How are veins different from arteries. Functions of blood vessels - arteries, capillaries, veins Arteries and veins structural features

Human arteries and veins perform different jobs in the body. In this regard, one can observe significant differences in the morphology and conditions for the passage of blood, although the general structure, with rare exceptions, is the same for all vessels. Their walls have three layers: inner, middle, outer.

The inner shell, called intima, without fail has 2 layers:

• the endothelium lining the inner surface is a layer of squamous epithelial cells;
• subendothelium - located under the endothelium, consists of connective tissue with a loose structure.

The middle shell is made up of myocytes, elastic and collagen fibers.

The outer shell, called "adventitia", is a fibrous connective tissue with a loose structure, equipped with vascular vessels, nerves, and lymphatic vessels.

arteries

These are blood vessels that carry blood from the heart to all organs and tissues. There are arterioles and arteries (small, medium, large). Their walls have three layers: intima, media and adventitia. Arteries are classified according to several criteria.

According to the structure of the middle layer, three types of arteries are distinguished:

• Elastic. Their middle layer of the wall consists of elastic fibers that can withstand the high blood pressure that develops when it is ejected. This species includes the pulmonary trunk and aorta.
• Mixed (muscular-elastic). The middle layer consists of a variable number of myocytes and elastic fibers. These include carotid, subclavian, iliac.
• Muscular. Their middle layer is represented by individual myocytes located circularly.

By location relative to the organs of the artery are divided into three types:

• Trunk - supply blood to parts of the body.
• Organ - carry blood to the organs.
• Intraorganic - have branches inside the organs.

They are non-muscular and muscular.

The walls of non-muscular veins consist of endothelium and loose connective tissue. Such vessels are found in bone tissue, placenta, brain, retina, and spleen.

Muscular veins, in turn, are divided into three types, depending on how myocytes are developed:

• poorly developed (neck, face, upper body);
• medium (brachial and small veins);
• strongly (lower body and legs).

The structure and its features:

• Larger in diameter than arteries.
• Poorly developed subendothelial layer and elastic component.
• The walls are thin and fall off easily.
• The smooth muscle elements of the middle layer are rather poorly developed.
• Pronounced outer layer.
• The presence of a valvular apparatus, which is formed by the inner layer of the vein wall. The base of the valves consists of smooth myocytes, inside the valves - fibrous connective tissue, outside they are covered with a layer of endothelium.
• All shells of the wall are endowed with vascular vessels.

The balance between venous and arterial blood is ensured by several factors:

• a large number of veins;
• their larger caliber;
• dense network of veins;
• formation of venous plexuses.

Differences

How are arteries different from veins? These blood vessels have significant differences in many ways.

Arteries and veins, first of all, differ in the structure of the wall

According to the structure of the wall

Arteries have thick walls, many elastic fibers, well developed smooth muscles, and do not collapse unless filled with blood. Due to the contractility of the tissues that make up their walls, oxygenated blood is quickly delivered to all organs. The cells that make up the layers of the walls ensure the unhindered passage of blood through the arteries. Their inner surface is corrugated. The arteries must withstand the high pressure that is created by the powerful ejections of blood.

The pressure in the veins is low, so the walls are thinner. They fall off in the absence of blood in them. Their muscle layer is not able to contract like that of the arteries. The surface inside the vessel is smooth. Blood moves slowly through them.

In veins, the thickest shell is considered to be the outer, in the arteries - the middle one. Veins do not have elastic membranes; arteries have internal and external.

By shape

Arteries have a fairly regular cylindrical shape, they are round in cross section.

Due to the pressure of other organs, the veins are flattened, their shape is tortuous, they either narrow or expand, which is associated with the location of the valves.

In count

There are more veins in the human body, fewer arteries. Most medium arteries are accompanied by a pair of veins.

By the presence of valves

Most veins have valves that prevent blood from flowing backwards. They are located in pairs opposite each other throughout the vessel. They are not found in the portal caval, brachiocephalic, iliac veins, as well as in the veins of the heart, brain and red bone marrow.

In the arteries, valves are located at the exit of the vessels from the heart.

By blood volume

The veins circulate about twice as much blood as the arteries.

By location

Arteries lie deep in the tissues and approach the skin only in a few places where the pulse is heard: on the temples, neck, wrist, and instep. Their location is about the same for all people.

The veins are mostly located close to the surface of the skin.

The location of the veins may vary from person to person.

To ensure the movement of blood

In the arteries, blood flows under the pressure of the force of the heart, which pushes it out. At first, the speed is about 40 m/s, then it gradually decreases.

Blood flow in the veins occurs due to several factors:

• pressure force, depending on the impulse of blood from the heart muscle and arteries;
• the suction force of the heart during relaxation between contractions, that is, the creation of negative pressure in the veins due to the expansion of the atria;
• suction action on the chest veins of respiratory movements;
• contraction of the muscles of the legs and arms.

In addition, about a third of the blood is in the venous depots (in the portal vein, spleen, skin, walls of the stomach and intestines). It is pushed out from there if it is necessary to increase the volume of circulating blood, for example, with massive bleeding, with high physical exertion.

By color and composition of blood

Arteries carry blood from the heart to the organs. It is enriched with oxygen and has a scarlet color.

Arterial and venous bleeding have different symptoms. In the first case, the blood is ejected in a fountain, in the second, it flows in a jet. Arterial - more intense and dangerous for humans.

Thus, the main differences can be identified:

• Arteries transport blood from the heart to the organs, veins carry it back to the heart. Arterial blood carries oxygen, venous blood returns carbon dioxide.
• Arterial walls are more elastic and thicker than venous ones. In the arteries, blood is pushed out with force and moves under pressure, in the veins it flows calmly, while valves do not allow it to move in the opposite direction.
• There are 2 times less arteries than veins, and they are deep. Veins are located in most cases superficially, their network is wider.

Veins, unlike arteries, are used in medicine to obtain material for analysis and to deliver drugs and other fluids directly into the bloodstream.

All about blood vessels: types, classifications, characteristics, meaning

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 ​​​​the eyes. And if they are assembled and stretched into one straight line, then the total length will be about 100 thousand km.

These tubular elastic formations function continuously, transferring blood from the constantly contracting heart to all corners 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 in a lifetime.

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

Division into types and their characteristics

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

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

human blood vessels

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 - circulatory circles.

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

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

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

arteries

They deliver blood saturated with useful substances and oxygen from the heart to all cells of the body. By structure, human arterial vessels are more durable than veins. Such a device (a denser and more durable middle layer) allows them to withstand the load of strong internal blood pressure.

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

• from the organ supplied by them (for example, renal, pulmonary);
• the bones to which they adjoin (ulna);
• places where they depart from a large vessel (superior mesenteric);
• directions of its movement (medial);
• depth of finding (surface).

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

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There are such types:

Elastic type. These are the arteries that branch directly from the heart - the aorta and other large arteries. Being close to the heart, they must withstand the highest blood pressure (up to 130 mm Hg) and its high speed of movement - 1.3 m / s.

They withstand such a load thanks to the fibers of collagen and elastin, which form the middle layer of the walls of this type of artery.

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

capillaries

These are the thinnest vessels, with a diameter much thinner than a human hair. This is the longest part of the circulatory system, and their total 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: the chemical exchange between the bloodstream and tissues.

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

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These are the blood vessels that carry oxygen-depleted blood back to the heart.

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

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

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

Separation by functional load

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

There are six groups:

1. Vessels with shock-absorbing function. The group includes such vessels, the middle layer of the wall of which consists of elastin and collagen. The elasticity and elasticity of their walls provide shock absorption, smoothing out systolic fluctuations in blood flow.

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

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

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

The structure of the veins

Features of the structure of the veins, their difference from the arteries due to the difference in their functions.

Conditions for the movement of blood through the venous system are completely different than in the arteries. In the capillary network, the pressure drops to 10 mm Hg. Art., exhausting almost completely the force of the cardiac impulse in the arterial system. Movement through the veins is due to two factors: the suction action of the heart and the pressure of more and more portions of blood entering the venous system. Hence, the pressure and speed of blood flow in the venous vessels is immeasurably lower than the arterial one. A much smaller volume of blood passes through the veins per unit time, which requires a much larger capacity from the entire venous system, thus causing a morphological difference in the structure of the veins. The venous system is also distinguished by the fact that the blood in it moves against gravity in parts of the body located below the level of the heart. Therefore, for the implementation of normal blood circulation, the walls of the veins must be adapted to hydrostatic pressure, which is reflected in the histological structure of the veins.

The increased capacity of the venous bed is provided by a significantly larger diameter of the venous branches and trunks - usually one artery on the limbs is accompanied by two to three veins. The capacity of the veins of the great circle is twice the capacity of its arteries. The conditions of the function of the venous system create the possibility of stagnation of blood and even its reverse flow. The possibility of centripetal movement of blood through the venous vessels is ensured by the presence of numerous valves of collaterals and anastomoses. In addition, the suction action of the chest and the movement of the diaphragm contribute to the movement of blood; muscle contractions favorably affect the emptying of the deep veins of the extremities.

The unloading function in the venous system is also possessed by numerous communications, extensive venous plexuses, especially strongly developed in the small pelvis, on the back of the hand. These collaterals allow blood to flow from one system to another.

The number of communications between the superficial and deep veins on the upper limb is calculated from 31 to 169, on the lower - from 53 to 112 with a diameter of 0.01 to 2 mm. There are direct anastomoses, directly connecting two venous trunks, and indirect, connecting separate branches of different trunks.

Venous valves

An exceptional role in the structure of the veins is played by valves, which are parietal folds of the intima of the veins. The basis of the valves is collagen tissue lined with endothelium. At the base of the valves are networks of elastic fibers. The pocket valves are always open towards the heart, so they do not interfere with blood flow. The wall of the vein involved in the formation of the pocket, at its location, forms a bulge - a sinus. Valves are available in one, two or three sails. The smallest caliber of venous vessels with valves is 0.5 mm. The localization of the valves is due to hemodynamic and hydrostatic conditions; valves withstand a pressure of 2-3 atm., the higher the pressure, the tighter they close. The valves are mainly located in those veins that are subject to maximum external influence - the veins of the subcutaneous tissue and muscles - and where the flow of blood is hindered by hydrostatic pressure, which is observed in the venous vessels located below the level of the heart, in which blood moves against gravity. Valves are also located in large numbers in those veins where the flow of blood is easily blocked mechanically. This is observed especially often in the veins of the extremities, and there are more valves in the deep veins than in the superficial ones.

The valve system, in their normal state, contributes to the forward movement of blood towards the heart. In addition, the valve system protects the capillaries from hydrostatic pressure. Valves also exist in venous anastomoses. Of exceptionally great practical importance are the valves located between the superficial and deep veins of the lower extremities, open towards the deep venous vessels. However, a number of valveless communications allow reverse blood flow: from deep veins to superficial ones. On the upper limbs, less than half of the communications are equipped with valves, therefore, during intense muscular work, part of the blood can pass from deep venous vessels to superficial ones.

The structure of the walls of the venous vessels reflects the features of the function of the venous system; the walls of venous vessels are thinner and more elastic than arterial ones. Extremely filled veins do not take a rounded shape, which also depends on the low blood pressure, which in the peripheral parts of the system is not more than 10 mm Hg. Art., at the level of the heart - 3-6 mm Hg. Art. In the large central veins, the pressure becomes negative due to the suction action of the chest. The veins are deprived of the active hemodynamic function that the powerful muscular walls of the arteries possess; the weaker musculature of the veins only counteracts the influence of hydrostatic pressure. In the venous vessels located above the heart, the muscular system is much less developed than in the venous vessels below this level. In addition to the pressure factor, their histological structure, determine the caliber and location of the veins.

The wall of the venous vessels has three layers. The structure of the veins has a powerful collagen skeleton, which is especially well developed in the adventitia and consists of longitudinal collagen bundles. The muscles of the veins rarely form a continuous layer, located in all elements of the wall in the form of bundles. The latter have a longitudinal direction in the intima and adventitia; the middle layer is characterized by their circular or spiral direction.

Of the large veins, the superior vena cava is completely devoid of muscles; the lower hollow has a powerful layer of muscles in the outer shell, but does not contain them in the middle one. The popliteal, femoral, and iliac veins contain muscles in all three layers. V. saphena magna has longitudinal and spiral muscle bundles. The collagen base laid in the structure of the veins is penetrated by elastic tissue, which also forms a single skeleton for all three layers of the wall. However, the elastic skeleton, which is also associated with the muscular one, is less developed in the veins than the collagen one, especially in the adventitia. Membrana elastica interna is also weakly expressed. Elastic fibers, like muscle fibers, have a longitudinal direction in the adventitia and intima, and a circular direction in the middle layer. The structure of the vein is stronger than the arteries for breaking, which is associated with the special strength of their collagen skeleton.

The intima in all veins contains the subendothelial cambial layer. Venules differ from arterioles in the annular direction of elastic fibers. Postcapillary venules differ from precapillaries in their large diameter and the presence of circular elastic elements.

The blood supply to the walls of the veins is carried out due to the arterial vessels located in their immediate vicinity. The arteries feeding the walls form numerous transverse anastomoses between themselves in the periadventitial tissue. From this arterial network, branches extend into the wall and at the same time supply the subcutaneous tissue and nerves. Arterial paravenous tracts can play the role of roundabout ways of blood circulation.

The innervation of the veins of the extremities is carried out similarly to the arterial branches of the adjacent nerves. In the structure of the veins, a rich nervous apparatus was found, consisting of receptor and motor nerve fibers.

Functions of blood vessels - arteries, capillaries, veins

What are vessels?

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

After many years, obstructions to the movement of blood - plaques - form on the vessels. These are formations on the inside of the vessels. Thus, the heart must pump blood more intensively in order to overcome the obstructions in the vessels, which disrupts the work of the heart. At this point, the heart can no longer deliver blood to the organs of the body and can not cope with the work. But at this stage it is still possible to recover. Vessels are cleansed of salts and cholesterol layers. (Read also: Cleansing of vessels)

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

human blood vessels

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

All blood vessels are made up of three layers:

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

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

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

arteries

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

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

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

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

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

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

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

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

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

capillaries

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

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

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

Arterioles - branch into precapillaries;

Precapillaries - transitional vessels between arterioles and capillaries proper;

Venules are places where capillaries pass into veins.

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

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

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

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

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

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

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

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

Functional groups of vessels

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

Cushioning Vessels

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

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

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

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

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

Resistive vessels

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

Vessels-sphincters

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

exchange vessels

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

capacitive vessels

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

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

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

Shunt vessels

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

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

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

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

Diseases of the blood vessels

The most dangerous vascular diseases that pose a threat to life: aneurysm of the abdominal and thoracic aorta, arterial hypertension, ischemic disease, stroke, renal vascular disease, atherosclerosis of the carotid arteries.

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

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

Varicose veins - a disease that results in the expansion and lengthening of the veins of the upper and lower extremities, thinning of their walls, the formation of varicose veins. The changes that occur in this case in the vessels are usually persistent and irreversible. Varicose veins are more common in women - in 30% of women after 40 and only 10% of men of the same age. (Read also: Varicose veins - causes, symptoms and complications)

Which doctor should I contact with vessels?

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

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

The structure of arteries, veins and capillaries;

General characteristics of the vascular system

BIG AND SMALL CIRCULATIONS. HEART.

THE CARDIOVASCULAR SYSTEM. ARTERIES. VIENNA. CAPILLARIES.

1. Offer type (BSP).

2. Number of predicative parts.

3. According to the purpose of the statement.

4. By emotional coloring.

5. The main means of communication of predicative parts.

6. Grammatical meaning.

7. Homogeneous or heterogeneous composition, open or closed structure.

8. Additional means of connecting predicative parts and expressions

a) order of parts (fixed/unfixed);

b) structural parallelism of parts;

c) the ratio of aspectual-temporal forms of verbs-predicates;

d) lexical indicators of connection (synonyms, antonyms, words of one lexico-semantic or thematic group);

e) incompleteness of one of the parts;

f) anaphoric or cataphoric words;

g) a common minor member or a common subordinate clause.

1. Transport- all the necessary substances (proteins, carbohydrates, oxygen, vitamins, mineral salts) are delivered to the tissues and organs through the blood vessels, and metabolic products and carbon dioxide are removed.

2. Regulatory - with the blood flow through the vessels, hormonal substances, which are specific regulators of metabolic processes, are carried to the organs and tissues produced by the endocrine glands.

3. Protective - antibodies are carried with the blood stream, which are necessary for the body's defense reactions against infectious diseases.

In collaboration with the nervous and humoral systems, the vascular system plays an important role in ensuring the integrity of the body.

Vascular system divided by circulatory and lymphatic. These systems are anatomically and functionally closely related, complement each other, but there are certain differences between them.

The branch of systemic anatomy that studies the structure of blood and lymphatic vessels is called angiology.

Arteries are vessels that carry blood from the heart to organs and tissues.

Veins are blood vessels that carry blood from organs to the heart .

The arterial and venous parts of the vascular system are interconnected capillaries, through the walls of which there is an exchange of substances between blood and tissues.

- parietal (parietal) - nourish the walls of the body;

- visceral (intraorgan)- arteries of internal organs .

There are connections between the branches of the arteries - arterial anastomoses.

Arteries that provide roundabout blood flow, bypassing the main path, are called collateral. Allocate intersystem and intrasystemic anastomoses. Intersystem form connections between branches of different arteries, intrasystem between branches of the same artery. Of particular importance is the presence of such a compensatory mechanism of blood circulation in case of occlusion of the main vessel, for example, by a thrombus or a progressively increasing atherosclerotic plaque.

Intraorganic vessels are successively divided into arteries of the 1st-5th order, forming microvasculature. It is formed from arterioles, precapillary arteriole(precapillaries), capillaries, postcapillary venules(postcapillaries) and venule. From the intraorgan vessels, blood enters the arterioles, which form rich circulatory networks in the tissues of the organs. Then the arterioles pass into thinner vessels - precapillaries, the diameter of which is 40-50 microns, and the latter - into smaller - capillaries with a diameter of 6 to 30-40 microns and a wall thickness of 1 microns. The narrowest capillaries are located in the lungs, brain, and smooth muscles, while the wide ones are located in the glands. The widest capillaries (sinuses) are observed in the liver, spleen, bone marrow and lacunae of the cavernous bodies of the lobar organs.

AT capillaries blood flows at a low speed (0.5-1.0 mm/s), has low pressure (up to 10-15 mm Hg). This is due to the fact that the most intensive exchange of substances between blood and tissues occurs in the walls of capillaries. Capillaries are found in all organs, except for the epithelium of the skin and serous membranes, tooth enamel and dentin, cartilage, cornea, heart valves, etc. Connecting with each other, capillaries form capillary networks, the features of which depend on the structure and function of the organ.

After passing through the capillaries, the blood enters the postcapillary venules, and then into the venules, the diameter of which is 30-40 microns. From the venules, the formation of intraorganic veins of the 1st-5th order begins, which then flow into the extraorganic veins.

In the circulatory system, there is also a direct transition of blood from arterioles to venules - arteriolo-venular anastomoses. The total capacity of venous vessels is 3-4 times greater than that of arteries. This is due to pressure and low blood velocity in the veins, compensated by the volume of the venous bed.

Veins are the depot for venous blood. The venous system contains about 2/3 of the body's blood. Extraorganic venous vessels, connecting with each other, form the largest venous vessels of the human body - the superior and inferior vena cava, which enter the right atrium.

Arteries differ in structure and function from veins. Thus, the walls of the arteries resist blood pressure, are more elastic and extensible, and pulsate. Thanks to these qualities, the rhythmic flow of blood becomes continuous. Depending on the diameter of the artery are divided into large, medium and small. The arteries are filled with scarlet blood, which spurts when an artery is damaged.

The wall of the arteries has 3 shells: .

Inner shell - intima formed by the endothelium, basement membrane and subendothelial layer. Middle shell - media It consists mainly of smooth muscle cells of a circular (spiral) direction, as well as of collagen and elastic fibers. outer shell - adventitia It is built from loose connective tissue, which contains collagen and elastic fibers and performs protective, insulating and fixing functions, has blood vessels and nerves. The inner shell does not have its own vessels, it receives nutrients directly from the blood.

Depending on the ratio of tissue elements in the wall of the artery, they are divided into elastic, muscular and mixed types. to elastic type include the aorta and pulmonary trunk. These vessels can be greatly stretched during the contraction of the heart. Muscular type arteries are located in organs that change their volume (intestines, bladder, uterus, arteries of the extremities). To mixed type(muscular-elastic) include carotid, subclavian, femoral and other arteries. As the distance from the heart in the arteries decreases, the number of elastic elements and the number of muscle increases, the ability to change the lumen increases. Therefore, small arteries and arterioles are the main regulators of blood flow in organs.

The wall of the capillaries is thin, the inner layer is endothelium consists of a single layer of endothelial cells located on the basement membrane. Capillaries have a porous structure, due to which they are capable of all types of exchange.

The wall of the veins has 3 shells: internal (intima), middle (media) and external (adventitia). The wall of the veins is thinner than the arteries, and they are filled with dark red blood, which, if the vessel is damaged, flows smoothly, without jerks.

The lumen of the veins is slightly larger than that of the arteries. The inner layer is lined with a layer of endothelial cells, the middle layer is relatively thin and contains few muscle and elastic elements, so the veins collapse on the cut. The outer layer is represented by a well-developed connective tissue membrane. Along the entire length of the veins are valves in pairs that prevent the reverse flow of blood. valves- these are the semilunar folds of the inner lining of the venous vessel, which are usually located in pairs, they pass blood towards the heart and prevent its reverse flow. There are more valves in the superficial veins than in the deep ones, in the veins of the lower extremities than in the veins of the upper extremities. The blood pressure in the veins is low, there is no pulsation.

Depending on the topography and position in the body and organs, the veins are divided into superficial and deep. On the extremities, deep veins accompany the arteries of the same name in pairs. The name of the deep veins is similar to the name of the arteries to which they adjoin (brachial artery - brachial vein, etc.). The superficial veins are connected to the deep veins by penetrating veins that act as anastomoses. Often adjacent veins, having joined together by numerous anastomoses, form venous plexuses on the surface or in the walls of a number of internal organs (bladder, rectum).

The movement of blood through the veins is facilitated by:

Contraction of the muscles adjacent to the neurovascular bundle (the so-called peripheral venous hearts);

Suction action of the chest and chambers of the heart;

Pulsation of an artery adjacent to a vein.

In the walls of the vessels there are nerve fibers associated with receptors that perceive changes in the composition of the blood and the vessel wall. There are especially many receptors in the aorta, carotid sinus, and pulmonary trunk.

The regulation of blood circulation both in the body as a whole and in individual organs, depending on their functional state, is carried out by the nervous and endocrine systems.

The largest artery is. Arteries depart from it, which, as they move away from the heart, branch and become smaller. The thinnest arteries are called arterioles. In the thickness of the organs, the arteries branch up to the capillaries (see). Nearby arteries are often connected, through which collateral blood flow occurs. Usually, arterial plexuses and networks are formed from the anastomosing arteries. An artery that supplies blood to a part of an organ (a segment of the lung, liver) is called segmental.

The wall of the artery consists of three layers: internal - endothelial, or intima, middle - muscular, or media, with a certain amount of collagen and elastic fibers, and external - connective tissue, or adventitia; the wall of the artery is richly supplied with vessels and nerves, located mainly in the outer and middle layers. Based on the structural features of the wall, the arteries are divided into three types: muscular, muscular - elastic (for example, carotid arteries) and elastic (for example, the aorta). Muscular-type arteries include small arteries and arteries of medium caliber (for example, radial, brachial, femoral). The elastic frame of the artery wall prevents its collapse, ensuring the continuity of blood flow in it.

Usually, the arteries lie for a long distance in depth between the muscles and near the bones, to which the artery can be pressed during bleeding. On a superficially lying artery (for example, the radial one), it is palpated.

The walls of the arteries have their own supplying blood vessels (“vessels of the vessels”). The motor and sensory innervation of the arteries is carried out by sympathetic, parasympathetic nerves and branches of the cranial or spinal nerves. The nerves of the artery penetrate into the middle layer (vasomotors - vasomotor nerves) and contract the muscle fibers of the vascular wall and change the lumen of the artery.

Rice. 1. Arteries of the head, trunk and upper limbs:
1-a. facialis; 2-a. lingualis; 3-a. thyreoidea sup.; 4-a. carotis communis sin.; 5-a. subclavia sin.; 6-a. axillaris; 7 - arcus aortae; £ - aorta ascendens; 9-a. brachialis sin.; 10-a. thoracica int.; 11 - aorta thoracica; 12 - aorta abdominalis; 13-a. phrenica sin.; 14 - truncus coeliacus; 15-a. mesenterica sup.; 16-a. renalis sin.; 17-a. testicular sin.; 18-a. mesenterica inf.; 19-a. ulnaris; 20-a. interossea communis; 21-a. radialis; 22-a. interossea ant.; 23-a. epigastric inf.; 24 - arcus palmaris superficialis; 25 - arcus palmaris profundus; 26 - a.a. digitales palmares communes; 27 - a.a. digitales palmares propriae; 28 - a.a. digitales dorsales; 29 - a.a. metacarpeae dorsales; 30 - ramus carpeus dorsalis; 31-a, profunda femoris; 32-a. femoralis; 33-a. interossea post.; 34-a. iliaca externa dextra; 35-a. iliaca interna dextra; 36-a. sacraiis mediana; 37-a. iliaca communis dextra; 38 - a.a. lumbales; 39-a. renalis dextra; 40 - a.a. intercostales post.; 41-a. profunda brachii; 42-a. brachialis dextra; 43 - truncus brachio-cephalicus; 44-a. subciavia dextra; 45-a. carotis communis dextra; 46-a. carotis externa; 47-a. carotis interna; 48-a. vertebralis; 49-a. occipitalis; 50 - a. temporalis superficialis.

Rice. 2. Arteries of the anterior surface of the lower leg and rear of the foot:
1 - a, genu descendens (ramus articularis); 2-ram! musculares; 3-a. dorsalis pedis; 4-a. arcuata; 5 - ramus plantaris profundus; 5-a.a. digitales dorsales; 7-a.a. metatarseae dorsales; 8 - ramus perforans a. peroneae; 9-a. tibialis ant.; 10-a. recurrens tibialis ant.; 11 - rete patellae et rete articulare genu; 12-a. Genu sup. lateralis.

Rice. 3. Arteries of the popliteal fossa and posterior surface of the lower leg:
1-a. poplitea; 2-a. Genu sup. lateralis; 3-a. Genu inf. lateralis; 4-a. peronea (fibularis); 5 - rami malleolares tat.; 6 - rami calcanei (lat.); 7 - rami calcanei (med.); 8 - rami malleolares mediales; 9-a. tibialis post.; 10-a. Genu inf. medialis; 11-a. Genu sup. medialis.

Rice. 4. Arteries of the plantar surface of the foot:
1-a. tibialis post.; 2 - rete calcaneum; 3-a. plantaris lat.; 4-a. digitalis plantaris (V); 5 - arcus plantaris; 6 - a.a. metatarsea plantares; 7-a.a. digitales propriae; 8-a. digitalis plantaris (hallucis); 9-a. plantaris medialis.

Rice. 5. Arteries of the abdominal cavity:
1-a. phrenica sin.; 2-a. gastric sin.; 3 - truncus coeliacus; 4-a. lienalis; 5-a. mesenterica sup.; 6-a. hepatica communis; 7-a. gastroepiploica sin.; 8 - a.a. jejunales; 9-a.a. ilei; 10-a. colica sin.; 11-a. mesenterica inf.; 12-a. iliaca communis sin.; 13 -aa, sigmoideae; 14-a. rectalis sup.; 15-a. appendicis vermiformis; 16-a. ileocolica; 17-a. iliaca communis dextra; 18-a. colica. dext.; 19-a. pancreaticoduodenal inf.; 20-a. colica media; 21-a. gastroepiploica dextra; 22-a. gastroduodenalis; 23-a. gastrica dextra; 24-a. hepatica propria; 25 - a, cystica; 26 - aorta abdominalis.

Arteries (Greek arteria) - a system of blood vessels extending from the heart to all parts of the body and containing oxygen-enriched blood (an exception is a. pulmonalis, which carries venous blood from the heart to the lungs). The arterial system includes the aorta and all its branches down to the smallest arterioles (Fig. 1-5). Arteries are usually designated by topographic feature (a. facialis, a. poplitea) or by the name of the supplied organ (a. renalis, aa. cerebri). Arteries are cylindrical elastic tubes of various diameters and are divided into large, medium and small. The division of arteries into smaller branches occurs according to three main types (V. N. Shevkunenko).

With the main type of division, the main trunk is well defined, gradually decreasing in diameter as the secondary branches depart from it. The loose type is characterized by a short main trunk, quickly disintegrating into a mass of secondary branches. Transitional, or mixed, type occupies an intermediate position. Branches of arteries are often connected to each other, forming anastomoses. There are intrasystemic anastomoses (between branches of one artery) and intersystemic (between branches of different arteries) (B. A. Dolgo-Saburov). Most anastomoses exist permanently as roundabout (collateral) circulatory pathways. In some cases, collaterals may reappear. Small arteries with the help of arteriovenous anastomoses (see) can directly connect to veins.

Arteries are derivatives of the mesenchyme. In the process of embryonic development, muscle, elastic elements and adventitia, also of mesenchymal origin, join the initial thin endothelial tubules. Histologically, three main membranes are distinguished in the wall of the artery: internal (tunica intima, s. interna), middle (tunica media, s. muscularis) and external (tunica adventitia, s. externa) (Fig. 1). According to the structural features, the arteries of the muscular, muscular-elastic and elastic types are distinguished.

Muscular-type arteries include small and medium-sized arteries, as well as most of the arteries of the internal organs. The inner lining of the artery includes the endothelium, subendothelial layers, and the inner elastic membrane. The endothelium lines the lumen of the artery and consists of flat cells elongated along the axis of the vessel with an oval nucleus. The boundaries between cells have the appearance of a wavy or finely serrated line. According to electron microscopy, a very narrow (about 100 A) gap is constantly maintained between cells. Endothelial cells are characterized by the presence in the cytoplasm of a significant number of bubble-like structures. The subendothelial layer consists of connective tissue with very thin elastic and collagen fibers and poorly differentiated stellate cells. The subendothelial layer is well developed in the arteries of large and medium caliber. The internal elastic, or fenestrated, membrane (membrana elastica interna, s.membrana fenestrata) has a lamellar-fibrillar structure with holes of various shapes and sizes and is closely connected with the elastic fibers of the subendothelial layer.

The middle shell consists mainly of smooth muscle cells, which are arranged in a spiral. Between muscle cells there is a small amount of elastic and collagen fibers. In medium-sized arteries, at the border between the middle and outer shells, elastic fibers can thicken, forming an outer elastic membrane (membrana elastica externa). The complex musculo-elastic skeleton of muscular-type arteries not only protects the vascular wall from overstretching and rupture and ensures its elastic properties, but also allows the arteries to actively change their lumen.

Arteries of the muscular-elastic, or mixed, type (for example, the carotid and subclavian arteries) have thicker walls with an increased content of elastic elements. Fenestrated elastic membranes appear in the middle shell. The thickness of the internal elastic membrane also increases. An additional inner layer appears in the adventitia, containing separate bundles of smooth muscle cells.

The vessels of the largest caliber belong to the elastic type arteries - the aorta (see) and the pulmonary artery (see). In them, the thickness of the vascular wall increases even more, especially the middle membrane, where elastic elements predominate in the form of 40-50 powerfully developed fenestrated elastic membranes connected by elastic fibers (Fig. 2). The thickness of the subendothelial layer also increases, and in addition to loose connective tissue rich in stellate cells (Langhans layer), separate smooth muscle cells appear in it. The structural features of the elastic type arteries correspond to their main functional purpose - mainly passive resistance to a strong push of blood ejected from the heart under high pressure. Different sections of the aorta, differing in their functional load, contain a different amount of elastic fibers. The wall of the arteriole retains a strongly reduced three-layer structure. Arteries that supply blood to internal organs have structural features and intraorgan distribution of branches. Branches of the arteries of hollow organs (stomach, intestines) form networks in the wall of the organ. Arteries in parenchymal organs have a characteristic topography and a number of other features.

Histochemically, a significant amount of mucopolysaccharides is found in the ground substance of all the membranes of the arteries, and especially in the inner membrane. The walls of the arteries have their own blood vessels supplying them (a. and v. vasorum, s. vasa vasorum). Vasa vasorum are located in adventitia. The nutrition of the inner shell and the part of the middle shell bordering it is carried out from the blood plasma through the endothelium by pinocytosis. Using electron microscopy, it was found that numerous processes extending from the basal surface of endothelial cells reach muscle cells through holes in the inner elastic membrane. When the artery contracts, many small and medium-sized windows in the internal elastic membrane partially or completely close, which makes it difficult for nutrients to flow through the processes of endothelial cells to muscle cells. Great importance in the nutrition of areas of the vascular wall, devoid of vasa vasorum, is attached to the main substance.

The motor and sensory innervation of the arteries is carried out by sympathetic, parasympathetic nerves and branches of the cranial or spinal nerves. The nerves of the arteries, which form plexuses in the adventitia, penetrate into the middle shell and are designated as vasomotor nerves (vasomotors), which contract the muscle fibers of the vascular wall and narrow the lumen of the artery. The walls of the artery are equipped with numerous sensitive nerve endings - angioreceptors. In some parts of the vascular system, there are especially many of them and they form reflexogenic zones, for example, at the place of division of the common carotid artery in the area of ​​the carotid sinus. The thickness of the walls of the artery and their structure are subject to significant individual and age-related changes. And arteries have a high ability to regenerate.

Pathology of the arteries - see Aneurysm, Aortitis, Arteritis, Atherosclerosis, Coronaritis., Coronarosclerosis, Endarteritis.

See also Blood vessels.

Carotid artery

Rice. 1. Arcus aortae and its branches: 1 - mm. stylohyoldeus, sternohyoideus and omohyoideus; 2 and 22 - a. carotis int.; 3 and 23 - a. carotis ext.; 4 - m. cricothyreoldeus; 5 and 24 - aa. thyreoideae superiores sin. et dext.; 6 - glandula thyreoidea; 7 - truncus thyreocervicalis; 8 - trachea; 9-a. thyreoidea ima; 10 and 18 - a. subclavia sin. et dext.; 11 and 21 - a. carotis communis sin. et dext.; 12 - truncus pulmonais; 13 - auricula dext.; 14 - pulmo dext.; 15 - arcus aortae; 16-v. cava sup.; 17 - truncus brachiocephalicus; 19 - m. scalenus ant.; 20 - plexus brachialis; 25 - glandula submandibularis.

Rice. 2. Arteria carotis communis dextra and its branches; 1-a. facialis; 2-a. occipitalis; 3-a. lingualis; 4-a. thyreoidea sup.; 5-a. thyreoidea inf.; 6-a. carotis communis; 7 - truncus thyreocervicalis; 8 and 10 - a. subclavia; 9-a. thoracica int.; 11 - plexus brachialis; 12-a. transversa colli; 13-a. cervicalis superficialis; 14-a. cervicalis ascendens; 15-a. carotis ext.; 16-a. carotis int.; 17-a. vagus; 18 - n. hypoglossus; 19-a. auricularis post.; 20-a. temporalis superficialis; 21-a. zygomaticoorbitalis.

Rice. 1. Cross section of the artery: 1 - outer shell with longitudinal bundles of muscle fibers 2, 3 - middle shell; 4 - endothelium; 5 - internal elastic membrane.

Rice. 2. Cross section of the thoracic aorta. The elastic membranes of the middle shell are shortened (o) and relaxed (b). 1 - endothelium; 2 - intima; 3 - internal elastic membrane; 4 - elastic membranes of the middle shell.

The venous and arterial network perform many important functions in the human body. For this reason, physicians note their morphological differences, which manifest themselves 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, external, internal and middle. The inner membrane is called the intima.
It, in turn, is divided into two layers presented: endothelium - it is the lining part of the inner surface of arterial vessels, consisting of flat epithelial cells and subendothelium - located under the endothelial layer. It consists of loose connective tissues. The middle shell consists of myocytes, collagen and elastin fibers. The outer shell, which is called "adventitia", is a fibrous loose tissue of the connective type, with vessels, nerve cells and a lymphatic vascular network.

Human arterial system

• Elastic. The middle layer of these arterial vessels is composed of elastic fibers that withstand the high blood pressure that is formed in them when the blood flow is ejected. They are represented by the aorta and pulmonary trunk.
• Mixed. Here, in the middle layer, a different amount of elastic and myocyte fibers is combined. They are represented by the carotid, subclavian and popliteal arteries.
• Muscular. The middle layer of these arteries consists of separate, circumferentially arranged, myocyte fibers.

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

• Trunk, providing blood flow in the lower and upper limbs.
• Organic, supplying blood to the internal organs of a person.
• Intraorganic, having their own network, branched out in all organs.

Vienna

The human venous system

Peculiarities

Consider some of the features of this network:

• Compared to arterial vessels, venous vessels have a larger diameter.
• They have an underdeveloped subendothelial layer and fewer elastic fibers.
• They have thin walls that fall off easily.
• The middle layer, consisting of smooth muscle elements, is poorly developed.
• The outer layer is quite pronounced.
• They have a valve mechanism created by the venous wall and inner layer. The valve consists of myocyte fibers, and the inner leaflets consist of connective tissue. Outside, 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 network, their large number, venous plexuses, larger than the arteries.

Net

The artery of the femoral region is located in a lacuna formed from vessels. The external iliac artery is its continuation. It passes under the inguinal ligamentous apparatus, after which it passes into the adductor canal, which consists of a wide medial muscle sheet and a large adductor and membranous membrane located between them. From the adducting canal, the arterial vessel exits into the popliteal cavity. The lacuna, consisting of vessels, is separated from its muscular area by the edge of the wide femoral muscular fascia in the form of a sickle. Nerve tissue passes through this area, providing sensitivity to the lower limb. Above is the inguinal ligamentous apparatus.
The femoral artery of the lower extremities has branches represented by:

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

The deep femoral arterial vessel also has a branching, 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 holes. In the place where the upper 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 arteries of the following types:

• Upper lateral / middle medial, passing under the knee joint.
• Inferior lateral / middle medial, passing through the knee joint.
• Middle genicular artery.
• 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 popliteal-shin area, located between the superficial and deep muscular apparatus of the posterior part of the leg (there are small arteries of the leg). Next, it passes near the medial malleolus, near the flexor digitorum brevis. Arterial vessels depart from it, enveloping the fibular bone area, a peroneal-type vessel, calcaneal and ankle ramifications.
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 an arcuate arterial area, the dorsal arteries and those that are responsible for blood flow in the fingers depart from it. The interdigital spaces are a conductor for the deep arterial vessel, from which the anterior and posterior sections of the recurrent tibial arteries, the medial and lateral ankle-type arteries, and muscular ramifications depart.
Anastomoses that help people maintain balance are represented by the calcaneal and dorsal anastomosis. The first passes between the medial and lateral arteries of the calcaneus. The second is between the external foot and arcuate arteries. Deep arteries make up an anastomosis of the vertical type.

Differences

What is the difference between the vascular network and the arterial network - 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 that make up 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 veins; in arteries, they are represented by internal and external sections.

The form

Arteries have a regular cylindrical shape and a round cross section. Venous vessels have flattening and tortuous shape. This is due to the valve system, thanks to which they can narrow and expand.

Quantity

Arteries in the body are about 2 times less than veins. There are several veins for each 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, the valve system is only at the outlet of the heart muscle.

Blood

More blood flows in veins than in arteries.

Location

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

Direction

Through the arteries, blood flows faster than through the veins, due to the pressure of the force of the heart. 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 tremors coming from the heart and arteries.
• Suction of cardiac force during relaxation 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 a large blood loss or strong physical exertion.

Color

Since arterial blood contains a large number of oxygen molecules, it has a scarlet color. Venous blood is dark because it contains decay elements and carbon dioxide.
During arterial bleeding, the blood gushes out, and during venous bleeding, it flows in a jet. The first carries 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 thickness, valvular system and strength of blood flow.
• number and depth of location.

Veins, unlike arterial vessels, are used by physicians 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, you can not only correctly provide first aid for bleeding, but also understand how blood circulates through the body.

Anatomy (video)

Circulatory system consists of a central organ - the heart - and closed tubes of various calibers connected to it, called blood vessels(Latin vas, Greek angeion - vessel; hence - angiology). The heart, with its rhythmic contractions, sets in motion the entire mass of blood contained in the vessels.

arteries. Blood vessels that run from the heart to the organs and carry blood to them called arteries(aer - air, tereo - I contain; arteries on corpses are empty, which is why in the old days they were considered air tubes).

The wall of the arteries consists of three layers.Inner shell, tunica intima. lined from the side of the lumen of the vessel with endothelium, under which lie the subendothelium and the internal elastic membrane; medium, tunica media, built from fibers of unstriated muscle tissue, myocytes, alternating with elastic fibers; outer shell, tunica externa, contains connective tissue fibers. The elastic elements of the arterial wall form a single elastic frame that acts like a spring and determines the elasticity of the arteries.

As they move away from the heart, the arteries divide into branches and become smaller and smaller. The arteries closest to the heart (the aorta and its large branches) perform the main function of conducting blood. In them, counteraction to stretching by a mass of blood, which is ejected by a cardiac impulse, comes to the fore. Therefore, structures of a mechanical nature, i.e., elastic fibers and membranes, are relatively more developed in their wall. Such arteries are called elastic arteries. In medium and small arteries, in which the inertia of the cardiac impulse is weakened and its own contraction of the vascular wall is required to further move the blood, the contractile function predominates.

It is provided by a relatively large development of muscle tissue in the vascular wall. Such arteries are called muscular arteries. Individual arteries supply blood to whole organs or parts of them.

In relation to the organ distinguish arteries, going outside the organ, before entering it - extraorganic arteries, and their continuation, branching inside it - intraorganic, or intraorganic, arteries. Lateral branches of the same trunk or branches of different trunks can be connected to each other. Such a connection of vessels before they break up into capillaries is called anastomosis, or fistula (stoma - mouth). Arteries that form anastomoses are called anastomosing (most of them).

Arteries that do not have anastomoses with neighboring trunks before they pass into capillaries (see below) are called terminal arteries (for example, in the spleen). The terminal, or terminal, arteries are more easily clogged with a blood plug (thrombus) and predispose to the formation of a heart attack (local necrosis of the organ).

The last ramifications of the arteries become thin and small and therefore stand out under the name of arterioles.

Arteriole differs from an artery in that its wall has only one layer of muscle cells, thanks to which it performs a regulatory function. The arteriole continues directly into the precapillary, in which the muscle cells are scattered and do not form a continuous layer. The precapillary differs from the arteriole in that it is not accompanied by a venule.

From precapillary numerous capillaries depart.

capillaries are the thinnest vessels that perform the metabolic function. In this regard, their wall consists of a single layer of flat endothelial cells, permeable to substances and gases dissolved in the liquid. Widely anastomosing with each other, the capillaries form networks (capillary networks), passing into postcapillaries, built similarly to the precapillary. The postcapillary continues into the venule accompanying the arteriole. Venules form thin initial segments of the venous bed, constituting the roots of the veins and passing into the veins.

Veins (lat. vena, Greek phlebs; hence phlebitis - inflammation of the veins) carry blood in the opposite direction to the arteries, from the organs to the heart. Walls they are arranged according to the same plan as the walls of the arteries, but they are much thinner and have less elastic and muscle tissue, due to which the empty veins collapse, while the lumen of the arteries gapes in the cross section; veins, merging with each other, form large venous trunks - veins that flow into the heart.

The veins anastomose widely with each other, forming venous plexuses.

The movement of blood through the veins It is carried out due to the activity and suction action of the heart and chest cavity, in which during inspiration a negative pressure is created due to the pressure difference in the cavities, as well as due to the contraction of the skeletal and visceral muscles of the organs and other factors.

The contraction of the muscular membrane of the veins is also important, which is more developed in the veins of the lower half of the body, where the conditions for venous outflow are more difficult, than in the veins of the upper body. The reverse flow of venous blood is prevented by special adaptations of the veins - valves, components features of the venous wall. The venous valves are composed of a fold of endothelium containing a layer of connective tissue. They face the free edge towards the heart and therefore do not interfere with the flow of blood in this direction, but keep it from returning back.

Arteries and veins usually go together, with small and medium arteries accompanied by two veins, and large ones by one. From this rule, except for some deep veins, the main exception is the superficial veins, which run in the subcutaneous tissue and almost never accompany the arteries. The walls of blood vessels have their own fine arteries and veins, vasa vasorum. They depart either from the same trunk, the wall of which is supplied with blood, or from the neighboring one and pass in the connective tissue layer surrounding the blood vessels and more or less closely associated with their outer shell; this layer is called vascular vagina, vagina vasorum.

Numerous nerve endings (receptors and effectors) associated with the central nervous system are laid in the wall of arteries and veins, due to which the nervous regulation of blood circulation is carried out by the mechanism of reflexes. Blood vessels are extensive reflexogenic zones that play an important role in the neurohumoral regulation of metabolism.

According to the function and structure of the various departments and the characteristics of innervation, all blood vessels have recently been sent to divide into 3 groups: 1) cardiac vessels that begin and end both circles of blood circulation - the aorta and pulmonary trunk (i.e., elastic-type arteries), vena cava and pulmonary veins; 2) the main vessels that serve to distribute blood throughout the body. These are large and medium extraorganic arteries of the muscular type and extraorganic veins; 3) organ vessels that provide exchange reactions between the blood and the parenchyma of organs. These are intraorgan arteries and veins, as well as links of the microcirculatory bed.

Human arteries and veins perform different jobs in the body. In this regard, one can observe significant differences in the morphology and conditions for the passage of blood, although the general structure, with rare exceptions, is the same for all vessels. Their walls have three layers: inner, middle, outer.

The inner shell, called intima, without fail has 2 layers:

• the endothelium lining the inner surface is a layer of squamous epithelial cells;
• subendothelium - located under the endothelium, consists of connective tissue with a loose structure.

The middle shell is made up of myocytes, elastic and collagen fibers.

The outer shell, called "adventitia", is a fibrous connective tissue with a loose structure, equipped with vascular vessels, nerves, and lymphatic vessels.

arteries

These are blood vessels that carry blood from the heart to all organs and tissues. There are arterioles and arteries (small, medium, large). Their walls have three layers: intima, media and adventitia. Arteries are classified according to several criteria.

According to the structure of the middle layer, three types of arteries are distinguished:

• Elastic. Their middle layer of the wall consists of elastic fibers that can withstand the high blood pressure that develops when it is ejected. This species includes the pulmonary trunk and aorta.
• Mixed (muscular-elastic). The middle layer consists of a variable number of myocytes and elastic fibers. These include carotid, subclavian, iliac.
• Muscular. Their middle layer is represented by individual myocytes located circularly.

By location relative to the organs of the artery are divided into three types:

• Trunk - supply blood to parts of the body.
• Organ - carry blood to the organs.
• Intraorganic - have branches inside the organs.

Vienna

They are non-muscular and muscular.

The walls of non-muscular veins consist of endothelium and loose connective tissue. Such vessels are found in bone tissue, placenta, brain, retina, and spleen.

Muscular veins, in turn, are divided into three types, depending on how myocytes are developed:

• poorly developed (neck, face, upper body);
• medium (brachial and small veins);
• strongly (lower body and legs).

In addition to the umbilical and pulmonary veins, blood is transported, which gave up oxygen and nutrients and took away carbon dioxide and decay products as a result of metabolic processes. It moves from the organs to the heart. Most often, she has to overcome gravity and her speed is less, which is associated with the peculiarities of hemodynamics (lower pressure in the vessels, the absence of its sharp drop, a small amount of oxygen in the blood).

The structure and its features:

• Larger in diameter than arteries.
• Poorly developed subendothelial layer and elastic component.
• The walls are thin and fall off easily.
• The smooth muscle elements of the middle layer are rather poorly developed.
• Pronounced outer layer.
• The presence of a valvular apparatus, which is formed by the inner layer of the vein wall. The base of the valves consists of smooth myocytes, inside the valves - fibrous connective tissue, outside they are covered with a layer of endothelium.
• All shells of the wall are endowed with vascular vessels.

The balance between venous and arterial blood is ensured by several factors:

• a large number of veins;
• their larger caliber;
• dense network of veins;
• formation of venous plexuses.

Differences

How are arteries different from veins? These blood vessels have significant differences in many ways.

Arteries and veins, first of all, differ in the structure of the wall

According to the structure of the wall

Arteries have thick walls, many elastic fibers, well developed smooth muscles, and do not collapse unless filled with blood. Due to the contractility of the tissues that make up their walls, oxygenated blood is quickly delivered to all organs. The cells that make up the layers of the walls ensure the unhindered passage of blood through the arteries. Their inner surface is corrugated. The arteries must withstand the high pressure that is created by the powerful ejections of blood.

The pressure in the veins is low, so the walls are thinner. They fall off in the absence of blood in them. Their muscle layer is not able to contract like that of the arteries. The surface inside the vessel is smooth. Blood moves slowly through them.

In veins, the thickest shell is considered to be the outer, in the arteries - the middle one. Veins do not have elastic membranes; arteries have internal and external.

By shape

Arteries have a fairly regular cylindrical shape, they are round in cross section.

Due to the pressure of other organs, the veins are flattened, their shape is tortuous, they either narrow or expand, which is associated with the location of the valves.

In count

There are more veins in the human body, fewer arteries. Most medium arteries are accompanied by a pair of veins.

By the presence of valves

Most veins have valves that prevent blood from flowing backwards. They are located in pairs opposite each other throughout the vessel. They are not found in the portal caval, brachiocephalic, iliac veins, as well as in the veins of the heart, brain and red bone marrow.

In the arteries, valves are located at the exit of the vessels from the heart.

By blood volume

The veins circulate about twice as much blood as the arteries.

By location

Arteries lie deep in the tissues and approach the skin only in a few places where the pulse is heard: on the temples, neck, wrist, and instep. Their location is about the same for all people.

The veins are mostly located close to the surface of the skin.

The location of the veins may vary from person to person.

To ensure the movement of blood

In the arteries, blood flows under the pressure of the force of the heart, which pushes it out. At first, the speed is about 40 m/s, then it gradually decreases.

Blood flow in the veins occurs due to several factors:

• pressure force, depending on the impulse of blood from the heart muscle and arteries;
• the suction force of the heart during relaxation between contractions, that is, the creation of negative pressure in the veins due to the expansion of the atria;
• suction action on the chest veins of respiratory movements;
• contraction of the muscles of the legs and arms.

In addition, about a third of the blood is in the venous depots (in the portal vein, spleen, skin, walls of the stomach and intestines). It is pushed out from there if it is necessary to increase the volume of circulating blood, for example, with massive bleeding, with high physical exertion.

By color and composition of blood

Arteries carry blood from the heart to the organs. It is enriched with oxygen and has a scarlet color.

Veins provide blood flow from tissues to the heart. , which contains carbon dioxide and decomposition products formed during metabolic processes, has a darker color.

Arterial and have different signs. In the first case, the blood is ejected in a fountain, in the second, it flows in a jet. Arterial - more intense and dangerous for humans.

Thus, the main differences can be identified:

• Arteries transport blood from the heart to the organs, veins carry it back to the heart. Arterial blood carries oxygen, venous blood returns carbon dioxide.
• Arterial walls are more elastic and thicker than venous ones. In the arteries, blood is pushed out with force and moves under pressure, in the veins it flows calmly, while valves do not allow it to move in the opposite direction.
• There are 2 times less arteries than veins, and they are deep. Veins are located in most cases superficially, their network is wider.

Veins, unlike arteries, are used in medicine to obtain material for analysis and to deliver drugs and other fluids directly into the bloodstream.