Suppuration from the external auditory canal is typical for. Otitis externa: rationale for treatment and prevention. The occurrence of otitis media also contributes to

Aorta in the blood supply system

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

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

The importance of arteries

Arteries are vessels that pump blood passing through the heart, already enriched with oxygen. The largest artery is the aorta. It “takes” 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 to systolic pressure, which is determined by the rhythm of 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 and there it is subsequently enriched with oxygen.

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

The pulsation of the arteries can control the heart rate. In order to count the heartbeats, just press the artery with your finger where it is located closer to the surface of the skin.

The body's blood circulation can be classified into a small and large circle. Small is responsible for the lungs: 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 big circle, which is already saturated with oxygen, rushes into the left ventricle, and from it into the aorta. Through small vessels - arterioles - it is delivered to all systems of the body, and then, through the veins, it goes into the right atrium.

The meaning of veins

Veins carry blood to the heart to enrich it with oxygen, and they are not exposed to high pressure. Therefore, venous walls are thinner than arterial walls. The largest vein has a diameter of 2.5 cm. Small veins are called venules. Among the veins there is also an exception - pulmonary vein. Blood from the lungs, saturated with oxygen, moves through it. Veins have internal valves that prevent blood from flowing back. Malfunction of internal valves causes varicose veins varying degrees gravity.

The 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 line of the aorta consists of the abdominal and thoracic parts.

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

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

There are two carotid arteries in the body

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

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

Impaired blood supply can lead to serious problems for the entire body. The closer the artery is to the heart, the more damage in the body if its function is disrupted.

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

Every millimeter of the body area of the body is penetrated by many capillary blood vessels, to which blood is delivered by arterioles and larger great vessels. And although the anatomy of the arteries is not difficult to understand, all the vessels of the body together form an integral branched transport system. Due to it, the tissues of the body are nourished and its vital functions are supported.

An artery is a blood vessel that is shaped like a tube. It directs blood from the central (heart) to distant tissues. Most often, oxygenated arterial blood is delivered through these vessels. Oxygen-poor venous blood normally flows through only one artery - the pulmonary artery. But overall plan The structure of the circulatory system is preserved, that is, in the center of the circulatory circles is the heart, from which arteries drain blood and supply it to veins.

Functions of arteries

Considering the anatomy of the artery, it is easy to assess its morphological qualities. This is a hollow elastic tube whose main function is to transport blood from the heart to the capillary bed. But this task is not the only one, since these vessels also perform others important functions. Among them:

participation in the hemostasis system, counteraction to intravascular thrombosis, closure of vascular damage by a thrombus;
formation pulse wave and its transfer to vessels with a smaller caliber;
level support blood pressure in the lumen of blood vessels at a great distance from the heart;
formation of venous pulse.

Hemostasis is a term that characterizes the presence of a coagulation and anticoagulation mechanism within each blood vessel. That is, after a non-critical injury, the artery itself is able to restore blood flow and close the defect with a blood clot. The second component of the hemostatic system is the anticoagulant system. This is a complex of enzymes and receptor molecules that destroy the blood clot that forms without violating the integrity vascular wall.

If a blood clot has formed independently due to disorders not related to bleeding, the hemostasis system of arteries and veins will dissolve it independently in the most effective way available. However, this becomes impossible if the thrombus blocks the lumen of the artery, which is why thrombolytics of the anticoagulation system will not be able to reach its surface, as happens with myocardial infarction or PE.

Artery pulse wave

The anatomy of veins and arteries is also different due to the difference in hydrostatic pressure in their lumen. In arteries, the pressure is much higher than in veins, which is why their wall contains more muscle cells, and the collagen fibers of the outer membrane are better developed in them. Blood pressure is generated by the heart at the moment of left ventricular systole. Then a large portion of blood stretches the aorta, which, due to its elastic properties, quickly contracts back. This allows blood to be taken from the left ventricle first and then sent onward when the aortic valve closes.

As it moves away from the heart, the pulse wave will weaken, and it will not be enough to push blood through elastic stretching and compression alone. To maintain a constant level of blood pressure in the vascular arterial bed, muscle contraction will be required. To do this, there are muscle cells in the medial layer of the arteries, which, after nervous sympathetic stimulation, will generate a contraction and push the blood to the capillaries.

The pulsation of the arteries also allows blood to be pushed through the veins, which are located in close proximity to the pulsating vessel. That is, arteries in contact with nearby veins generate their pulsation and help return blood to the heart. A similar function is performed by skeletal muscles during its reduction. Such assistance is necessary to push venous blood upward against gravity.

Types of arterial vessels

The anatomy of an artery varies depending on its diameter and distance from the heart. More precisely, the general plan of the structure remains the same, but the expression of elastic fibers and muscle cells changes, as well as the development connective tissue outer layer. The artery consists of a multilayer wall and cavity. The inner layer is the endothelium, located on the basement membrane and subendothelial connective tissue base. The latter is also called the internal elastic membrane.

Differences in Artery Types

The middle layer is where the greatest differences exist between artery types. It contains elastic fibers and muscle cells. On top of it is an outer elastic membrane, completely covered on top with loose connective tissue, allowing the smallest arteries and nerves to penetrate into the middle shell. And depending on the caliber, as well as the structure of the middle shell, there are 4 types of arteries: elastic, transitional and muscular, as well as arterioles.

Arterioles are the smallest arteries with the thinnest connective tissue membrane and absent elastic fibers in the middle membrane. These are one of the most common arterial vessels directly adjacent to the capillary bed. In these areas, the main blood supply changes to regional and capillary. It flows in the interstitial fluid directly near the group of cells to which the vessel approaches.

Main arteries

These are the human arteries whose anatomy is of critical importance for surgery. These include large vessels of elastic and transitional type: aorta, iliac, renal arteries, subclavian and carotid. They are called trunk for the reason that they deliver blood not to the organs, but to areas of the body. For example, the aorta, as the most large vessel, carries blood to all parts of the body.

The carotid arteries, the anatomy of which will be discussed below, deliver nutrients and oxygen to the head and brain. The great vessels also include the femoral, brachial arteries, celiac trunk, mesenteric vessels and many others. This concept not only defines the context for studying the anatomy of arteries, but is intended to clarify the regions of blood supply. This makes it possible to understand that blood is delivered from the heart through large to small arteries and in the huge area where the great vessels are present, neither gas exchange nor exchange of metabolites is possible. They perform only a transport function and participate in hemostasis.

Arteries of the neck and head

The arteries of the head, which allow us to understand the nature of vascular lesions of the brain, originate from the aortic arch and subclavian vessels. The most significant is the pool of the carotid arteries (right and left), through which the tissues of the head enter greatest number oxygenated blood.

The right common branches from the brachiocephalic trunk, which originates on the aortic arch. To the left is a branch of the left common carotid and left subclavian arteries.

Blood supply to the brain

Both carotid arteries are divided into two large branches - the external and internal carotid arteries. The anatomy of these vessels is notable for the multiple anastomoses between the branches of these basins in the area of the facial skull.

The external carotid arteries are responsible for supplying blood to the muscles and skin of the face, tongue, and larynx, while the internal ones are responsible for supplying blood to the brain. Inside the skull there is an additional source of blood supply - the basin of the vertebral arteries (anatomy has thus provided a reserve source of blood supply). They originate from and then head up and enter the cranial cavity.

Then they merge and form an anastomosis between the arteries of the internal basin carotid artery, creating the Willis circle of blood circulation in the brain. After the vertebral and internal carotid territories of the carotid arteries are united, the anatomy of the blood supply to the brain becomes more complicated. This is a backup mechanism that protects main body nervous system from most ischemic episodes.

Arteries of the upper limbs

It is supplied by a group of arteries that originate from the aorta. To the right of it the brachiocephalic trunk branches off, giving rise to the right subclavian artery. The anatomy of the blood supply to the left limb is slightly different: the subclavian artery on the left is separated directly from the aorta, and not from the trunk common with the carotid arteries. Due to this feature, there may be special feature: with significant hypertrophy of the left atrium or severe stretching, it presses on the subclavian artery, causing its pulsation to weaken.

From the subclavian arteries, after departing from the aorta or right brachiocephalic trunk, a group of vessels later branches off to the free upper limb and shoulder joint.

The largest arteries in the arm are the brachial and ulnar arteries. for a long time running along with nerves and veins in the same channel. Is it true, this description highly imprecise, and location varies from person to person. Therefore, the course of blood vessels should be studied on a macroscopic specimen, using diagrams or anatomical atlases.

Arterial bed of the abdominal cavity

In the abdominal cavity, the blood supply is also of the main type. The celiac trunk and several mesenteric arteries branch off from the aorta. From the celiac trunk branches go to the stomach, pancreas, and liver. To the spleen, the artery sometimes branches off from the left gastric, and sometimes from the right gastroduodenal. These features of blood supply are individual and variable.

In the retroperitoneal space there are two kidneys, to each of which two short renal vessels are directed. The left renal artery is much shorter and less often affected by atherosclerosis. Both of these vessels are capable of withstanding high pressure, and a quarter of each systolic ejection of the left ventricle flows through them. This proves the fundamental importance of the kidneys as organs regulating blood pressure.

Pelvic arteries

The pelvic cavity includes the aorta, which is divided into two large branches - the common iliac arteries. The right and left external and internal iliac vessels depart from them, each of which is responsible for the blood circulation of its parts of the body. The external iliac artery gives off a number of small branches and goes to the lower limb. From now on, its continuation will be called the femoral artery.

The internal iliac arteries give many branches to the genitals and bladder, muscles of the perineum and rectum, as well as to the sacrum.

Arteries of the lower extremities

The anatomy is simpler than that of the pelvic vessels, due to a more pronounced blood supply. In particular, the femoral artery, branching from the external iliac, descends and gives off many branches to supply blood to the muscles, bones and skin of the lower extremities.

On its way, it gives off a large descending branch, the popliteal, anterior and posterior tibial, and fibular branches. On the foot, branches already extend from the tibial and peroneal arteries to the ankles and ankle joints, heel bones, foot muscles and toes.

The blood circulation pattern of the lower extremities is symmetrical - the vessels are the same on both sides.

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

The inner shell, called intima, necessarily 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 consists of myocytes, elastic and collagen fibers.

The outer shell, called “adventitia,” is a fibrous connective tissue with a loose structure, supplied 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.

Based on 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 high pressure blood, developing during its release. This type includes the pulmonary trunk and aorta.
Mixed (muscular-elastic). The middle layer consists of varying numbers of myocytes and elastic fibers. These include the carotid, subclavian, and iliac.
Muscular. Their middle layer is represented by individual myocytes arranged in a circular pattern.

According to their location relative to the organs, arteries are divided into three types:

Trunk – supply parts of the body with blood.
Organ - carry blood to the organs.
Intraorgan - have branches inside organs.

Vienna

They are non-muscular and muscular.

The walls of muscleless veins consist of endothelium and connective tissue of a loose structure. Such vessels are found in bone tissue, placenta, brain, retina, and spleen.

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

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

Veins, in addition to the umbilical and pulmonary veins, carry blood, which gives up oxygen and nutrients and takes away carbon dioxide and breakdown products as a result of metabolic processes. It moves from the organs to the heart. Most often, she has to overcome the force of gravity and her speed is lower, which is due to the peculiarities of hemodynamics (lower pressure in the vessels, the absence of its sharp drop, a small amount of oxygen in the blood).

Structure and its features:

Larger in diameter compared to arteries.
The subendothelial layer and elastic component are poorly developed.
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 valve apparatus, which is formed by the inner layer of the vein wall. The base of the valves consists of smooth myocytes, inside the valves there is fibrous connective tissue, and on the outside they are covered by a layer of endothelium.
All wall membranes 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;
density of the vein network;
formation of venous plexuses.

Differences

How are arteries different from veins? These blood vessels differ significantly 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, they have a lot of elastic fibers, smooth muscles are well developed, they do not fall off unless they are 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 smooth passage of blood through the arteries. Inner surface theirs is corrugated. The arteries must withstand the high pressure that is created by powerful surges of blood.

The pressure in the veins is low, so the walls are thinner. They fall off when there is no blood in them. Their muscle layer is not able to contract like arteries. The surface inside the vessel is smooth. Blood moves through them slowly.

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

By shape

The 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 due to the location of the valves.

In count

In the human body there are more veins and fewer arteries. Most middle arteries are accompanied by a pair of veins.

According to the presence of valves

Most veins have valves that prevent blood from flowing into reverse side. They are located in pairs opposite each other throughout the entire length of the vessel. They are not in the portal hollow, brachiocephalic, iliac veins, as well as in the veins of the heart, head and red bone marrow.

In arteries, valves are located as vessels exit the heart.

By blood volume

Veins circulate approximately twice as much blood as arteries.

By location

The 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 of the feet. Their location is approximately the same for all people.

Veins are mostly located close to the surface of the skin

Localization of veins different people may vary.

To ensure blood movement

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 gradually decreases.

Blood flow in the veins occurs due to several factors:

pressure forces depending on the push 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 effect on the chest veins of respiratory movements;
contractions of the muscles of the legs and arms.

In addition, approximately a third of the blood is in the venous depots (in 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 activity.

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. Venous blood, which contains carbon dioxide and breakdown products formed during metabolic processes, differs more dark color.

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

Thus, the main differences can be identified:

Arteries transport blood from the heart to the organs, veins transport blood back to the heart. Arterial blood carries oxygen, venous blood returns carbon dioxide.
The walls of the arteries are more elastic and thicker than the walls of the veins. In arteries, blood is pushed out with force and moves under pressure, in veins it flows calmly, while valves prevent it from moving in the opposite direction.
There are twice as many arteries as veins, and they are located deep. The veins are located in most cases superficially, their network is wider.

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

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

The artery wall consists of three layers: the inner - endothelial, or intima, the middle - muscular, or media, with a certain amount of collagen and elastic fibers and the outer - 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, arteries are divided into three types: muscular, muscular-elastic (for example, carotid arteries) and elastic (for example, the aorta). To the arteries muscular type These include small and medium-sized arteries (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 deep between the muscles and near the bones, to which the artery can be pressed during bleeding. It can be felt on a superficial artery (for example, the radial artery).

The walls of the arteries have their own blood vessels (“vasa vasa”) supplying them. 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. thyroidea 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. epigastrica inf.; 24 - arcus palmaris superficialis; 25 - arcus palmaris profundus; 26 - aa. digitales palmares communes; 27 - aa. digitales palmares propriae; 28 - aa. digitales dorsales; 29 - aa. 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 - aa. lumbales; 39- a. renalis dextra; 40 - aa. 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 leg and dorsum of the foot:
1 - a, genu descendens (ramus articularis); 2-ram! musculares; 3 - a. dorsalis pedis; 4 - a. arcuata; 5 - ramus plantaris profundus; 5 -aa. digitales dorsales; 7 -aa. 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 back surface shins:
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 - aa. metatarseae plantares; 7 -aa. digitales propriae; 8 - a. digitalis plantaris (hallucis); 9 - a. plantaris medialis.

Rice. 5. Abdominal arteries:
1 - a. phrenica sin.; 2 - a. gastrica sin.; 3 - truncus coeliacus; 4 -a. lienalis; 5 -a. mesenterica sup.; 6 - a. hepatica communis; 7 -a. gastroepiploica sin.; 8 - aa. jejunales; 9 -aa. 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 blood enriched with oxygen (the exception is a. pulmonalis, which carries venous blood from heart to lungs). The arterial system includes the aorta and all its branches down to the smallest arterioles (Fig. 1-5). Arteries are usually designated by topographical characteristics (a. facialis, a. poplitea) or by the name of the organ they supply (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 secondary branches move away from it. The loose type is characterized by a short main trunk that quickly breaks up into a mass of secondary branches. The transitional, or mixed, type occupies an intermediate position. The branches of the arteries often connect with each other, forming anastomoses. There are intrasystemic anastomoses (between the branches of one artery) and intersystemic anastomoses (between the branches of different arteries) (B. A. Dolgo-Saburov). Most anastomoses exist continuously as roundabout (collateral) blood circulation pathways. In some cases, collaterals may reappear. Small arteries can be directly connected to veins using arteriovenous anastomoses (see).

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

Muscular arteries include small and medium-sized arteries, as well as most arteries of internal organs. The inner lining of the artery includes the endothelium, subendothelial layers and internal 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 jagged line. According to electron microscopy, a very narrow (about 100 A) gap is constantly maintained between the cells. Endothelial cells are characterized by the presence of a significant number of vesicle-like structures in the cytoplasm. The subendothelial layer consists of connective tissue with very thin elastic and collagen fibers and poorly differentiated stellate-shaped cells. The subendothelial layer is well developed in large and medium-sized arteries. The internal elastic, or fenestrated, membrane (membrana elastica interna, s.membrana fenestrata) has a lamellar fibrillar structure with holes various shapes and size and is closely related to the elastic fibers of the subendothelial layer.

The tunica media 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 membranes, elastic fibers can thicken, forming an outer elastic membrane (membrana elastica externa). The complex muscular-elastic framework 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, carotid and subclavian artery) 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 internal layer appears in the adventitia, containing individual bundles of smooth muscle cells.

The arteries of the elastic type include the vessels of the largest caliber - the aorta (see) and the pulmonary artery (see). In them, the thickness of the vascular wall increases even more, especially the middle shell, 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 it, in addition to loose connective tissue rich in stellate cells (Langhans layer), individual smooth muscle cells appear. The structural features of elastic arteries correspond to their main functional purpose - predominantly passive resistance to a strong push of blood ejected from the heart under high pressure. Various departments aortas, differing in their functional load, contain different amounts of elastic fibers. The arteriole wall retains a highly reduced three-layer structure. Arteries supplying blood internal organs, have structural features and intraorgan distribution of branches. The branches of the arteries of hollow organs (stomach, intestines) form a network 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 arterial membranes 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 the adventitia. Nutrition of the inner membrane and the part of the middle membrane bordering it is carried out from blood plasma through the endothelium by pinocytosis. Using electron microscopy, it was established that numerous processes extending from the basal surface of endothelial cells reach muscle cells through holes in the internal 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 lacking vasa vasorum is attached to the ground substance.

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, forming plexuses in the adventitia, penetrate the tunica media 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 certain areas of the vascular system there are especially many of them and they form reflexogenic zones, for example, at the site of division of the common carotid artery in the area carotid sinus. The thickness of the artery walls 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, Coronary artery disease, Coronary sclerosis, Endarteritis.

Carotid artery

Rice. 1. Arcus aortae and its branches: 1 - mm. stylohyoldeus, sternohyoideus et 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 pulmonaiis; 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. thyroidea 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. Transverse section of the artery: 1 - outer membrane with longitudinal bundles of muscle fibers 2, 3 - middle membrane; 4 - endothelium; 5 - internal elastic membrane.

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

The principle of functional adaptation is clearly expressed in the structure of arteries. The walls of the arteries resist the blood pressure; as blood passes through them, longitudinal and circular stresses arise. This is accompanied by external longitudinal tension, for example during movements of the limbs. At the same time, arterial walls have significant extensibility and elasticity. Due to the stretching and contraction of the arteries, the rhythmic flow of blood ejected by the heart becomes continuous. If the arteries had inextensible walls, then in order for blood to move through them, the power of heart contractions would have to be three times greater.

The walls of the arteries have a multilayer structure. They distinguish between inner, middle and outer shells. The inner lining, the intima, is lined with endothelium. The inner lining of the artery is the weakest part of the vascular wall and is easily damaged. The middle shell consists of muscle and connective tissue elements. Smooth muscles in the wall of arteries are arranged in a spiral. Collagen and elastic fibers are located between the myocytes. The latter are at a certain angle to the longitudinal axis of the vessel, forming a kind of spiral spring, which stretches when the pulse wave passes and returns to its original state. Due to the spiral arrangement of muscle elements and fibrous structures, the movement of blood in the arteries becomes turbulent rather than linear. The middle shell, which has an elastic frame, absorbs mainly the circular stresses of the artery walls; due to its contractile elements, the lumen of the vessel can actively decrease. The outer shell is made of connective tissue and also contains collagen and elastic fibers. This membrane absorbs external longitudinal tension and substantially connects the arteries with the surrounding tissues. The outer shell contains blood vessels and nerves that supply the walls of the arteries.

The vascular vessels, vasa vasorum, originate from branches of nearby arteries. These arteries and their corresponding veins are connected by many anastomoses and form a paraarterial vascular bed. Vascular vessels form in the outer and middle linings of arteries capillary networks. The inner lining does not have its own vessels and receives nutrients directly from the blood flowing through the artery.

The innervation of the arteries is carried out by the vascular branches of the autonomic nerves, forming plexuses in the outer shell. From here, the nerve fibers penetrate into the deeper membranes. Sympathetic nerves are vasoconstrictors, they cause narrowing of arteries and arterioles. Parasympathetic nerves have a vasodilating effect, being vasodilators; Their effect is most pronounced on the blood vessels of the pelvic organs.

Approaching the vessels, the nerves branch, anastomosing with each other, and form a plexus in the superficial layers of the outer shell of the vessels. Thinner branches are separated from it, which, at the border with the middle (muscular) shell, form the second (border, or supramuscular) supramuscular plexus of nerves. Even thinner nerve branches and bundles extend from the latter nerve fibers, which are immersed in the middle layer of the artery wall. Here the intramuscular (intramuscular) plexus of nerves is formed. Individual nerve fibers penetrate even deeper into the inner layer of the vascular wall.

The sensitive fibers that make up all these plexuses end in receptors. In the outer, middle and inner membranes of blood vessels there are a large number of receptor apparatus and sensitive endings. Sensitive nervous apparatus is distributed throughout the vascular system in the form of various angioreceptors, lamellar bodies (Vater-Pacini bodies), bushes or tree-like branches of nerve fibers.

The branching of sensory nerve fibers is very rich in the middle layer of the arterial wall between the plates of smooth muscle and elastic tissue. There are especially many branches of sensory nerve fibers in those places where the arteries begin and where there are fewer muscle and more elastic elements in their wall. Nerve endings of various shapes are also present in the inner lining of the arterial wall.

Receptors perceive changes in the chemical composition of the blood, pressure in the vessel, and tension in the artery wall. The aortic arch near the beginning of the brachiocephalic trunk, the carotid sinus, the pulmonary trunk and the abdominal aorta at the origin of the mesenteric arteries are especially saturated with receptors. These areas of the arterial system are reflexogenic zones; irritation of them causes changes in cardiac activity and blood pressure. The nervous system carries out reflex regulation blood circulation both in the whole body and in individual bodies depending on their functional state. Impulses arising in the receptors of blood vessels are sent not only to the lower floors of the central nervous system, but also to its higher parts, up to the cerebral cortex.

An expression of the functional conditionality of the structure of the arteries are differences in the design of the vessel walls depending on hemodynamic conditions. According to the ratio of tissue elements, elastic, mixed and muscular arteries are distinguished. The elastic type includes the aorta, pulmonary trunk and pulmonary arteries. These vessels can greatly stretch and contract. Contraction of the aorta occurs due to a powerful longitudinal bundle of elastic fibers, which runs along the convex side of its arch and continues to the abdominal region. When removed from the body, the aorta is shortened by almost one third. The contracted aorta can be stretched again by approximately half. The external and internal carotid, all iliac, and femoral artery, coronary, renal, upper and lower mesenteric arteries, celiac trunk. The vertebral artery, cerebral arteries, brachial arteries, arteries of the forearm and hand, arteries of the lower leg and foot, and organ arteries are built according to the muscle type.

The general pattern of the structure of arterial walls is a decrease in the number of elastic elements and an increase in the number of muscle elements as they move away from the heart. Accordingly, the distensibility of the arteries decreases towards the periphery, but their ability to change the lumen increases. Therefore, small arteries and especially arterioles are the main regulators of resistance, and, consequently, blood flow in the arterial bed.

There is a certain relationship between the thickness of the artery wall and the size of their lumen. The ratio of wall thickness to the internal radius of the vessel is 10-15.5% in elastic-type arteries, and 15.5-20% in muscular-type arteries. In the pulmonary arteries this ratio is 7.4-9.4%. This indicator can be used to judge the elasticity of the vascular wall. Knowing the values of the outer and inner radii, it is possible to calculate the tension of the walls of the arteries and the pressure of the blood flowing in them. Due to the indicated relationships between the parameters of the vessels, the increase in the lumen of the arteries during the growth process is accompanied by an increase in the thickness of their walls, which should counteract the increasing blood pressure. With age, morphological changes occur in the walls of arteries, which are accompanied by dilation of blood vessels and a decrease in their deformation-strength properties. Thus, the extensibility of aortic segments decreases by 4-5 times, and the tensile strength decreases by more than 1/4. Changes in the biomechanical parameters of arteries are already observed in people 30-39 years old.