Types, functions, structure of human blood vessels, vascular diseases. Human cardiovascular system The structure of the human vascular system

If you follow the definition, the blood vessels of a person are flexible, elastic tubes through which the force of a rhythmically contracting heart or a pulsating vessel moves blood through the body: to organs and tissues through arteries, arterioles, capillaries, and from them to the heart through venules and veins, blood flow circulates.

Of course, this is the cardiovascular system. Thanks to blood circulation, oxygen, as well as nutrients are delivered to the organs and tissues of the body, and carbon dioxide and other products and vital functions are excreted.

Blood and nutrients are delivered through vessels, a kind of "hollow tubes", without which nothing would have happened. A kind of "highways". In fact, our vessels are not “hollow tubes”. Of course, they are much more complex and do their job properly. It depends on the health of the vessels - how exactly, with what speed, under what pressure and to which parts of the body our blood will reach. A person depends on the state of blood vessels.

This is how a person would look if only one circulatory system remained of him .. On the right is a person's finger, consisting of an incredible set of vessels.

Human blood vessels, interesting facts

• The largest vein in the human body is the inferior vena cava. Through this vessel, blood returns from the lower body to the heart.
• The human body contains both large and small vessels. The second group includes capillaries. Their diameter does not exceed 8-10 microns. It's so small that red blood cells have to line up and literally squeeze through one at a time.
• The speed of blood flow through the vessels varies depending on their types and sizes. If the capillaries do not allow blood to exceed the speed of 0.5 mm / sec, then in the inferior vena cava the speed reaches 20 cm / sec.
• Every second, 25 billion cells pass through the circulatory system. It takes 60 seconds for the blood to make a full circle throughout the body. It is noteworthy that in a day blood has to flow through the vessels, overcoming 270-370 km.
• If all the blood vessels were to be expanded to their full length, they would be able to wrap the planet Earth twice. Their total length is 100,000 km.
• The capacity of all human blood vessels reaches 25-30 liters. As you know, an adult body on average holds no more than 6 liters of blood, however, accurate data can only be found out by studying individual characteristics organism. As a result, blood has to constantly move through the vessels in order to maintain the work of muscles and organs throughout the body.
• There is only one place in the human body where the circulatory system is absent. This is the cornea of \u200b\u200bthe eye. Since its feature is perfect transparency, it cannot contain vessels. However, it gets oxygen directly from the air.
• Since the thickness of the vessels does not exceed 0.5 mm, during operations, surgeons use instruments that are even thinner. For example, sutures require a thread that is thinner than a human hair. To cope with it, doctors look through a microscope.
• It is estimated that it takes 1,120,000 mosquitoes to suck all the blood out of an average adult.
• Your heart beats about 42,075,900 times per year, and over an average life span - about 3 billion, give or take a few million.
• Throughout our lives, the heart pushes about 150 million liters of blood.

Now we are convinced that our circulatory system is unique, and the heart is the strongest muscle in our body.

At a young age, no one worries about any vessels, and so everything is in order! But after twenty years, after the body has grown, metabolism begins to slow down imperceptibly, motor activity decreases over the years, therefore the belly grows, excess weight appears, high blood pressure and, suddenly, and you are only fifty years old! What should I do?

Moreover, plaques can form anywhere. If in the vessels of the brain, then a stroke is possible. The vessel bursts and that's it. If in the aorta, then a heart attack is possible. Smokers usually barely walk by the age of sixty, all

Look, cardiovascular diseases are confidently ranked first in the number of deaths.

That is, your inaction for thirty years can clog the vascular system with all sorts of rubbish. Then a natural question arises, how to get out, then everything from there, so that the vessels are clean? How to get rid of cholesterol plaques, for example? Well, an iron pipe can be cleaned with a brush, but human vessels are far from being a pipe.

Although, there is such a procedure. Angioplasty is called, mechanically drilled out or crushed by a balloon with a balloon and put a stent. People love to do a procedure such as plasmapheresis. Yes, it is a very valuable procedure, but only where it is justified, in case of strictly outlined diseases. It is extremely dangerous to do it to cleanse blood vessels and improve health. Remember the famous Russian athlete, record holder in power sports, as well as TV and radio host, showman, actor and entrepreneur, Vladimir Turchinsky, who died after this procedure.

They came up with laser cleaning of blood vessels, that is, a light bulb is inserted into the vein and it glows inside the vessel and does something there. It seems like there is laser evaporation of plaques. It is clear that this procedure has been put on a commercial basis. The wiring is complete.

Basically, a person believes doctors, and therefore pays money to restore his health. At the same time, the bulk does not want to change anything in their lives. How can you give up dumplings, sausages, bacon or beer with a cigarette. Logically, it turns out that if you have problems with blood vessels, then first you need to remove the damaging factor, for example, quit smoking. If you are overweight, balance your diet, do not overeat at night. Move more. Change your lifestyle. Well, we can't!

No, as usual, we hope for a miracle pill, for a miracle procedure or just for a miracle. Miracles do happen, but they are extremely rare. Well, you paid the money, cleaned the vessels, for a while the condition improved, then everything quickly returns to its original state. ... You don't want to change your lifestyle, and your body will return its own, even in excess.

Famous in the last century ukrainian, Soviet thoracic surgeon, medical scientist, cyberneticist, writer, said: "Do not hope that doctors will make you healthy. Doctors treat diseases, but health must be obtained by yourself."

Nature has endowed us with good, strong vessels - arteries, veins, capillaries, each of which performs its own function. Look at how reliably and coolly our circulatory system is arranged, to which we sometimes treat very casually. In our body, there are two circles of blood circulation. Big circle and small circle.

Small circle of blood circulation

The small circle of blood circulation supplies blood to the lungs. First, the right atrium contracts and blood flows into the right ventricle. The blood is then pushed into the pulmonary trunk, which branches to the pulmonary capillaries. Here the blood is saturated with oxygen and through the pulmonary veins it returns back to the heart - to the left atrium.

A large circle of blood circulation

Passed through the small circle of blood circulation. (through the lungs) and oxygenated blood returns to the heart. Oxygenated blood from the left atrium passes into the left ventricle, after which it enters the aorta. The aorta is the largest human artery, from which many smaller vessels depart, then the blood is delivered through the arterioles to the organs and returns through the veins back to the right atrium, where the cycle begins anew.

Arteries

Oxygenated blood is arterial blood. Therefore, it is bright red. Arteries are vessels that carry oxygen-rich blood from the heart. The arteries have to cope with the high pressure that comes out of the heart. Therefore, there is a very thick muscle layer in the wall of the arteries. Therefore, the arteries practically cannot change their lumen. They are not very good at contracting and relaxing. but they take heart beats very well. Arteries resist pressure. which the heart creates.

Arterial wall structure Vein wall structure

Arteries are composed of three layers. The inner layer of the artery is a thin layer of integumentary tissue - the epithelium. Then comes a thin layer of connective tissue (not visible in the picture) elastic like rubber. Next comes the thick layer of muscle and the outer shell.

Arterial assignment or arterial function

• Oxygen-enriched blood through the arteries. flows from the heart to the organs.
• Artery function. it is the delivery of blood to organs. ensuring high pressure.
• Oxygenated blood flows in the arteries (except for the pulmonary artery).
• The blood pressure in the arteries is 120 ⁄ 80 mm. rt. Art.
• The speed of movement of blood in the arteries is 0.5 m / sec.
• arterial pulse. this is a rhythmic oscillation of the walls of the arteries during the period of systole of the ventricles of the heart.
• Maximum pressure - during heart contraction (systole)
• Minimal during relaxation (diastole)

Veins - structure and function

The layers of the vein are exactly the same as those of the artery. The epithelium is the same everywhere, in all vessels. But the vein, relative to the artery, has a very thin layer of muscle tissue. The muscles in the vein need not so much to resist the pressure of the blood, but to contract and expand. The vein is compressed - the pressure increases and vice versa.

Therefore, in terms of their structure, the veins are quite close to the arteries, but, with their own characteristics, for example, in the veins, there is already low pressure and low blood velocity. These features give some features to the walls of the veins. Compared to arteries, veins are large in diameter, with a thin inner wall and a well-defined outer wall. Due to its structure, the venous system contains about 70% of the total blood volume.

Another feature of veins is that valves are constantly running in the veins. about the same as at the exit from the heart. This is so that the blood does not flow in the opposite direction, but is pushed forward.

The valves open with the blood flow. When the vein fills with blood, the valve closes, making it impossible for blood to flow back. The most developed valve apparatus is in the veins, in the lower body.

It's simple, the blood returns easily from the head to the heart, since gravity acts on it, but it is much more difficult for it to rise from the legs. it is necessary to overcome this force of gravity. The valve system helps push the blood back to the heart.

Valves. good, but not enough to push the blood back to the heart. There is one more power. The fact is that veins, unlike arteries, run along muscle fibers. and when the muscle contracts, it compresses the vein. In theory, the blood should go in both directions, but there are valves that prevent blood from flowing in the opposite direction, only forward to the heart. In this way, the muscle pushes blood to the next valve. This is important because the lower outflow of blood is mainly due to the muscles. And if your muscles have long been weak from idleness? Creeped up unnoticed What will happen? It is clear that nothing good.

The movement of blood through the veins occurs against the force of gravity, in this regard, the venous blood experiences the force of hydrostatic pressure. Sometimes, when the valves are malfunctioning, the force of gravity is so great that it interferes with normal blood flow. In this case, the blood stagnates in the vessels and deforms them. Then the veins are called varicose veins.

Varicose veins have a swollen appearance, which is justified by the name of the disease (from Lat. Varix, genus varicis - "swelling"). The treatments for varicose veins today are very extensive, from folk advice to sleep with the feet above the level of the heart to surgery and vein removal.

Another disease is vein thrombosis. With thrombosis, blood clots (thrombi) form in the veins. This is a very dangerous disease because blood clots, breaking off, can move through the circulatory system to the vessels of the lung. If the clot is large enough, it can be fatal if it enters the lungs.

• Vienna. vessels carrying blood to the heart.
• The walls of the veins are thin, easily stretchable, unable to contract independently.
• A feature of the structure of the veins is the presence of pocket valves.
• Veins are distinguished - large (hollow veins), medium veins and small venulls.
• Blood saturated with carbon dioxide moves through the veins (except for the pulmonary vein)
• The blood pressure in the veins is 15 - 10 mm. rt. Art.
• The speed of blood flow in the veins is 0.06 - 0.2 m. Sec.
• Veins are superficial, unlike arteries.

Capillaries

The capillary is the thinnest vessel in the human body. Capillaries are tiny blood vessels 50 times thinner than a human hair. The average capillary diameter is 5-10 microns. By connecting arteries and veins, it participates in the exchange of substances between blood and tissues.

The capillary walls consist of one layer of endothelial cells. The thickness of this layer is so small that it allows the exchange of substances between tissue fluid and blood plasma through the walls of the capillaries. Waste products from the body (such as carbon dioxide and urea) can also pass through capillary walls to transport them to the site of elimination from the body.

Endothelium

It is through the walls of the capillaries that nutrients enter our muscles and tissues, saturating them, moreover, with oxygen. It should be noted that not all substances pass through the walls of the endothelium, but only those that are necessary for the body. For example, oxygen passes, but other impurities do not. This is called endothelial permeability, and it is the same with food. ... Without this function, we would have been poisoned long ago.

The vascular wall of the endothelium is the thinnest organ that performs a number of important functions. The endothelium secretes a substance as needed to force the platelets to stick together and repair, such as a cut. But so that platelets do not stick together just like that, the endothelium secretes a substance that prevents our platelets from sticking together and forming into blood clots. Entire institutes are working on the study of the endothelium to fully understand this amazing organ.

Another function is angiogenesis - the endothelium makes small vessels grow bypassing the clogged ones. For example, bypassing the cholesterol plaque.

Fight against vascular inflammation. This is also a function of the endothelium. Atherosclerosis. this is a kind of vascular inflammation. To date, even begin to treat atherosclerosis with antibiotics.

Regulation of vascular tone. This is also the responsibility of the endothelium. Nicotine is very detrimental to the endothelium. Immediately there is a vasospasm, or rather endothelial paralysis, which causes nicotine, and the combustion products contained in nicotine. There are about 700 of these products.

The endothelium must be strong and elastic. like all our vessels. arises in the event that a particular person begins to move a little, eat improperly and, accordingly, release a little of his own hormones into the blood.

The vessels can only be cleaned if regularly release hormones into the blood, then they will heal the walls of blood vessels, there will be no holes and cholesterol plaques nowhere will be formed. Eat right. control sugar and cholesterol levels. Folk remedies can be used as a supplement, the basis is still physical activity. For example, a health-improving system - just was invented for the health of anyone.

The venous and arterial networks perform many important functions in the human body. For this reason, doctors note their morphological differences, which are manifested in different types of blood flow, but the anatomy of all vessels is the same. The arteries of the lower extremities consist of three layers, outer, inner and middle. The inner membrane is called "intima".

It, in turn, is subdivided into two layers represented: the endothelium - it is the lining part of the inner surface of the arterial vessels, consisting of flat epithelial cells and the subendothelium - located under the endothelium. It is composed of loose connective tissue. The middle shell consists of myocytes, collagen and elastin fibers. The outer shell, which is called "adventitia", is a fibrous loose tissue connecting type, with vessels, nerve cells and lymphatic vascular network.

Human arterial system

The arteries of the lower extremities are blood vessels through which the blood pumped by the heart is distributed to all organs and parts of the human body, including the lower extremities. Arterial vessels are also represented by arterioles. They have three-layer walls consisting of intima, media and adventitia. They have their own classification signs. These vessels have three varieties, which differ from each other in the structure of the middle layer. They are:

• Elastic. The middle layer of these arterial vessels contains elastic fibers that withstand high blood pressureformed in them during the release of the blood stream. They are represented by the aorta and pulmonary trunk.
• Mixed. Here, in the middle layer, a different number of elastic and myocytic fibers is combined. They are represented by the carotid, subclavian and popliteal arteries.
• Muscular. The middle layer of these arteries consists of separate, circularly located, myocytic fibers.

The scheme of arterial vessels, according to the location of the internal ones, is divided into three types, presented:

• Trunk, providing blood flow in the lower and upper limbs.
• The organs that supply blood to the internal organs of a person.
• Intraorgan, having their own network, branched out across all organs.

Veins

Venous system human

Considering the arteries, do not forget that the human circulatory system also includes venous vessels, which must be viewed in conjunction with the arteries to create an overall picture. Arteries and veins have a number of differences, but still their anatomy always involves a cumulative examination.

Veins are divided into two types and can be muscular or non-muscular.

The venous walls of the non-muscular type include endothelium and loose connective tissue. Such veins are found in bone tissue, in internal organs, in the brain and retina.

The venous vessels of the muscular type, depending on the development of the myocytic layer, are divided into three types, and they are underdeveloped, moderately developed and highly developed. The latter are located in the lower extremities, providing them with tissue nutrition.

Veins transport blood, which lacks nutrients and oxygen, but it is saturated with carbon dioxide and decay substances synthesized as a result of metabolic processes. The blood stream travels through the limbs and organs, moving directly to the heart. Blood often overcomes speed and gravity at times less than its own. A similar property is provided by the hemodynamics of the venous circulation. In the arteries, this process is different. These differences will be discussed below. The only venous vessels that have different hemodynamics and blood properties are the umbilical and pulmonary.

Features:

Let's consider some of the features of this network:

• In comparison with arterial vessels, venous vessels have a larger diameter.
• They have an underdeveloped subendothelial layer and have fewer elastic fibers.
• They have thin walls that fall off easily.
• The middle layer, which consists of smooth muscle elements, is poorly developed.
• The outer layer is quite pronounced.
• They have a valve mechanism created by the venous wall and the inner layer. The valve consists of myocytic fibers, and the inner leaflets are composed of connective tissue. The outside of the valve is lined with an endothelial layer.
• All venous membranes have vascular vessels.

The balance between venous and arterial blood flow is ensured due to the density of the venous networks, their large number, venous plexuses, and larger sizes compared to arteries.

Network

The artery of the femoral region is located in the lacuna formed from the vessels. The external iliac artery is its continuation. It passes under the inguinal ligamentous apparatus, after which it passes into the adductor canal, consisting of a medial wide muscular tissue and a large adductor and membrane sheath located between them. From the adductor canal, the arterial vessel goes into the popliteal cavity. The lacuna, consisting of blood vessels, is separated from its muscle area by the edge of the wide femoral muscle fascia in the form of a sickle. In this area, nerve tissue passes, providing sensitivity to the lower limb. At the top is the inguinal ligamentous apparatus.

The femoral artery of the lower extremities has branches represented by:

• Superficial epigastric.
• Surface envelope.
• External genital.
• Deep femoral.

The deep femoral arterial vessel also bifurcates, consisting of a lateral and medial artery and a network of perforating arteries.

The popliteal arterial vessel starts from the adductor canal and ends with a membranous interosseous junction with two openings. In the place where the superior opening is located, the vessel is divided into anterior and posterior arterial sections. Its lower border is represented by the popliteal artery. Further, it branches into five parts, represented by the following types of arteries:

• Upper lateral / middle medial, passing under the knee articulation.
• Lower lateral / middle medial, passing in the knee joint.
• Middle knee artery.
• The posterior artery of the tibial region of the lower limb.

Then there are two tibial arterial vessels - posterior and anterior. The posterior one passes in the podkleno-tibial area, located between the superficial and deep muscular apparatus of the posterior part of the lower leg (there are small arteries of the lower leg). Further, it passes next to the medial malleolus, near the short-barreled digital flexor. From it depart arterial vessels, enveloping the peroneal bone area, a vessel of the peroneal type, calcaneal and ankle branches.

The anterior arterial vessel passes close to the muscular apparatus of the ankle. It is continued by the dorsal foot artery. Further, an anastomosis occurs with the arcuate arterial site, the dorsal arteries and those that are responsible for blood flow in the fingers depart from it. The interdigital spaces are a conduit for a deep arterial vessel, from which the anterior and posterior portion of the recurrent tibial arteries, medial and lateral arteries of the ankle type and muscle ramifications depart.

Anastomoses that help people maintain balance are represented by the heel and dorsal anastomosis. The first passes between the medial and lateral arteries of the calcaneal area. The second is between the external foot and arcuate arteries. Deep arteries make up the vertical anastomosis.

Differences

What is the difference between the vascular network and the arterial - these vessels have not only similarities, but also differences, which will be discussed below.

Structure

Arterial vessels are thicker-walled. They contain a large amount of elastin. They have well-developed smooth muscles, that is, if there is no blood in them, they will not fall off. They provide fast delivery of oxygen-enriched blood to all organs and limbs, due to the good contractility of their walls. The cells entering the wall layers allow blood to circulate through the arteries without obstruction.

They have an internal corrugated surface. They have such a structure due to the fact that the vessels must withstand the pressure formed in them due to powerful blood emissions.

Venous pressure is much lower, so their walls are thinner. If there is no blood in them, then the walls fall off. Their muscle fibers have weak contractile activity. Inside, the veins have a smooth surface. The blood flow through them is much slower.

Their thickest layer is considered to be the outer one, in the arteries - the middle one. There are no elastic membranes in the veins; in the arteries, they are represented by internal and external sections.

The form

The arteries have a regular cylindrical shape and a round cross-section. Venous vessels are flattened and sinuous in shape. This is due to the valve system, thanks to which they can contract and expand.

number

There are about 2 times less arteries in the body than veins. There are several veins per middle artery.

Valves

Many veins have a valve system that prevents blood flow from moving in the opposite direction. The valves are always paired and are located along the entire length of the vessels opposite each other. Some veins do not have them. In the arteries, there is a valve system only at the outlet of the heart muscle.

Blood

Blood flows in veins many times more than in arteries.

Location

Arteries are located deep in the tissues. They go to the skin only in the heart rate listening zones. All people have approximately the same heart rate zones.

Direction

Blood flows faster through the arteries than through the veins due to the pressure of the heart. At first, the blood flow is accelerated and then it decreases.

Venous blood flow is represented by the following factors:

• The force of pressure, which depends on the blood impulses coming from the heart and arteries.
• Suction heart power when relaxing between contractile movements.
• Suction venous action during breathing.
• Contractile activity of the upper and lower extremities.

Also, the blood supply is located in the so-called venous depot, represented by the portal vein, the walls of the stomach and intestines, the skin and the spleen. This blood will be pushed out of the depot in the event of heavy blood loss or intense physical exertion.

Colour

Since arterial blood contains a large number of oxygen molecules, it has a scarlet color. Venous blood is dark, since it contains decay elements and carbon dioxide.

During arterial bleeding, blood beats with a fountain, and with venous bleeding, it flows in a stream. The first is a serious danger to human life, especially if the arteries of the lower extremities are damaged.

Distinctive features of veins and arteries are:

• Transportation of blood and its composition.
• Different wall thicknesses, valve system and blood flow strength.
• The number and depth of location.

Veins, unlike arterial vessels, are used by doctors to draw blood and inject drugs directly into the bloodstream to treat various ailments.

Knowing the anatomical features and the layout of the arteries and veins not only on the lower extremities, but throughout the body, one can not only correctly provide first aid for bleeding, but also understand how the blood circulates through the body.

Anatomy (video)

An indispensable condition for the existence of an organism is the circulation of fluids through the blood vessels that carry blood and the lymphatic vessels through which the lymph moves

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

Blood vessels

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

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

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

The wall of the arteries is thicker than that of the veins and consists of three sheaths of layers (Fig. 2). The middle shell is built from bundles of smooth muscle tissue, between which elastic fibers are located. In the inner shell, lined from the side of the vessel lumen by the endothelium, and at the border between the middle and outer shells, there are elastic membranes. Elastic membranes and fibers form a peculiar frame of the vessel, which gives strength and elasticity to its walls.

In the wall of the large arteries closest to the heart (the 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 thrown out of the heart during its contraction. As you 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 weakens and its own contraction of the vascular wall is required for further blood flow, muscle tissue is well developed. Under the influence of nervous stimuli, such arteries are able to change their lumen.

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

Lymphatic vessels

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

Lymphatic vessels and flowing through them lymph also refer to the cardiovascular system. The lymphatic vessels, together with the veins, ensure the absorption of water with substances dissolved in it from the tissues: large protein molecules, droplets of fat, cellular debris, foreign bacteria and others. The smallest lymphatic vessels are lymphatic 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 the blood capillaries, enter the lymphatic capillaries. Lymph is similar in composition to blood plasma; from cells it contains only leukocytes (lymphocytes).

The lymph formed in the tissues through the lymphatic capillaries, and further along the larger lymphatic vessels, constantly flows into the circulatory system, into the veins of the systemic circulation. 1200-1500 ml of lymph enters the bloodstream per day. It is important that before the lymph flowing from the organs enters the circulatory system and mixes with the blood, it passes through a cascade lymph nodes, which are located along the lymphatic vessels. IN lymph nodes substances foreign to the body and pathogens are retained and rendered harmless, and the lymph is enriched with lymphocytes.

Arrangement of vessels

Figure: 3. Venous system
Figure: 3a. Arterial system

The distribution of blood vessels in the human body obeys certain patterns. Arteries and veins usually run together, with the small and medium 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 (Fig. 3 and 3a). The aorta and large veins run along the spinal column, branches branching from them are located in the intercostal spaces. On the limbs, in those sections 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, tibia), there are two main arteries, and with the radial structure of the skeleton (hand, foot), the arteries are located correspondingly to each finger ray. The vessels are directed to the organs at the shortest distance. Vascular bundles pass in sheltered places, in the canals formed by bones and muscles, and only on the flexor surfaces of the body.

In some places, the arteries are superficial, 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 the adjacent bone to stop bleeding.

Both the branching of the arteries and the tributaries of the veins are widely interconnected, forming the so-called anastomoses. In case of violations of blood flow or its outflow through the main vessels, anastomoses contribute to the movement of blood in different 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 with 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 the capillaries. Blood capillaries are found in almost all organs and tissues (they are absent only in the outermost layer of the skin - the epidermis, cornea and lens of the eye, in hair, nails, tooth enamel). The length of all capillaries in the human body is approximately 100,000 km. If you stretch them in one line, then you can gird the earth at the equator 2.5 times. Inside the organ, the blood capillaries interconnect to form capillary networks. Blood enters the capillary networks of organs through arterioles, and flows out through venules.

Microcirculation

The movement of blood through capillaries, arterioles and venules, and lymph through 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 organs, and the fine mechanisms of microcirculation allow regulating the activity of the organ and adapting it to the specific conditions of the organism's functioning. At every moment, it works, that is, it is open and allows blood to pass 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. When physical activity most of them open, as a working muscle requires an intense influx of 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 arterioles allowed the Russian physiologist I.M. Sechenov called them "taps of the circulatory system."

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

Blood pressure

An important characteristic of cardio- vascular system is the value of blood pressure (BP). In connection with rhythmic work heart, it fluctuates, rising during systole (contraction) of the ventricles and decreasing during diastole (relaxation). The highest blood pressure observed during systole is called maximum, or systolic. The lowest blood pressure is called minimum, or diastolic. BP is usually measured in the brachial artery. In healthy adults, the maximum blood pressure is normally 110-120 mm Hg, and the minimum is 70-80 mm Hg. In children, due to the high 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 muscular work, systolic blood pressure rises, while diastolic blood pressure does not change or decreases. The latter is due to vasodilation in working muscles. Decrease in maximum blood pressure below 100 mm Hg. called hypotension, and an increase above 130 mm Hg. - hypertension.

Blood pressure is maintained by a 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 are a significant amount of chemicals, under the influence of which the lumen of the vessels changes. Some of these substances are formed in the body itself (hormones, mediators, carbon dioxide), others come from external environment (medicinal and food substances). During emotional stress (anger, fear, pain, joy), the hormone adrenaline enters the bloodstream from the adrenal glands. It enhances the activity of the heart and constricts blood vessels, while blood pressure rises. The hormone does the same thyroid gland thyroxine.

Each person should know that his body has powerful self-regulation mechanisms, with the help of which the normal state of blood vessels and blood pressure levels are maintained. This ensures 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.

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Blood vessels are the most important part of the body, 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 \u200b\u200bthe eyes. And if they are assembled and stretched into one flat line, the total length will be about 100 thousand km.

These tubular elastic formations function continuously, transferring blood from the constantly beating heart to all corners of the human body, saturating them with oxygen and nourishing them, and then returning it back. By the way, the heart pushes more than 150 million liters of blood through the vessels during the entire human life.

There are the following main types of blood vessels: capillaries, arteries, and veins. Each species performs its own 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 - the circles of blood circulation.

The general thing in the device is the following: the walls of both arteries and veins have a three-layer structure:

• inner layer, providing smoothness, built of endothelium;
• medium, which is a guarantee of strength, consisting of muscle fibers, elastin and collagen;
• upper 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 saturated useful substances and oxygen from the heart to all cells of the body. By their structure, human arterial vessels are more durable in comparison with veins. This device (a denser and stronger middle layer) allows them to withstand the stress of high internal blood pressure.

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

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 the following types:

Arteries, leaving the heart, thin out to small arterioles. This is the name of the thin branches of the arteries that pass into the precapillaries, which form the capillaries.

These are the finest vessels, much thinner in diameter than a human hair. This is the longest part of the circulatory system, and their total number 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 a very important activity: chemical exchange between the bloodstream and tissues.

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The capillaries are then connected to the postcapillaries, which pass into the venules - small and thin venous vessels that flow into the veins.

Veins

These are blood vessels through which oxygen depleted blood goes back to the heart.

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

The venous vessels (all except 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 shut off its reverse outflow. Without them, the blood would flow to the feet.

Arteriovenous anastomoses are branches of arteries and veins, interconnected by anastomosis.

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 factconcerning this unique system of the human body. In the presence of excess weight, more than 10 km are created in the body (per 1 kg of fat) additional vesselscarrying blood. All this creates a very large load on the heart muscle.

Heart disease and being overweight, and even worse, obesity, are always very closely related. But the good thing is that the human body is also capable of the opposite process - the removal of unnecessary vessels while getting rid of excess fat (from it, and not just from extra pounds).

What role do blood vessels play in human life? On the whole, they are doing very serious and important work. They are a vehicle that ensures the delivery of the necessary 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 overemphasized.

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- the most important physiological mechanism responsible for nourishing the cells of the body and removing harmful substances from the body. The main structural component is the vessels. There are several types of vessels that differ in structure and function. Vascular diseases lead to serious consequences that negatively affect the entire body.

General information

A blood vessel is a tube-shaped hollow formations that penetrate 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. Transportation through the vessels is carried out due to the work of the heart, which performs a pumping function.

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

The vessels consist of three layers:

• External. The outer surface of the vessel is coated 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 a full-fledged unhindered blood flow occurs.
• 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 the venous vessels are much thinner than the arteries. This is due to the small amount of muscle fibers. The movement of venous blood occurs under the influence of skeletal blood, while arterial blood moves due to the work of the heart.

In general, the blood vessel is the main structural component the cardiovascular system, along which blood flows into tissues and organs.

Types of vessels

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

Types of blood vessels:

• ... The vessels provide the movement of blood from the heart to the tissues. They are characterized by thick walls with a high content of muscle fibers. The arteries constantly narrow and widen, depending on the level of pressure, preventing excess blood flow to some organs and deficiency in others.
• Arterioles. Small vessels that represent the terminal branches of the arteries. They consist mainly of muscle tissue. They are a transitional link between arteries and capillaries.
• Capillaries. The smallest vessels that penetrate organs and tissues. A feature is the very thin walls through which blood is able to penetrate outside the vessels. Due to the capillaries, the cells are supplied with oxygen. At the same time, the blood is saturated with carbon dioxide, which is further removed from the body through the venous pathways.

• Venules. They are small vessels that connect the capillaries and veins. They transport oxygen spent by the cells, residual waste products, and dying blood particles.
• Vienna. Provide the movement of blood from organs to the heart. They contain less muscle fibers, which is associated with low resistance. This makes the veins less thick and more prone to damage.

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. At the moment, there are 6 main functional groups.

The functional groups of vessels include:

• Shock absorbing. The vessels belonging to this group have the largest number of muscle fibers. They are the largest in the human body and are located in the immediate vicinity of the heart (aorta, pulmonary artery). These vessels are the most elastic and resilient, which is necessary to smooth out the systolic waves formed during heartbeat. The amount of muscle tissue in the walls of blood vessels decreases depending on the distance from the heart.
• Resistive. These include the final, thinnest blood vessels. Due to the smallest lumen, these vessels have the greatest resistance to blood flow. Resistive vessels contain many muscle fibers that control the lumen. Due to this, the volume of blood entering the organ is regulated.
• Capacitive. They perform a reservoir function, preserving large volumes of blood. 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 stress on the heart.
• Sphincters. They are located in the terminal branches of small capillaries. By narrowing and expanding, the sphincter vessels control the amount of blood supplied. When the sphincters narrow, blood does not flow, which is why the trophic process is disturbed.
• Exchange. Represented by the end branches of the capillaries. The metabolism takes place in the vessels, providing tissue nutrition and the removal of harmful substances. Venules perform similar functional tasks.
• Shunting. Vessels provide communication between veins and arteries. This does not affect the capillaries. These include the atrial, trunk and organ vessels.

In general, several functional groups of vessels are distinguished, providing a full blood flow and nutrition for all cells of the body.

Regulation of vascular activity

The cardiovascular system instantly reacts to external changes or the impact of negative factors inside the body. For example, when stressful situations arise, heart palpitations are noted. The vessels are narrowed, due to which it increases, and muscle tissue are supplied with a lot of blood. While 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 the vascular tone. Later, through the nerve fibers, the impulse moves 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, signaling possible danger. This makes it possible to adapt to changing environmental conditions, such as temperature changes.

The work of the heart and blood vessels is influenced. This process is called humoral regulation. The greatest effect on blood vessels is exerted by adrenaline, vasopressin, acetylcholine.

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

Diseases

Like any organ, a vessel can be affected by diseases. The reasons for the development of vascular pathologies are often associated with the wrong lifestyle of a person. Less commonly, diseases develop as a result of 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 such a pathology, the blood flow through the vessels that feed the myocardium - the heart muscle - is disrupted. Gradually, due to atrophy, the muscle weakens. As a complication, a heart attack, as well as heart failure, in which a sudden cardiac arrest is possible, act.
• Cardiopsychoneurosis. Disease in which arteries are affected by malfunctioning nerve centers... In the vessels, due to excessive sympathetic influence on muscle fibers, spasm develops. Pathology often manifests itself in the vessels of the brain, and also affects the arteries located in other organs. The patient has intense pain, interruptions in the work of the heart, dizziness, pressure changes.
• Atherosclerosis. A disease in which the walls of blood vessels narrow. This leads to a number of negative consequences, including atrophy of the nourishing tissues, as well as a decrease in the elasticity and strength of the vessels located behind the constriction. is a provoking factor in many cardiovascular diseases, and leads to the formation of blood clots, heart attack, stroke.
• Aortic aneurysm. With this pathology, saccular protrusions form on the walls of the aorta. In the future, scar tissue is formed, and the tissues gradually atrophy. As a rule, pathology develops against the background chronic form hypertension, infectious lesions, including syphilis, as well as with anomalies in the development of the vessel. In the absence of treatment, the disease provokes a rupture of the vessel and the death of the patient.
• ... Pathology in which the veins of the lower extremities are affected. They expand greatly due to increased stress, 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.

• ... A disease in which varicose veins develop in the area of \u200b\u200bthe hemorrhoidal veins that feed the lower intestines. The late stages of the disease are accompanied by prolapse of hemorrhoids, severe bleeding, and stool disorders. Infectious lesions, including blood poisoning, act as a complication.
• Thrombophlebitis. Pathology affects the venous vessels. The danger of the disease is explained by the potential for a thrombus to rupture, due to which the lumen of the pulmonary arteries is blocked. However, large veins are rarely affected. Thrombophlebitis affects small veins, the defeat of which does not pose a significant threat to life.

Exists wide range vascular pathologies that have a negative impact on the work of the whole organism.

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

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