What is an artery. Anatomy of the coronary arteries: functions, structure and mechanism of blood supply. Functional groups of vessels

The human body consists of biological tissues permeated with a mass of blood vessels. They are responsible for the nutrition of cells and the removal of metabolites, supporting their vital activity. Arteries are a type of blood vessels that carry blood directly to the capillaries. All cells of the body receive solutes from them through the interstitial fluid.

Morphology

An artery is an anatomical structure in the form of an elastic tube with a wall and a lumen. It passes in body cavities or connective tissue veins of parenchymal organs, where it constantly gives off small branches to nourish the surrounding tissues. An artery is a vessel that constantly conducts a pulse wave.

In large vessels, its distribution is achieved mainly due to the elastic qualities of the wall, and in small vessels due to muscle contraction. Like the heart, arterial vessels are constantly in good shape and experience periods of stretching and contraction. The muscular wall also alternates periods of contraction with relaxation.

Histological structure

Any artery is a formation with a multilayer wall, which consists of elastic fibers intertwined with each other and muscle cells embedded between them. This is how the middle wall of the vessel is arranged, which is covered with a connective tissue membrane from the inside. It is based on the endothelial layer, facing the inside of the vessel. It is a single-layer protozoan epithelium, the cells of which fit tightly with their edges in order to prevent platelet cells from reaching the connective tissue membrane. The latter contains platelet adhesion receptors, which is the basis of the mechanism of thrombus formation in case of damage to the endothelial layer.

Outside the middle shell, represented by smooth muscle cells woven into an elastic network, there is another layer of connective tissue. It serves to ensure the mechanical strength of the artery. What is it in terms of histology? This shell is a strong network of embedded single cells. It is connected to a looser adventitia, which connects the artery with the stromal tissue of the parenchymal organs.

Regulation of arterial tone

All arterial vessels of the body have their own blood circulation, since only the endothelium can feed on the blood in their lumen. These vessels and nerves run in the outer connective tissue sheath and supply blood to the middle layer - the muscle cells. The smallest nerves of the autonomic system also go to them. They transmit sympathetic impulses that accelerate the conduction of the pulse wave with an increase in the heart rate.

In addition, the artery is a hormone-dependent structure that expands or narrows depending on the presence of humoral factors: adrenaline, dopamine, norepinephrine. Through them, the body regulates the tone of the entire vascular system. The main goal is to rapidly increase blood flow to the muscles by dilating peripheral blood vessels in the event of suprathreshold stress. This is an evolutionary mechanism for saving the life of an organism by fleeing from danger.

main arteries of the body

The largest artery that can withstand maximum pressure is the aorta - the main vessel, from which regional branches depart. The aorta originates in the left outflow tract of the corresponding ventricle. The pulmonary artery originates in the right outflow tract of the heart. This system demonstrates the separation of circulation circles: the aorta carries blood into a large circle, and the pulmonary trunk into a small one. Both of these vessels drain blood from the heart, and the veins deliver it to it, where the circulatory system is crossed.

Among the most important arteries of the body, renal, carotid, subclavian, mesenteric, and vessels of the extremities should be distinguished. Albeit not the largest, but extremely important for the body, coronary arteries stand separately. What does this mean and why are they special? Firstly, they nourish the heart and form two mutually perpendicular circles of blood circulation of this organ. Secondly, they are special because they are the only arterial vessels that fill in ventricular diastole before the development of the pulse wave of the ascending aorta.

The most important task of the cardiovascular system is to provide tissues and organs with nutrients and oxygen, as well as to remove the products of cell metabolism (carbon dioxide, urea, creatinine, bilirubin, uric acid, ammonia, etc.). Enrichment with oxygen and removal of carbon dioxide occurs in the capillaries of the pulmonary circulation, and saturation with nutrients in the vessels of the systemic circulation during the passage of blood through the capillaries of the intestine, liver, adipose tissue and skeletal muscles.

a brief description of

The human circulatory system consists of the heart and blood vessels. Their main function is to ensure the movement of blood, carried out thanks to the work on the principle of a pump. With the contraction of the ventricles of the heart (during their systole), blood is expelled from the left ventricle into the aorta, and from the right ventricle into the pulmonary trunk, from which, respectively, the large and small circles of blood circulation (BCC and ICC) begin. The large circle ends with the inferior and superior vena cava, through which venous blood returns to the right atrium. And the small circle is represented by four pulmonary veins, through which arterial, oxygenated blood flows to the left atrium.

Based on the description, arterial blood flows through the pulmonary veins, which does not correspond to everyday ideas about the human circulatory system (it is believed that venous blood flows through the veins, and arterial blood flows through the arteries).

After passing through the cavity of the left atrium and ventricle, the blood with nutrients and oxygen enters the capillaries of the BCC through the arteries, where it exchanges oxygen and carbon dioxide between it and the cells, delivers nutrients and removes metabolic products. The latter with the blood flow reach the excretory organs (kidneys, lungs, glands of the gastrointestinal tract, skin) and are excreted from the body.

BPC and ICC are connected sequentially. The movement of blood in them can be demonstrated using the following scheme: right ventricle → pulmonary trunk → small circle vessels → pulmonary veins → left atrium → left ventricle → aorta → large circle vessels → inferior and superior vena cava → right atrium → right ventricle.

Functional classification of vessels

Depending on the function performed and the structural features of the vascular wall, the vessels are divided into the following:

1. Shock-absorbing (vessels of the compression chamber) - aorta, pulmonary trunk and large arteries of the elastic type. They smooth out periodic systolic waves of blood flow: soften the hydrodynamic shock of blood ejected by the heart during systole, and ensure the movement of blood to the periphery during diastole of the ventricles of the heart.
2. Resistive (vessels of resistance) - small arteries, arterioles, metarterioles. Their walls contain a huge number of smooth muscle cells, thanks to the contraction and relaxation of which they can quickly change the size of their lumen. Providing variable resistance to blood flow, resistive vessels maintain blood pressure (BP), regulate the amount of organ blood flow and hydrostatic pressure in the vessels of the microvasculature (MCR).
3. Exchange - ICR vessels. Through the wall of these vessels there is an exchange of organic and inorganic substances, water, gases between blood and tissues. The blood flow in the MCR vessels is regulated by arterioles, venules and pericytes - smooth muscle cells located outside the precapillaries.
4. Capacitive - veins. These vessels are highly extensible, due to which they can deposit up to 60–75% of the circulating blood volume (CBV), regulating the return of venous blood to the heart. The veins of the liver, skin, lungs and spleen have the most depositing properties.
5. Shunting - arteriovenous anastomoses. When they open, arterial blood is discharged along the pressure gradient into the veins, bypassing the ICR vessels. For example, this happens when the skin is cooled, when the blood flow is directed through arteriovenous anastomoses to reduce heat loss, bypassing the skin capillaries. At the same time, the skin turns pale.

Pulmonary (small) circulation

The ICC serves to oxygenate the blood and remove carbon dioxide from the lungs. After the blood has entered the pulmonary trunk from the right ventricle, it is sent to the left and right pulmonary arteries. The latter are a continuation of the pulmonary trunk. Each pulmonary artery, passing through the gates of the lung, branches into smaller arteries. The latter, in turn, pass into the ICR (arterioles, precapillaries and capillaries). In the ICR, venous blood is converted into arterial blood. The latter enters from the capillaries into venules and veins, which, merging into 4 pulmonary veins (2 from each lung), flow into the left atrium.

Bodily (large) circle of blood circulation

BPC serves to deliver nutrients and oxygen to all organs and tissues and remove carbon dioxide and metabolic products. After the blood has entered the aorta from the left ventricle, it is directed to the aortic arch. Three branches depart from the latter (brachiocephalic trunk, common carotid and left subclavian arteries), which supply blood to the upper limbs, head and neck.

After that, the aortic arch passes into the descending aorta (thoracic and abdominal). The latter at the level of the fourth lumbar vertebra is divided into common iliac arteries, which supply blood to the lower limbs and pelvic organs. These vessels are divided into external and internal iliac arteries. The external iliac artery passes into the femoral artery, supplying arterial blood to the lower extremities below the inguinal ligament.

All arteries, heading to tissues and organs, in their thickness pass into arterioles and further into capillaries. In the ICR, arterial blood is converted into venous blood. Capillaries pass into venules and then into veins. All veins accompany arteries and are named similarly to arteries, but there are exceptions (portal vein and jugular veins). Approaching the heart, the veins merge into two vessels - the inferior and superior vena cava, which flow into the right atrium.

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

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

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

All blood vessels are made up of three layers:

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

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

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

arteries

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

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

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

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

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

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

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

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

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

capillaries

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

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

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

Arterioles - branch into precapillaries;

Precapillaries - transitional vessels between arterioles and capillaries proper;

True capillaries;

Postcapillaries;

Venules are places where capillaries pass into veins.

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

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

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

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

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

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

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

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

Functional groups of vessels

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

Cushioning Vessels

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

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

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

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

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

Resistive vessels

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

Vessels-sphincters

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

exchange vessels

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

capacitive vessels

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

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

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

Shunt vessels

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

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

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

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

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

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

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

Which doctor should I contact with vessels?

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

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

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

Aorta in the circulatory system

The blood supply system includes all the circulatory organs that produce blood, enrich it with oxygen, and carry it throughout the body. The aorta - the largest artery - is included in a large circle of water supply.

Living beings cannot exist without a circulatory system. In order for normal life to proceed at the proper level, blood must regularly flow to all organs and all parts of the body. The circulatory system includes the heart, arteries, veins - all blood and hematopoietic vessels and organs.

The meaning of the arteries

Arteries are blood vessels that pump blood passing through the heart, already enriched with oxygen. The largest artery is the aorta. It "takes" the blood leaving the left side of the heart. Its diameter is 2.5 cm. The walls of the arteries are very strong - they are designed for systolic pressure, which is determined by the rhythm of the heart contractions.

But not all arteries carry arterial blood. Among the arteries there is an exception - the pulmonary trunk. Through it, blood rushes to the respiratory organs, where it will subsequently be enriched with oxygen.

In addition, there are systemic diseases in which the arteries can contain mixed blood. An example is heart disease. But keep in mind that this is not the norm.

The heart rate can be controlled by the pulsation of the arteries. In order to count the beats of the heart, it is enough to press the artery with your finger where it is located closer to the surface of the skin.

The circulation of the body can be classified into a small and a large circle. The small one is responsible for the lungs: the right atrium contracts, pushing blood into the right ventricle. From there, it passes into the pulmonary capillaries, is enriched with oxygen and again goes into the left atrium.

Arterial blood in a large circle, which is already saturated with oxygen, rushes into the left ventricle, and from it the aorta. Through small vessels - arterioles - it is delivered to all body systems, and then, through the veins, it goes to the right atrium.

The meaning of veins

The veins carry blood to the heart for oxygenation, and they are not subjected to high pressure. Therefore, the venous walls are thinner than the arterial ones. The largest vein has a diameter of 2.5 cm. Small veins are called venules. Among the veins there is also an exception - the pulmonary vein. It carries oxygenated blood from the lungs. Veins have internal valves that prevent blood from backflowing. Violation of the internal valves causes varicose veins of varying severity.

A large artery - the aorta - is located as follows: the ascending part leaves the left ventricle, the trunk deviates behind the sternum - this is the aortic arch, and goes down, forming the descending part. The descending aortic line consists of the abdominal and thoracic aorta.

The ascending line carries blood to the arteries, which are responsible for cardiac blood supply. They are called crowns.

From the aortic arch, blood flows into the left subclavian artery, the left common carotid artery, and into the brachiocephalic trunk. They carry oxygen to the upper parts of the body: the brain, neck, upper limbs.

There are two carotid arteries in the body

One goes outside, the second inside. One feeds the parts of the brain, the other - the face, thyroid gland, organs of vision ... The subclavian artery carries blood to smaller arteries: axillary, radial, etc.

The descending part of the aorta supplies the internal organs. The division into two iliac arteries, called internal and external, occurs at the level of the lower back, its fourth vertebra. The internal carries blood to the pelvic organs - the external to the limbs.

Violation of the blood supply is fraught with serious problems for the whole body. The closer the artery is to the heart, the more damage in the body in case of violation of its work.

The largest artery of the body performs an important function - it carries blood into arterioles, small branches. If it is damaged, the normal functioning of the whole organism is disrupted.

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, muscular, 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 muscle-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, in the main substance of all the membranes of the arteries, and especially in the inner membrane, a significant amount of mucopolysaccharides is found. 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 are partially or completely closed, 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.

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.