressure. If lower - about lowered.

High blood pressure indicates that the heart is working with excess load: it needs more effort to push blood through the vessels.

It also suggests that a person has an increased risk of heart disease.

blood vessels in the human body great importance, thanks to them, blood from the heart muscle flows to all tissues of the body and vice versa. The scheme of vessels in the bloodstream is intertwined and makes it possible to ensure the work of tissues, systems, organs, valves without interruption. total length human vessels in the human body reaches one hundred thousand kilometers.

Human circulatory system: structure and functions

Blood vessels are structures similar to tubes of various lengths and diameters through which blood moves. The heart muscle is a kind of pump, so the blood under powerful pressure circulates throughout the body.

The speed of blood circulation is quite high, since the system of movement of the biofluid itself is closed. To put it simply, human vessels are flexible, elastic tubes through which blood flows. Vessels are distinguished by good strength, they can withstand even chemical exposure. The highest strength is associated with the structure.

The structure is not complicated, the vessels include 3 main layers:

1. Layering inside. The layer consists of a thin epithelium, which gives smoothness to the walls of blood vessels, provides protection from toxic enzymes of the blood composition.
2. middle layer. Slightly thicker than a layer of epithelium, consists of collagen, muscle tissue. The layer is elastic, gives the vessels strength.
3. outer layer. A layer of fabric made of fibers of a non-dense texture is presented, which creates protection against the negative effects of a number of factors.

The entire network of blood vessels, as well as types of blood vessels, consists of millions of small nerve endings, which are called in medical practice effectors, receptor compounds. They are interconnected with nerve endings, which reflexively provide nervous regulation of blood flow in the vascular cavity. How are blood vessels classified?

Medicine subdivides the system according to the type of structure, characteristics, functional purpose into 3 types and are called: arteries; veins; capillaries.

Each of the varieties of vessels is of great importance in the structure of the overall network. Below we consider the functions of all types of blood vessels.

Human arteries and capillaries

Arteries are blood vessels that originate from the heart muscle and myocardium and go to the organs of the human body. It must be said that in ancient medical practice these tubes were considered to carry air, since when a corpse was opened, they were empty. The movement of blood through the arteries occurs under highest pressure. The walls of the cavity are quite strong, elastic, several millimeters thick in density in different anatomical regions.

Arteries can be divided into 2 groups:

• By elasticity;
• By muscle type.

The arteries of the first group are the aorta and its large branches, they are located as close as possible to the heart muscle, they drive blood away - these are their the main task. Under the influence of powerful rhythms of the heart, blood under the strongest pressure flows through the arteries. The walls of the artery from this group are quite strong and perform the functions of mechanics.

Arteries from the second group are represented by a large number of small and medium-sized arteries. In them, the pressure of the biofluid is no longer so great, so the vascular walls are constantly contracting for further movement of blood. The walls of the arteries are composed of a smooth muscle structure with fibers, the walls are constantly narrowing or expanding in order to ensure a constant flow of blood along their paths.

Capillaries are small vessels present in the vascular system.

They are located between the arteries, vena cava. The diameter of the capillaries is approximately 5-10 microns. They take part in the organization of the exchange process between gaseous substances and special nutrients between tissues and the biofluid itself. Molecules containing oxygen, carbon dioxide, and metabolic products penetrate the tissues and organs through the finest structure of the capillary walls.

Veins and functions: human blood vessels

Veins, on the contrary, carry a different function - they create the flow of blood to the heart. The active movement of blood through the cavity of the veins goes in the opposite direction from the flow of blood through the arterial vessels or capillaries. The blood in the veins does not pass under significant pressure, so the walls of the veins do not contain much muscle structure.

The vascular system is closed, it constantly circulates biofluid from the heart muscle throughout the body, and then back through the veins to the myocardium. There is a complete cycle that ensures the full life of a person. The circulatory system of blood vessels is not only a "carrier" of blood, but carries the most powerful functionality for the body as a whole.

Anatomically, there are six functions:

• shock-absorbing;
• resistive;
• exchange;
• capacitive;
• Shunting.

Vessels, like other organs, can be affected by specific diseases, have pathologies, abnormal phenomena that are the result of other dangerous diseases and their cause. In medical practice, there are a number of dangerous pathologies vessels with severe leakage and consequences for the human body. Which?

The most common pathologies are as follows:

• aortic aneurysm;
• Arteriosclerosis;
• Pulmonary artery pathology, birth defects;
• Varicose veins;
• Thrombophlebitis.

Human vessels in the human body are a special system for moving biofluid to the most important systems and organs, tissues and muscles. This system removes decay products in the process of life. The circulatory system must function correctly, therefore, with any development negative symptoms you need to see a doctor as soon as possible and start prevention and treatment. Only a doctor can find out what is the lesion of arterial or venous vessels.

Vascular doctor

In this situation, you need to contact the following narrow specialists.

Namely:

• Phlebologist;
• Vascular surgeon;
• Angiologist.

Together with doctors, I often work with specialists who specialize in the field of human examination: ultrasound diagnostics, angiography. If a person does not know which doctor to go to, then it would be right to make an appointment with a therapist, and he will already write out a referral to a narrow specialist. A phlebologist is a doctor who studies the anatomy and physiology of a complete and pathological change in blood flow, a clinic for diseases of the vessels of the legs.

The competence of the phlebologist includes the diagnosis and treatment of such pathologies.:

• varicose disease;
• Venous insufficiency, in a chronic form;
• Thrombosis;
• thrombophlebitis;
• Trophic ulcers.

People with a genetic predisposition to develop varicose veins should visit a doctor from time to time in order to diagnose the pathology in time.

Blood vessels (video)

Blood vessels are important in the human body and in the development pathological condition problems can arise, which is why it is important to identify the disease in time and treat it. It is also important to take preventive measures vascular pathologies.

Carries out the transport of liquids and substances dissolved in them (nutrient, waste products of cells, hormones, oxygen, etc.). The cardiovascular system is the most important integrating system of the body. The heart in this system acts as a pump, and the vessels serve as a kind of pipeline through which everything necessary is delivered to every cell of the body.

Blood vessels

Among the blood vessels, larger ones are distinguished - arteries and smaller ones arterioles that carry blood from the heart to the organs venules and veins through which blood returns to the heart, and capillaries, through which blood passes from arterial to venous vessels (Fig. 1). The most important metabolic processes between blood and organs occur in the capillaries, where the blood gives off the oxygen and nutrients contained in it to the surrounding tissues, and takes metabolic products from them. Due to the constant blood circulation, the optimal concentration of substances in the tissues is maintained, which is necessary for the normal functioning of the body.

Blood vessels form a large and small circles of blood circulation, which begin and end in the heart. The volume of blood in a person weighing 70 kg is 5-5.5 liters (approximately 7% of body weight). The blood consists of a liquid part - plasma and cells - erythrocytes, leukocytes and platelets. Due to the high speed of circulation, 8000-9000 liters of blood flows through the blood vessels daily.

In different vessels, blood moves from different speed. In the aorta emerging from the left ventricle of the heart, the blood velocity is the highest - 0.5 m / s, in the capillaries - the smallest - about 0.5 mm / s, and in the veins - 0.25 m / s. Differences in the speed of blood flow are due to the unequal width overall cross section bloodstream in different areas. The total lumen of the capillaries is 600-800 times greater than the lumen of the aorta, and the width of the lumen of the venous vessels is approximately 2 times greater than that of the arterial ones. According to the laws of physics, in a system of communicating vessels, the fluid flow rate is higher in narrower places.

The wall of arteries is thicker than that of veins and consists of three sheath layers (Fig. 2). Middle shell It is built from bundles of smooth muscle tissue, between which elastic fibers are located. In the inner shell, lined from the side of the lumen of the vessel by the endothelium, and on the border between the middle and outer shells have elastic membranes. Elastic membranes and fibers form a kind of skeleton of the vessel, giving its walls strength and elasticity.

In the wall closest to the heart large arteries(aorta and its branches) there are relatively more elastic elements. This is due to the need to counteract the stretching of the mass of blood that is ejected from the heart during its contraction. As they move away from the heart, the arteries divide into branches and become smaller. In medium and small arteries, in which the inertia of the cardiac impulse is weakened and its own contraction of the vascular wall is required for the further movement of blood, muscle tissue is well developed. Under the influence nervous irritations such arteries are able to change their lumen.

The walls of the veins are thinner, but consist of the same three shells. Since they have much less elastic and muscle tissue, the walls of the veins can collapse. A feature of the veins is the presence in many of them of valves that prevent the reverse flow of blood. Vein valves are pocket-like outgrowths of the inner lining.

Lymphatic vessels

have a relatively thin wall and lymphatic vessels . They also have many valves that allow lymph to move in only one direction - towards the heart.

Lymphatic vessels and flowing through them lymph are also related to the cardiovascular system. Lymphatic vessels, together with veins, provide absorption from tissues of water with substances dissolved in it: large protein molecules, fat droplets, cell decay products, foreign bacteria, and others. The smallest lymphatic vessels lymph capillaries- closed at one end and located in the organs next to the blood capillaries. The permeability of the walls of the lymphatic capillaries is higher than that of the blood capillaries, and their diameter is larger, therefore, those substances that, due to their large size, cannot get from the tissues into blood capillaries enter the lymphatic capillaries. Lymph in its composition resembles blood plasma; of the cells it contains only leukocytes (lymphocytes).

The lymph formed in the tissues through the lymphatic capillaries, and then through the larger lymphatic vessels, constantly flows into the circulatory system, into the veins great circle circulation. During the day, 1200-1500 ml of lymph enters the blood. It is important that before the lymph flowing from the organs enters the circulatory system and mixes with the blood, it passes through the cascade lymph nodes, which are located along the lymphatic vessels. AT lymph nodes substances alien to the body and pathogens are retained and neutralized, and the lymph is enriched with lymphocytes.

The location of the vessels

Rice. 3. Venous system
Rice. 3a. Arterial system

The distribution of blood vessels in the human body obeys certain patterns. Arteries and veins usually go together, with small and medium-sized arteries accompanied by two veins. Lymphatic vessels also pass through these vascular bundles. The course of the vessels corresponds to the general plan of the structure of the human body (Figs. 3 and 3a). The aorta and large veins run along the spinal column, branches extending from them are located in the intercostal spaces. On the limbs, in those departments where the skeleton consists of one bone (shoulder, thigh), there is one main artery accompanied by veins. Where there are two bones in the skeleton (forearm, lower leg), there are also two main arteries, and with a radial structure of the skeleton (hand, foot), the arteries are located corresponding to each digital ray. Vessels are directed to organs shortest distance. Vascular bundles pass in hidden places, in channels formed by bones and muscles, and only on the flexion surfaces of the body.

In some places, the arteries are located superficially, and their pulsation can be felt (Fig. 4). So, the pulse can be examined on the radial artery in the lower part of the forearm or on carotid artery in the lateral region of the neck. In addition, superficial arteries can be pressed against adjacent bone to stop bleeding.

Both the branches of the arteries and the tributaries of the veins are widely interconnected, forming the so-called anastomoses. In case of violations of blood inflow or its outflow through the main vessels, anastomoses contribute to the movement of blood in various directions and its movement from one area to another, which leads to the restoration of blood supply. This is especially important in case of a sharp violation of the patency of the main vessel in atherosclerosis, trauma, injury.

The most numerous and thinnest vessels are blood capillaries. Their diameter is 7-8 microns, and the thickness of the wall formed by one layer of endothelial cells lying on the basement membrane is about 1 micron. The exchange of substances between blood and tissues takes place through the wall of capillaries. Blood capillaries are found in almost all organs and tissues (they are not only in the outermost layer of the skin - the epidermis, cornea and lens of the eye, hair, nails, tooth enamel). The length of all capillaries in the human body is approximately 100,000 km. If they are stretched in one line, then you can encircle the globe along the equator 2.5 times. Inside the body, the blood capillaries are interconnected, forming capillary networks. Blood enters the capillary networks of organs through the arterioles, and flows out through the venules.

microcirculation

The movement of blood through the capillaries, arterioles and venules, and lymph through the lymphatic capillaries is called microcirculation, and the smallest vessels themselves (their diameter, as a rule, does not exceed 100 microns) - microvasculature. The structure of the last channel has its own characteristics in different bodies, and the subtle mechanisms of microcirculation allow you to regulate the activity of the organ and adapt it to the specific conditions of the functioning of the body. At every moment it works, that is, it is open and lets blood through, only part of the capillaries, while others remain in reserve (closed). So, at rest, more than 75% of the capillaries of skeletal muscles can be closed. At physical activity most of them open, as the working muscle requires an intense influx nutrients and oxygen.

The function of blood distribution in the microvasculature is performed by arterioles, which have a well-developed muscular membrane. This allows them to narrow or expand, changing the amount of blood entering the capillary networks. This feature of the arterioles allowed the Russian physiologist I.M. Sechenov call them "cranes circulatory system».

The study of the microvasculature is possible only with the help of a microscope. That is why an active study of microcirculation and the dependence of its intensity on the state and needs of surrounding tissues became possible only in the 20th century. Capillary researcher August Krogh was awarded in 1920 Nobel Prize. In Russia, a significant contribution to the development of ideas about microcirculation in the 70-90s was made by scientific schools academicians V.V. Kupriyanov and A.M. Chernukha. At present, thanks to modern technical advances, microcirculation research methods (including those using computer and laser technologies) are widely used in clinical practice and experimental work.

Arterial pressure

An important characteristic of activity of cardio-vascular system serves as the value of blood pressure (BP). In connection with the rhythmic work of the heart, it fluctuates, rising during systole (contraction) of the ventricles of the heart and decreasing during diastole (relaxation). The highest blood pressure observed during systole is called the maximum, or systolic. The lowest blood pressure is called the minimum, or diastolic. BP is usually measured in the brachial artery. In adults healthy people the maximum blood pressure is normally 110-120 mm Hg, and the minimum is 70-80 mm Hg. In children, due to the greater elasticity of the arterial wall, blood pressure is lower than in adults. With age, when the elasticity of the vascular walls decreases due to sclerotic changes, the level of blood pressure rises. During muscle work, systolic blood pressure increases, while diastolic blood pressure does not change or decreases. The latter is explained by the expansion of blood vessels in the working muscles. Reducing the maximum blood pressure below 100 mm Hg. called hypotension, and an increase above 130 mm Hg. - hypertension.

BP level maintained complex mechanism involving the nervous system and various substances carried by the blood itself. So, there are vasoconstrictor and vasodilating nerves, the centers of which are located in the oblong and spinal cord. There is a significant amount chemical substances, under the influence of which the lumen of blood vessels changes. Some of these substances are formed in the body itself (hormones, mediators, carbon dioxide), others come from the external environment (drugs and nutrients). During emotional stress(anger, fear, pain, joy) the hormone adrenaline enters the blood from the adrenal glands. It enhances the activity of the heart and constricts blood vessels, while increasing blood pressure. This is how the hormone works. thyroid gland thyroxine.

Every person should know that his body has powerful self-regulation mechanisms that support normal condition vessels and blood pressure. This provides the necessary blood supply to all tissues and organs. However, it is necessary to pay attention to failures in the activity of these mechanisms and, with the help of specialists, to identify and eliminate their cause.

- the most important physiological mechanism responsible for the nutrition of body cells and excretion from the body harmful substances. The main structural component is the vessels. There are several types of vessels that differ in structure and function. Vascular disease leads to serious consequences negatively affecting the entire body.

General information

The blood vessel is hollow formations in the form of a tube penetrating the tissues of the body. Blood is transported through the vessels. In humans, the circulatory system is closed, as a result of which the movement of blood in the vessels occurs under high pressure. Transportation through the vessels is carried out due to the work of the heart, which performs a pumping function.

Blood vessels can change under the influence of certain factors. Depending on the external influence they expand or contract. The process is regulated nervous system. The ability to expand and contract provides specific structure human blood vessels.

Vessels are made up of three layers:

• External. The outer surface of the vessel is covered connective tissue. Its function is to protect against mechanical stress. Also, the task of the outer layer is to separate the vessel from nearby tissues.
• Average. Contains muscle fibers characterized by mobility and elasticity. They provide the ability of the vessel to expand or contract. In addition, the function of the muscle fibers of the middle layer is to maintain the shape of the vessel, due to which there is a full-fledged unhindered blood flow.
• Interior. The layer is represented by flat single-layer cells - endothelium. The tissue makes the vessels smooth inside, thereby reducing the resistance to blood flow.

It should be noted that the walls of venous vessels are significantly thinner arteries. This is due to a small amount of muscle fibers. Traffic venous blood occurs under the action of the skeletal, while the arterial moves due to the work of the heart.

In general, a blood vessel is the main structural component of the cardiovascular system, through which blood moves to tissues and organs.

Types of vessels

Previously, the classification of human blood vessels included only 2 types - arteries and veins. At the moment, 5 types of vessels are distinguished, differing in structure, size, and functional tasks.

Types of blood vessels:

• . Vessels provide the movement of blood from the heart to the tissues. Characterized by thick walls high content muscle fibres. Arteries are constantly narrowing and expanding, depending on the level of pressure, preventing excess blood flow to some organs and deficiency in others.
• Arterioles. Small vessels that are the terminal branches of arteries. Composed primarily of muscle tissue. They are a transitional link between arteries and capillaries.
• capillaries. smallest vessels penetrating organs and tissues. A feature is very thin walls through which blood is able to penetrate outside the vessels. The capillaries supply the cells with oxygen. At the same time, blood is saturated carbon dioxide, which is then excreted from the body through the veins.

• Venules. They are small vessels that connect capillaries and veins. They transport oxygen used by cells, residual waste products, and dying blood particles.
• Vienna. They ensure the movement of blood from the organs to the heart. Contain fewer muscle fibers, which is associated with low resistance. Because of this, the veins are less thick and more likely to be damaged.

Thus, several types of vessels are distinguished, the totality of which forms the circulatory system.

Functional groups

Depending on the location, the vessels perform different functions. In accordance with the functional load, the structure of the vessels differs. Currently there are 6 main functional groups.

The functional groups of vessels include:

• Shock-absorbing. Vessels belonging to this group have the most large quantity muscle fibres. They are the largest in the human body and are located in close proximity to the heart (aorta, pulmonary artery). These vessels are the most elastic and resilient, which is necessary to smooth out the systolic waves that form during cardiac contraction. The amount of muscle tissue in the walls of blood vessels decreases depending on the degree of remoteness from the heart.
• Resistive. These include the final, thinnest blood vessels. Due to the smallest lumen, these vessels provide the greatest resistance to blood flow. The resistive vessels contain many muscle fibers that control the lumen. Due to this, the volume of blood entering the body is regulated.
• Capacitive. They perform a reservoir function, keeping large volumes of blood. AT this group includes large venous vessels that can hold up to 1 liter of blood. Capacitive vessels regulate the movement of blood to, controlling its volume in order to reduce the workload on the hearts.
• Sphincters. They are located in the terminal branches of small capillaries. By constriction and expansion, the sphincter vessels control the amount of incoming blood. With the narrowing of the sphincters, the blood does not flow, as a result of which the trophic process is disturbed.
• Exchange. Represented by the terminal branches of capillaries. The exchange of substances takes place in the vessels, providing nutrition to the tissues and removal of harmful substances. Similar functional tasks perform venules.
• Shunting. Vessels provide communication between veins and arteries. This does not affect the capillaries. These include atrial, main and organ vessels.

In general, there are several functional groups of vessels that provide a full flow of blood and nutrition of all body cells.

Regulation of vascular activity

The cardiovascular system immediately responds to external changes or impact negative factors inside the body. For example, when there is stressful situations palpitations are noted. The vessels narrow, due to which it increases, and muscle tissues are supplied with a large amount of blood. Being at rest, more blood flows to the brain tissues and digestive organs.

The nerve centers located in the cerebral cortex and hypothalamus are responsible for the regulation of the cardiovascular system. The signal arising from the reaction to the stimulus affects the center that controls vascular tone. Later, through nerve fibers the impulse travels to the vascular walls.

In the walls of blood vessels there are receptors that perceive pressure surges or changes in the composition of the blood. Vessels are also able to transmit nerve signals to the appropriate centers, notifying about possible danger. This makes it possible to adapt to changing environmental conditions, such as changes in temperature.

The work of the heart and blood vessels is affected. This process called humoral regulation. Biggest Influence adrenaline, vasopressin, acetylcholine exert on the vessels.

Thus, the activity of the cardiovascular system is regulated by the nerve centers of the brain and endocrine glands responsible for the production of hormones.

Diseases

Like any organ, the vessel can be affected by diseases. The causes of the development of vascular pathologies are often associated with in the wrong way human life. Less often, diseases develop due to congenital abnormalities, acquired infections, or against the background of concomitant pathologies.

Common vascular diseases:

• . It is considered one of the most dangerous pathologies of the cardiovascular system. With this pathology, blood flow through the vessels that feed the myocardium, the heart muscle, is disrupted. Gradually, due to atrophy, the muscle weakens. As a complication are a heart attack, as well as heart failure, in which it is possible sudden stop hearts.
• Cardiopsychoneurosis. A disease in which the arteries are affected due to malfunctions nerve centers. Spasm develops in the vessels due to excessive sympathetic influence on muscle fibers. Pathology often manifests itself in the vessels of the brain, also affects the arteries located in other organs. The patient has intense pain, interruptions in the work of the heart, dizziness, changes in pressure.
• Atherosclerosis. A disease in which the walls of blood vessels narrow. This leads to a range of negative consequences, including atrophy of the supply tissues, as well as a decrease in the elasticity and strength of the vessels located behind the narrowing. is a provoking factor in many cardiovascular diseases, and leads to the formation of blood clots, heart attack, stroke.
• aortic aneurysm. With such a pathology, saccular bulges form on the walls of the aorta. Later, it forms scar tissue and tissues gradually atrophy. As a rule, pathology develops against the background chronic form hypertension, infectious lesions, including syphilis, as well as anomalies in the development of the vessel. If left untreated, the disease provokes rupture of the vessel and death of the patient.
• . Pathology in which the veins are affected lower extremities. They expand greatly due to increased load, while the outflow of blood to the heart is greatly slowed down. This leads to swelling and pain. Pathological changes in the affected veins of the legs are irreversible, the disease in the later stages is treated only surgically.

• . The disease in which varicose veins develops in the hemorrhoidal veins that feed the lower intestines. Late stages diseases are accompanied by loss hemorrhoids, heavy bleeding, violation of the chair. As a complication are infectious lesions including blood poisoning.
• Thrombophlebitis. Pathology affects the venous vessels. The danger of the disease is explained potential opportunity separation of a blood clot, due to which the lumen is blocked pulmonary arteries. However, large veins are rarely affected. Thrombophlebitis affects small veins, the defeat of which does not pose a significant danger to life.

There is a wide range of vascular pathologies that Negative influence for the work of the whole organism.

While watching the video, you will learn about the cardiovascular system.

Blood vessels - important element human body, responsible for the movement of blood. There are several types of vessels that differ in structure, functionality, size, location.