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 take place in the capillaries, where the blood gives off the oxygen it contains and nutrients surrounding tissues, and takes away 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 high speed circulation daily through the blood vessels flows 8000-9000 liters of blood.

Blood moves at different speeds in different vessels. 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 of the total cross section of the 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 venous vessels about 2 times more than 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 arteries is thicker than that of veins and consists of three sheath 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 lumen of the vessel with endothelium, and on the border between the middle and outer shells, there are elastic membranes. Elastic membranes and fibers form a kind of skeleton of the vessel, giving its walls strength and elasticity.

There are relatively more elastic elements in the wall of the large arteries closest to the heart (the aorta and its branches). 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 heart impulse weakens and its own contraction of the vascular wall is required to further move the blood, muscle tissue is well developed. Under the influence of nerve stimuli, 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, so 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 of the systemic 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. IN 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 sent to the organs along the 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 the 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 the case sharp violation 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 absent only in the outermost layer of the skin - the epidermis, cornea and lens of the eye, hair, nails, tooth enamel). Length of all capillaries 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 organs, 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 supply 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 the arterioles allowed the Russian physiologist I.M. Sechenov to call them "faucets of the 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 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. At present, thanks to modern technical achievements, 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 in which they participate nervous system and various substances carried by the blood itself. So, there are vasoconstrictor and vasodilator nerves, the centers of which are located in the medulla oblongata and spinal cord. Available significant amount chemicals, 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 external environment(drugs and food). 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. The thyroid hormone thyroxine works in the same way.

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

In mammals, blood vessels are divided into arteries, capillaries, and veins.

The arteries carry blood from the heart to the capillaries. Under the influence of the work of the heart, the blood in the arteries is under high pressure, reaching 200 mm Hg. The walls of the arteries are thick and very strong. Severed arteries usually have a gaping lumen.

Capillaries (or hair vessels) are feeding vessels, i.e., areas of the vascular bed, in which, according to the laws of osmosis and transudation, the exchange of substances between blood and cells occurs. The number of capillaries that permeate the entire body of an animal is incalculable, and the bloodstream in them expands 500 or even 800 times compared to the diameter of the aorta. This entails a strong drop in blood pressure - up to 10-30 mm Hg. Thanks to this low pressure the walls of the capillaries, even in adult animals, retain their primitive state. They are very thin, which creates the necessary conditions for metabolism.

Veins serve, like arteries, only for carrying blood, but in the opposite direction, that is, from the capillary network to the heart. However, the conditions of blood flow in the veins are completely different than in the arteries, which is reflected in the structure of their walls. Since the blood pressure in the veins is lower than even in the capillaries, the walls of the veins are usually much thinner than the walls of the arteries, although the diameter of the veins is most often larger than the diameter of the corresponding arteries.

It can be seen from the foregoing that the structural features of the walls various vessels are formed under the influence of the work of the heart, which is the organizing principle in this respect; this is confirmed by the entire history of the development of the vascular bed.

In animals that are lower than fish, i.e., do not have a concentrated heart, the vessels, corresponding in their significance to arteries and veins, in their structure do not differ in any way not only from each other, but also from capillaries, which occurs in lancelet.

With the appearance of a real heart (concentrated) in cruelostomes And fish differentiation of the vascular walls begins due to the difference

in blood pressure in arteries and veins. Already in lampreys, in addition to the endothelial membrane (Fig. 78-2), consisting of one layer of flat cells, additional membranes develop in the arteries and veins. These include: from the elastic elements - the inner shell, or intima (2), from the muscular elements - the middle shell, or media (4), and, finally, from the connective tissue elements, the outer shell, or adventitia (5). A later appearance of additional membranes is also observed during embryonic development.

In lower animals, all these shells pass one into another without sharp boundaries / Only in birds and especially in mammals additional shells not only clearly differ in their structure, but also make it possible, according to the structure of the media, to divide all arteries into three types - m-zygomatic, elastic and mixed, which is also primarily due to the work of the heart.

Vessels do not play the simple role of channels for conducting blood, but serve as tubes that are actively involved not only in the promotion of blood (arteries and veins), but also in the phenomena of osmosis and extravasation, as well as in the blood filling of organs (capillaries), adapting to constantly changing conditions . This adaptation goes so far that in cases of prolonged strengthening of the work of one or another organ, the capillary network in it becomes denser, which ensures sufficient blood flow. Moreover, when a vessel is blocked (due to the formation of a thrombus or the growth of some kind of tumor), when blood flow in it, even with a large lumen, becomes impossible, due to the existing or newly formed capillary network, new pathways for blood flow develop, overcompensating off vessel. (The development of new vessels after ligation or transection of arteries under experimental conditions has been studied in great detail by the anatomical school of V.N. Tonkov.)

In order to have a clear idea of ​​the function of the vascular bed, it is necessary to take a closer look at the structure of arteries, veins, and capillaries.

* Capillaries

Of all the vessels, capillaries-vasacapillaria are more primitive. Their walls are formed by flat endothelial cells. Large capillaries are dressed on the outside with a delicate homogeneous membrane and Rouget cells, or pericytes (Fig. 76- 3). Capillaries are located in the connective tissue, with which they are closely associated; the exception in this regard is the capillaries of the brain and muscles, where they are surrounded by special perivascular spaces"

Both endothelial cells and Rouget cells have the ability to contract; as a result, the lumen of the capillaries may temporarily close. In addition, the cellular elements of capillaries are actively involved in the metabolism between blood and tissues, passing some substances and retaining others. This ability is more pronounced in the capillaries of the brain. Finally, the significance of the endothelial membrane of capillaries (as well as arteries and veins) is that it protects the blood from direct contact with other tissues, which would inevitably lead to blood clotting.

The diameter of the capillaries in different animals varies greatly (ranging from 4 to 50!*). The largest capillaries are found in the liver, bone marrow, dental pulp, the smallest ones are in the brain and spinal cord, in muscles, in the retina of the eye and in all other organs in which there is an intensive metabolism.

624 circulatory organs

The length of the capillaries usually does not exceed 2 mm, more often it is 0.6 -1.0 mm. In humans, the total length of the capillaries is estimated at 100,000 km, i.e., almost three times longer than the equator, the surface of all capillaries reaches 6,000 m 2 . Capillaries in organs and tissues form a network of very diverse shapes. Wide-loop networks of capillaries are usually found in inactive tissues (in the formed connective tissue of tendons, ligaments, etc.), narrow-loop networks, on the contrary, are characteristic of the most active organs.

Rice. 76. Capillary network, Fig. 77. Capillary network in the deep pectoral muscle: connecting the arteriole A-chicken, B-pigeon.

From the venule. A- muscle fiber (according to E. F. Lissitzky).

1 - arteriole, 2 - precapillary arteriole, 3 - Yuetki Ru-eke, 4 - capillaries, 5 -postcapillary venule 6 -venule-

(lungs, muscles and glands). Even in organs of the same structure, capillary networks can be different in nature depending on the particular function of the organs, for example, in different muscles or in the same muscle, but in different animals (Figure 77- A, B).

The number of capillaries is enormous and is determined by the intensity of metabolism in a given animal or in a given organ. So, frogs have only about 400 capillaries per 1 mm 2, while horses have up to 1,350, dogs have up to 2,630, and small animals have even more, up to 4,000. The number of capillaries depends on the intensity of work organ, for example, in the human heart there are up to 5,500 capillaries per 1 mm 2.

STRUCTURE OF BLOOD VESSELS 625

However, not all capillaries are filled with blood in every period of time. Since the walls of the capillaries can contract, a significant number of them at rest are closed to the blood flow and turn on only with increased work of this organ. The blood supply of a working muscle can increase 4-5 times, and according to some authors even 20 times, compared with the blood supply to the same muscle at rest. By turning off the capillaries from the bloodstream, an even distribution of blood in the body between the working organs is achieved, since, generally speaking, there is much less blood than the bloodstream as a whole can accommodate.

Capillaries are absent only in epithelial tissue, dentin and hyaline cartilage.

Arteries represent the most differentiated segments of the vascular bed. They are characterized, in addition to the presence of an endothelial membrane (Fig. 78-i), well-developed additional membranes: intima (2), media (4) and adventitia (5).

The closer to the heart, the larger the diameter of the artery and the thicker its walls; the farther from the heart, the smaller the diameter of the artery and the thinner its walls, since as the vessels branch, the bloodstream expands and blood pressure drops; the arteries closest to the capillaries are the most narrow and thin-walled. Fig 78 Schematic layout

In the arteries, the dia- arteries are especially strongly developed.

differentiated media. It is built from smooth 2 __ endothelium; g-intimacy; s-internal muscle or elastic fibers of the renn ^ m | dia ^! 1 adventation (! chka; or from both together. All these elements go circularly.

According to the structure of the media artery, they are classified as elastic, muscular or mixed type. *

In the arteries of the elastic type, the media is built almost exclusively of elastic tissue, which determines the enormous strength and extensibility of the walls of such arteries. For example, the aortic lumen can increase by 30%, and the carotid arteries in dogs can withstand pressures up to 20 times normal.

Arteries of the elastic type are found where the vessels experience the strongest blood pressure, for example, in the aorta and in other closest to heart arteries, somehow: going to the head, chest limbs and lungs. This is quite understandable: when the heart jolts blood into the aorta, its walls experience great stress and stretch greatly, as this helps to reduce blood friction against the walls. When the heart relaxes again, the stretched walls of the vessels, due to their elasticity, return to normal state and when reduced, they drive blood into smaller arteries and capillaries. This explains the fact that although the blood is ejected from the heart in rhythmic shocks, it nevertheless flows out of the smaller arteries in a uniform stream.

In muscle-type arteries, by contrast, the media consists almost exclusively of smooth muscle cells. Such arteries are found where the vessels experience strong pressure from the surrounding organs (in the abdominal cavity, on the extremities).

The musculature of the arteries performs not only the passive function of elastic tissue, but, which is especially important, actively contracting, pushes

626 circulatory organs

blood to the periphery. Since the sum of all the muscle fibers of the arteries is greater than the muscles of the heart, the role of the muscles of the arteries in the movement of blood is very large. This can be seen from the fact that the contraction of the muscles of the arteries, and hence the narrowing of their lumen, entails an increase in the work of the heart, and the expansion of blood vessels, on the contrary, causes a weakening of the work of the heart or even its paralysis. That's why "peripheral heart" (M. V. Yanovsky), by which they mean not only the entire musculature of the arteries, but also their elastic elements, clinicians pay very much great attention, because changes in vascular walls cause a significant restructuring of not only the heart, but also the blood circulation as a whole.

A mixed-type arteries are transitional between the elastic and muscular arteries, therefore their middle shell is built from both elastic and smooth muscle elements. The number of both

Rice. 79. Location

venous valves for

cut vein.

I- venous valves; 2 - expansion of the vein between the valves.

Rice. 80. Veins of the veins (increase 19 times).

I - paravenous arteries; 2 - vascular network in the vein adventitia; 3 - vein (according to A. T. Akilova).

varies depending on the distance from the heart and on the conditions in which this vessel is located: the closer to the heart, the more elastic elements in the walls of the arteries.

In the media, the structural elements are arranged circularly, and in the intima and adventitia, they are longitudinal: elastic in the intima, connective tissue and smooth muscle in the adventitia.

In the body, the arteries are in a somewhat stretched state, which creates better conditions for blood flow in them. This also explains the divergence from each other of the cut ends of the arteries in wounds, which should always be borne in mind when bleeding in surgical practice.

STRUCTURE OF BLOOD VESSELS

Vienna

The veins are basically arranged in the same way as the artery, with the essential difference that their media is extremely weakly developed and very indistinctly separated from the powerful adventitia. There are very few elastic elements in the veins, but smooth muscle and connective tissue elements that run longitudinally predominate. This explains the collapse of the thin walls of the veins in the absence of blood in them. Particularly characteristic of veins valves(Fig. 79- 1), located in them in pairs, at intervals of 2-10 cm. The valves are pocket-like semilunar doublings of the endothelial membrane. Their placement allows blood flow only in the direction of the heart.

There are more valves where the blood flow is counteracted by the force of its own gravity, for example, in the limbs; on the contrary, there are fewer valves in horizontally running veins. They are not at all in both vena cava, in the portal vein system (with the exception of the omental veins), in the hepatic veins, veins of the brain and spinal cord, in the pulmonary, renal and milk veins, in the cavernous bodies of the genital organs, in the veins of the bones, the skin wall of the hoof ; there are also no valves in all small veins, with a diameter of less than 1-1.5 mm (it has been noted that in humans the number of valves greatly decreases with age).

The presence of valves contributes to a faster pushing of blood in the veins, especially when the animal moves, when the muscles, contracting, squeeze the veins and drive blood to the heart, or, on the contrary, expand the veins, as a result of which they are filled with blood. The possibility of passive expansion of the veins is explained by the fact that the venous walls fuse with the fascia of the muscles and tendons (popliteal, axillary, subclavian veins and etc.).

Vessels vessels

Fig..81. Scheme of sensitive innervation of the aorta.

1 -intima with endothelium; 2 -media; 3 - adventitia; 4 - perivascular tissue; 5 - nerve waves; 6 -encapsulated bodies and nerve endings (according to T. A. Grigorieva).

The shells of the vessels, as secondary formations, have their own blood vessels, through which they are fed (Fig. 80). These vascular vessels - vasa vasorum - depart either from the same vessel, the walls of which they feed, or from the nearest arterial branches and their main branches are located in the outer shell, from where they give radial branches already to the middle shell.

Lymphatic vessels are also located in the outer shell of vessels, especially large ones; in addition, some arteries are entwined with a dense network of lymphatic vessels that form perivascular lymphatic spaces, separating blood vessels from surrounding tissues. Such spaces are found in the brain, liver, spleen, haversian canals of bones, in the gastric mucosa, and finally around the capillaries in the muscles.

BLOOD CIRCULATION ORGANS

Arteries are blood vessels that carry blood from the heart to organs and parts of the body. Arteries have thick walls made up of three layers. The outer layer is represented by a connective tissue membrane and is called adventitia. The middle layer, or media, consists of smooth muscle tissue and contains connective tissue elastic fibers. Inner layer, or intima, is formed by the endothelium, under which are the subendothelial layer and the internal elastic membrane. The elastic elements of the arterial wall form a single framework that acts like a spring and determines the elasticity of the arteries. Depending on the organs and tissues supplied with blood, the arteries are divided into parietal (parietal), blood-supplying walls of the body, and visceral (internal), blood-supplying internal organs. Before the artery enters the organ, it is called extraorganic, entering the organ - intraorganic, or intraorganic.

Depending on the development of the various layers of the wall, arteries of the muscular, elastic or mixed type are distinguished. Muscular-type arteries have a well-developed median sheath, the fibers of which are spirally arranged like a spring. These vessels include small arteries. Mixed-type arteries in the walls have an approximately equal number of elastic and muscle fibers. These are the carotid, subclavian and other arteries of medium diameter. Arteries of the elastic type have a thin outer and a more powerful inner shell. They are represented by the aorta and the pulmonary trunk, into which blood enters under high pressure. Lateral branches of one trunk or branches of different trunks can be connected to each other. Such a connection of the arteries before their disintegration into capillaries is called an anastomosis, or fistula. Arteries that form anastomoses are called anastomosing (most of them). Arteries that do not have anastomoses are called terminal (for example, in the spleen). Terminal arteries are more easily blocked by a thrombus and are prone to the development of a heart attack.

After the birth of a child, the circumference, diameter, wall thickness and length of the arteries increase, and the level of arterial branches from the main vessels also changes. Difference between diameter main arteries and their branches are small at first, but increase with age. The diameter of the main arteries grows faster than their branches. With age, the circumference of the arteries also increases, their length increases in proportion to the growth of the body and limbs. The levels of branches from the main arteries in newborns are located more proximally, and the angles at which these vessels depart are greater in children than in adults. The radius of curvature of the arcs formed by the vessels also changes. In proportion to the growth of the body and limbs and the increase in the length of the arteries, the topography of these vessels changes. As age increases, the type of branching of the arteries changes: mainly from loose to main. Formation, growth, tissue differentiation of vessels of the intraorganic bloodstream in various bodies human proceeds in the process of ontogenesis unevenly. The wall of the arterial part of the intraorganic vessels, unlike the venous part, already has three membranes by the time of birth. After birth, the length and diameter of intraorganic vessels, the number of anastomoses, and the number of vessels per unit volume of the organ increase. This happens especially intensively up to a year and from 8 to 12 years.

The smallest branches of arteries are called arterioles. They differ from arteries in having only one layer of muscle cells, thanks to which they carry out a regulatory function. The arteriole continues into the precapillary, in which the muscle cells are scattered and do not form a continuous layer. The precapillary is not accompanied by a venule. Numerous capillaries depart from it.

In places of transition of one type of vessels to others, smooth muscle cells are concentrated, forming sphincters that regulate blood flow at the microcirculatory level.

Capillaries are the smallest blood vessels with a lumen of 2 to 20 microns. The length of each capillary does not exceed 0.3 mm. Their number is very large: for example, there are several hundred capillaries per 1 mm2 of tissue. The total lumen of the capillaries of the whole body is 500 times greater than the lumen of the aorta. In the resting state of the body, most of the capillaries do not function and the blood flow in them stops. The capillary wall consists of a single layer of endothelial cells. The surface of the cells facing the lumen of the capillary is uneven, folds form on it. This promotes phagocytosis and pinocytosis. There are feeding and specific capillaries. Feeding capillaries provide the organ with nutrients, oxygen and remove metabolic products from the tissues. Specific capillaries contribute to the organ's function (gas exchange in the lungs, excretion in the kidneys). Merging, the capillaries pass into postcapillaries, which are similar in structure to the precapillary. Postcapillaries merge into venules with a lumen of 4050 µm.

Veins are blood vessels that carry blood from organs and tissues to the heart. They, like the arteries, have walls consisting of three layers, but contain fewer elastic and muscle fibers, therefore they are less elastic and fall off easily. Veins have valves that open with blood flow, allowing blood to flow in one direction. The valves are semi-lunar folds of the inner membrane and are usually located in pairs at the confluence of two veins. In the veins of the lower extremity, blood moves against the action of gravity, the muscular membrane is better developed and valves are more common. They are absent in the vena cava (hence their name), the veins of almost all internal organs, the brain, head, neck and small veins.

Arteries and veins usually go together, with large arteries supplied by one vein, and medium and small ones by two companion veins, repeatedly anastomosing with each other. As a result, the total capacity of the veins is 10-20 times greater than the volume of the arteries. Superficial veins going to subcutaneous tissue do not accompany arteries. The veins, together with the main arteries and nerve trunks, form the neurovascular bundles. By function, blood vessels are divided into cardiac, main and organ. Cardiacs begin and end both circulations. These are the aorta, pulmonary trunk, hollow and pulmonary veins. Main vessels serve to distribute blood throughout the body. These are large extraorganic arteries and veins. Organ vessels provide exchange reactions between blood and organs.

By the time of birth, the vessels are well developed, and the arteries are larger than the veins. The structure of blood vessels changes most intensively between the ages of 1 and 3 years. At this time, the middle shell develops intensively, the shape and size of the blood vessels finally take shape by 1418. Starting from 4045 years, the inner shell thickens, fat-like substances are deposited in it, and atherosclerotic plaques appear. At this time, the walls of the arteries are sclerosed, the lumen of the vessels decreases.

General characteristics of the respiratory system. Fetal respiration. Pulmonary ventilation in children of different ages. Age-related changes in depth, breathing rate, vital capacity lungs, regulation of respiration.

Respiratory organs ensure the supply of oxygen to the body, which is necessary for oxidation processes, and the release of carbon dioxide, which is the end product. metabolic processes. The need for oxygen is more important for humans than the need for food or water. Without oxygen, a person dies within 57 minutes, while without water he can live up to 710 days, and without food - up to 60 days. The cessation of breathing leads to the death of primarily nerve cells, and then other cells. There are three main processes in respiration: the exchange of gases between environment and lungs (external respiration), gas exchange in the lungs between alveolar air and blood, gas exchange between blood and interstitial fluid (tissue respiration).

The inspiratory and expiratory phases make up the respiratory cycle. The change in the volume of the chest cavity occurs due to contractions of the inspiratory and expiratory muscles. The main inspiratory muscle is the diaphragm. During a quiet breath, the dome of the diaphragm drops by 1.5 cm. The external oblique intercostal and intercartilaginous muscles also belong to the inspiratory muscles, with the contraction of which the ribs rise, the sternum moves forward, the lateral parts of the ribs move to the sides. With very deep breathing, a number of auxiliary muscles participate in the act of inhalation: sternocleidomastoid, scalene, pectoralis major and minor, serratus anterior, as well as muscles that extend the spine and fix the shoulder girdle (trapezius, rhomboid, levator scapula).

With active exhalation, the muscles of the abdominal wall contract (oblique, transverse and straight), as a result, the volume of the abdominal cavity decreases and the pressure in it increases, it is transmitted to the diaphragm and raises it. Due to the contraction of the internal oblique and intercostal muscles, the ribs descend and approach. The accessory expiratory muscles are the muscles that flex the spine.

The respiratory tract is formed by the nasal cavity, nose and oropharynx, larynx, trachea, bronchi of various calibers, including bronchioles.

In the human body there are vessels (arteries, veins, capillaries) that supply blood to organs and tissues. These vessels form a large and small circle of blood circulation.

Large vessels (aorta, pulmonary artery, vena cava and pulmonary veins) serve mainly as pathways for the movement of blood. All other arteries and veins can, in addition, regulate the flow of blood to the organs and its outflow by changing their lumen. Capillaries are the only part of the circulatory system where the exchange between blood and other tissues takes place. According to the predominance of a particular function, the walls of vessels of different calibers have an unequal structure.

The structure of the walls of blood vessels

The wall of the artery consists of three layers. The outer shell (adventitia) is formed by loose connective tissue and contains vessels that feed the wall of the arteries, vascular vessels (vasa vasorum). The middle shell (media) is formed mainly by smooth muscle cells of a circular (spiral) direction, as well as elastic and collagen fibers. It is separated from the outer shell by an outer elastic membrane. The inner shell (intima) is formed by the endothelium, basement membrane and subendothelial layer. It is separated from the middle shell by an internal elastic membrane.

In large arteries in the middle shell, elastic fibers predominate over muscle cells, such arteries are called elastic-type arteries (aorta, pulmonary trunk). The elastic fibers of the vessel wall counteract the excessive stretching of the vessel by blood during systole (contraction of the ventricles of the heart), as well as the movement of blood through the vessels. During diastole

bleating of the ventricles of the heart), they also ensure the movement of blood through the vessels. In the arteries of "medium" and small caliber in the middle shell, muscle cells predominate over elastic fibers, such arteries are muscle-type arteries. The middle arteries (muscular-elastic) are classified as mixed-type arteries (carotid, subclavian, femoral, etc.).

Veins are large, medium and small. The walls of veins are thinner than the walls of arteries. They have three shells: outer, middle, inner. In the middle shell of the veins, there are few muscle cells and elastic fibers, so the walls of the veins are pliable and the lumen of the vein does not gape on the cut. Small, medium and some large veins have venous valves - semilunar folds on the inner shell, which are located in pairs. Valves allow blood to flow towards the heart and prevent it from flowing back. The veins of the lower extremities have the greatest number of valves. Both vena cava, veins of the head and neck, renal, portal, pulmonary veins do not have valves.

Veins are divided into superficial and deep. Superficial (saphenous) veins follow independently, deep - in pairs adjacent to the same name arteries of the limbs, so they are called accompanying veins. In general, the number of veins exceeds the number of arteries.

Capillaries - have a very small lumen. Their walls consist of only one layer of flat endothelial cells, to which individual connective tissue cells adjoin only in places. Therefore, capillaries are permeable to substances dissolved in the blood and function as an active barrier that regulates the transfer of nutrients, water and oxygen from the blood to the tissues and the reverse flow of metabolic products from the tissues into the blood. The total length of human capillaries in skeletal muscles, according to some estimates, is equal to 100 thousand km, their surface area reaches 6000 m.

Small circle of blood circulation

The pulmonary circulation begins with the pulmonary trunk and originates from the right ventricle, forms a bifurcation of the pulmonary trunk at the level of the IV thoracic vertebra and divides into the right and left pulmonary arteries, which branch out in the lungs. In the tissue of the lung (under the pleura and in the region of the respiratory bronchioles) small branches pulmonary artery and bronchial branches of the thoracic aorta form a system of interarterial anastomoses. They are the only place in the vascular system where

the movement of blood along a short path from the systemic circulation directly to the pulmonary circulation. From the capillaries of the lung, venules begin, which merge into larger veins and, ultimately, in each lung form two pulmonary veins. The right superior and inferior pulmonary veins and the left superior and inferior pulmonary veins pierce the pericardium and empty into the left atrium.

Systemic circulation

The systemic circulation begins from the left ventricle of the heart by the aorta. Aorta (aorta) - the largest unpaired arterial vessel. Compared to other vessels, the aorta has the largest diameter and a very thick wall, consisting of a large number of elastic fibers, which is elastic and durable. It is divided into three sections: the ascending aorta, the aortic arch and the descending aorta, which, in turn, is divided into the thoracic and abdominal parts.

The ascending aorta (pars ascendens aortae) exits the left ventricle and enters primary department has an extension - the bulb of the aorta. At the location of the aortic valves on its inner side there are three sinuses, each of them is located between the corresponding semilunar valve and the aortic wall. The right and left coronary arteries of the heart depart from the beginning of the ascending aorta.

The aortic arch (arcus aortae) is a continuation of the ascending aorta and passes into its descending part, where it has aortic isthmus - a slight narrowing. From the aortic arch originate: the brachiocephalic trunk, the left common carotid artery and the left subclavian artery. In process of an otkhozhdeniye of these branches diameter of an aorta noticeably decreases. At level IV of the thoracic vertebrae, the aortic arch passes into the descending part of the aorta.

The descending part of the aorta (pars descendens aortae), in turn, is divided into the thoracic and abdominal aorta.

Thoracic aorta (a. thoracalis) passes through the chest cavity in front of the spine. Its branches feed the internal organs of this cavity, as well as the walls of the chest and abdominal cavities.

The abdominal aorta (a. abdominalis) lies on the surface of the bodies of the lumbar vertebrae, behind the peritoneum, behind the pancreas, duodenum and root of the mesentery of the small intestine. The aorta gives off large branches to the abdominal viscera. At level IV of the lumbar vertebra, it divides into two common iliac arteries (the place of separation is called the aortic bifurcation). The iliac arteries supply the walls and innards of the pelvis and lower extremities.

Branches of the aortic arch

The brachiocephalic trunk (truncus brachiocephalicus) departs from the arc at level II of the right costal cartilage, has a length of about 2.5 cm, goes up and to the right, and at the level of the right sternoclavicular joint is divided into the right common carotid artery and the right subclavian artery.

The common carotid artery (a. carotis communis) on the right departs from the brachiocephalic trunk, on the left - from the aortic arch (Fig. 86).

Coming out of the chest cavity, the common carotid artery rises as part of the neurovascular bundle of the neck, lateral to the trachea and esophagus; does not give branches; at the top edge thyroid cartilage divides into internal and external carotid arteries. Not far from this point, the aorta passes anterior to the transverse process VI. cervical vertebra which can be pressed against to stop bleeding.

The external carotid artery (a. carotis externa), rising along the neck, gives branches to thyroid gland, larynx, tongue, submandibular and sublingual glands and a large external maxillary artery.

The external maxillary artery (a. mandibularis externa) bends over the edge of the lower jaw in front of the chewing muscle, where it branches in the skin and muscles. The branches of this artery go to the upper and lower lip, anastomose with similar branches of the opposite side, and form a perioral arterial circle around the mouth.

At inner corner the facial artery anastomoses with the ophthalmic artery, one of the major branches of the internal carotid artery.

Rice. 86. Arteries of the head and neck:

1 - occipital artery; 2 - superficial temporal artery; 3 - posterior ear artery; 4 - internal carotid artery; 5 - external carotid artery; 6 - ascending cervical artery; 7 - thyroid trunk; 8 - common carotid artery; 9 - superior thyroid artery; 10 - lingual artery; 11 - facial artery; 12 - lower alveolar artery; 13 - maxillary artery

Medial to the mandibular joint, the external carotid artery divides into two terminal branches. One of them - the superficial temporal artery - is located directly under the skin of the temple, in front of the ear opening and nourishes the parotid gland, temporalis muscle and scalp. Another, deep branch - the internal maxillary artery - feeds the jaws and teeth, masticatory muscles, walls

nasal cavity and adjacent

Rice. 87. Arteries of the brain:

11 with them bodies; gives away

I - anterior communicating artery; 2 - before- „,

the lower cerebral artery smelling the cerebral artery; 3 - internal carotid ar-Ґ Ґ

teriya; 4 - middle cerebral artery; 5 - posterior lobes penetrating the skull. communicating artery; 6 - posterior cerebral ar- Internal SONNYA artery; 7 - main artery; 8 - vertebral artery (a. carotis interna) sub-terium; 9 - rear lower cerebellar artery; taken from the side of the throat

Ш - anterior inferior cerebellar artery; to the base of the skull,

II - superior cerebellar artery

into it through the canal of the temporal bone of the same name and, penetrating the dura mater, gives off a large branch - the ophthalmic artery, and then at the level of the optic chiasm it divides into its terminal branches: the anterior and middle cerebral arteries (Fig. 87).

The ophthalmic artery (a. ophthalmica), enters the orbit through the optic canal and supplies blood eyeball, its muscles and the lacrimal gland, the terminal branches supply blood to the skin and muscles of the forehead, anastomosing with the terminal branches of the external maxillary artery.

The subclavian artery (a. subclavia), starting to the right of the brachial trunk, and to the left of the aortic arch, exits the chest cavity through its upper opening. On the neck, the subclavian artery appears along with the brachial nerve plexus and lies superficially, bending over the first rib and, passing under the clavicle outward, enters the axillary fossa and is called the axillary (Fig. 88). Having passed the fossa, the artery under a new name - the brachial - goes to the shoulder and in the region of the elbow joint is divided into its terminal branches - the ulnar and radial arteries.

A number of large branches depart from the subclavian artery, feeding the organs of the neck, occiput, part of the chest wall, spinal cord and brain. One of them is the vertebral artery - a steam room, departs at the level of the transverse process of the VII cervical vertebra, rises vertically upward through the openings of the transverse processes of the VI-I cervical vertebrae

and through the greater occipital

Rice. 88. Arteries of the axillary region:

the hole enters the skull

o-7h t-g 1 - transverse artery of the neck; 2 - breast acromi-

(Fig. 87). Along the way she gives back,

K1 "J al artery; 3 - artery that envelopes the scapula;

branches penetrating through 4 - subscapular artery; 5 - lateral thoracic-intervertebral foramen to the naia artery; 6 - thoracic artery; 7 - intra-spinal cord and its sheathed thoracic artery; 8 - subclavian arte-

kam. Behind the head ria bridge; 9 - common carotid artery; 10 - thyroid

trunk; 11 - vertebral artery

brain, this artery connects with a similar one and forms the basilar artery, which is unpaired, and in turn is divided into two terminal branches - the posterior left and right cerebral arteries. The remaining branches of the subclavian artery feed the body's own muscles (diaphragm, I and II intercostal, upper and lower serratus posterior, rectus abdominis), almost all the muscles of the shoulder girdle, skin of the chest and back, neck organs and mammary glands.

The axillary artery (a. axillaris) is a continuation of the subclavian artery (from the level of the 1st rib), located deep in the axillary fossa and surrounded by trunks of the brachial plexus. It gives branches to the region of the scapula, chest and humerus.

The brachial artery (a. brachialis) is a continuation of the axillary artery and is located on the anterior surface of the brachial muscle, medial to the biceps of the shoulder. In the cubital fossa, at the level of the neck of the radius, the brachial artery divides into the radial and ulnar arteries. A number of branches depart from the brachial artery to the muscles of the shoulder and the elbow joint (Fig. 89).

The radial artery (a. radialis) has arterial branches in the forearm, in the distal forearm it passes to the back of the hand, and then to the palm. Terminal section of the radial artery anastomosis

It is a palmar branch of the ulnar artery, forming a deep palmar arch, from which the palmar metacarpal arteries originate, which flow into the common palmar digital arteries and anastomose with the dorsal metacarpal arteries.

The ulnar artery (a. ul-naris) is one of the branches of the brachial artery, located in the forearm, gives branches to the muscles of the forearm and penetrates into the palm, where it anastomoses ^ with the superficial palmar branch of the radial artery,

forming a superficial laris 89 Arteries of the forearm and hand, right:

bottom arc. IN ADDITION to arcs, A - front view; B - rear view; 1 - shoulder ar-on the BRUSH, lateria is formed; 2 - radial recurrent artery; 3 - radial-bottom and dorsal carpal artery; 4 - front

o 5 - palmar network of the wrist; 6 - own la networks. From last

bottom finger arteries; 7 - common palmar to Interosseous interdigital arteries; 8 - superficial palmar ki the dorsal metacarpal arch departs; 9 - ulnar artery; 10 - ulnar ascending arteries. Each of them is a portal artery; 13 - back network of the wrist; divides into two thin arterial - 14 - dorsal metacarpal arteries; 15 - rear

digital arteries

terii fingers, so the brush

in general, and the fingers in particular, are richly supplied with blood from many sources, which anastomose well with each other due to the presence of arcs and networks.

Branches of the thoracic aorta

The branches of the thoracic aorta are divided into parietal and visceral branches (Fig. 90). Parietal branches:

1. Superior phrenic artery (a. phrenica superior) - steam room, supplies blood to the diaphragm and the pleura covering it.

2. Posterior intercostal arteries (a. a. intercostales posteriores) - paired, supply blood to the intercostal muscles, ribs, chest skin.

Visceral branches:

1. Bronchial branches (r. r. bronchiales) supply blood to the walls of the bronchi and lung tissue.

2. Esophageal branches (r.r. oesophageales) supply blood to the esophagus.

3. Pericardial branches (r.r. pericardiaci) go to the pericardium

4. Mediastinal branches (r.r. mediastinales) supply blood to the connective tissue of the mediastinum and lymph nodes.

Branches of the abdominal aorta

Parietal branches:

1. The lower phrenic arteries (a.a. phenicae inferiores) are paired, supply blood to the diaphragm (Fig. 91).

2. Lumbar arteries (a.a. lumbales) (4 pairs) - supply blood to the muscles in the lumbar region and the spinal cord.

Rice. 90. Aorta:

1 - aortic arch; 2 - ascending aorta; 3 - bronchial and esophageal branches; 4 - descending part of the aorta; 5 - posterior intercostal arteries; 6 - celiac trunk; 7 - abdominal part of the aorta; 8 - inferior mesenteric artery; 9 - lumbar arteries; 10 - renal artery; 11 - superior mesenteric artery; 12 - thoracic aorta

Rice. 91. Abdominal aorta:

1 - lower phrenic arteries; 2 - celiac trunk; 3 - superior mesenteric artery; 4 - renal artery; 5 - inferior mesenteric artery; 6 - lumbar arteries; 7 - median sacral artery; 8 - common iliac artery; 9 - testicular (ovarian) artery; 10 - lower suprapo-chechnic artery; 11 - middle adrenal artery; 12 - superior adrenal artery

Visceral branches (unpaired):

1. The celiac trunk (truncus coeliacus) has branches: the left ventricular artery, the common hepatic artery, the splenic artery - it supplies blood to the corresponding organs.

2. Superior mesenteric and inferior mesenteric arteries (a. mes-enterica superior et a. mesenterica inferior) - supply blood to the small and large intestines.

Visceral branches (paired):

1. Middle adrenal, renal, testicular arteries - supply blood to the corresponding organs.

2. At level IV of the lumbar vertebrae, the abdominal aorta divides into two common iliac arteries, forming an aortic bifurcation, and continues into the median sacral artery.

The common iliac artery (a. iliaca communis) follows the direction of the small pelvis and is divided into the internal and external iliac arteries.

Internal iliac artery (a. iliaca interna).

It has branches - sub-ilio-lumbar lateral sacral arteries, superior gluteal, inferior gluteal, umbilical artery, inferior urinary bladder, uterine middle rectal, internal

pudendal and obturator arte- 92 Arteries of the pelvis:

rii - supply blood to the walls; 1 - the abdominal part of the aorta; 2 - common sub-ki and pelvic organs (Fig. 92). iliac artery; 3 - outer gtodudosh-

TT - - naya artery; 4 - internal iliac

External iliac.

artery; 5 - median sacral artery;

art ^ riYa ((1. iliaca eXtema). 6 - posterior branch of the internal iliac

Serves as a continuation of the ob-artery; 7 - lateral sacral arte-

shchi iliac artery ria; 8 - anterior branch of the internal sub-

in the thigh region it passes into the iliac artery; 9 - middle rectal

renal artery. External artery; 10 - lower rectal

artery; 11 - internal genital artery;

12 - dorsal artery of the penis;

13 - lower vesical artery; 14 - superior vesical artery; 15 - bottom

the iliac artery has branches - the inferior epigastric artery and the deep artery

the circumflex iliac artery is the epigastric artery; 16 - deep artery;

new bone (Fig. 93). 140

envelope ilium

Arteries of the lower limb

The femoral artery (a. femoralis) is a continuation of the external iliac artery, has branches: superficial epigastric artery, superficial artery, envelope of the ilium, external pudendal, deep artery of the thigh, descending artery - blood supply to the muscles of the abdomen and thigh. The femoral artery passes into the patella artery, which in turn divides into the anterior and posterior tibial arteries.

Front tibial artery(a. tibialis anterior) - continuation of the popliteal artery, goes along the front surface of the lower leg and passes to the rear of the foot, has branches: anterior and posterior tibial recurrent arteries,

hips; 4 - lateral artery; envelope femur; 5 - medial artery, enveloping the femur; 6 - perforating arteries; 7 - descending -

Rice. 93. Arteries of the thigh, right: A - front view; B - rear view; 1 - on the lateral and medial ventral iliac artery; 2 - hip arteries, dorsal artrenal artery; 3 - deep artery

feet, supplying blood knee-joint and anterior leg muscles.

Posterior tibial artery genicular artery; 8 - superior yagotheria (a. tibialis posterior) - prodative artery; 9 - wide berry

due to the popliteal artery. artery; 10 - popliteal artery Goes along the medial surface of the lower leg and passes to the sole, has branches: muscular; branch around the fibula; peroneal medial and lateral plantar arteries, feeding the muscles of the lateral group of the lower leg.

Veins of the systemic circulation

The veins of the systemic circulation are combined into three systems: the system of the superior vena cava, the system of the inferior vena cava and the system of the veins of the heart. The portal vein with its tributaries is isolated as a system portal vein. Each system has a main trunk, into which veins flow, carrying blood from a certain group of organs. These trunks flow into the right atrium (Fig. 94).

Superior vena cava system

The superior vena cava (v. cava superior) drains blood from the upper half of the body - the head, neck, upper limbs and chest wall. It is formed from the confluence of two brachiocephalic veins (behind the junction of the first rib with the sternum and lies in the upper part of the mediastinum). The inferior end of the superior vena cava empties into the right atrium. The diameter of the superior vena cava is 20-22 mm, the length is 7-8 cm. The unpaired vein flows into it.

Rice. 94. Veins of the head and neck:

I - subcutaneous venous network; 2 - superficial temporal vein; 3 - supraorbital vein; 4 - angular vein; 5 - right labial vein; 6 - mental vein; 7- facial vein; 8 - anterior jugular vein; 9 - internal jugular vein; 10 - mandibular vein;

II - pterygoid plexus; 12 - posterior ear vein; 13 - occipital vein

Unpaired vein (v. azygos) and its branch (semi-unpaired). These are pathways that drain venous blood away from the walls of the body. The azygous vein lies in the mediastinum and originates from the parietal veins, which penetrate the diaphragm from the abdominal cavity. It takes in the right intercostal veins, veins from the mediastinal organs and the semi-unpaired vein.

Semi-unpaired vein (v. hemiazygos) - lies to the right of the aorta, receives the left intercostal veins and repeats the course of the unpaired vein, into which it flows, which creates the possibility of outflow of venous blood from the walls of the chest cavity.

The brachiocephalic veins (v.v. brachiocephalics) originate behind the sterno-pulmonary articulation, in the so-called venous angle, from the junction of three veins: internal, external jugular and subclavian. The brachiocephalic veins collect blood from the veins associated with the branches of the subclavian artery, as well as from the veins of the thyroid, thymus, laryngeal, trachea, esophagus, venous plexuses of the spine, deep veins of the neck, veins of the upper intercostal muscles and the mammary gland. The connection between the systems of the superior and inferior vena cava is carried out through the terminal branches of the vein.

The internal jugular vein (v. jugularis interna) begins at the level of the jugular foramen as a direct continuation of the sigmoid sinus of the dura mater and descends along the neck in the same vascular bundle with the carotid artery and the vagus nerve. It collects blood from the head and neck, from the sinuses of the dura mater, into which blood enters from the veins of the brain. The common facial vein consists of the anterior and posterior facial veins and is the largest tributary of the internal jugular vein.

The external jugular vein (v. jugularis externa) is formed at the level of the angle of the lower jaw and descends along the outer surface of the sternocleidomastoid muscle, covered subcutaneous muscle neck. It drains blood from the skin and muscles of the neck and occipital region.

The subclavian vein (v. subclavia) continues the axillary, serves to drain blood from upper limb and has no permanent branches. The walls of the vein are firmly connected to the surrounding fascia, which holds the lumen of the vein and increases it with a raised arm, providing an easier outflow of blood from the upper extremities.

Veins of the upper limb

Venous blood from the fingers of the hand enters the dorsal veins of the hand. The superficial veins pass larger than the deep ones and form the venous plexuses of the back of the hand. Of the two venous arches of the palm, corresponding to the arterial ones, the deep arch serves as the main venous collector of the hand.

The deep veins of the forearm and shoulder are accompanied by a double number of arteries and bear their name. They repeatedly anastomose with each other. Both brachial veins merge into the axillary vein, which receives all the blood not only from the deep, but also the superficial veins of the upper extremities. One of the branches of the axillary vein, descending along the side wall of the body, anastomoses with the saphenous branch of the femoral vein, forming an anastomosis between the system of the superior and inferior vena cava. The main saphenous veins of the upper limb are the head and main (Fig. 95).

Rice. 95. Superficial veins of the arm, right:

A - rear view; B - front view; 1 - lateral saphenous vein of the arm; 2 - intermediate vein of the elbow; 3 - medial saphenous vein of the arm; 4 - dorsal venous network of the hand

Rice. 96. Deep veins of the upper limb, right:

A - veins of the forearm and hand: 1 - ulnar veins; 2 - radial veins; 3 - superficial palmar venous arch; 4 - palmar fingers veins. B - veins of the shoulder and shoulder girdle: 1 - axillary vein; 2 - brachial veins; 3 - lateral saphenous vein of the arm; 4 - medial saphenous vein of the arm

The lateral saphenous vein of the arm (v. cephalica) originates from the deep palmar arch and superficial venous plexus of the rear of the hand and stretches along the lateral edge of the forearm and shoulder, taking superficial veins along the way. It flows into the axillary vein (Fig. 96).

The medial saphenous vein of the hand (v. basilica) starts from the deep palmar arch and the superficial venous plexus of the back of the hand. Moving to the forearm, the vein is significantly replenished with blood from the head vein through an anastomosis with it in the area of ​​​​the elbow bend - the middle cubital vein (drugs are injected into this vein and blood is taken). The main vein flows into one of the brachial veins.

Inferior vena cava system

The inferior vena cava (v. cava inferior) begins at the level of the V lumbar vertebra from the confluence of the right and left common iliac veins, lies behind the peritoneum to the right of the aorta (Fig. 97). Passing behind the liver, the inferior vena cava sometimes plunges into its tissue, and then through the hole

stiya in tendon center diaphragm penetrates the mediastinum and the pericardial sac, opening into the right atrium. The cross section at its beginning is 20 mm, and near the mouth - 33 mm.

The inferior vena cava receives paired branches both from the walls of the body and from the viscera. The parietal veins include the lumbar veins and the veins of the diaphragm.

Lumbar veins (v.v. lumbales) in the amount of 4 pairs correspond to the lumbar arteries, as well as segmental, as well as intercostal veins. The lumbar veins communicate with each other by vertical anastomoses, due to which thin venous trunks are formed on both sides of the inferior vena cava, which at the top continue into the unpaired (right) and semi-unpaired (left) veins, being one of the anastomoses between the inferior and superior vena cava. The internal branches of the inferior vena cava include: internal testicular and ovarian veins, renal, adrenal and hepatic. The latter through the venous network of the liver are connected with the portal vein.

Testicular vein (v. tecticularis) begins in the testicle and its epididymis, forms inside spermatic cord dense plexus and flows into the inferior vena cava on the right, and on the left into the renal vein.

The ovarian vein (v. ovarica) starts from the hilum of the ovary, passing through the wide ligament of the uterus. It accompanies the artery of the same name and further goes like the testicular vein.

The renal vein (v. renalis) begins at the gate of the kidney with several fairly large branches that lie in front renal artery and empty into the inferior vena cava.

Adrenal vein (v. suprarenalis) - on the right flows into the inferior vena cava, and on the left - into the renal.

Rice. 97. Inferior vena cava and its tributaries:

1 - inferior vena cava; 2 - adrenal vein; 3 - renal vein; 4 - testicular veins; 5 - common iliac vein; 6 - femoral vein; 7 - external iliac vein; 8 - internal iliac vein; 9 - lumbar veins; 10 - lower diaphragmatic veins; 11 - hepatic veins

Hepatic veins (v. le-

raisae) - there are 2-3 large ones and several small ones, through which the blood that enters the liver flows. These veins drain into the inferior vena cava.

portal vein system

Portal vein (liver)

(V. robae (heratis)) - collects blood from the walls of the digestive canal, starting from the stomach and up to the upper rectum, as well as from the gallbladder, pancreas and spleen (Fig. 98). This is a short thick trunk, formed behind the head of the pancreas as a result of the confluence of three large veins - the splenic, superior and inferior mesenteric, which branch in the region of the arteries of the same name. The portal vein enters the liver through its gate.

Rice. 98. Portal vein system and inferior vena cava:

1 - anastomoses between the branches of the portal and superior vena cava in the wall of the esophagus; 2- splenic vein; 3 - superior mesenteric vein; 4 - inferior mesenteric vein; 5 - external iliac vein; 6 - internal iliac vein; 7 - anastomoses between the branches of the portal and inferior vena cava in the wall of the rectum; 8 - common iliac vein; 9 - portal vein; 10 - hepatic vein; 11 - inferior vena cava

Veins of the pelvis

The common iliac vein (v. iliaca communis) begins at the level of the sacral vertebral articulation from the confluence of the internal and external iliac veins.

The internal iliac vein (v. iliaca interna) lies behind the artery of the same name and has a branching area in common with it. The branches of the vein, carrying blood from the viscera, form abundant plexuses around the organs. These are the hemorrhoidal plexuses surrounding the rectum, especially in its lower section, the plexuses behind the symphysis, which receive blood from the genitals, the venous plexus of the bladder, and in women, the plexuses around the uterus and vagina.

The external iliac vein (v. iliaca externa) starts above the inguinal ligament and serves as a direct continuation of the femoral vein. It carries the blood of all superficial and deep veins of the lower limb.

Veins of the lower limb

On the foot, venous arches of the rear and soles, as well as subcutaneous venous networks, are isolated. The small saphenous vein of the lower leg and the great saphenous vein of the leg begin from the veins of the foot (Fig. 99).

Rice. 99. Deep veins of the lower limb, right:

A - leg veins, medial surface; B - veins of the back surface of the leg; B - veins of the thigh, anteromedial surface; 1 - venous network heel area; 2 - venous network in the ankles; 3 - posterior tibial veins; 4 - peroneal veins; 5 - anterior tibial veins; 6 - popliteal vein; 7 - great saphenous vein of the leg; 8 - small saphenous vein of the leg; 9 - femoral vein; 10 - deep vein of the thigh; 11 - perforating veins; 12 - lateral veins enveloping the femur; 13 - external iliac vein

The small saphenous vein of the lower leg (v. saphena parva) passes to the lower leg behind external ankle and flows into the popliteal vein.

The great saphenous vein of the leg (v. saphena magna) rises to the lower leg in front of the inner ankle. On the thigh, gradually increasing in diameter, it reaches the inguinal ligament, under which it flows into the femoral vein.

The deep veins of the foot, lower leg and thigh in double quantity accompany the arteries and bear their names. All these veins have many

lazy valves. Deep veins abundantly anastomose with superficial ones, through which a certain amount of blood rises from the deep parts of the limb.

Questions for self-control

1. Describe the importance of the cardiovascular system for the human body.

2. Tell us about the classification of blood vessels, describe their functional significance.

3. Describe the large and small circles of blood circulation.

4. Name the links of the microvasculature, explain the features of their structure.

5. Describe the structure of the walls of blood vessels, differences in the morphology of arteries and veins.

6. List the patterns of the course and branching of blood vessels.

7. What are the boundaries of the heart, their projection on the anterior chest wall?

8. Describe the structure of the chambers of the heart, their features in connection with the function.

9. Give a structural and functional description of the atria.

10. Describe the features of the structure of the ventricles of the heart.

11. Name the valves of the heart, explain their meaning.

12. Describe the structure of the heart wall.

13. Tell us about the blood supply to the heart.

14. Name the parts of the aorta.

15. Describe the thoracic part of the aorta, name its branches and areas of blood supply.

16. Name the branches of the aortic arch.

17. List the branches of the external carotid artery.

18. Name the terminal branches of the external carotid artery, describe the areas of their vascularization.

19. List the branches of the internal carotid artery.

20. Describe the blood supply to the brain.

21. Name the branches of the subclavian artery.

22. What are the features of the branching of the axillary artery?

23. Name the arteries of the shoulder and forearm.

24. What are the features of the blood supply to the hand?

25. List the arteries of the organs of the chest cavity.

26. Tell us about the abdominal part of the aorta, its holotopy, skeletopy and syntopy.

27. Name the parietal branches of the abdominal aorta.

28. List the splanchnic branches of the abdominal aorta, explain the areas of their vascularization.

29. Describe the celiac trunk and its branches.

30. Name the branches of the superior mesenteric artery.

31. Name the branches of the inferior mesenteric artery.

32. List the arteries of the walls and organs of the pelvis.

33. Name the branches of the internal iliac artery.

34. Name the branches of the external iliac artery.

35. Name the arteries of the thigh and leg.

36. What are the features of the blood supply to the foot?

37. Describe the system of the superior vena cava, its roots.

38. Tell us about the inner jugular vein and its channels.

39. What are the features of blood flow from the brain?

40. How is the blood flow from the head?

41. List the internal tributaries of the internal jugular vein.

42. Name the intracranial tributaries of the internal jugular vein.

43. Describe the blood flow from the upper limb.

44. Describe the system of the inferior vena cava, its roots.

45. List the parietal tributaries of the inferior vena cava.

46. ​​Name the splanchnic tributaries of the inferior vena cava.

47. Describe the portal vein system, its tributaries.

48. Tell us about the tributaries of the internal iliac vein.

49. Describe the blood flow from the walls and organs of the small pelvis.

50. What are the features of blood flow from the lower limb?

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

From the inside, their walls are lined with 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 carry oxygen-rich blood from the heart to tissues and organs. This blood is bright red so all the arteries look red.

Blood moves through the arteries with great force, so their walls are thick and elastic. They consist of a large number 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 deoxygenated blood 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 the 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 with a 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 a measure of the pressure during a heartbeat. 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 arterial pressure indicates that the heart is working with overload: it takes more effort to push blood through the vessels.

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