What structures of the body do not have blood vessels. The functionality of vessels depending on the type. What are the largest blood vessels in the human body?

1 - dorsal artery of the foot; 2 - anterior tibial artery (with accompanying veins); 3 - femoral artery; 4 - femoral vein; 5 - superficial palmar arch; 6 - right outer iliac artery and the right external iliac vein; 7-right internal iliac artery and right internal iliac vein; 8 - anterior interosseous artery; 9 - radial artery (with accompanying veins); 10 - ulnar artery (with accompanying veins); 11 - inferior vena cava; 12 - superior mesenteric vein; 13 - right renal artery and right renal vein; 14 - portal vein; 15 and 16 - saphenous veins of the forearm; 17- brachial artery (with accompanying veins); 18 - superior mesenteric artery; 19 - right pulmonary veins; 20 - right axillary artery and right axillary vein; 21 - right pulmonary artery; 22 - superior vena cava; 23 - right brachiocephalic vein; 24 - right subclavian vein and right subclavian artery; 25 - right common carotid artery; 26 - right internal jugular vein; 27 - external carotid artery; 28 - internal carotid artery; 29 - brachiocephalic trunk; 30 - external jugular vein; 31 - left common carotid artery; 32 - left internal jugular vein; 33 - left brachiocephalic vein; 34 - left subclavian artery; 35 - aortic arch; 36 - left pulmonary artery; 37 - pulmonary trunk; 38 - left pulmonary veins; 39 - ascending aorta; 40 - hepatic veins; 41 - splenic artery and vein; 42 - celiac trunk; 43 - left renal artery and left renal vein; 44 - inferior mesenteric vein; 45 - right and left artery testicles (with accompanying veins); 46 - inferior mesenteric artery; 47 - median vein of the forearm; 48 - abdominal aorta; 49 - left common iliac artery; 50 - left common iliac vein; 51 - left internal iliac artery and left internal iliac vein; 52 - left external iliac artery and left external iliac vein; 53 - left femoral artery and left femoral vein; 54 - venous palmar network; 55 - a large saphenous (hidden) vein; 56 - small saphenous (hidden) vein; 57 - venous network of the rear of the foot.

1 - venous network of the rear of the foot; 2 - small saphenous (hidden) vein; 3 - femoral-popliteal vein; 4-6 - venous network of the rear of the Hand; 7 and 8 - saphenous veins of the forearm; 9 - posterior ear artery; 10 - occipital artery; 11- superficial cervical artery; 12 - transverse artery of the neck; 13 - suprascapular artery; 14 - posterior circumflex artery; 15 - artery, enveloping the scapula; 16 - deep artery of the shoulder (with accompanying veins); 17 - posterior intercostal arteries; 18 - superior gluteal artery; 19 - lower gluteal artery; 20 - posterior interosseous artery; 21 - radial artery; 22 - dorsal carpal branch; 23 - perforating arteries; 24 - outdoor superior artery knee joint; 25 - popliteal artery; 26-popliteal vein; 27-external lower artery of the knee joint; 28 - posterior tibial artery (with accompanying veins); 29 - peroneal, artery.

Diagram of the human cardiovascular system

The most important task of cardio-vascular 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 great circle during the passage of blood through the capillaries of the intestine, liver, adipose tissue and skeletal muscles.

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.

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

1. 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. 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. 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. 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. 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.

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.

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 arterial blood lower limbs 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.

Sometimes a third circle of blood circulation is isolated - cardiac, which serves the heart itself.

Arterial blood is indicated in black in the picture, and venous blood is indicated in white. 1. Common carotid artery. 2. Aortic arch. 3. Pulmonary arteries. 4. Aortic arch. 5. Left ventricle of the heart. 6. Right ventricle of the heart. 7. Celiac trunk. 8. Superior mesenteric artery. 9. Inferior mesenteric artery. 10. Inferior vena cava. 11. Bifurcation of the aorta. 12. Common iliac arteries. 13. Vessels of the pelvis. 14. Femoral artery. 15. Femoral vein. 16. Common iliac veins. 17. Portal vein. 18. Hepatic veins. 19. Subclavian artery. 20. Subclavian vein. 21. Superior vena cava. 22. Internal jugular vein.

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Vessels

Blood circulates through the body through a complex system blood vessels. This transport system delivers blood to every cell in the body so that it "exchanges" oxygen and nutrients for waste products and carbon dioxide.

Some numbers

There are over 95,000 kilometers of blood vessels in the body of a healthy adult. More than seven thousand liters of blood are pumped through them daily.

The size of blood vessels varies from 25 mm (aortic diameter) to eight microns (capillary diameter).

What are the vessels?

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

From the inside, their walls are lined with flat cells - endothelium. With the exception of capillaries, all vessels contain tough and elastic collagen fibers and smooth muscle fibers that can contract and expand in response to chemical or neural stimuli.

Arteries carry oxygen-rich blood from the heart to tissues and organs. This blood is bright red, which is why all the arteries look red.

Blood moves through the arteries from great strength, so their walls are thick and elastic. They are made up of large amounts of collagen, which allows them to withstand blood pressure. The presence of muscle fibers helps to turn the intermittent supply of blood from the heart into a continuous flow in the tissues.

As they move away from the heart, the arteries begin to branch, and their lumen becomes thinner and thinner.

The thinnest vessels that deliver blood to every corner of the body are capillaries. Unlike arteries, their walls are very thin, so oxygen and nutrients can pass through them into the cells of the body. This same mechanism allows waste products and carbon dioxide to pass from the cells into the bloodstream.

Capillaries, through which oxygen-poor blood flows, gather into thicker vessels - veins. Due to the lack of oxygen, venous blood is darker than arterial blood, and the veins themselves appear bluish. They carry blood to the heart and from there to the lungs for oxygenation.

The walls of the veins are thinner than the arterial ones, since the venous blood does not create such strong pressure like arterial.

What are the largest blood vessels in the human body?

The two largest veins in the human body are the inferior vena cava and the superior vena cava. They bring blood to the right atrium: the superior vena cava from the upper body, and the inferior vena cava from the bottom.

The aorta is the largest artery in the body. It comes out of the left ventricle of the heart. Blood enters the aorta through the aortic canal. The aorta branches into large arteries that carry blood throughout the body.

What is blood pressure?

Blood pressure is the force with which blood presses against the walls of the arteries. It increases when the heart contracts and pumps out blood, and decreases when the heart muscle relaxes. Blood pressure is stronger in the arteries and weaker in the veins.

Blood pressure is measured special device- tonometer. Pressure indicators are usually written in two digits. So, the normal pressure for an adult is considered to be 120/80.

The first number, systolic pressure, is a measure of the pressure during a heartbeat. The second is diastolic pressure, the pressure when the heart relaxes.

Pressure is measured in the arteries and is expressed in millimeters of mercury. In the capillaries, the pulsation of the heart becomes imperceptible and the pressure in them drops to about 30 mm Hg. Art.

A blood pressure reading can tell your doctor how your heart is working. If one or both numbers are higher than normal, this indicates increased pressure. If lower - about lowered.

High blood pressure indicates that the heart is working with excess load: it needs more effort to push blood through the vessels.

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

The most important

Vessels are needed by the body to deliver blood rich in nutrients and oxygen to all organs and tissues. Learn how to keep blood vessels healthy.

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Large human vessels

Title: Human Anatomy

Genre: Biology with the basics of genetics

Blood vessels

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

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

The structure of the walls of blood vessels

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

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

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

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

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

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

Small circle of blood circulation

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

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

Systemic circulation

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

The ascending aorta (pars ascendens aortae) emerges from the left ventricle and in the initial section has an extension - the aortic bulb. At the location of the aortic valves on its inner side there are three sinuses, each of them is located between the corresponding semilunar valve and the aortic wall. From the origin of the ascending aorta, the right and left coronary arteries hearts.

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

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

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

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

Branches of the aortic arch

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

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

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

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

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

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

Rice. 86. Arteries of the head and neck:

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

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

nasal cavity and adjacent

Rice. 87. Arteries of the brain:

11 with them bodies; gives away

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

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

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

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

II - superior cerebellar artery

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

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

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

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

and through the greater occipital

Rice. 88. Arteries of the axillary region:

the hole enters the skull

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

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

K1 ‘J al artery; 3 - artery, enveloping the scapula;

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

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

trunk; 11 - vertebral artery

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

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

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

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

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

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

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

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

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

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

terii fingers, so the brush

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

Branches of the thoracic aorta

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

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

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

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

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

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

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

Branches of the abdominal aorta

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

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

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

Rice. 91. Abdominal aorta:

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

Visceral branches (unpaired):

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

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

Visceral branches (paired):

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

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

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

Internal iliac artery (a. iliaca interna).

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

pudendal and obturator arte- 92 Arteries of the pelvis:

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

TT - - naya artery; 4 - internal iliac

artery; 5 - median sacral artery;

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

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

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

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

renal artery. External artery; 10 - lower rectal

artery; 11 - internal genital artery;

12 - dorsal artery of the penis;

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

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

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

new bone (Fig. 93). 140

iliac circumflex

Arteries of the lower limb

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

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

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

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

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

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

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

Veins of the systemic circulation

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

Superior vena cava system

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

Rice. 94. Veins of the head and neck:

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

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

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

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

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

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

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

The subclavian vein (v. subclavia) continues the axillary, serves to drain blood from the upper limb and does not have permanent branches. The walls of the vein are firmly connected to the surrounding fascia, which holds the lumen of the vein and increases it with a raised arm, providing an easier outflow of blood from the upper extremities.

Veins of the upper limb

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

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

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

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

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

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

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

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

Inferior vena cava system

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

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

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

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

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

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

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

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

Rice. 97. Inferior vena cava and its tributaries:

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

Hepatic veins (v. le-

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

portal vein system

Portal vein (liver)

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

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

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

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

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

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

Veins of the lower limb

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

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

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

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

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

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

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

Questions for self-control

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

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

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

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

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

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

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

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

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

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

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

12. Describe the structure of the heart wall.

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

14. Name the parts of the aorta.

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

16. Name the branches of the aortic arch.

17. List the branches of the external carotid artery.

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

19. List the branches of the internal carotid artery.

20. Describe the blood supply to the brain.

21. Name the branches of the subclavian artery.

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

23. Name the arteries of the shoulder and forearm.

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

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

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

27. Name the parietal branches of the abdominal aorta.

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

29. Describe the celiac trunk and its branches.

30. Name the branches of the superior mesenteric artery.

31. Name the branches of the inferior mesenteric artery.

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

33. Name the branches of the internal iliac artery.

34. Name the branches of the external iliac artery.

35. Name the arteries of the thigh and leg.

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

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

38. Tell us about the internal jugular vein and its ducts.

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

40. How is the blood flow from the head?

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

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

43. Describe the blood flow from the upper limb.

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

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

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

47. Describe the portal vein system, its tributaries.

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

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

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

Zmist

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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.

Upper layer vascular walls make up connective tissues, it separates blood 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:

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, no blood enters 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, therefore, 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 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 on tiny 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 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, form 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 depreciation effect under consideration is also called the Windkessel effect, which is 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 precapillary sphincters. 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, disease renal vessels, 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 carried out by phlebologists and angiosurgeons. After all necessary diagnostic procedures, the doctor draws up a course of treatment, where they combine conservative methods and surgical intervention. Drug therapy of vascular diseases is aimed at improving blood rheology, lipid metabolism in order to prevent atherosclerosis and other vascular diseases caused by increased level blood cholesterol. (Read also:) The doctor may prescribe vasodilators, medicines to combat comorbidities, 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.

The human body is all permeated with blood vessels. These peculiar highways provide continuous delivery of blood from the heart to the most remote parts of the body. Due to the unique structure of the circulatory system, each organ receives a sufficient amount of oxygen and nutrients. The total length of blood vessels is about 100 thousand km. This is true, though hard to believe. The movement of blood through the vessels is provided by the heart, which acts as a powerful pump.

To deal with the answer to the question: how does the human circulatory system work, you need, first of all, to carefully study the structure of blood vessels. In simple terms, these are strong elastic tubes through which blood moves.

The blood vessels branch throughout the body but eventually form a closed circuit. For normal blood flow, there must always be excess pressure in the vessel.

The walls of blood vessels consist of 3 layers, namely:

• The first layer is epithelial cells. The fabric is very thin and smooth, providing protection against blood elements.
• The second layer is the densest and thickest. Consists of muscle, collagen and elastic fibers. Thanks to this layer, blood vessels have strength and elasticity.
• The outer layer - consists of connective fibers having a loose structure. Thanks to this tissue, the vessel can be securely fixed on different parts of the body.

Blood vessels additionally contain nerve receptors that connect them to the CNS. Due to this structure, the nervous regulation of blood flow is ensured. In anatomy, there are three main types of vessels, each of which has its own functions and structure.

arteries

The main vessels that transport blood directly from the heart to the internal organs are called the aorta. Within these elements, a very high pressure, so they should be as dense and elastic as possible. Physicians distinguish two types of arteries.

Elastic. The largest blood vessels that are located in the human body closest to the heart muscle. The walls of such arteries and the aorta are made up of dense, elastic fibers that can withstand continuous heartbeats and surges of blood. The aorta can expand, filling with blood, and then gradually return to its original size. It is thanks to this element that the continuity of blood circulation is ensured.

Muscular. Such arteries are smaller than the elastic type of blood vessels. Such elements are removed from the heart muscle, and are located near the peripheral internal organs and systems. The walls of the muscular arteries can contract strongly, which ensures blood flow even at reduced pressure.

The main arteries provide all the internal organs with a sufficient amount of blood. Some blood elements are located around the organs, while others go directly into the liver, kidneys, lungs, etc. Arterial system very branched, it can smoothly pass into capillaries or veins. Small arteries are called arterioles. Such elements can directly take part in the self-regulation system, since they consist of only one layer of muscle fibers.

capillaries

Capillaries are the smallest peripheral vessels. They can freely penetrate any tissue, as a rule, they are located between larger veins and arteries.

The main function of microscopic capillaries is to transport oxygen and nutrients from the blood to the tissues. Blood vessels of this type are very thin, as they consist of only one layer of epithelium. Thanks to this feature useful elements can easily penetrate through their walls.

Capillaries are of two types:

• Open - constantly involved in the process of blood circulation;
• Closed - are, as it were, in reserve.

From 150 to 300 capillaries can fit on 1 mm of muscle tissue. When muscles are stressed, they need more oxygen and nutrients. In this case, reserve closed blood vessels are additionally involved.

Vienna

The third type of blood vessels are veins. They are similar in structure to arteries. However, their function is completely different. After the blood has given up all the oxygen and nutrients, it rushes back to the heart. At the same time, it is transported precisely through the veins. The pressure in these blood vessels is reduced, so their walls are less dense and thick, their middle layer is less thin than in the arteries.

The venous system is also very branched. Small veins are located in the region of the upper and lower extremities, which gradually increase in size and volume towards the heart. The outflow of blood is provided by back pressure in these elements, which is formed during the contraction of muscle fibers and exhalation.

Diseases

In medicine, many pathologies of blood vessels are distinguished. Such diseases can be congenital or acquired throughout life. Each type of vessel can have a particular pathology.

Vitamin therapy is the best prevention of diseases of the circulatory system. Saturation of the blood with useful trace elements allows you to make the walls of arteries, veins and capillaries stronger and more elastic. People who are at risk of developing vascular pathologies should definitely include the following vitamins in their diet:

• C and R. These trace elements strengthen the walls of blood vessels, prevent capillary fragility. Contained in citrus fruits, rose hips, fresh herbs. You can also additionally use the therapeutic gel Troxevasin.
• Vitamin B. To enrich your body with these trace elements, include legumes, liver, cereals, meat in the menu.
• AT 5. This vitamin is rich in chicken meat, eggs, broccoli.

Eat oatmeal with fresh raspberries for breakfast, and your blood vessels will always be healthy. Dress up salads olive oil, and from drinks, give preference to green tea, rosehip broth or fresh fruit compote.

The circulatory system performs the most important functions in the body - it delivers blood to all tissues and organs. Always take care of the health of blood vessels, regularly undergo a medical examination, and take all the necessary tests.

Circulation (video)

Blood vessels are a closed system of branched tubes of different diameters, which are part of the large and small circles of blood circulation. This system distinguishes: arteries through which blood flows from the heart to organs and tissues veins- through them the blood returns to the heart, and a complex of vessels microcirculation, providing, along with the transport function, the exchange of substances between the blood and surrounding tissues.

Blood vessels develop from the mesenchyme. In embryogenesis, the earliest period is characterized by the appearance of numerous cell accumulations of mesenchyme in the wall of the yolk sac - blood islands. Inside the islet, blood cells are formed and a cavity is formed, and the cells located along the periphery become flat, interconnected by cell contacts and form the endothelial lining of the resulting tubule. Such primary blood tubules, as they form, are interconnected and form a capillary network. Surrounding mesenchymal cells develop into pericytes, smooth muscle cells, and adventitial cells. In the body of the embryo, blood capillaries are formed from mesenchymal cells around slit-like spaces filled with tissue fluid. When blood flow increases through the vessels, these cells become endothelial, and elements of the middle and outer membranes are formed from the surrounding mesenchyme.

The vascular system has a very large plasticity. First of all, there is a significant variability in the density of the vascular network, since, depending on the needs of the organ in nutrients and oxygen, the amount of blood brought to it varies widely. Changes in blood flow velocity and blood pressure lead to the formation of new vessels and the restructuring of existing vessels. There is a transformation of a small vessel into a larger one with characteristic features of the structure of its wall. The greatest changes occur in the vascular system during the development of roundabout, or collateral, blood circulation.

Arteries and veins are built according to a single plan - three membranes are distinguished in their walls: internal (tunica intima), middle (tunica media) and external (tunica adventicia). However, the degree of development of these membranes, their thickness and tissue composition are closely related to the function performed by the vessel and hemodynamic conditions (blood pressure height and blood flow velocity), which are not the same in different parts of the vascular bed.

arteries. According to the structure of the walls, the arteries of the muscular, muscular-elastic and elastic types are distinguished.

To the arteries of the elastic type include the aorta and pulmonary artery. In accordance with the high hydrostatic pressure (up to 200 mm Hg) created by the pumping activity of the ventricles of the heart, and the high blood flow velocity (0.5 - 1 m / s), these vessels have pronounced elastic properties that ensure the strength of the wall when it is stretched and return to the starting position, and also contribute to the transformation of pulsating blood flow into a constant continuous one. The wall of the elastic type arteries is distinguished by a significant thickness and the presence of a large number of elastic elements in the composition of all membranes.

Inner shell consists of two layers - endothelial and subendothelial. Endothelial cells that form a continuous inner lining have a different size and shape, contain one or more nuclei. Their cytoplasm contains few organelles and many microfilaments. Beneath the endothelium is the basement membrane. The subendothelial layer consists of loose, fine-fibred connective tissue, which, along with a network of elastic fibers, contains poorly differentiated stellate cells, macrophages, and smooth muscle cells. The amorphous substance of this layer, which is of great importance for wall nutrition, contains a significant amount of glycosaminoglycans. When the wall is damaged and the pathological process (atherosclerosis) develops, lipids (cholesterol and its esters) accumulate in the subendothelial layer. Cellular elements of the subendothelial layer play an important role in wall regeneration. On the border with the middle shell is a dense network of elastic fibers.

Middle shell consists of numerous elastic fenestrated membranes, between which obliquely oriented bundles of smooth muscle cells are located. Through the windows (fenestra) of the membranes, intra-wall transport of substances necessary for the nutrition of wall cells is carried out. Both membranes and cells of smooth muscle tissue are surrounded by a network of elastic fibers, which, together with the fibers of the inner and outer shells, form a single frame that provides. high elasticity of the wall.

The outer shell is formed by connective tissue, which is dominated by bundles of collagen fibers oriented longitudinally. Vessels are located and branch in this shell, providing nutrition to both the outer shell and the outer zones of the middle shell.

Muscular type arteries. The arteries of this type of different caliber include most of the arteries that deliver and regulate blood flow to various parts and organs of the body (brachial, femoral, splenic, etc.). During microscopic examination, the elements of all three shells are clearly visible in the wall (Fig. 5).

Inner shell consists of three layers: endothelial, subendothelial and internal elastic membrane. The endothelium has the form of a thin plate, consisting of cells elongated along the vessel with oval nuclei protruding into the lumen. The subendothelial layer is more developed in large diameter arteries and consists of stellate or spindle-shaped cells, thin elastic fibers and an amorphous substance containing glycosaminoglycans. On the border with the middle shell lies internal elastic membrane, clearly visible on the preparations in the form of a shiny, light pink wavy strip stained with eosin. This membrane is permeated with numerous holes that are important for the transport of substances.

Middle shell built mainly of smooth muscle tissue, the bundles of cells of which go in a spiral, however, when the position changes arterial wall(stretching) the location of muscle cells can change. The contraction of the muscle tissue of the middle shell is important in regulating the flow of blood to organs and tissues in accordance with their needs and maintaining blood pressure. Between the bundles of muscle tissue cells there is a network of elastic fibers, which, together with the elastic fibers of the subendothelial layer and the outer shell, form a single elastic frame that gives the wall elasticity when it is squeezed. On the border with the outer shell in the large arteries of the muscular type there is an outer elastic membrane, consisting of a dense plexus of longitudinally oriented elastic fibers. In smaller arteries, this membrane is not expressed.

outer shell consists of connective tissue in which collagen fibers and networks of elastic fibers are elongated in the longitudinal direction. Between the fibers are cells, mainly fibrocytes. The outer sheath contains nerve fibers and small blood vessels that feed the outer layers of the artery wall.

Rice. 5. Scheme of the structure of the wall of the artery (A) and vein (B) of the muscular type:

1 - inner shell; 2 - middle shell; 3 - outer shell; a - endothelium; b - internal elastic membrane; c - nuclei of cells of smooth muscle tissue in the middle shell; d - nuclei of adventitia connective tissue cells; e - vessels of vessels.

Arteries of the muscular-elastic type in terms of the structure of the wall, they occupy an intermediate position between the arteries of the elastic and muscular types. In the middle shell, spirally oriented smooth muscle tissue, elastic plates and a network of elastic fibers are equally developed.

Vessels of the microvasculature. A dense network of small pre-capillary, capillary and post-capillary vessels is formed at the site of the transition of the arterial to the venous bed in organs and tissues. This complex of small vessels, which provides blood supply to organs, transvascular metabolism and tissue homeostasis, is united by the term microvasculature. It consists of various arterioles, capillaries, venules and arteriolo-venular anastomoses (Fig. 6).

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Fig.6. Scheme of vessels of the microvasculature:

1 - arteriole; 2 - venule; 3 - capillary network; 4 - arteriolo-venular anastomosis

Arterioles. As the diameter decreases in the muscular arteries, all membranes become thinner and they pass into arterioles - vessels with a diameter of less than 100 microns. Their inner shell consists of the endothelium, located on the basement membrane, and individual cells of the subendothelial layer. Some arterioles may have a very thin internal elastic membrane. In the middle shell, one row of spirally arranged cells of smooth muscle tissue is preserved. In the wall of the terminal arterioles, from which the capillaries branch off, smooth muscle cells do not form a continuous row, but are located separately. it precapillary arterioles. However, at the point of branching from the arteriole, the capillary is surrounded by a significant number of smooth muscle cells, which form a kind of precapillary sphincter. Due to changes in the tone of such sphincters, the blood flow in the capillaries of the corresponding tissue or organ is regulated. There are elastic fibers between muscle cells. The outer shell contains individual adventitial cells and collagen fibers.

capillaries- the most important elements of the microcirculatory bed, in which the exchange of gases and various substances between blood and surrounding tissues. In most organs, branching structures form between arterioles and venules. capillary networks located in loose connective tissue. The density of the capillary network in different organs can be different. The more intense the metabolism in the organ, the denser the network of its capillaries. The most developed network of capillaries in the gray matter of organs nervous system, in the organs of internal secretion, the myocardium of the heart, around the pulmonary alveoli. In skeletal muscles, tendons, and nerve trunks, capillary networks are oriented longitudinally.

The capillary network is constantly in a state of restructuring. In organs and tissues, a significant number of capillaries do not function. In their greatly reduced cavity, only blood plasma circulates ( plasma capillaries). The number of open capillaries increases with the intensification of the work of the body.

Capillary networks are also found between vessels of the same name, for example, venous capillary networks in the lobules of the liver, adenohypophysis, and arterial networks in the renal glomeruli. In addition to forming branched networks, capillaries can take the form of a capillary loop (in the papillary dermis) or form glomeruli (vascular glomeruli of the kidneys).

Capillaries are the narrowest vascular tubes. On average, their caliber corresponds to the diameter of an erythrocyte (7-8 microns), however, depending on the functional state and organ specialization, the diameter of the capillaries can be different. Narrow capillaries (4-5 microns in diameter) in the myocardium. Special sinusoidal capillaries with a wide lumen (30 microns or more) in the lobules of the liver, spleen, red bone marrow, organs of internal secretion.

The wall of blood capillaries consists of several structural elements. The inner lining is formed by a layer of endothelial cells located on the basement membrane, the latter contains cells - pericytes. Adventitial cells and reticular fibers are located around the basement membrane (Fig. 7).

Fig.7. Scheme of the ultrastructural organization of the wall of a blood capillary with a continuous endothelial lining:

1 - endotheliocyte: 2 - basement membrane; 3 - pericyte; 4 - pinocytic microvesicles; 5 - contact zone between endothelial cells (Fig. Kozlov).

flat endothelial cells elongated along the length of the capillary and have very thin (less than 0.1 μm) peripheral non-nuclear areas. Therefore, with light microscopy of the transverse section of the vessel, only the region of the nucleus with a thickness of 3-5 μm is distinguishable. The nuclei of endotheliocytes are often oval in shape, contain condensed chromatin, concentrated near the nuclear membrane, which, as a rule, has uneven contours. In the cytoplasm, the bulk of the organelles is located in the perinuclear region. The inner surface of endothelial cells is uneven, the plasmolemma forms microvilli, protrusions, and valve-like structures of various shapes and heights. The latter are especially characteristic of the venous section of the capillaries. Along the inner and outer surfaces of endotheliocytes are numerous pinocytic vesicles, indicating intensive absorption and transfer of substances through the cytoplasm of these cells. Endothelial cells, due to their ability to quickly swell and then, releasing liquid, decrease in height, can change the size of the capillary lumen, which, in turn, affects the passage of blood cells through it. In addition, electron microscopy revealed microfilaments in the cytoplasm, which determine the contractile properties of endotheliocytes.

basement membrane, located under the endothelium, is detected by electron microscopy and is a plate 30-35 nm thick, consisting of a network of thin fibrils containing type IV collagen and an amorphous component. The latter, along with proteins, contains hyaluronic acid, the polymerized or depolymerized state of which determines the selective permeability of capillaries. The basement membrane also provides elasticity and strength to the capillaries. In the splitting of the basement membrane, there are special process cells - pericytes. They cover the capillary with their processes and, penetrating through the basement membrane, form contacts with endotheliocytes.

In accordance with the structural features of the endothelial lining and basement membrane, there are three types of capillaries. Most capillaries in organs and tissues belong to the first type ( general type capillaries). They are characterized by the presence of a continuous endothelial lining and basement membrane. In this continuous layer, the plasmolemms of neighboring endothelial cells are as close as possible and form connections according to the type of tight contact, which is impermeable to macromolecules. There are also other types of contacts, when the edges of adjacent cells overlap each other like tiles or are connected by jagged surfaces. Along the length of the capillaries, a narrower (5 - 7 microns) proximal (arteriolar) and a wider (8 - 10 microns) distal (venular) parts are distinguished. In the cavity of the proximal part, the hydrostatic pressure is greater than the colloid osmotic pressure created by the proteins in the blood. As a result, the liquid is filtered behind the wall. In the distal part, the hydrostatic pressure becomes less than the colloid osmotic pressure, which causes the transfer of water and substances dissolved in it from the surrounding tissue fluid into the blood. However, the output fluid flow is greater than the input, and excess fluid as an integral part of the tissue fluid of the connective tissue enters the lymphatic system.

In some organs in which the processes of absorption and excretion of fluid are intensive, as well as the rapid transport of macromolecular substances into the blood, the capillary endothelium has rounded submicroscopic holes with a diameter of 60-80 nm or rounded areas covered with a thin diaphragm (kidneys, organs of internal secretion). it capillaries with fenestra(lat. fenestrae - windows).

Capillaries of the third type - sinusoidal, are characterized by a large diameter of their lumen, the presence of wide gaps between endothelial cells and a discontinuous basement membrane. Capillaries of this type are found in the spleen, red bone marrow. Through their walls penetrate not only macromolecules, but also blood cells.

Venules- the outlet section of the micropirculous bed and the initial link of the venous section of the vascular system. They collect blood from the capillaries. The diameter of their lumen is wider than in capillaries (15-50 microns). In the wall of venules, as well as in capillaries, there is a layer of endothelial cells located on the basement membrane, as well as a more pronounced outer connective tissue membrane. In the walls of venules, passing into small veins, there are separate smooth muscle cells. AT postcapillary venules of the thymus, lymph nodes, the endothelial lining is represented by high endothelial cells that contribute to the selective migration of lymphocytes during their recycling. In venules, due to the thinness of their walls, slow blood flow and low blood pressure, a significant amount of blood can be deposited.

Arterio-venular anastomoses. Tubes were found in all organs, through which blood from arterioles can be sent directly to venules, bypassing the capillary network. There are especially many anastomoses in the dermis of the skin, in the auricle, the crest of birds, where they play a certain role in thermoregulation.

By structure, true arteriolo-venular anastomoses (shunts) are characterized by the presence in the wall of a significant number of longitudinally oriented bundles of smooth muscle cells located either in the subendothelial layer of the intima (Fig. 8) or in the inner zone of the middle shell. In some anastomoses, these cells acquire an epithelial-like appearance. Longitudinally located muscle cells are also in the outer shell. There are not only simple anastomoses in the form of single tubules, but also complex ones, consisting of several branches extending from one arteriole and surrounded by a common connective tissue capsule.

Fig.8. Arterio-venular anastomosis:

1 - endothelium; 2 - longitudinally located epithelioid-muscle cells; 3 - circularly located muscle cells of the middle shell; 4 - outer shell.

With the help of contractile mechanisms, anastomoses can reduce or completely close their lumen, as a result of which the flow of blood through them stops and blood enters the capillary network. Thanks to this, the organs receive blood depending on the need associated with their work. In addition, high arterial blood pressure is transmitted through the anastomoses to the venous bed, thereby contributing to a better movement of blood in the veins. Significant role of anastomoses in the enrichment of venous blood with oxygen, as well as in the regulation of blood circulation during the development pathological processes in the organs.

Vienna- blood vessels through which blood from organs and tissues flows to the heart, to the right atrium. The exception is the pulmonary veins, which direct oxygen-rich blood from the lungs to the left atrium.

The wall of the veins, as well as the wall of the arteries, consists of three shells: internal, middle and external. However, the specific histological structure of these membranes in different veins is very diverse, which is associated with the difference in their functioning and local (according to the localization of the vein) conditions of blood circulation. Most veins of the same diameter as the same-named arteries have a thinner wall and a wider lumen.

In accordance with hemodynamic conditions - low blood pressure (15-20 mm Hg) and low blood flow velocity (about 10 mm / s) - elastic elements are relatively poorly developed in the vein wall and a smaller amount of muscle tissue in the middle shell. These signs make it possible to change the configuration of the veins: with a small blood supply, the walls of the veins become collapsed, and if the outflow of blood is difficult (for example, due to blockage), the wall is easily stretched and the veins expand.

Essential in the hemodynamics of venous vessels are valves located in such a way that, passing blood towards the heart, they block the path of its reverse flow. The number of valves is greater in those veins in which blood flows in the opposite direction to gravity (for example, in the veins of the extremities).

According to the degree of development in the wall of muscle elements, veins of non-muscular and muscular types are distinguished.

Muscleless veins. The characteristic veins of this type include the veins of the bones, the central veins of the hepatic lobules, and the trabecular veins of the spleen. The wall of these veins consists only of a layer of endothelial cells located on the basement membrane and an outer thin layer of fibrous connective tissue. With the participation of the latter, the wall fuses tightly with the surrounding tissues, as a result of which these veins are passive in moving blood through them and do not collapse. Muscleless veins meninges and the retinas of the eye, filling with blood, are able to easily stretch, but at the same time, the blood, under the influence of its own gravity, easily flows into larger venous trunks.

Muscular veins. The wall of these veins, like the wall of arteries, consists of three shells, but the boundaries between them are less distinct. The thickness of the muscular membrane in the wall of the veins of different localization is not the same, which depends on whether the blood moves in them under the influence of gravity or against it. On the basis of this, the muscular type veins are subdivided into veins with weak, medium and strong development of muscle elements. The veins of the first variety include horizontally located veins of the upper body of the body and veins of the digestive tract. The walls of such veins are thin, in their middle shell, smooth muscle tissue does not form a continuous layer, but is located in bundles, between which there are layers of loose connective tissue.

to the veins with strong development muscle elements include large veins of the limbs of animals, through which blood flows upward, against gravity (femoral, brachial, etc.). They are characterized by longitudinally located small bundles of cells of smooth muscle tissue in the subendothelial layer of the intima and well-developed bundles of this tissue in the outer shell. The contraction of the smooth muscle tissue of the outer and inner shells leads to the formation of transverse folds of the vein wall, which prevents reverse blood flow.

The middle shell contains circularly arranged bundles of smooth muscle cells, the contractions of which contribute to the movement of blood to the heart. In the veins of the extremities there are valves, which are thin folds formed by the endothelium and the subendothelial layer. The basis of the valve is fibrous connective tissue, which at the base of the valve leaflets may contain a certain number of cells of smooth muscle tissue. The valves also prevent backflow of venous blood. For the movement of blood in the veins, the suction action of the chest during inspiration and the contraction of the skeletal muscle tissue surrounding venous vessels.

Vascularization and innervation of blood vessels. The walls of large and medium-sized arterial vessels are nourished both from the outside - through the vessels of the vessels (vasa vasorum), and from the inside - due to the blood flowing inside the vessel. Vascular vessels are branches of thin perivascular arteries passing in the surrounding connective tissue. In the outer shell of the vessel wall, arterial branches branch, capillaries penetrate into the middle one, the blood from which is collected in the venous vessels of the vessels. The intima and the inner zone of the middle membrane of the arteries do not have capillaries and are fed from the side of the lumen of the vessels. Due to the significantly lower strength of the pulse wave, the smaller thickness of the middle membrane, and the absence of an internal elastic membrane, the mechanism of supplying the vein from the side of the cavity is of no particular importance. In the veins, the vessels of the vessels supply all three membranes with arterial blood.

Constriction and expansion of blood vessels, maintenance of vascular tone occur mainly under the influence of impulses coming from the vasomotor center. Impulses from the center are transmitted to the cells of the lateral horns of the spinal cord, from where they enter the vessels along the sympathetic nerve fibers. The terminal branches of the sympathetic fibers, which include the axons of the nerve cells of the sympathetic ganglia, form motor nerve endings on the cells of smooth muscle tissue. The efferent sympathetic innervation of the vascular wall determines the main vasoconstrictor effect. The question of the nature of vasodilators has not been finally resolved.

It has been established that parasympathetic nerve fibers are vasodilating in relation to the vessels of the head.

In all three shells of the vessel wall, the terminal branches of the dendrites of nerve cells, mainly the spinal ganglia, form numerous sensitive nerve endings. In the adventitia and perivascular loose connective tissue, among the diverse free endings, there are also encapsulated bodies. Of particular physiological importance are specialized interoreceptors that perceive changes in blood pressure and its chemical composition, concentrated in the wall of the aortic arch and in the region of the carotid artery branching into internal and external - the aortic and carotid reflexogenic zones. It has been established that in addition to these zones, there are a sufficient number of other vascular territories that are sensitive to changes in blood pressure and chemical composition (baro- and chemoreceptors). From the receptors of all specialized territories, impulses along the centripetal nerves reach the vasomotor center of the medulla oblongata, causing an appropriate compensatory neuroreflex reaction.

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 you collect them and stretch them in one straight line, then total length will be about 100 thousand km.

These tubular elastic formations function continuously, transferring blood from the constantly contracting heart to all corners. human body, oxygenating them and nourishing them, and then bringing 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.

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 - circles of blood circulation.

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 ones contain valves.

arteries

They deliver blood rich 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:

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:

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.

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 in the human body ranges from 100 to 160 billion.

The density of their accumulation is different everywhere, but the greatest in the brain and myocardium. They consist only of endothelial cells. They carry out very important activities: chemical exchange between bloodstream and fabrics.

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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.

Vienna

These are the blood vessels through which the oxygen-depleted blood is coming back to the heart.

The walls of the veins are thinner than the walls of the arteries, because there is no strong pressure. The most developed layer of smooth muscles in middle wall vessels of the legs, 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. 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:

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 capable of reverse process- removal of unnecessary vessels when getting rid of excess fat(precisely from him, and not just from extra pounds).

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

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