The structure and properties of the vascular walls depend on the functions performed by the vessels in the integral human vascular system. In the composition of the walls of blood vessels, an internal ( intimacy), average ( media) and outer ( adventitia) shell.

All blood vessels and cavities of the heart are lined from the inside with a layer of endothelial cells, which forms part of the intima of the vessels. The endothelium in intact vessels forms a smooth inner surface, which helps to reduce resistance to blood flow, protects against damage and prevents thrombus formation. Endothelial cells are involved in the transport of substances through the vascular walls and respond to mechanical and other influences by the synthesis and secretion of vasoactive and other signaling molecules.

The structure of the inner membrane (intima) of the vessels also includes a network of elastic fibers, which is especially strongly developed in vessels of the elastic type - the aorta and large arterial vessels.

V middle layer smooth muscle fibers (cells) are located circularly, capable of contracting in response to various influences. There are especially many such fibers in the vessels of the muscular type - the terminal small arteries and arterioles. With their reduction, there is an increase in the tension of the vascular wall, a decrease in the lumen of blood vessels and blood flow in more distally located vessels until it stops.

Outer layer the vascular wall contains collagen fibers and fat cells. Collagen fibers increase the resistance of the walls of arterial vessels to the action of high blood pressure and protect them and the venous vessels from excessive stretching and rupture.

Rice. The structure of the walls of blood vessels

Table. Structural and functional organization of the vessel wall

Name	Characteristic
Endothelium (intima)	The inner, smooth surface of the vessels, consisting mainly of one layer of flat cells, the main membrane and the inner elastic plate
	Consists of several interpenetrating muscle layers between the inner and outer elastic plates
Elastic fibers	They are located in the inner, middle and outer shells and form a relatively dense network (especially in the intima), can easily be stretched several times and create elastic tension
Collagen fibers	Located in the middle and outer shells, they form a network that provides much more resistance to stretching the vessel than elastic fibers, but, having a folded structure, they resist blood flow only if the vessel is stretched to a certain extent
Smooth muscle cells	They form a middle shell, are connected with each other and with elastic and collagen fibers, create active tension of the vascular wall (vascular tone)
Adventitia	It is the outer shell of the vessel and consists of loose connective tissue (collagen fibers), fibroblasts. mast cells, nerve endings, and in large vessels it additionally includes small blood and lymphatic capillaries, depending on the type of vessels, it has a different thickness, density and permeability

Functional classification and types of vessels

The activity of the heart and blood vessels ensures the continuous movement of blood in the body, its redistribution between organs, depending on their functional state. A difference in blood pressure is created in the vessels; the pressure in the large arteries is much higher than the pressure in the small arteries. The difference in pressure determines the movement of blood: blood flows from those vessels where the pressure is higher, to those vessels where the pressure is low, from arteries to capillaries, veins, from veins to the heart.

Depending on the function performed, the large and small vessels are divided into several groups:

• shock-absorbing (elastic-type vessels);
• resistive (resistance vessels);
• sphincter vessels;
• exchange vessels;
• capacitive vessels;
• shunting vessels (arteriovenous anastomoses).

Shock-absorbing vessels(main, compression chamber vessels) - the aorta, pulmonary artery and all large arteries extending from them, arterial vessels of the elastic type. These vessels receive blood expelled by the ventricles at a relatively high pressure (about 120 mm Hg for the left and up to 30 mm Hg for the right ventricles). The elasticity of the great vessels will be created by a layer of elastic fibers well expressed in them, located between the layers of the endothelium and muscles. The shock-absorbing vessels are stretched, taking in the blood expelled under the pressure of the ventricles. This softens the hydrodynamic shock of the ejected blood against the walls of blood vessels, and their elastic fibers store potential energy, which is spent on maintaining blood pressure and moving blood to the periphery during diastole of the ventricles of the heart. The shock-absorbing vessels have little resistance to blood flow.

Resistive vessels(resistance vessels) - small arteries, arterioles and metarterioles. These vessels offer the greatest resistance to blood flow, since they have a small diameter and contain a thick layer of circularly located smooth muscle cells in the wall. Smooth muscle cells, which contract under the influence of neurotransmitters, hormones and other vasoactive substances, can sharply reduce the lumen of blood vessels, increase resistance to blood flow and reduce blood flow in organs or their individual areas. When smooth myocytes relax, the vascular lumen and blood flow increase. Thus, resistive vessels perform the function of regulating organ blood flow and affect the arterial blood pressure.

Exchange vessels- capillaries, as well as pre- and post-capillary vessels, through which the exchange of water, gases and organic substances between blood and tissues takes place. The capillary wall consists of one layer of endothelial cells and a basement membrane. There are no muscle cells in the capillary wall that could actively change their diameter and resistance to blood flow. Therefore, the number of open capillaries, their lumen, the rate of capillary blood flow and transcapillary exchange change passively and depend on the state of pericytes - smooth muscle cells located circularly around the precapillary vessels, and the state of arterioles. With expansion of arterioles and relaxation of pericytes, capillary blood flow increases, and with narrowing of arterioles and contraction of pericytes, it slows down. A slowdown in blood flow in the capillaries is also observed with narrowing of the venules.

Capacitive vessels represented by veins. Due to their high extensibility, the veins can accommodate large volumes of blood and thus provide a kind of deposition - slowing down the return to the atria. Veins of the spleen, liver, skin and lungs have especially pronounced depositing properties. The transverse lumen of the veins in low blood pressure is oval in shape. Therefore, with an increase in blood flow, the veins, even without stretching, but only taking a more rounded shape, can accommodate more blood (deposit it). In the walls of the veins there is a pronounced muscle layer, consisting of circularly located smooth muscle cells. With their reduction, the diameter of the veins decreases, the amount of deposited blood decreases and the return of blood to the heart increases. Thus, the veins are involved in the regulation of the volume of blood returning to the heart, influencing its contraction.

Shunt vessels Are anastomoses between arterial and venous vessels. There is a muscle layer in the wall of the anastomosing vessels. When the smooth myocytes of this layer relax, the anastomosing vessel opens and the resistance to blood flow decreases. Arterial blood is discharged along a pressure gradient through the anastomosing vessel into a vein, and blood flow through the vessels of the microvasculature, including capillaries, decreases (up to cessation). This may be accompanied by a decrease in local blood flow through an organ or part of it and a violation of tissue metabolism. There are especially many bypass vessels in the skin, where arteriovenous anastomoses are turned on to reduce heat transfer, with the threat of a decrease in body temperature.

Blood return vessels in the heart are represented by medium, large and vena cava.

Table 1. Characteristics of the architectonics and hemodynamics of the vascular bed

Atlas: Human Anatomy and Physiology. Complete practical guide Elena Yurievna Zigalova

Blood supply to the body

Blood supply to the body

In humans and other mammals, the circulatory system is divided into two circles of blood circulation. Big circle begins in the left ventricle and ends in the right atrium, a small circle begins in the right ventricle and ends in the left atrium ( rice. 62 A, B).

Small, or pulmonary, circle of blood circulation begins in the right ventricle of the heart, from where the pulmonary trunk exits, which divides into the right and left pulmonary arteries, and the latter branch out in the lungs according to the branching of the bronchi into arteries that pass into the capillaries. In the capillary networks that encircle the alveoli, the blood gives off carbon dioxide and is enriched with oxygen. Oxygen-enriched arterial blood flows from the capillaries into the veins, which, merging into four pulmonary veins (two on each side), flow into the left atrium, where the small (pulmonary) circle of blood circulation ends.

Rice. 62. Blood supply to the human body. A. Scheme of the large and small circles of blood circulation. 1 - capillaries of the head, upper body and upper extremities; 2 - common carotid artery; 3 - pulmonary veins; 4 - aortic arch; 5 - left atrium; 6 - left ventricle; 7 - aorta; 8 - hepatic artery; 9 - liver capillaries; 10 - capillaries of the lower parts of the trunk and lower extremities; 11 - superior mesenteric artery; 12 - inferior vena cava; 13 - portal vein; 14 - hepatic veins; 15 - right ventricle; 16 - right atrium; 17 - superior vena cava; 18 - pulmonary trunk; 19 - capillaries of the lungs. B. Human circulatory system, front view. 1 - left common carotid artery; 2 - internal jugular vein; 3 - aortic arch; 4 - subclavian vein; 5 - pulmonary artery (left) 6 - pulmonary trunk; 7 - left pulmonary vein; 8 - left ventricle (heart); 9 - the descending part of the aorta; 10 - brachial artery; 11 - left gastric artery; 12 - inferior vena cava; 13 - common iliac artery and vein; 14 - femoral artery; 15 - popliteal artery; 16 - posterior tibial artery; 17 - anterior tibial artery; 18 - dorsal artery and veins and feet; 19 - posterior tibial artery and veins; 20 - femoral vein; 21 - internal iliac vein; 22 - external iliac artery and vein; 23 - superficial palmar arch (arterial); 24 - radial artery and veins; 25 - ulnar artery and veins; 26 - portal vein of the liver; 27 - brachial artery and veins; 28 - axillary artery and vein; 29 - superior vena cava; 30 - right brachiocephalic vein; 31 - brachiocephalic trunk; 32 - left brachiocephalic vein

Large, or corporal, circle of blood circulation supplies all organs and tissues with blood, which means nutrients and oxygen, and removes metabolic products and carbon dioxide. The large circle begins in the left ventricle of the heart, where arterial blood flows from the left atrium. The aorta leaves the left ventricle, from which arteries depart, going to all organs and tissues of the body and branching in their thickness up to arterioles and capillaries, the latter pass into venules and further into veins. The veins merge into two large trunks - the superior and inferior vena cava, which flow into the right atrium of the heart, where the systemic circulation ends. The addition to the large circle is cardiac circulation feeding the heart itself. It starts exiting the aorta coronary arteries hearts and ends veins of the heart... The latter merge into coronary sinus, which flows into the right atrium, and the rest of the smallest veins open directly into the cavity of the right atrium and ventricle.

Aorta located to the left of the midline of the body and with its branches supplies blood to all organs and tissues of the body (see. rice. 62). A part of it, about 6 cm long, directly coming out of the heart and rising up, is called the ascending part of the aorta... It starts by expanding aortic bulb, inside which there are three aortic sinus located between the inner surface of the aortic wall and the flaps of its valve. From the aortic bulb right and left coronary artery... Bending to the left, the aortic arch lies over the pulmonary arteries diverging here, throws over the beginning of the left main bronchus and passes into descending aorta... From the concave side of the aortic arch, branches begin to the trachea, bronchi and to the thymus gland, three large vessels depart from the convex side of the arch: the brachiocephalic trunk lies on the right, and the left common carotid and left subclavian arteries are on the left.

Brachiocephalic trunk about 3 cm long departs from the aortic arch, goes up, back and to the right, in front of the trachea. At the level of the right sternoclavicular joint, it is divided into the right common carotid and subclavian arteries. The left common carotid and left subclavian arteries extend directly from the aortic arch to the left of the brachiocephalic trunk.

Common carotid artery(right and left) goes up next to the trachea and esophagus. At the level of the upper edge of the thyroid cartilage, it divides into the external carotid artery, which branches outside the cranial cavity, and the internal carotid artery, which runs inside the skull and travels to the brain. External carotid artery goes up, passes through the tissue of the parotid gland. On its way, the artery gives off lateral branches that supply blood to the skin, muscles and bones of the head and neck, organs of the mouth and nose, tongue, large salivary glands. Internal carotid artery goes up to the base of the skull, without giving up branches, enters the cranial cavity through the carotid artery canal in the temporal bone, rises along the carotid sulcus of the sphenoid bone, lies in the cavernous sinus and, after passing through the dura mater and arachnoid, is divided into a number of branches that supply blood to the brain and the organ of vision.

Subclavian artery on the left, it departs directly from the aortic arch, to the right of the brachiocephalic trunk, bends around the dome of the pleura, passes between the clavicle and the first rib, goes to the armpit. The subclavian artery and its branches supply blood to the cervical spinal cord with membranes, the brain stem, occipital and partially temporal lobes of the cerebral hemispheres, deep and partly superficial muscles of the neck, chest and back, cervical vertebrae, diaphragm, mammary gland, larynx, trachea, esophagus , thyroid and thymus. A circular arterial anastomosis forms at the base of the brain arterial(Willisiev) large brain circle involved in the blood supply to the brain.

The subclavian artery in the axillary region becomes axillary artery, which lies in the axillary fossa medially from the shoulder joint and the humerus next to the vein of the same name. The artery supplies the muscles of the shoulder girdle, the skin and muscles of the lateral chest wall, the shoulder and clavicular-acromial joints, the contents of the axillary fossa. Brachial artery is a continuation of the axillary, it passes in the medial groove of the biceps brachii and is divided into the radial and ulnar arteries in the ulnar fossa. The brachial artery supplies blood to the skin and muscles of the shoulder, the humerus, and the elbow joint.

Radial artery located on the forearm laterally in the radial groove, parallel to the radius. In the lower section, near its styloid process, the artery is easily palpable, being covered only by the skin and fascia, the pulse is easily determined here. The radial artery passes to the hand, supplies blood to the skin and muscles of the forearm and hand, the radius, the ulnar and wrist joints. Ulnar artery located on the forearm medially in the ulnar groove parallel to the ulna, passes to the palmar surface of the hand. It supplies blood to the skin and muscles of the forearm and hand, ulna, elbow and wrist joints. The ulnar and radial arteries form two arterial networks of the wrist on the hand: the back and the palmar, feeding the hand and two arterial palmar arch deep and superficial... The vessels departing from them supply the hand with blood.

Descending aorta divided into two parts: chest and abdominal. Thoracic aorta located on the spine asymmetrically, to the left of the midline and supplies blood to the organs of the chest cavity, its walls and diaphragm. From the thoracic cavity, the aorta passes into the abdominal cavity through the aortic opening of the diaphragm. The abdominal aorta is gradually displaced medially, at the site of its division into two common iliac arteries at the level of the IV lumbar vertebra ( aortic bifurcation) is located along the midline. The abdominal aorta supplies blood to the abdominal viscera and abdominal walls.

From the abdominal aorta unpaired and paired vessels depart. The first includes three very large arteries: the celiac trunk, the superior and inferior mesenteric arteries. Paired arteries - middle adrenal, renal and testicular (ovarian in women). Parietal branches: lower phrenic, lumbar and median sacral artery. Celiac trunk departs immediately under the diaphragm at the level of the XII thoracic vertebra and immediately divides into three branches that supply blood to the abdominal part of the esophagus, stomach, duodenum, pancreas, liver and gallbladder, spleen, small and large omentums.

Superior mesenteric artery departs directly from the abdominal part of the aorta and goes to the root of the mesentery of the small intestine. The artery supplies blood to the pancreas, small intestine, and the right side of the colon, including the right side of the transverse colon. Inferior mesenteric artery directed retroperitoneally downward and to the left, it supplies blood to the large intestine. The branches of these three arteries anastomose with each other.

The abdominal aorta divides in two common iliac arteries - the largest human arteries (with the exception of the aorta). After passing a certain distance at an acute angle to each other, each of them is divided into two arteries: the internal iliac and the external iliac. Internal iliac artery starts from the common iliac artery at the level of the sacroiliac joint, is located retroperitoneally, goes to the small pelvis. It nourishes the pelvic bone, sacrum and all muscles of the small, large pelvis, gluteal region and partly the adductor muscles of the thigh, as well as internal organs located in the cavity of the small pelvis: rectum, bladder; in men, the seminal vesicles, the vas deferens, the prostate gland; in women, the uterus and vagina, external genitals and perineum. External iliac artery begins at the level of the sacroiliac joint from the common iliac artery, goes retroperitoneally down and forward, passes under the inguinal ligament and passes into the femoral artery. The external iliac artery supplies the thigh muscles, in men - the scrotum, in women - the pubis and labia majora.

Femoral artery is a direct continuation of the external iliac artery. It passes in the femoral triangle, between the muscles of the thigh, enters the popliteal fossa, where it passes into the popliteal artery. The femoral artery supplies blood to the femur, skin and muscles of the thigh, the skin of the anterior abdominal wall, external genitalia, and the hip joint. Popliteal artery is a continuation of the femoral. It lies in the fossa of the same name, passes to the lower leg, where it is immediately divided into the anterior and posterior tibial arteries. The artery supplies blood to the skin and nearby muscles of the thigh and the back of the lower leg, the knee joint. Posterior tibial artery goes down, in the area of ​​the ankle joint, passes to the sole behind the medial ankle under the flexor muscle retainer. The posterior tibial artery supplies the skin of the posterior surface of the leg, bones, leg muscles, knee and ankle joints, and foot muscles. Anterior tibial artery goes down along the front surface of the interosseous membrane of the lower leg. The artery supplies blood to the skin and muscles of the anterior surface of the lower leg and dorsum of the foot, knee and ankle joints, on the foot passes into the dorsal artery of the foot. Both tibial arteries form the plantar arterial arch on the foot, which lies at the level of the base of the metatarsal bones. Arteries that feed the skin and muscles of the foot and toes extend from the arch.

Veins of the systemic circulation form systems: superior vena cava; inferior vena cava (including the hepatic portal vein system); system of veins of the heart, forming the coronary sinus of the heart. The main trunk of each of these veins opens with an independent opening into the cavity of the right atrium. The veins of the superior and inferior vena cava systems anastomose with each other.

Superior vena cava(5-6 cm long, 2-2.5 cm in diameter) is devoid of valves, located in the chest cavity in the mediastinum. It is formed due to the fusion of the right and left brachiocephalic veins behind the junction of the cartilage of the I right rib with the sternum, descends to the right and posterior to the ascending part of the aorta and flows into the right atrium. The superior vena cava collects blood from the upper body, head, neck, upper limb, and chest cavity. From the head, blood flows through the external and internal jugular veins. Through the internal jugular vein, blood flows from the brain.

On the upper limb, deep and superficial veins are distinguished, which abundantly anastomose with each other. Deep veins are usually accompanied by two arteries of the same name. Only both brachial veins merge to form one axillary vein. Superficial veins form a wide-looped network, from which blood enters the lateral saphenous and medial saphenous veins. Blood from the superficial veins flows into the axillary vein.

Inferior vena cava The largest vein in the human body (its diameter at the point of confluence with the right atrium reaches 3–3.5 cm) is formed by the fusion of the right and left common iliac veins at the level of the intervertebral cartilage, between IV and V lumbar vertebrae on the right. The inferior vena cava is located retroperitoneally to the right of the aorta, passes through the opening of the diaphragm of the same name into the chest cavity and enters the pericardial cavity, where it flows into the right atrium. The inferior vena cava collects blood from the lower extremities, walls and internal organs of the pelvis and abdomen. The inflows of the inferior vena cava correspond to the paired branches of the aorta (with the exception of the hepatic).

Portal vein collects blood from unpaired abdominal organs: spleen, pancreas, greater omentum, gallbladder and digestive tract, starting with the cardiac stomach and ending with the upper rectum. The portal vein is formed by the fusion of the superior mesenteric and splenic veins, the inferior mesenteric vein joins the latter. Unlike all other veins, the portal vein, having entered the gate of the liver, splits into smaller and smaller branches, up to the sinusoidal capillaries of the liver, which flow into the central vein of the lobule (see section "Liver", p. XX). From the central veins, sub-lobular veins are formed, which, when enlarged, collect in the hepatic veins, which flow into the inferior vena cava.

Common iliac vein steam room, short, thick, begins due to the fusion of the internal and external iliac veins at the level of the sacroiliac joints and connects to the vein of the other side, forming the inferior vena cava. The internal iliac vein, devoid of valves, collects blood from the walls and organs of the pelvis, external and internal genital organs.

External iliac vein - direct continuation of the femoral, collects blood from all superficial and deep veins of the lower limb.

The circulatory system contains a large number of arterial and venous anastomoses (anastomoses). Distinguish between intersystem anastomoses, connecting branches of arteries or tributaries of veins of different systems with each other, and intrasystemic between branches (tributaries) within one system. The most important intersystem anastomoses are between the superior and inferior vena cava, superior vena cava and portal veins; the inferior cavity and portal, which were named kavacaval and part-caval anastomoses, by the names of the large veins, the tributaries of which they connect.

ATTENTION

In the lung, there are only intersystem anastomoses between the vessels of the large and pulmonary circulation - small branches of the pulmonary and bronchial arteries.

The structure of the cardiovascular system and its functions- this is the key knowledge that a personal trainer needs to build a competent training process for wards, based on loads adequate to their level of training. Before proceeding with the construction of training programs, it is necessary to understand the principle of operation of this system, how blood is pumped through the body, in what ways it happens and what affects the capacity of its vessels.

The cardiovascular system is needed by the body for the transfer of nutrients and components, as well as for the elimination of metabolic products from the tissues, maintaining the constancy of the internal environment of the body, optimal for its functioning. The heart is its main component, which acts as a pump that pumps blood throughout the body. At the same time, the heart is only a part of the entire circulatory system of the body, which first drives blood from the heart to the organs, and then from them back to the heart. We will also consider separately the arterial and separately the venous circulatory systems of a person.

The structure and function of the human heart

The heart is a kind of pump, consisting of two ventricles, which are interconnected and at the same time independent of each other. The right ventricle drives blood through the lungs, the left ventricle drives it through the rest of the body. Each half of the heart has two chambers: the atrium and the ventricle. You can see them in the image below. The right and left atria act as reservoirs from which blood flows directly into the ventricles. Both ventricles, at the time of contraction of the heart, push blood out and drive it through the pulmonary system, as well as peripheral vessels.

The structure of the human heart: 1 pulmonary trunk; 2-valve of the pulmonary artery; 3-superior vena cava; 4-right pulmonary artery; 5-right pulmonary vein; 6-right atrium; 7-tricuspid valve; 8-right ventricle; 9-inferior vena cava; 10-descending aorta; 11-arch of the aorta; 12-left pulmonary artery; 13-left pulmonary vein; 14-left atrium; 15-aortic valve; 16-mitral valve; 17-left ventricle; 18-interventricular septum.

The structure and function of the circulatory system

The blood circulation of the whole body, both central (heart and lungs) and peripheral (the rest of the body) forms an integral closed system, divided into two circuits. The first circuit drives blood away from the heart and is called the arterial circulatory system, the second circuit returns blood to the heart and is called the venous circulatory system. Blood returning from the periphery to the heart initially enters the right atrium through the superior and inferior vena cava. From the right atrium, blood flows into the right ventricle, and through the pulmonary artery enters the lungs. After the exchange of oxygen with carbon dioxide occurs in the lungs, the blood through the pulmonary veins returns to the heart, first entering the left atrium, then into the left ventricle, and then only through the new into the arterial blood supply system.

The structure of the human circulatory system: 1-superior vena cava; 2-vessels going to the lungs; 3-aorta; 4-inferior vena cava; 5-hepatic vein; 6-portal vein; 7-pulmonary vein; 8-superior vena cava; 9-inferior vena cava; 10-vessels of internal organs; 11 vessels of the extremities; 12 head vessels; 13-pulmonary artery; 14-heart.

I-small circle of blood circulation; II-systemic circulation; III-vessels going to the head and arms; IV-vessels going to the internal organs; V-vessels going to the legs

The structure and function of the human arterial system

The function of the arteries is to transport blood, which is released by the heart as it contracts. Since this release occurs under a rather high pressure, nature has provided the arteries with strong and elastic muscle walls. Smaller arteries, called arterioles, are designed to control circulation and act as vessels that carry blood directly into tissues. Arterioles play a key role in the regulation of blood flow in the capillaries. They are also protected by elastic muscle walls, which enable the vessels to either block their lumen as needed, or significantly expand it. This makes it possible to change and control blood circulation within the capillary system, depending on the needs of specific tissues.

The structure of the human arterial system: 1-brachiocephalic trunk; 2-subclavian artery; 3-arch of the aorta; 4-axillary artery; 5-internal thoracic artery; 6-descending aorta; 7-internal thoracic artery; 8-deep brachial artery; 9-beam recurrent artery; 10-superior epigastric artery; 11-descending aorta; 12 lower epigastric artery; 13-interosseous arteries; 14-ray artery; 15-elbow artery; 16-palmar carpal arch; 17 dorsal carpal arch; 18 palmar arches; 19-finger arteries; 20-descending branch of the circumflex artery; 21-descending knee artery; 22 upper knee arteries; 23 lower knee arteries; 24-peroneal artery; 25-posterior tibial artery; 26-large tibial artery; 27-peroneal artery; 28-arterial arch of the foot; 29-metatarsal artery; 30-anterior cerebral artery; 31-middle cerebral artery; 32-posterior cerebral artery; 33-basilar artery; 34-external carotid artery; 35-internal carotid artery; 36 vertebral arteries; 37 common carotid arteries; 38 pulmonary vein; 39-heart; 40-intercostal arteries; 41 celiac trunk; 42 gastric arteries; 43-splenic artery; 44-common hepatic artery; 45 superior mesenteric artery; 46 renal artery; 47-inferior mesenteric artery; 48-internal seminal artery; 49-common iliac artery; 50-internal iliac artery; 51-external iliac artery; 52 enveloping arteries; 53-common femoral artery; 54-piercing branches; 55-deep thigh artery; 56-superficial femoral artery; 57-popliteal artery; 58-dorsal metatarsal arteries; 59-dorsal digital arteries.

The structure and functions of the human venous system

The purpose of venules and veins is to return blood back to the heart through them. From tiny capillaries, blood flows into small venules, and from there into larger veins. Since the pressure in the venous system is much lower than in the arterial system, the vessel walls are much thinner here. However, the walls of the veins are also surrounded by elastic muscle tissue, which, by analogy with the arteries, allows them either to narrow strongly, completely blocking the lumen, or to expand strongly, in this case, acting as a reservoir for blood. A feature of some veins, for example in the lower extremities, is the presence of one-way valves, the task of which is to ensure the normal return of blood to the heart, thereby preventing its outflow under the influence of gravity when the body is in an upright position.

The structure of the human venous system: 1-subclavian vein; 2-internal thoracic vein; 3-axillary vein; 4-lateral vein of the arm; 5-brachial veins; 6 intercostal veins; 7-medial vein of the hand; 8-median ulnar vein; 9-sterno-epigastric vein; 10-lateral vein of the arm; 11-elbow vein; 12-medial vein of the forearm; 13-epigastric inferior vein; 14-deep palmar arch; 15-surface palmar arch; 16 palmar digital veins; 17-sigmoid sinus; 18-external jugular vein; 19-internal jugular vein; 20-inferior thyroid vein; 21 pulmonary arteries; 22-heart; 23-inferior vena cava; 24 hepatic veins; 25 renal veins; 26-abdominal vena cava; 27-seed vein; 28-common iliac vein; 29-piercing branches; 30-external iliac vein; 31-internal iliac vein; 32-external genital vein; 33-deep vein of the thigh; 34-large vein of the leg; 35-femoral vein; 36-accessory vein of the leg; 37 upper knee veins; 38-popliteal vein; 39 lower knee veins; 40-large vein of the leg; 41-small vein of the leg; 42-anterior / posterior tibial vein; 43-deep plantar vein; 44-dorsal venous arch; 45 dorsal metacarpal veins.

The structure and function of the small capillary system

The function of the capillaries is to carry out the exchange of oxygen, fluids, various nutrients, electrolytes, hormones and other vital components between the blood and body tissues. The supply of nutrients to the tissues occurs due to the fact that the walls of these vessels are very thin. Thin walls allow nutrients to penetrate the tissues and provide them with all the necessary components.

The structure of microcirculation vessels: 1 arteries; 2-arterioles; 3 veins; 4-venules; 5-capillaries; 6-cell tissue

The work of the circulatory system

The movement of blood throughout the body depends on the capacity of the vessels, more precisely on their resistance. The lower this resistance, the more the blood flow increases, while the higher the resistance, the weaker the blood flow. The resistance itself depends on the size of the lumen of the vessels of the arterial circulatory system. The total resistance of all vessels of the circulatory system is called the total peripheral resistance. If in the body in a short period of time there is a reduction in the lumen of the vessels, the total peripheral resistance increases, and with the expansion of the lumen of the vessels, it decreases.

Both the expansion and contraction of the vessels of the entire circulatory system occurs under the influence of many different factors, such as the intensity of training, the level of stimulation of the nervous system, the activity of metabolic processes in specific muscle groups, the course of heat exchange processes with the external environment, and more. During training, stimulation of the nervous system leads to vasodilation and increased blood flow. At the same time, the most significant increase in blood circulation in muscles is primarily the result of metabolic and electrolytic reactions in muscle tissues under the influence of both aerobic and anaerobic physical activity. This includes an increase in body temperature and an increase in the concentration of carbon dioxide. All these factors contribute to vasodilation.

At the same time, blood flow in other organs and parts of the body that are not involved in the performance of physical activity decreases as a result of contraction of the arterioles. This factor, along with the narrowing of the large vessels of the venous circulatory system, contributes to an increase in blood volume, which is involved in the blood supply to the muscles involved in the work. The same effect is observed in the course of performing power loads with low weights, but with a large number of repetitions. The body's response in this case can be equated with aerobic exercise. At the same time, when performing strength work with large weights, the resistance to blood flow in the working muscles increases.

Conclusion

We examined the structure and function of the human circulatory system. As we now understand, it is needed to pump blood through the body with the help of the heart. The arterial system drives blood away from the heart, the venous system returns blood back to it. In terms of physical activity, it can be summarized as follows. The blood flow in the circulatory system depends on the degree of resistance of the blood vessels. When vascular resistance decreases, blood flow increases, and when resistance increases, it decreases. The contraction or expansion of blood vessels, which determines the degree of resistance, depends on factors such as the type of exercise, the reaction of the nervous system and the course of metabolic processes.

Blood vessels are elastic, elastic tubes through which blood flows. The total length of all human vessels is more than 100 thousand kilometers long, this is enough for 2.5 turns around the earth's equator. During sleep and wakefulness, work and rest - every moment of life, blood moves through the vessels by the force of a rhythmically contracting heart.

Human circulatory system

Circulatory system of the human body divided into lymphatic and circulatory... The main function of the vascular (vascular) system is to deliver blood to all parts of the body. Constant circulation is necessary for gas exchange in the lungs, protection against harmful bacteria and viruses, and metabolism. Thanks to blood circulation, heat exchange processes are carried out, as well as humoral regulation of internal organs. Large and small vessels connect all parts of the body into a single well-coordinated mechanism.

Vessels are present in all tissues of the human body with one exception. They do not exist in the transparent tissue of the iris.

Blood transport vessels

Blood circulation is carried out through the vascular system, which are divided into 2 types: human arteries and veins. The layout of which can be represented in the form of two interconnected circles.

Arteries- these are rather thick vessels with a three-layer structure. From above they are covered with a fibrous membrane, in the middle is a layer of muscle tissue, and from the inside they are lined with epithelial scales. Through them, oxygenated blood is distributed under high pressure throughout the body. The main and thickest artery in the body is called the aorta. As you move away from the heart, the arteries become thinner and pass into arterioles, which, depending on the need, can contract or be in a relaxed state. Arterial blood is bright red.

Veins are similar in structure to arteries, they also have a three-layer structure, but these vessels have thinner walls and a larger internal lumen. Through them, the blood returns back to the heart, for which the venous vessels are equipped with a system of valves that pass only in one direction. The pressure in the veins is always lower than in the arteries, and the fluid has a dark tint - this is their feature.

Capillaries are a ramified network of small vessels, covering all corners of the body. The structure of the capillaries is very thin, they are permeable, due to which metabolism occurs between the blood and cells.

Device and principle of operation

The vital activity of the body is ensured by the constant well-coordinated work of all elements of the human circulatory system. The structure and functions of the heart, blood cells, veins and arteries, as well as the capillaries of a person ensure his health and the normal functioning of the whole body.

Blood belongs to fluid connective tissue. It consists of plasma, in which three types of cells move, as well as nutrients and minerals.

With the help of the heart, blood moves in two interconnected circles of blood circulation:

1. large (bodily), which carries blood enriched with oxygen throughout the body;
2. small (lung), it passes through the lungs, which enrich the blood with oxygen.

The heart is the main engine of the circulatory system, which works all human life. During the year, this organ makes about 36.5 million contractions and passes more than 2 million liters through itself.

The heart is a muscular organ made up of four chambers:

• right atrium and ventricle;
• left atrium and ventricle.

The right side of the heart receives blood with a lower oxygen content, which flows through the veins, is pushed by the right ventricle into the pulmonary artery and is sent to the lungs to saturate them with oxygen. From the capillary system of the lungs, it enters the left atrium and is pushed by the left ventricle into the aorta and further throughout the body.

The arterial blood fills the system of small capillaries, where it gives the cells oxygen, nutrients and is saturated with carbon dioxide, after which it becomes venous and goes to the right atrium, from where it is sent back to the lungs. Thus, the anatomy of the blood vessel network is a closed system.

Atherosclerosis is a dangerous pathology

There are many diseases and pathological changes in the structure of the human circulatory system, for example, narrowing of the lumen of blood vessels... Due to violations of protein-fat metabolism, such a serious disease as atherosclerosis, a narrowing in the form of plaques caused by the deposition of cholesterol on the walls of arterial vessels, often develops.

Progressive atherosclerosis can significantly reduce the inner diameter of the arteries up to complete blockage and can lead to coronary heart disease. In severe cases, surgical intervention is inevitable - the clogged vessels have to be shunted. Over the years, the risk of getting sick increases significantly.

If you follow the definition, then human blood vessels are flexible, elastic tubes through which the force of a rhythmically contracting heart or a pulsating vessel moves blood through the body: to organs and tissues through arteries, arterioles, capillaries, and from them to the heart through venules and veins, the blood stream circulates.

Of course, this is the cardiovascular system. Thanks to blood circulation, oxygen, as well as nutrients are delivered to the organs and tissues of the body, and carbon dioxide and other products and vital functions are excreted.

Blood and nutrients are delivered through vessels, a kind of "hollow tubes", without which nothing would have happened. A kind of "highways". In fact, our vessels are not “hollow tubes”. Of course, they are much more complex and do their job properly. It depends on the health of the vessels - how exactly, with what speed, under what pressure and to which parts of the body our blood will reach. A person depends on the state of blood vessels.

This is how a person would look if only one circulatory system was left of him .. On the right is a person's finger, consisting of an incredible set of vessels.

Human blood vessels, interesting facts

• The largest vein in the human body is the inferior vena cava. Through this vessel, blood returns from the lower body to the heart.
• The human body contains both large and small vessels. The second group includes capillaries. Their diameter does not exceed 8-10 microns. This is so small that the red blood cells have to line up and literally squeeze through one at a time.
• The speed of blood flow through the vessels varies depending on their types and sizes. If the capillaries do not allow blood to exceed the speed of 0.5 mm / sec, then in the inferior vena cava the speed reaches 20 cm / sec.
• Every second, 25 billion cells pass through the circulatory system. It takes 60 seconds for the blood to make a full circle throughout the body. It is noteworthy that in a day blood has to flow through the vessels, overcoming 270-370 km.
• If all the blood vessels were expanded to their full length, they would be able to wrap the planet Earth twice. Their total length is 100,000 km.
• The capacity of all human blood vessels reaches 25-30 liters. As you know, an adult organism on average holds no more than 6 liters of blood, however, accurate data can be found only by studying the individual characteristics of the organism. As a result, blood has to constantly move through the vessels in order to maintain the work of muscles and organs throughout the body.
• There is only one place in the human body where the circulatory system is absent. This is the cornea of ​​the eye. Since its feature is perfect transparency, it cannot contain vessels. However, it gets oxygen directly from the air.
• Since the thickness of the vessels does not exceed 0.5 mm, during operations, surgeons use instruments that are even thinner. For sutures, for example, you have to work with thread that is thinner than a human hair. To cope with it, doctors look through a microscope.
• It is estimated that it takes 1,120,000 mosquitoes to suck all the blood out of an average adult.
• Your heart beats about 42,075,900 times a year, and over an average life span - about 3 billion, give or take a few million ..
• Throughout our lives, the heart pushes about 150 million liters of blood.

Now we are convinced that our circulatory system is unique, and the heart is the strongest muscle in our body.

At a young age, no one worries about any vessels, and so everything is in order! But after twenty years, after the body has grown, metabolism begins to slow down imperceptibly, physical activity decreases over the years, therefore the stomach grows, excess weight appears, high blood pressure and, suddenly, you are only fifty years old! What should I do?

Moreover, plaques can form anywhere. If in the vessels of the brain, then a stroke is possible. The vessel bursts and that's it. If in the aorta, then a heart attack is possible. Smokers usually barely walk by the age of sixty, all

Look, cardiovascular diseases are confidently ranked first in the number of deaths.

That is, your inaction for thirty years can clog the vascular system with all sorts of rubbish. Then a natural question arises, how to get out, then everything from there, so that the vessels are clean? How to get rid of plaque cholesterol, for example? Well, an iron pipe can be cleaned with a brush, but human vessels are far from being a pipe.

Although, there is such a procedure. Angioplasty is called, mechanically drilled out or crushed by a balloon with a balloon and placed a stent. People also like to do a procedure such as plasmapheresis. Yes, it is a very valuable procedure, but only where it is justified, for strictly outlined diseases. It is extremely dangerous to do it to cleanse blood vessels and improve health. Remember the famous Russian athlete, record holder in power sports, as well as TV and radio host, showman, actor and entrepreneur, Vladimir Turchinsky, who died after this procedure.

They came up with laser cleaning of blood vessels, that is, a light bulb is inserted into a vein and it glows inside the vessel and does something there. It seems like there is laser evaporation of plaques. It is clear that this procedure has been put on a commercial basis. The wiring is complete.

Basically, a person believes doctors, and therefore pays money to restore his health. At the same time, the bulk does not want to change anything in their lives. How can you give up dumplings, sausages, bacon or beer with a cigarette. Logically, it turns out that if you have problems with blood vessels, then first you need to remove the damaging factor, for example, quit smoking. If you are overweight, balance your diet, do not overeat at night. Move more. Change your lifestyle. Well, we can't!

No, as usual, we hope for a miracle pill, for a miracle procedure or just for a miracle. Miracles happen, but they are extremely rare. Well, you paid the money, cleaned the vessels, for a while the condition improved, then everything quickly returns to its original state ... You don't want to change your lifestyle, and your body will return its own, even in excess.

Famous in the last century Ukrainian, Soviet thoracic surgeon, medical scientist, cyberneticist, writer, said: "Do not hope that doctors will make you healthy. Doctors treat diseases, but health must be obtained by yourself."

Nature has endowed us with good, strong vessels - arteries, veins, capillaries, each of which performs its own function. Look at how reliably and coolly our circulatory system is arranged, to which we are sometimes very careless. In our body, there are two circles of blood circulation. Big circle and small circle.

Small circle of blood circulation

The small circle of blood circulation supplies blood to the lungs. First, the right atrium contracts and blood flows into the right ventricle. The blood is then pushed into the pulmonary trunk, which branches to the pulmonary capillaries. Here the blood is saturated with oxygen and through the pulmonary veins returns back to the heart - to the left atrium.

A large circle of blood circulation

Passed through the pulmonary circulation. (through the lungs) and, enriched with oxygen, the blood returns to the heart. Oxygenated blood from the left atrium passes into the left ventricle, after which it enters the aorta. The aorta is the largest human artery, from which many smaller vessels depart, then the blood is delivered through the arterioles to the organs and returns through the veins back to the right atrium, where the cycle begins anew.

Arteries

Oxygenated blood is arterial blood. Therefore, it is bright red. Arteries are vessels that carry oxygen-rich blood from the heart. The arteries have to cope with the high pressure that comes out of the heart. Therefore, there is a very thick muscle layer in the wall of the arteries. Therefore, the arteries practically cannot change their lumen. They are not very good at contracting and relaxing. but they take heart beats very well. Arteries resist pressure. which the heart creates.

Artery wall structure Vein wall structure

Arteries are made up of three layers. The inner layer of an artery is a thin layer of integumentary tissue - the epithelium. Then comes a thin layer of connective tissue (not visible in the picture) elastic like rubber. Next comes the thick layer of muscle and the outer shell.

Arterial assignment or arterial function

• Oxygen-enriched blood through the arteries. flows from the heart to the organs.
• Function of the arteries. it is the delivery of blood to organs. ensuring high pressure.
• Oxygenated blood flows in the arteries (except for the pulmonary artery).
• The blood pressure in the arteries is 120 ⁄ 80 mm. rt. Art.
• The speed of movement of blood in the arteries is 0.5 m / sec.
• arterial pulse. this is a rhythmic oscillation of the walls of the arteries during the period of systole of the ventricles of the heart.
• Maximum pressure - during contraction of the heart (systole)
• Minimal during relaxation (diastole)

Veins - structure and function

The layers of the vein are exactly the same as those of the artery. The epithelium is the same everywhere, in all vessels. But the vein, relative to the artery, has a very thin layer of muscle tissue. The muscles in the vein need not so much to resist the pressure of the blood, but to contract and expand. The vein contracts - the pressure increases and vice versa.

Therefore, in terms of their structure, the veins are quite close to the arteries, but, with their own characteristics, for example, in the veins, there is already low pressure and low speed of blood movement. These features give some features to the walls of the veins. Compared to arteries, veins are large in diameter, a thin inner wall and a well-defined outer wall. Due to its structure, the venous system contains about 70% of the total blood volume.

Another feature of veins is that valves are constantly running in the veins. about the same as at the exit from the heart. This is necessary so that the blood does not flow in the opposite direction, but is pushed forward.

The valves open with the blood flow. When the vein fills with blood, the valve closes, making it impossible for blood to flow back. The most developed valve apparatus is in the veins, in the lower part of the body.

It's simple, the blood returns easily from the head to the heart, since gravity acts on it, but it is much more difficult for it to rise from the legs. it is necessary to overcome this force of gravity. The valve system helps push the blood back to the heart.

Valves. that's good, but not enough to push the blood back to the heart. There is one more power. The fact is that veins, unlike arteries, run along muscle fibers. and when the muscle contracts, it compresses the vein. In theory, the blood should go in both directions, but there are valves that prevent blood from flowing in the opposite direction, only forward to the heart. Thus, the muscle pushes blood to the next valve. This is important because the lower outflow of blood is mainly due to the muscles. And if your muscles have long been weak from idleness? Crept up unnoticed What will happen? It is clear that nothing good.

The movement of blood through the veins occurs against the force of gravity, in this regard, the venous blood experiences the force of hydrostatic pressure. Sometimes, when the valves are malfunctioning, the force of gravity is so great that it interferes with normal blood flow. In this case, the blood stagnates in the vessels and deforms them. Then the veins are called varicose veins.

Varicose veins have a swollen appearance, which is justified by the name of the disease (from Lat. Varix, genus varicis - "swelling"). The treatments for varicose veins today are very extensive, from folk advice to sleep in such a position that the feet are above the level of the heart to surgery and vein removal.

Another disease is vein thrombosis. With thrombosis, blood clots (thrombi) form in the veins. This is a very dangerous disease, because blood clots, breaking off, can move along the circulatory system to the vessels of the lung. If the clot is large enough, it can be fatal if it enters the lungs.

• Vienna. vessels carrying blood to the heart.
• The walls of the veins are thin, easily stretchable, unable to contract on their own.
• A feature of the structure of the veins is the presence of pocket valves.
• Veins are distinguished - large (hollow veins), medium veins and small venulls.
• Blood saturated with carbon dioxide moves through the veins (except for the pulmonary vein)
• The blood pressure in the veins is 15 - 10 mm. rt. Art.
• The speed of blood flow in the veins is 0.06 - 0.2 m. Sec.
• Veins are superficial, unlike arteries.

Capillaries

The capillary is the thinnest vessel in the human body. Capillaries are tiny blood vessels 50 times thinner than a human hair. The average capillary diameter is 5-10 microns. By connecting arteries and veins, it participates in the exchange of substances between blood and tissues.

The walls of the capillaries consist of a single layer of endothelial cells. The thickness of this layer is so small that it allows the exchange of substances between tissue fluid and blood plasma through the walls of the capillaries. Waste products from the body (such as carbon dioxide and urea) can also pass through capillary walls to transport them to the site of elimination from the body.

Endothelium

It is through the walls of the capillaries that nutrients enter our muscles and tissues, saturating them, moreover, with oxygen. It should be noted that not all substances pass through the walls of the endothelium, but only those that are necessary for the body. For example, oxygen passes, but other impurities do not. This is called endothelial permeability, and it is the same with food. ... Without this function, we would have been poisoned long ago.

The vascular wall of the endothelium is the thinnest organ that performs a number of important functions. The endothelium releases a substance as needed to force the platelets to stick together and repair, for example, a cut. But so that platelets do not stick together just like that, the endothelium secretes a substance that prevents our platelets from sticking together and forming into blood clots. Whole institutions are working on the study of the endothelium to fully understand this amazing organ.

Another function is angiogenesis - the endothelium forces small vessels to grow, bypassing the clogged ones. For example, bypassing the cholesterol plaque.

Fight against vascular inflammation. This is also a function of the endothelium. Atherosclerosis. this is a kind of vascular inflammation. Today, they even begin to treat atherosclerosis with antibiotics.

Regulation of vascular tone. This is also done by the endothelium. Nicotine has a very detrimental effect on the endothelium. Immediately there is a vasospasm, or rather endothelial paralysis, which causes nicotine, and the combustion products contained in nicotine. There are about 700 of these products.

The endothelium must be strong and elastic. like all our vessels. arises in the event that a particular person begins to move a little, eat improperly and, accordingly, secrete a little of his own hormones into the blood.

It is possible to clean the vessels only if regularly release hormones into the blood, then they will heal the walls of blood vessels, there will be no holes and cholesterol plaques will have nowhere to form. Eat right. control sugar and cholesterol levels. Folk remedies can be used as a supplement, the basis is still physical activity. For example, a health-improving system - just was invented for the health of anyone.