Advertising on the portal

Vascular wall. Types of blood vessels Types of blood vessels

The human body is completely riddled with blood vessels. These peculiar highways ensure continuous delivery of blood from the heart to the most distant parts of the body. Thanks to the unique structure of the circulatory system, each organ receives a sufficient amount of oxygen and nutrients. Total length blood vessels– about 100 thousand km. This is really so, although it is hard to believe. The movement of blood through the vessels is ensured by the heart, which acts as a powerful pump.

To understand the answer to the question: how the human circulatory system works, you need, first of all, to carefully study the structure of blood vessels. If we talk in simple words, these are strong elastic tubes through which blood moves.

Blood vessels branch throughout the body, but ultimately 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 with a loose structure. Thanks to this fabric, the vessel can be securely fixed to different areas bodies.

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

Arteries

Main vessels that transport blood directly from the heart to internal organs, are called the aorta. Within these elements, very high blood pressure, so they should be as dense and elastic as possible. Doctors 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 of dense elastic fibers that can withstand continuous heartbeats and sudden 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 in size compared to the elastic type of blood vessels. Such elements are removed from the heart muscle and are located near peripheral internal organs and systems. The walls of muscle arteries can contract strongly, allowing blood to flow even at low pressure.

The main arteries supply all internal organs with a sufficient amount of blood. Some circulatory elements are located around the organs, while others go directly into the liver, kidneys, lungs, etc. The arterial system is very branched, it can smoothly turn into capillaries or veins. Small arteries are called arterioles. Such elements can directly participate in the self-regulation system, since they consist of only one layer 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, so they consist of only one layer of epithelium. Thanks to this feature, useful elements can easily penetrate through their walls.

There are two types of capillaries:

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

1 mm of muscle tissue can accommodate from 150 to 300 capillaries. When muscles are under stress, they need more oxygen and nutrients. In this case, reserve closed blood vessels are additionally used.

Vienna

The third type of blood vessel is veins. Their structure is the same as 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, and their middle layer is less thin than in the arteries.

The venous system is also very branched. In the area of ​​the upper and lower limbs small veins are located, which gradually increase in size and volume towards the heart. The outflow of blood is ensured by back pressure in these elements, which is formed during contraction of muscle fibers and exhalation.

Diseases

In medicine, there are many pathologies of blood vessels. Such diseases can be congenital or acquired throughout life. Each type of vessel may have one or another pathology.

Vitamin therapy is best prevention diseases of the circulatory system. Saturating the blood with useful microelements allows you to make the walls of arteries, veins and capillaries stronger and more elastic. People at risk of developing vascular pathologies must additionally include the following vitamins in their diet:

  • C and R. These microelements strengthen the walls of blood vessels and prevent capillary fragility. Contained in citrus fruits, rose hips, and fresh herbs. You can also additionally use Troxevasin medicinal gel.
  • Vitamin B. To enrich your body with these microelements, include legumes, liver, grain porridge, and meat in your menu.
  • B5. Chicken meat, eggs, and broccoli are rich in this vitamin.

Eat for breakfast oatmeal with fresh raspberries, and your blood vessels will always be healthy. Dress your salads olive oil, and for drinks, give preference to green tea, rosehip decoction 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 your blood vessels, undergo regular medical examinations, and take all necessary tests.

Blood circulation (video)

Based on their function and structure, blood vessels are divided into conducting and feeding. Conducting - arteries - arteria - conduct blood from the heart, veins - vena (phlebos) - to the heart and feeding, trophic, - capillaries - microscopic vessels, located in the tissues of the organ. The main function of the vascular bed is twofold: conducting blood (through arteries and veins), as well as (Ensuring metabolism between blood and tissues (links microvasculature) and blood redistribution. The structure of the vascular wall is extremely diverse and is determined by their functional purpose. Arteries (aeg - air, tereo - contain) are vessels through which blood is carried out of the heart. On a corpse they are empty, which is why Hippocrates considered them to be air-carrying tubes. These vessels not only transport blood, but also help the heart move it to the organs.

Arteries, depending on their caliber, are divided into large, medium and small. The walls of the arteries (Fig. 293) consist of three membranes. The inner lining - tunica intima - is formed by endothelium, basement membrane and subendothelial layer. This membrane is common to all blood vessels and the heart. It is separated from the middle membrane by an internal elastic membrane. The middle membrane, tunica media, is formed by muscle cells oriented in different directions, as well as elastic and collagen fibers. It is separated from the outer membrane by an outer elastic membrane. Outer shell- adventitia - tunica adventitia is formed by loose connective tissue. It fixes the artery in a certain position and limits its stretching. Contains vessels that supply the arterial wall - vascular vessels - vasa vasorum and nerves - nervi vasorum.

Rice. 293. Structure of the vessel wall (according to N. Gray, 1967)

Sensitive innervation of blood vessels - angioinnervation is carried out by sensitive nerve fibers, which are processes of cells of the spinal or cranial nodes. These are fibers covered with a myelin sheath. Motor - effector innervation is provided from the centers of the sympathetic nervous system, located in the lateral horns of the thoracolumbar spinal cord. Path sympathetic innervation consists of two neurons lying in spinal cord and sympathetic ganglia. Their efferent fibers end on the smooth muscles of blood vessels, through which the movement of the vascular wall is regulated - vascular tone.

Some vessels have special reflexogenic zones, for example, at the beginning of the internal carotid artery, in the aortic arch, etc. From them, impulses are transmitted reflexively to the heart and peripheral vessels through the central nervous system. The opinion that sensory innervation concentrated only in reylexogenic zones of occurrence of reflexes to blood circulation, is currently recognized as erroneous, since the sensory nervous apparatus is distributed throughout the vascular system in the form of various angioreceptors, lamellar bodies, bushes or tree-like branches of nerve fibers.

The structure of arteries changes depending on their topography. The arteries closest to the heart (aorta and its large branches) primarily perform the function of conducting blood. In them, the foreground is the resistance to stretching by the mass of blood, which is ejected under high pressure by a cardiac impulse, therefore, in the wall of these vessels, structures of a mechanical nature, i.e., elastic fibers and membranes, are relatively more developed. The elastic elements of the arterial wall form a single elastic frame that works like a spring and determines the elasticity of the arteries. Such arteries are called elastic arteries. They can withstand high pressure (up to 200 mm Hg). In middle and small arteries, in which the inertia of the cardiac impulse weakens and contraction of the vascular wall is required for further movement of blood, contractile elements predominate. It is ensured by the relatively powerful development of smooth muscle tissue in the vascular wall. Such arteries are called muscular arteries. Arteries of the transitional type are characterized by the fact that as they move away from the heart, the number of elastic elements in them decreases and the number of muscle elements increases. On this basis, elastic-muscular and muscular-elastic types of arteries are distinguished.

The diameter of the arteries and the thickness of the walls depend on the functions of the organ. Thus, in the most mobile mammals, the thickness of the wall of the brachial artery is equal to V3-V4 of the diameter of its lumen, in birds even the whole diameter, while in less mobile ones it is only the diameter of the lumen of the vessel (P. M. Mazhuga, 1964). Practical knowledge of arterial vessels as a kind of peripheral “heart” is fundamental; disruption of its functions entails disruption of the activity of the entire vascular system. If the structure of the wall is disturbed (vascular sclerosis), the possibility of their full contraction and stretching is excluded, which creates unbearable conditions for the functioning of the heart and leads to heart disease. Thus, stenosis of the arteries is accompanied by the movement of myocytes from the middle (muscular) membrane to the inner (intima), which leads to thickening of the intima and narrowing of the lumen of the vessel (M. D. Richter, 1990).

The walls of blood vessels provide: 1) blood flow speed; 2) height blood pressure; 3) capacity of the vascular bed. All this is due to the movement of the vascular wall. If it is pathologically changed, then, as a rule, metabolic processes are disrupted. The vessel wall is very sensitive to gravitational overloads, changes atmospheric pressure. She is the body's barometer.

Having entered the organ, the arteries branch repeatedly into arterioles; precapillaries, turning into capillaries and then into postcapillaries and venules (Fig. 294). Venules, which are the last link of the microvorculatory bed, merge with each other and enlarge to form veins that carry blood out of the organ.

Rice. 294. Diagram of the structure and blood supply of the lobule of the parotid salivary gland (according to N.V. Zelenevsky)

Capillaries - vasa cnpillaria - are the smallest vessels located between arterioles and venules and are pathways for transorgan blood circulation. They perform trophic and metabolic functions. The capillary wall consists of a single layer of endothelial cells, a perivascular membrane with pericytes and nerve fibers. The structure of the wall is closely related to the maintenance of metabolism in the organ. The diameter of the capillaries is insignificant and can range from 4 to 50 microns. They are distinguished by their straightness of motion. Their number in each organ depends on its functional load and the intensity of metabolism in it. For example, a horse has up to 1350 capillaries per 1 mm2, a dog has up to 2650. There are especially many capillaries in the glands, gray matter of the brain, in the lungs, and the least in tendons and ligaments. In phylogenesis, capillaries arose as a result of the replacement of extravascular circulation with intravascular circulation.

In the resting state of organs, not all capillaries function, only 10% of the total number. Some capillaries are in reserve and are included in the bloodstream in case of functional need. Capillaries are common wherever there is connective tissue. They are absent in epithelial tissue and its horny derivatives, dentin and enamel of teeth, the cornea and lens of the eye, and articular cartilage. Widely anastomosing among themselves, the capillaries form networks that pass into the postcapillary. The postcapillary continues into the venule accompanying the arteriole. Venules form thin initial segments of the venous bed, which make up the roots of the veins and pass into the veins.

Veins are vessels through which blood flows to the heart, their walls are arranged according to the same plan as the walls of arteries, but they are thinner, they have less elastic and muscle tissue, due to which empty veins collapse, while the lumen of the artery gapes in a cross section.

Blood circulation begins in the tissues where metabolism occurs through the walls of capillaries (blood and lymphatic). Microcirculation is the movement of blood and lymph through microscopic vessels located in organs. This part of the vascular bed is located between the arteries and veins. Through the microcirculatory bed, plasma is filtered into the tissues of the body. It is divided into links: inflow and distribution (arteriole and precapillary), exchange (capillary), drainage-depositing link (postcapillary and venule). In the wall of the arteriole, the ictyma, media and outer connective tissue membrane are distinguished. The main criterion defining a precapillary is the absence of elastic elements in the wall. They own important role in resistance to blood flow. At the point where the arterioles branch, the capillary is surrounded smooth muscle cells, forming the sphincter. Postcapillaries are constructed similarly to precapillaries. Together with venules, they are the first to be included in tissue drainage and remove toxic substances, metabolic products, regulate the balance between the volumes of arterial and venous blood. Postcapillaries, merging, form collecting venules, in the walls of which they already appear muscle cells(myocytes). The microvasculature ends with postcapillaries and venules. Venules become veins.

In addition to the named vessels, anatomists of our country have proven that arteriovenular anastomoses, which represent paths of shortened blood flow from the arterial to the vesal bed, bypassing the capillary, belong to the microcirculatory bed. Thanks to their presence, the terminal blood flow is divided into two paths of blood movement: transcapillary (through capillaries); juxtacapillary (through arteriovenular anastomoses). Thanks to the latter, the capillary bed is unloaded and blood transport in the organ is accelerated.

The microvasculature is not a mechanical sum various vessels, but a complex anatomical and physiological complex that ensures the main process of the body - metabolism! The structure of the microvasculature varies in different organs and depends on their morphofunctional state. Thus, in the liver there are wide capillaries - sinusoids, into which arterial and venous blood flows, in the kidneys - arterial capillary glomeruli, special sinusoids - in the bone marrow.

Patterns of distribution of blood vessels in the body. The distribution of blood vessels in the body of animals is subject to certain patterns. They were outlined by the founder of functional anatomy P. F. Lesgaft (1837-1909) in his book “Fundamentals of Theoretical Anatomy”.

1. General plan the location of the main vascular trunks corresponds to the structure of the main supporting skeletal parts of the body: a) uniaxial location of the main rod of the body (head and torso); b) bilateral symmetry; c) segmentation. The longitudinal vessels are the aorta and its continuation - the median sacral and caudal arteries. Segmental vessels are present where metamerism is expressed (skeleton and musculature of the trunk): intercostal, lumbar, sacral arteries and veins. The presence of the same right and left arteries in the area of ​​the walls of the torso and limbs is a reflection of the bilateral symmetry of the body.

2 The vessels usually go together with nerve trunks, forming neurovascular bundles enclosed in fascial sheaths.

3. The topography of the vessels is strictly natural. They pass in the area of ​​the torso, head and limbs along highways, i.e., along the shortest path. In this regard, on the body, large vessels follow ventrally from spinal column, on the limbs - on them medial surface, inside the angle of the joint, as the sides are most protected and less injured. The name of the highway corresponds to the part of the body and limb along which they follow. For example, in the shoulder area there are brachial artery and vein, in the thigh area - femoral artery and vein, respectively, etc.

4. The order of origin of vessels to organs, their number, diameter are closely related to the functional activity of organs and embryonic anlage. So, the first to depart from the aorta are the right and left coronary arteries, which supply blood to the heart, then the brachiocephalic trunk, which sends the cut to the head, withers, neck, thoracic limbs, the last vessels leaving the aorta are the paired iliac arteries, which supply blood to the pelvic limbs and organs of the pelvic cavity. The vessels approach the internal organs from the side facing the source of blood supply, and enter the organ through its gate.

5. There are four types of branching of arteries: diffuse, main, dichocomic and terminal, which are determined by the development and function of the blood-supplying organs. The loose type is characterized by the division of the descending vessel into several small branches of different sizes (like the crown of a tree) - these are the vessels of the internal organs. With the main type, there is a main main artery and branches sequentially extending from it (parietal and visceral vessels of the aorta). With dichotomous branching, one arterial trunk is divided fork-shaped into two identical trunks, thereby achieving uniform blood supply to the body area (division of the pulmonary trunk). The terminal type of branching is characterized by the absence of anastomoses between the branches of adjacent arteries (in the brain, heart, lungs, liver); such vessels are often clogged with blood clots (for example, during a stroke).

6. In addition to the highways, the body has vessels that accompany the highways and provide a roundabout flow of blood that bypasses the main path (lateral collateral vessels). When the main line is turned off, due to the presence of anastomoses, the blood supply to an organ or part of the body can be compensated by the collateral. A large number of collaterals in the extremities. They are of practical interest in surgical interventions. Collaterals also include bypass networks. They are located in the area of ​​the joints and lie on their extensor side. The importance of bypass networks lies in the fact that when the joints are flexed, there is a strong stretching of the vessels, which makes it difficult for blood to flow through them. As a counteracting mechanism, vascular networks are formed in such areas, receiving blood from different sources, as a result of which, in any position of the joint, favorable conditions for blood flow, if not from one, then from another vessel.

7. The lateral branches of the highways form connections with each other - anastomoses, which are an important compensatory device for equalizing blood pressure, regulating and redistributing blood flow and ensuring blood supply to the body. They are present in all areas and organs characterized by significant mobility. Anastomoses occur between large, medium and small vessels. There are intersystem arterial anastomoses - connections between branches of different arteries and intrasystemic anastomoses - between branches of one artery. The anastomoses also include arterial arches that are formed between arterial trunks going to the same organ (for example, the terminal arch formed in a horse inside the coffin bone between the digital arteries, arterial arches between the intestinal vessels, etc.), as well as arterial arches networks - plexuses of terminal branches of vessels (dorsal network of the wrist).

There are also arteriovenous anastomoses (between arteries and veins), as well as arteriovenular (shunts). They act as a shortened blood flow from arteries or arterioles to veins or venules, bypassing the microcirculatory or capillary bed, i.e., they participate in the redistribution of blood both normally and when the body is overloaded.

8. The functional determination of the architecture of the vascular bed and the structure of its walls are directly dependent on the characteristics of hemodynamics and are associated with the ecological characteristics of animals.

Self-test questions

1. What are the significance and functions of the cardiovascular system?

2. What is the anatomical composition of the cardiovascular system?

3. What are the patterns of distribution of blood vessels in the body?

4. What are the names of the vessels that carry blood to and from the heart, and what are they? distinctive features their buildings?

5. What vessels carry out the metabolic (trophic) function and what are the features of their structure in connection with this? What do they form in the organ?

6. What are anastomoses and collaterals (features of their structure, topography and significance)?

7. Name the circles of blood circulation.

8. How is the vessel wall innervated?

9. Name the main types of development of the vascular system in phylo- and ontogenesis.

10. What are the features of blood circulation in the fetus?

Anatomy of the heart.

1. General characteristics cardiovascular system and its importance.

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

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 connects the heart and blood vessels. Lymphatic system includes branches 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(adventitia) membrane is composed of connective tissue, average– smooth muscle, internal– endothelial (intima). In addition to the endothelial lining, the inner lining of most arteries also has 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 of the upper extremities, and fewer in the veins of the torso and neck. Only both do not have valves vena cava, veins of the head, 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. When the inflow or outflow of blood through the main vessels is disrupted, anastomoses promote the movement of blood in different 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 into the capillaries of organs and tissues throughout the body. Through the walls of the body's capillaries, the exchange of substances between blood and tissues occurs. Arterial blood gives oxygen to 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, venous blood, enriched with oxygen and freed from carbon dioxide, turns into arterial blood. 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 circle – 5 seconds.

Coronary circulation (cardiac) includes the vessels of the heart itself to supply blood to the heart muscle. It starts left and right coronary arteries, which extend 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.

Structure of the heart.

Heart(cor; Greek cardia) – hollow muscular organ, having the shape of a cone, the top of which faces down, left and forward, and the base – 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, back– 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– external, middle and internal; 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 epithelial cells and is the inner layer of the pericardium. 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. Four 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 into the vessels great circle blood 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 the inner surface of the right and left ventricles there are papillary muscles- these are outgrowths of the myocardium.

Topography of the heart.

Upper limit corresponds to the upper edge of the cartilages III pairs 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

Lower limit– 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.

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

The inner shell, called intima, necessarily has 2 layers:

  • the endothelium lining the inner surface is a layer of cells squamous epithelium;
  • subendothelium - located under the endothelium, consists of connective tissue with a loose structure.

The middle shell consists of myocytes, elastic and collagen fibers.

The outer shell, called “adventitia,” is a fibrous connective tissue with a loose structure, supplied with vascular vessels, nerves, and lymphatic vessels.

Arteries

These are blood vessels that carry blood from the heart to all organs and tissues. There are arterioles and arteries (small, medium, large). Their walls have three layers: intima, media and adventitia. Arteries are classified according to several criteria.

Based on the structure of the middle layer, three types of arteries are distinguished:

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

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

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

Vienna

They are non-muscular and muscular.

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

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

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

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

Structure and its features:

  • Larger in diameter compared to arteries.
  • The subendothelial layer and elastic component are poorly developed.
  • The walls are thin and fall off easily.
  • The smooth muscle elements of the middle layer are rather poorly developed.
  • Pronounced outer layer.
  • The presence of a valve apparatus, which is formed by the inner layer of the vein wall. The base of the valves consists of smooth myocytes, inside the valves there is fibrous connective tissue, and on the outside they are covered by a layer of endothelium.
  • All wall membranes are endowed with vascular vessels.

The balance between venous and arterial blood is ensured by several factors:

  • a large number veins;
  • their larger caliber;
  • density of the vein network;
  • formation of venous plexuses.

Differences

How are arteries different from veins? These blood vessels differ significantly in many ways.


Arteries and veins, first of all, differ in the structure of the wall

According to the structure of the wall

Arteries have thick walls, they have a lot of elastic fibers, smooth muscles are well developed, they do not fall off unless they are filled with blood. Due to contractility The tissues that make up their walls provide rapid delivery of oxygenated blood to all organs. The cells that make up the layers of the walls ensure the unhindered passage of blood through the arteries. Inner surface theirs is corrugated. The arteries must withstand the high pressure that is created by powerful surges of blood.

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

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

By shape

The arteries have a fairly regular cylindrical shape, they are round in cross section.

Due to the pressure of other organs, the veins are flattened, their shape is tortuous, they either narrow or expand, which is due to the location of the valves.

By quantity

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

According to the presence of valves

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

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

By blood volume

Veins circulate approximately twice as much blood as arteries.

By location

The arteries lie deep in the tissues and approach the skin only in a few places, where the pulse is heard: on the temples, neck, wrist, and instep of the feet. Their location is approximately the same for all people.


Veins are mostly located close to the surface of the skin

Localization of veins different people may vary.

To ensure blood movement

In the arteries, blood flows under the pressure of the force of the heart, which pushes it out. At first the speed is about 40 m/s, then gradually decreases.

Blood flow in the veins occurs due to several factors:

  • pressure forces depending on the push of blood from the heart muscle and arteries;
  • suction force of the heart when relaxing between contractions, that is, the creation in the veins negative pressure due to enlargement of the atria;
  • suction effect on the veins of the chest breathing movements;
  • contractions of the muscles of the legs and arms.

In addition, approximately a third of the blood is in the venous depots (in the portal vein, spleen, skin, walls of the stomach and intestines). It is pushed out from there if it is necessary to increase the volume of circulating blood, for example, with massive bleeding, with high physical activity.

By color and composition of blood

Arteries carry blood from the heart to the organs. It is enriched with oxygen and has a scarlet color.

Veins provide blood flow from tissues to the heart. Venous blood, which contains carbon dioxide and breakdown products formed during metabolic processes, differs more dark color.

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

Thus, the main differences can be identified:

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

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