Small arterial vessels. Functions of blood vessels - arteries, capillaries, veins

Anatomy of the heart.

1. general characteristics of cardio-vascular system and its meaning.

2. Types blood vessels, features of their structure and functions.

3. Structure of the heart.

4. Topography of the heart.

1. General characteristics of the cardiovascular system and its significance.

The cardiovascular system includes two systems: circulatory (circulatory system) and lymphatic (lymph circulation system). The circulatory system combines the heart and blood vessels. Lymphatic system includes branched in organs and tissues lymphatic capillaries, lymphatic vessels, lymphatic trunks and lymphatic ducts through which lymph flows towards large venous vessels. The doctrine of SSS is called angiocardiology.

The circulatory system is one of the main systems of the body. It ensures the delivery of nutrients, regulatory, protective substances, oxygen to tissues, removal of metabolic products, and heat exchange. It is a closed vascular network that penetrates all organs and tissues, and has a centrally located pumping device - the heart.

Types of blood vessels, features of their structure and function.

Anatomically, blood vessels are divided into arteries, arterioles, precapillaries, capillaries, postcapillaries, venules And veins.

Arteries – these are blood vessels that carry blood from the heart, regardless of what type of blood is in them: arterial or venous. They are cylindrical tubes, the walls of which consist of 3 shells: outer, middle and inner. Outdoor(adventitial) membrane is represented by connective tissue, average– smooth muscle, internal– endothelial (intima). Beyond the endothelial lining inner shell Most arteries also have an internal elastic membrane. The outer elastic membrane is located between the outer and middle membranes. Elastic membranes give the artery walls additional strength and elasticity. The thinnest arterial vessels are called arterioles. They go to precapillaries, and the latter - in capillaries, the walls of which are highly permeable, allowing the exchange of substances between blood and tissues.

Capillaries – these are microscopic vessels that are found in tissues and connect arterioles to venules through precapillaries and postcapillaries. Postcapillaries are formed from the fusion of two or more capillaries. As postcapillaries merge, they form venules- the smallest venous vessels. They flow into the veins.

Vienna These are blood vessels that carry blood to the heart. The walls of veins are much thinner and weaker than arterial ones, but consist of the same three membranes. However, the elastic and muscular elements in the veins are less developed, so the vein walls are more pliable and can collapse. Unlike arteries, many veins have valves. The valves are semilunar folds of the inner membrane that prevent blood from flowing back into them. There are especially many valves in the veins of the lower extremities, in which the movement of blood occurs against gravity and creates the possibility of stagnation and reverse blood flow. There are many valves in the veins upper limbs, less - in the veins of the torso and neck. Only both vena cavae and the veins of the head do not have valves. renal veins, portal and pulmonary veins.

The branches of the arteries are connected to each other, forming arterial anastomosis - anastomoses. The same anastomoses connect veins. In violation of the inflow or outflow of blood through the main vessels, anastomoses contribute to the movement of blood in various directions. Vessels that provide blood flow bypassing the main path are called collateral (roundabout).

The blood vessels of the body are united into big And pulmonary circulation. In addition, there is an additional coronary circulation.

Systemic circulation (bodily) starts from the left ventricle of the heart, from which blood enters the aorta. From the aorta through the system of arteries, blood is carried away into the capillaries of the organs and tissues of the whole body. Through the walls of the body's capillaries, the exchange of substances between blood and tissues occurs. Arterial blood gives oxygen to the tissues and, saturated with carbon dioxide, turns into venous blood. The systemic circulation ends with two vena cavae flowing into right atrium.

Pulmonary circulation (pulmonary) begins with the pulmonary trunk, which arises from the right ventricle. It delivers blood to the pulmonary capillary system. In the capillaries of the lungs deoxygenated blood, enriched with oxygen and freed from carbon dioxide, turns into arterial. Arterial blood flows from the lungs through 4 pulmonary veins into the left atrium. The pulmonary circulation ends here.

Thus, blood moves through a closed circulatory system. The speed of blood circulation in a large circle is 22 seconds, in a small one - 5 seconds.

Coronary circulation (cardiac) includes the vessels of the heart itself to supply blood to the heart muscle. It begins with the left and right coronary arteries, which arise from the initial part of the aorta - the aortic bulb. Flowing through the capillaries, the blood delivers oxygen and nutrients to the heart muscle, receives breakdown products, and turns into venous blood. Almost all the veins of the heart flow into a common venous vessel - the coronary sinus, which opens into the right atrium.

The structure of the heart.

Heart(cor; Greek cardia) is a hollow muscular organ shaped like a cone, the apex of which faces down, left and forward, and the base faces up, right and back. The heart is located in the chest cavity between the lungs, behind the sternum, in the anterior mediastinum. Approximately 2/3 of the heart is in the left half of the chest and 1/3 is in the right.

The heart has 3 surfaces. Front surface the heart is adjacent to the sternum and costal cartilages, rear– to the esophagus and thoracic aorta, lower- to the diaphragm.

The heart also has edges (right and left) and grooves: coronary and 2 interventricular (anterior and posterior). The coronary groove separates the atria from the ventricles, and the interventricular grooves separate the ventricles. Vessels and nerves are located in the grooves.

The size of the heart varies individually. The size of the heart is usually compared to the size of the fist. this person(length 10-15 cm, transverse size – 9-11 cm, anteroposterior size – 6-8 cm). The average weight of an adult human heart is 250-350 g.

The wall of the heart consists of 3 layers:

- inner layer (endocardium) lines the cavities of the heart from the inside, its outgrowths form the heart valves. It consists of a layer of flattened, thin, smooth endothelial cells. The endocardium forms the atrioventricular valves, valves of the aorta, pulmonary trunk, as well as the valves of the inferior vena cava and coronary sinus;

- middle layer (myocardium) is the contractile apparatus of the heart. The myocardium is formed by striated cardiac muscle tissue and is the thickest and functionally powerful part of the heart wall. The thickness of the myocardium is not the same: the greatest is in the left ventricle, the smallest in the atria.

The ventricular myocardium consists of three muscle layers - outer, middle and inner; the atrial myocardium is made up of two layers of muscles - superficial and deep. The muscle fibers of the atria and ventricles originate from the fibrous rings that separate the atria from the ventricles. fibrous rings are located around the right and left atrioventricular openings and form a kind of heart skeleton, which includes thin rings of connective tissue around the openings of the aorta, pulmonary trunk and the adjacent right and left fibrous triangles.

- outer layer (epicardium) covers outer surface the heart and the areas closest to the heart of the aorta, pulmonary trunk and vena cava. It is formed by a layer of cells of the epithelial type and represents the inner layer of the pericardial serous membrane - pericardium. The pericardium insulates the heart from surrounding organs, protects the heart from excessive stretching, and the fluid between its plates reduces friction during cardiac contractions.

The human heart is divided by a longitudinal septum into two halves that do not communicate with each other (right and left). At the top of each half is located atrium(atrium) right and left, in the lower part – ventricle(ventriculus) right and left. Thus, the human heart has 4 chambers: 2 atria and 2 ventricles.

The right atrium receives blood from all parts of the body through the superior and inferior vena cava. 4 pulmonary veins flow into the left atrium, carrying arterial blood from the lungs. The pulmonary trunk emerges from the right ventricle, through which venous blood enters the lungs. The aorta emerges from the left ventricle, carrying arterial blood to the vessels of the systemic circulation.

Each atrium communicates with the corresponding ventricle through atrioventricular orifice, stocked flap valve. The valve between the left atrium and ventricle is bicuspid (mitral), between the right atrium and ventricle – tricuspid. The valves open towards the ventricles and allow blood to flow only in that direction.

The pulmonary trunk and aorta at their origin have semilunar valves, consisting of three semilunar valves and opening in the direction of blood flow in these vessels. Special protrusions of the atria form right And left atrial appendage. On inner surface right and left ventricles are present papillary muscles- these are outgrowths of the myocardium.

Topography of the heart.

Upper limit corresponds to the upper edge of the cartilages of the third pair of ribs.

Left border runs along an arcuate line from the cartilage of the third rib to the projection of the apex of the heart.

Top the heart is determined in the left 5th intercostal space 1–2 cm medial to the left midclavicular line.

Right border passes 2 cm to the right of the right edge of the sternum

Bottom line– from the upper edge of the cartilage of the fifth right rib to the projection of the apex of the heart.

There are age-related and constitutional features of the location (in newborn children, the heart lies entirely horizontally in the left half of the chest).

Main hemodynamic parameters is volumetric blood flow velocity, pressure in various departments vascular bed.

AFO of the cardiovascular system.

Anatomy and physiology of the heart.

The structure of the circulatory system. Structural features at different age periods. The essence of the blood circulation process. Structures that carry out the blood circulation process. Basic indicators of blood circulation (number of heartbeats, arterial pressure, electrocardiogram indicators). Factors affecting blood circulation (physical and nutritional stress, stress, lifestyle, bad habits etc.). Circles of blood circulation. Vessels, types. The structure of the walls of blood vessels. Heart - location external structure, anatomical axis, projection onto the surface of the chest at different age periods. Heart chambers, orifices and heart valves. Principles of operation of heart valves. The structure of the heart wall - endocardium, myocardium, epicardium, location, physiological properties. Conduction system of the heart. Physiological properties. The structure of the pericardium. Vessels and nerves of the heart. Phases and duration cardiac cycle. Physiological properties of the heart muscle.

Circulatory system

The functions of the blood are performed due to the continuous operation of the circulatory system. Blood circulation - This is the movement of blood through the vessels, ensuring the exchange of substances between all tissues of the body and external environment. The circulatory system includes the heart and blood vessels. Blood circulation in the human body through a closed cardiovascular system is ensured by rhythmic contractions hearts- its central organ. The vessels through which blood from the heart is carried to tissues and organs are called arteries, and those through which blood is delivered to the heart - veins. In tissues and organs, thin arteries (arterioles) and veins (venules) are interconnected by a dense network blood capillaries.

Structural features at different age periods.

The heart of a newborn is rounded. Its transverse diameter is 2.7-3.9 cm, the average length of the heart is 3.0-3.5 cm. Anterior-posterior size- 1.7-2.6 cm. The atria are large compared to the ventricles, and the right one is much larger than the left one. The heart grows especially quickly during a child's year of life, and its length increases more than its width. Individual parts of the heart change differently at different ages: during the 1st year of life, the atria grow more than the ventricles. At the age of 2 to 6 years, the growth of the atria and ventricles occurs equally rapidly. After 10 years, the ventricles increase faster than the atria. The total mass of the heart in a newborn is 24 g, at the end of the 1st year of life it increases approximately 2 times, by 4-5 years - by 3 times, at 9-10 years - by 5 times and by 15-16 years - by 10 once. Up to 5-6 years of age, the heart weight is greater in boys than in girls; at 9-13 years of age, on the contrary, it is greater in girls, and at 15 years of age, the heart weight is again greater in boys than in girls. In newborns and children infancy the heart is located high and lies transversely. The transition of the heart from a transverse to an oblique position begins at the end of the 1st year of a child’s life.

Factors affecting blood circulation (physical and nutritional stress, stress, lifestyle, bad habits, etc.).

Circles of blood circulation.

Large and small circles of blood circulation. IN In the human body, blood moves through two circles of blood circulation - large (trunk) and small (pulmonary).

Systemic circulation begins in the left ventricle, from which arterial blood is ejected into the largest artery in diameter - aorta. The aorta arches to the left and then runs along the spine, branching into smaller arteries that carry blood to the organs. In the organs, the arteries branch into smaller vessels - arterioles, that go online capillaries, penetrating tissues and delivering oxygen and nutrients to them. Venous blood through the veins is collected in two large vessels - top And inferior vena cava, which infuse it into the right atrium.

Small circle of blood circulation begins in the right ventricle, from where the arterial pulmonary trunk emerges, which divides into colorpulmonary arteries, carrying blood to the lungs. In the lungs, large arteries branch into smaller arterioles, which pass into a network of capillaries that densely entwine the walls of the alveoli, where the exchange of gases occurs. Oxygenated arterial blood flows through the pulmonary veins into the left atrium. Thus, venous blood flows in the arteries of the pulmonary circulation, and arterial blood flows in the veins.

Not all the blood volume in the body circulates evenly. A significant portion of the blood is in blood depots- liver, spleen, lungs, subcutaneous vascular plexuses. The importance of blood depots lies in the ability to quickly provide oxygen to tissues and organs in emergency situations.

Vessels, types. The structure of the walls of blood vessels.

The wall of the vessel consists of three layers:

1. The inner layer is very thin, it is formed by one row of endothelial cells, which give the smoothness of the inner surface of the vessels.

2. The middle layer is the thickest, it contains a lot of muscle, elastic and collagen fibers. This layer ensures the strength of the blood vessels.

3. Outer layer connective tissue, it separates the vessels from the surrounding tissues.

Arteries The blood vessels that go from the heart to the organs and carry blood to them are called arteries. Blood flows from the heart through the arteries under high pressure, so the arteries have thick elastic walls.

According to the structure of the walls, arteries are divided into two groups:

Elastic type arteries - the arteries closest to the heart (the aorta and its large branches) perform mainly the function of conducting blood.

Arteries muscular type- medium and small arteries, in which the inertia of the heart impulse weakens and its own contraction of the vascular wall is required to further move the blood

In relation to the organ, there are arteries that go outside the organ, before entering it - extraorganic arteries - and their continuations, branching inside it - intraorganic or intraorganic arteries. Lateral branches of the same trunk or branches of different trunks can be connected to each other. Such a connection of vessels before they break up into capillaries is called anastomosis or anastomosis (they are the majority). Arteries that do not have anastomoses with neighboring trunks before they pass into capillaries are called terminal arteries(for example, in the spleen). The terminal, or terminal, arteries are more easily clogged with a blood plug (thrombus) and predispose to the formation of a heart attack (local necrosis of the organ).

The last branches of the arteries become thin and small and are therefore called arterioles. They directly pass into the capillaries, and due to the presence of contractile elements in them, they perform a regulatory function.

An arteriole differs from an artery in that its wall has only one layer of smooth muscle, thanks to which it carries out a regulatory function. The arteriole continues directly into the precapillary, in which the muscle cells are scattered and do not form a continuous layer. The precapillary differs from the arteriole in that it is not accompanied by a venule, as is observed with the arteriole. Numerous capillaries extend from the precapillary.

Capillaries- the smallest blood vessels located in all tissues between arteries and veins. The main function of capillaries is to ensure the exchange of gases and nutrients between blood and tissues. In this regard, the capillary wall is formed by only one layer of flat endothelial cells, permeable to substances and gases dissolved in the liquid. Through it, oxygen and nutrients easily penetrate from the blood to the tissues, and carbon dioxide and waste products in the opposite direction.

In every this moment Only part of the capillaries functions (open capillaries), while the other remains in reserve (closed capillaries).

Vienna- blood vessels that carry venous blood from organs and tissues to the heart. The exception is the pulmonary veins, which carry arterial blood from the lungs to the left atrium. The collection of veins forms the venous system, which is part of the cardiovascular system. The network of capillaries in organs turns into small postcapillaries, or venules. At a considerable distance, they still retain a structure similar to the structure of capillaries, but have a wider lumen. The venules merge into larger veins, which are connected by anastomoses, and form venous plexuses in or near organs. Veins are collected from the plexuses, carrying blood out of the organ. There are superficial and deep veins. Superficial veins located in the subcutaneous fatty tissue, starting from the superficial venous networks; their number, size and position vary greatly. Deep veins , starting on the periphery from small deep veins, accompany the arteries; Often one artery is accompanied by two veins (“companion veins”). As a result of the fusion of the superficial and deep veins, two large venous trunks are formed - the superior and inferior vena cava, which flow into the right atrium, where the common drainage of the cardiac veins - the coronary sinus - also flows. Portal vein carries blood from unpaired organs abdominal cavity.
Low pressure and low blood flow speed cause poor development of elastic fibers and membranes in the venous wall. The need to overcome the gravity of blood in the veins lower limb led to the development of muscle elements in their wall, in contrast to the veins of the upper extremities and the upper half of the body. On the inner lining of the vein there are valves that open along the blood flow and promote the movement of blood in the veins towards the heart. Feature venous vessels is the presence of valves in them, which are necessary to ensure unidirectional blood flow. The walls of the veins are arranged according to the same plan as the walls of the arteries, however, the blood pressure in the veins is very low, so the walls of the veins are thin, they have less elastic and muscle tissue, causing empty veins to collapse.

Heart- a hollow fibromuscular organ that, functioning as a pump, ensures the movement of blood in the circulatory system. The heart is located in the anterior mediastinum in the pericardium between the layers of the mediastinal pleura. It has the shape of an irregular cone with the base at the top and the apex facing downwards, to the left and anteriorly. The sizes of S. are individually different. The length of the S. of an adult varies from 10 to 15 cm (usually 12-13 cm), the width at the base is 8-11 cm (usually 9-10 cm) and the anteroposterior size is 6-8.5 cm (usually 6.5-7 cm ). The average weight of S. in men is 332 g (from 274 to 385 g), in women - 253 g (from 203 to 302 g).
Towards midline the body of the heart is located asymmetrically - about 2/3 to the left of it and about 1/3 to the right. Depending on the direction of the projection of the longitudinal axis (from the middle of its base to the apex) on the anterior chest wall distinguish between transverse, oblique and vertical position of the heart. Vertical position more common in people with narrow and long hair chest, transverse - in persons with a wide and short chest.

The heart consists of four chambers: two (right and left) atria and two (right and left) ventricles. The atria are at the base of the heart. The aorta and pulmonary trunk exit from the heart in front, the superior vena cava flows into it in the right part, the inferior vena cava in the posteroinferior part, the left pulmonary veins behind and to the left, and the right pulmonary veins somewhat to the right.

The function of the heart is to rhythmically pump blood into the arteries, which comes to it through the veins. The heart beats about 70-75 times per minute when the body is at rest (1 time per 0.8 s). More than half of this time it rests - relaxes. The continuous activity of the heart consists of cycles, each of which consists of contraction (systole) and relaxation (diastole).

There are three phases of cardiac activity:

· contraction of the atria - atrial systole - takes 0.1 s

· contraction of the ventricles - ventricular systole - takes 0.3 s

general pause - diastole (simultaneous relaxation of the atria and ventricles) - takes 0.4 s

Thus, during the entire cycle, the atria work for 0.1 s and rest for 0.7 s, the ventricles work for 0.3 s and rest for 0.5 s. This explains the ability of the heart muscle to work without getting tired throughout life. High efficiency cardiac muscle is due to increased blood supply to the heart. Approximately 10% of the blood ejected by the left ventricle into the aorta enters the arteries that branch from it, which supply the heart.

Blood circulates throughout the body using a complex system of blood vessels. This transport system carries blood to every cell in the body so it can “exchange” oxygen and nutrients for waste products and carbon dioxide.

Some numbers

There are more than 95 thousand kilometers of blood vessels in the body of a healthy adult. More than seven thousand liters of blood are pumped through them every day.

Blood vessel size varies from 25 mm(aortic diameter) up to eight microns(capillary diameter).

What types of vessels are there?

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

The inside of 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 dilate in response to chemical or nerve stimuli.

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

Blood moves through the arteries with great force, which is why their walls are thick and elastic. They consist of large quantity collagen, which allows them to withstand blood pressure. Availability muscle fibers helps turn the intermittent blood supply from the heart into a continuous flow to 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 move from cells into the bloodstream.

Capillaries, through which oxygen-poor blood flows, gather into thicker vessels - veins. Due to lack of oxygen venous blood is darker than the arterial one, and the veins themselves appear bluish. Through them, blood flows to the heart and from there to the lungs to be enriched with oxygen.

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 vessels in the human body?

The two largest veins in the human body are inferior vena cava and 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.

Aorta- the largest artery of the body. It leaves 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 readings are usually recorded in two numbers. So, normal pressure for an adult it is considered indicator 120/80.

First number - systolic pressure is an indicator of pressure during heart rate. Second - diastolic pressure– pressure during relaxation of the heart.

Pressure is measured in the arteries and 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 high blood pressure. If it’s lower, it means it’s reduced.

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

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

Functional classification of blood vessels.

Main vessels.

Resistive vessels.

Exchange vessels.

Capacitive vessels.

Shunt vessels.

The main vessels are the aorta, large arteries. The wall of these vessels contains many elastic elements and many smooth muscle fibers. Meaning: Turn the pulsating ejection of blood from the heart into a continuous blood flow.

Resistive vessels - pre- and post-capillary. Precapillary vessels - small arteries and arterioles, capillary sphincters - vessels have several layers of smooth muscle cells. Postcapillary vessels - small veins, venules - also contain smooth muscles. Meaning: have the greatest resistance to blood flow. Precapillary vessels regulate blood flow in the microvasculature and maintain a certain value blood pressure V large arteries. Postcapillary vessels - maintain a certain level of blood flow and pressure in the capillaries.

Exchange vessels - 1 layer of endothelial cells in the wall - high permeability. They carry out transcapillary exchange.

Capacitive vessels are all venous. They contain 2/3 of all blood. They have the least resistance to blood flow, their wall is easily stretched. Meaning: due to expansion, they deposit blood.

Shunt vessels - connect arteries with veins bypassing capillaries. Meaning: provide unloading of the capillary bed.

The number of anastomoses is not a constant value. They occur when there is poor circulation or lack of blood supply.

Sensitivity - there are many receptors in all layers of the vascular wall. When changing pressure, volume, chemical composition blood - receptors are excited. Nerve impulses go to the central nervous system and reflexively affect the heart, blood vessels, internal organs. Due to the presence of receptors vascular system connected to other organs and tissues of the body.

Mobility - the ability of blood vessels to change the lumen in accordance with the needs of the body. The change in the lumen occurs due to the smooth muscles of the vascular wall.

Vascular smooth muscles have the ability to spontaneously generate nerve impulses. Even at rest there is a moderate tension of the vascular wall - basal tone. Under the influence of factors, smooth muscles either contract or relax, changing the blood supply.

Meaning:

regulation of a certain level of blood flow,

ensuring constant pressure, blood redistribution;

the capacity of the vessels is adjusted to the volume of blood

Circulation time - the time during which the cow passes both circles of blood circulation. With a heart rate of 70 per minute, the time is 20 - 23 s, of which 1/5 of the time is for a small circle; 4/5 of the time - for a large circle. Time is determined using control substances and isotopes. - they are administered intravenously into v.venaris right hand and is determined after how many seconds, this substance will appear in the v.venaris of the left hand. Time is affected by volumetric and linear speeds.

Volumetric velocity - the volume of blood that flows through the vessels per unit time. Vlin. - the speed of movement of any blood particle in the vessels. The highest linear velocity in the aorta, the smallest - in the capillaries (respectively 0.5 m/s and 0.5 mm/s). Linear velocity depends on the total cross-sectional area of ​​the vessels. Due to the low linear velocity in the capillaries, the conditions for transcapillary exchange. This speed in the center of the vessel is greater than at the periphery.

Blood movement is subject to physical and physiological laws. Physical: - laws of hydrodynamics.

1st law: the amount of blood flowing through the vessels and the speed of its movement depends on the pressure difference at the beginning and end of the vessel. The greater this difference, the better the blood supply.

2nd law: blood flow is prevented by peripheral resistance.

Physiological patterns of blood movement through vessels:

heart function;

closedness of the cardiovascular system;

suction effect of the chest;

elasticity of blood vessels.

During the systole phase, blood enters the vessels. The wall of blood vessels stretches. There is no ejection of blood in diastole, the elastic vascular wall returns to its original state, and energy accumulates in the wall. With a decrease in the elasticity of blood vessels, a pulsating blood flow appears (normally in the vessels of the pulmonary circulation). In pathological sclerotic vessels - Musset's symptom - head movements in accordance with pulsation.

Classification of blood vessels

Among the vessels circulatory system differentiate arteries, arterioles, hemocapillaries, venules, veins And arteriole-venous anastomoses; The vessels of the microcirculatory system mediate the relationship between arteries and veins. Vessels different types differ not only in their thickness, but also in tissue composition and functional features.

• Arteries are vessels through which blood moves away from the heart. Arteries have thick walls that contain muscle fibers as well as collagen and elastic fibers. They are very elastic and can contract or expand, depending on the amount of blood pumped by the heart.
• Arterioles are small arteries that immediately precede capillaries in the blood flow. In their vascular wall smooth muscle fibers predominate, thanks to which arterioles can change the size of their lumen and, thus, resistance.
• Capillaries are the smallest blood vessels, so thin that substances can freely penetrate through their wall. Recoil occurs through the capillary wall nutrients and oxygen from the blood to the cells and the transfer of carbon dioxide and other waste products from the cells to the blood.
• Venules are small blood vessels that provide big circle outflow of oxygen-depleted and rich in products vital activity of blood from capillaries to veins.
• Veins are vessels through which blood moves to the heart. The walls of the veins are less thick than the walls of the arteries and contain correspondingly fewer muscle fibers and elastic elements.

The structure of blood vessels (using the example of the aorta)

Structure of the aorta: 1. elastic membrane ( outer shell or Tunica externa, 2. muscular layer (Tunica media), 3. inner layer (Tunica intima)

This example describes the structure of an arterial vessel. The structure of other types of vessels may differ from those described below. See related articles for more details.