Features of the structure of the left atrium. The membranes of the heart. The structure of the human heart. The structure of the human heart: diagram, blood circulation circles

Anatomy and physiology of the heart: structure, functions, hemodynamics, cardiac cycle, morphology

The structure of the heart of any organism has many characteristic nuances. In the process of phylogenesis, that is, the evolution of living organisms to more complex ones, the heart of birds, animals and humans acquires four chambers instead of two chambers in fish and three chambers in amphibians. This complex structure is best suited for separating the flow of arterial and venous blood. In addition, the anatomy of the human heart involves many the smallest details, each of which performs its strictly defined functions.

Heart as an organ

So, the heart is nothing more than a hollow organ consisting of specific muscle tissue, which carries out the motor function. The heart is located in chest behind the sternum, more to the left, and its longitudinal axis is directed anteriorly, to the left and down. In front, the heart borders on the lungs, almost completely covering them, leaving only a small part directly adjacent to the chest from the inside. The boundaries of this part are otherwise called absolute cardiac dullness, and they can be determined by tapping chest wall ().

In people with a normal constitution, the heart has a semi-horizontal position in chest cavity, in persons with an asthenic constitution (thin and tall) - almost vertical, and in hypersthenics (dense, stocky, with a large muscle mass) – almost horizontal.

heart position

The posterior wall of the heart is adjacent to the esophagus and large main vessels(To thoracic region aorta, to the inferior vena cava). Bottom part the heart is located on the diaphragm.

external structure of the heart

Age characteristics

The human heart begins to form in the third week of the intrauterine period and continues throughout the entire period of gestation, passing through stages from a single-chamber cavity to a four-chamber heart.

development of the heart in utero

The formation of four chambers (two atria and two ventricles) occurs already in the first two months of pregnancy. The smallest structures are fully formed by birth. It is in the first two months that the embryonic heart is most vulnerable to negative influence some factors on the expectant mother.

The fetal heart participates in the blood flow throughout its body, but differs in the circles of blood circulation - the fetus does not yet have its own breathing with lungs, and it “breathes” through placental blood. There are some openings in the fetal heart that allow pulmonary blood flow to be “switched off” from the circulation before birth. During childbirth, accompanied by the first cry of the newborn, and, consequently, at the moment of increased intrathoracic pressure and pressure in the baby's heart, these openings close. But this does not always happen, and the child may still have them, for example, (not to be confused with such a defect as a defect interatrial septum). Open window is not a heart defect, and subsequently, as the child grows, it heals.

hemodynamics in the heart before and after birth

The heart of a newborn baby has a round shape, and its dimensions are 3-4 cm in length and 3-3.5 cm in width. In the first year of a child's life, the heart increases significantly in size, more in length than in width. The weight of a newborn baby's heart is about 25-30 grams.

As the baby grows and develops, the heart also grows, sometimes significantly ahead of the development of the body itself according to age. By the age of 15, the mass of the heart increases almost tenfold, and its volume increases more than fivefold. The heart grows most rapidly until the age of five, and then during puberty.

In an adult, the size of the heart is about 11-14 cm in length and 8-10 cm in width. Many people rightly believe that the size of each person’s heart corresponds to the size of his clenched fist. The weight of the heart in women is about 200 grams, and in men it is about 300-350 grams.

After age 25, changes begin in the connective tissue of the heart, which forms the heart valves. Their elasticity is no longer the same as in childhood and adolescence, and the edges may become uneven. As a person grows and then ages, changes occur in all structures of the heart, as well as in the vessels that feed it (the coronary arteries). These changes can lead to the development of numerous cardiac diseases.

Anatomical and functional features of the heart

Anatomically, the heart is an organ divided into four chambers by septa and valves. The “upper” two are called atria (atrium), and the “lower” two are called ventricles (ventriculum). Between the right and left atria is the interatrial septum, and between the ventricles is the interventricular septum. Normally, these septa do not have holes in them. If there are holes, this leads to mixing of arterial and venous blood, and, accordingly, to hypoxia of many organs and tissues. Such holes are called septal defects and are classified as.

basic structure of the chambers of the heart

The boundaries between the upper and lower chambers are the atrioventricular openings - the left one, covered by the mitral valve leaflets, and the right one, covered by the tricuspid valve leaflets. The integrity of the partitions and correct work Valve leaflets prevent mixing of blood flows in the heart and promote clear unidirectional blood flow.

The atria and ventricles are different - the atria are smaller than the ventricles and have thinner walls. Thus, the wall of the atria is about only three millimeters, the wall of the right ventricle is about 0.5 cm, and the wall of the left is about 1.5 cm.

The atria have small projections called ears. They have a slight suction function for better pumping of blood into the atrium cavity. IN right atrium The mouth of the vena cava flows near its ear, and four (less often five) pulmonary veins flow into the left one. The pulmonary artery (more often called the pulmonary trunk) on the right and the aortic bulb on the left depart from the ventricles.

structure of the heart and its vessels

From the inside, the upper and lower chambers of the heart are also different and have their own characteristics. The surface of the atria is smoother than the ventricles. Thin connective tissue valves originate from the valve ring between the atrium and the ventricle - bicuspid (mitral) on the left and tricuspid (tricuspid) on the right. The other edge of the valves faces the inside of the ventricles. But so that they do not hang freely, they are supported, as it were, by thin tendon threads called chords. They are like springs, stretch when the valve flaps close and compress when the valve flaps open. The chordae originate from the papillary muscles from the wall of the ventricles - three in the right and two in the left ventricle. That is why the ventricular cavity has an uneven and lumpy inner surface.

The functions of the atria and ventricles also differ. Due to the fact that the atria need to push blood into the ventricles, and not into larger and longer vessels, they have to overcome less resistance from muscle tissue, therefore the atria are smaller in size and their walls are thinner than those of the ventricles. The ventricles push blood into the aorta (left) and into pulmonary artery(on right). Conventionally, the heart is divided into right and left half. The right half serves for the flow of exclusively venous blood, and the left half for arterial blood. Schematically " right heart" is indicated in blue, and " left heart- red. Normally, these flows never mix.

hemodynamics in the heart

One cardiac cycle lasts about 1 second and is carried out as follows. At the moment the atria are filled with blood, their walls relax - atrial diastole occurs. The valves of the vena cava and pulmonary veins are open. The tricuspid and mitral valves are closed. Then the atrial walls tense and push blood into the ventricles, the tricuspid and mitral valves are open. At this moment, systole (contraction) of the atria and diastole (relaxation) of the ventricles occur. After the ventricles receive blood, the tricuspid and mitral valves close, and the aortic and pulmonary valves open. Next, the ventricles contract (ventricular systole), and the atria fill with blood again. The general diastole of the heart begins.

cardiac cycle

The main function of the heart is reduced to pumping, that is, to pushing a certain blood volume into the aorta with such pressure and speed that the blood is delivered to the most distant organs and to the smallest cells of the body. Moreover, arterial blood is pushed into the aorta with high content oxygen and nutrients, entering the left half of the heart from the vessels of the lungs (flows to the heart through the pulmonary veins).

Venous blood, low in oxygen and other substances, is collected from all cells and organs from the venous cava system, and flows into the right half of the heart from the superior and inferior vena cava. Further deoxygenated blood is pushed from the right ventricle into the pulmonary artery, and then into the pulmonary vessels in order to carry out gas exchange in the alveoli of the lungs and for the purpose of oxygen enrichment. In the lungs, arterial blood collects in the pulmonary venules and veins, and again flows into the left side of the heart (the left atrium). And so the heart regularly pumps blood throughout the body at a frequency of 60-80 beats per minute. These processes are designated by the concept "Circles of Blood Circulation". There are two of them - small and large:

• Small circle includes the flow of venous blood from the right atrium through the tricuspid valve into the right ventricle - then into the pulmonary artery - then into the pulmonary arteries - oxygenation of blood in the pulmonary alveoli - flow arterial blood into the smallest veins of the lungs - into the pulmonary veins - into the left atrium.
• Big circle includes the flow of arterial blood from the left atrium through the mitral valve into the left ventricle - through the aorta into the arterial bed of all organs - after gas exchange in tissues and organs, the blood becomes venous (with high content carbon dioxide instead of oxygen) - further into the venous bed of the organs - into the system of vena cava - into the right atrium.

circulation circles

Video: cardiac anatomy and cardiac cycle briefly

Morphological features of the heart

In order for the heart muscle fibers to contract synchronously, electrical signals must be supplied to them, which excite the fibers. This is another ability of the heart – .

Conduction and contractility are possible due to the fact that the heart autonomously generates electricity. Function data (automatism and excitability) are provided by special fibers that are integral part conducting system. The latter is represented by electrically active cells of the sinus node, atrioventricular node, the bundle of His (with two legs - right and left), as well as Purkinje fibers. In the case when a patient’s myocardial damage affects these fibers, they develop, otherwise called.

cardiac cycle

Normally, the electrical impulse originates in the cells of the sinus node, which is located in the area of ​​the right atrium appendage. In a short period of time (about half a millisecond), the impulse spreads throughout the atrial myocardium and then enters the cells of the atrioventricular junction. Typically, signals are transmitted to the AV node through three main tracts - the Wenkenbach, Thorel and Bachmann bundles. In the cells of the AV node, the impulse transmission time is extended to 20-80 milliseconds, and then the impulses travel through the right and left branches (as well as the anterior and posterior branches of the left branch) of the His bundle to the Purkinje fibers, and ultimately to the working myocardium. The frequency of impulse transmission along all pathways is equal to the heart rate and is 55-80 impulses per minute.

So, the myocardium, or cardiac muscle, is the middle layer in the wall of the heart. The inner and outer shells are connective tissue, and are called the endocardium and epicardium. The last layer is part of the pericardial sac, or cardiac “shirt”. Between the inner layer of the pericardium and the epicardium, a cavity is formed, filled with a very small amount of fluid, to ensure better sliding of the pericardial layers during heart contractions. Normally, the fluid volume is up to 50 ml; exceeding this volume may indicate pericarditis.

structure of the heart wall and membrane

Blood supply and innervation of the heart

Despite the fact that the heart is a pump to supply the entire body with oxygen and nutrients, it itself also needs arterial blood. In this regard, the entire wall of the heart has a well-developed arterial network, which is represented by the branching of the coronary (coronary) arteries. The orifices of the right and left coronary arteries depart from the root of the aorta and are divided into branches that penetrate the thickness of the heart wall. If these important arteries become clogged with blood clots and atherosclerotic plaques, the patient will develop and the organ will no longer be able to perform its functions fully.

location coronary arteries, supplying blood to the heart muscle (myocardium)

The frequency and strength with which the heart beats is influenced by nerve fibers, extending from the most important nerve conductors - the vagus nerve and the sympathetic trunk. The first fibers have the ability to slow down the rhythm frequency, the latter - to increase the frequency and strength of the heartbeat, that is, they act like adrenaline.

innervation of the heart

In conclusion, it should be noted that the anatomy of the heart may have any deviations in individual patients Therefore, only a doctor can determine the norm or pathology in a person after conducting an examination that can most informatively visualize the cardiovascular system.

Video: lecture on cardiac anatomy

The heart is the main organ of the human body. It is a muscular organ, hollow inside and cone-shaped. In newborns, the heart weighs about thirty grams, and in an adult it weighs about three hundred.

The topography of the heart is as follows: it is located in the chest cavity, and one third of it is located on the right side of the mediastinum, and two thirds on the left. The base of the organ is directed upward and somewhat posteriorly, and narrow part, that is, the top, is directed down, to the left and anteriorly.

Organ boundaries

The boundaries of the heart allow us to determine the location of the organ. There are several of them:

1. Upper. It corresponds to the cartilage of the third rib.
2. Bottom. This border connects right side with the top.
3. The top. located in the fifth intercostal space, towards the left midclavicular straight line.
4. Right. Between the third and fifth ribs, a couple of centimeters to the right of the edge of the sternum.
5. Left. The topography of the heart at this border has its own characteristics. It connects the apex with the upper border, and itself runs along which faces the left lung.

According to topography, the heart is located behind and just below half of the sternum. The most large vessels located behind, at the top.

Topography changes

The topography and structure of the heart in humans changes with age. IN childhood the organ makes two revolutions around its axis. The boundaries of the heart change during breathing and depending on the position of the body. So, when lying on the left side and bending over, the heart approaches the chest wall. When a person stands, it is located lower than when he lies. Because of this feature it shifts. According to anatomy, the topography of the heart changes and as a result breathing movements. So, as you inhale, the organ moves further away from the chest, and as you exhale, it returns back.

Changes in the function, structure, topography of the heart are observed in different phases cardiac activity. These indicators depend on gender, age, and also on individual characteristics body: location of the digestive organs.

Structure of the heart

The heart has an apex and a base. The latter faces up, to the right and back. At the back the base is formed by the atria, and at the front - by the pulmonary trunk and large artery- aorta.

The top of the organ faces down, forward and to the left. According to the topography of the heart, it reaches the fifth intercostal space. The apex is usually located at a distance of eight centimeters from the mediastinum.

The walls of the organ have several layers:

1. Endocardium.
2. Myocardium.
3. Epicardium.
4. Pericardium.

The endocardium lines the organ from the inside. This tissue forms the valves.

The myocardium is the heart muscle that contracts involuntarily. The ventricles and atria also consist of muscles, and in the former the muscles are more developed. Surface layer the atrial muscles consist of longitudinal and circular fibers. They are independent for each atrium. And in the ventricles there are the following layers of muscle tissue: deep, superficial and middle circular. From the deepest part, fleshy bridges and papillary muscles are formed.

The epicardium is epithelial cells, covering outer surface and the organ and the nearest vessels: the aorta, vein, and also the pulmonary trunk.

The pericardium is the outer layer of the pericardial sac. Between the leaves there is a slit-like formation - the pericardial cavity.

Holes

The heart has several holes and chambers. The organ has a longitudinal septum that divides it into two parts: left and right. At the top of each part are the atria, and at the bottom are the ventricles. There are openings between the atria and ventricles.

The first of them have some protrusion, which forms the cardiac ear. The walls of the atria have different thicknesses: the left one is more developed than the right one.

Inside the ventricles there are papillary muscles. Moreover, there are three of them on the left, and two on the right.

Fluid enters the right atrium from the superior and inferior pudendal veins and the veins of the sinus of the heart. Four lead to the left. From the right ventricle, the aorta leaves and from the left.

Valves

The heart has tricuspid and bicuspid valves that close the gastroatrial openings. The absence of reverse blood flow and eversion of the walls is ensured by tendon threads passing from the edge of the valves to the papillary muscles.

The bicuspid or mitral valve closes the left ventricular orifice. Tricuspid - right ventricular-atrial opening.

In addition, in the heart there is one that closes the opening of the aorta, and the other that closes the pulmonary trunk. Valve defects are defined as heart disease.

Circulation circles

In the human body there are several circles of blood circulation. Let's look at them:

1. The great circle (BC) starts from the left ventricle and ends at the right atrium. Through it, blood flows through the aorta, then through the arteries, which diverge into precapillaries. After this, the blood enters the capillaries, and from there to the tissues and organs. In these small vessels Nutrients are exchanged between tissue cells and blood. After this, the reverse flow of blood begins. From the capillaries it enters the postcapillaries. They form venules from which venous blood enters the veins. Along them she approaches the heart, where vascular beds converge into the vena cava and enter the right atrium. This is how the blood supply to all organs and tissues occurs.
2. The pulmonary circle (PV) starts from the right ventricle and ends at the left atrium. Its origin is the pulmonary trunk, which divides into a pair of pulmonary arteries. Venous blood flows through them. It enters the lungs and is enriched with oxygen, turning into an arterial one. The blood then collects in the pulmonary veins and flows into the left atrium. MKK is intended to enrich the blood with oxygen.
3. There is also a coronal circle. It starts from the aortic bulb and the right coronary artery, passes through capillary network heart and returns through the venules and coronary veins, first to the coronary sinus, and then to the right atrium. This circle supplies nutrients to the heart.

The heart, as you can see, is a complex organ that has its own circulation. Its boundaries change, and the heart itself changes its angle of inclination with age, turning around its axis twice.

The heart has a complex structure and performs no less complex and important work. Contracting rhythmically, it ensures blood flow through the vessels.

The heart is located behind the sternum, in the middle section of the chest cavity and is almost completely surrounded by the lungs. It may move slightly to the side as it hangs freely on the blood vessels. The heart is located asymmetrically. Its long axis is inclined and forms an angle of 40° with the axis of the body. It is directed from top to right, forward, down to the left, and the heart is rotated so that its right section is tilted more forward, and the left one – back. Two-thirds of the heart is to the left of the midline and one-third (the vena cava and right atrium) is to the right. Its base is turned towards the spine, and its apex is facing the left ribs, to be more precise, the fifth intercostal space.

Anatomy of the heart

Sternocostal surface the hearts are more convex. It is located behind the sternum and cartilages of the III-VI ribs and is directed forward, upward, and to the left. The transverse coronary groove runs along it, which separates the ventricles from the atria and thereby divides the heart into top part, formed by the atria, and the lower one, consisting of the ventricles. Another groove of the sternocostal surface - the anterior longitudinal - runs along the border between the right and left ventricles, with the right one forming the largest part of the anterior surface, the left one the smaller one.

Diaphragmatic surface flatter and adjacent to the tendon center of the diaphragm. A longitudinal posterior groove runs along this surface, separating the surface of the left ventricle from the surface of the right. In this case, the left one makes up the majority of the surface, and the right one makes up the smaller part.

Anterior and posterior longitudinal grooves they merge at their lower ends and form a cardiac notch to the right of the cardiac apex.

There are also side surfaces located on the right and left and facing the lungs, which is why they are called pulmonary.

Right and left edges hearts are not the same. The right edge is more pointed, the left is more blunt and rounded due to the thicker wall of the left ventricle.

The boundaries between the four chambers of the heart are not always clearly defined. The grooves in which the blood vessels hearts covered with fatty tissue and the outer layer of the heart - the epicardium. The direction of these grooves depends on how the heart is located (obliquely, vertically, transversely), which is determined by the body type and the height of the diaphragm. In mesomorphs (normosthenics), whose proportions are close to the average, it is located obliquely, in dolichomorphs (asthenics) with a thin physique - vertically, in brachymorphs (hypersthenics) with wide short forms– transversely.

The heart seems to be suspended by the base on large vessels, while the base remains motionless, and the apex is in a free state and can move.

Structure of heart tissue

The heart wall is made up of three layers:

1. Endocardium - inner layer epithelial tissue, lining the cavities of the heart chambers from the inside, accurately repeating their relief.
2. Myocardium – thick layer, educated muscle tissue(cross-striped). The cardiac myocytes of which it consists are connected by many bridges that link them into muscle complexes. This muscle layer ensures the rhythmic contraction of the chambers of the heart. The myocardium is thinnest at the atria, the greatest is at the left ventricle (about 3 times thicker than the right), since it needs more force to push blood into the systemic circulation, in which the resistance to flow is several times greater than in the small circle. The atrial myocardium consists of two layers, the ventricular myocardium - of three. The atrial myocardium and ventricular myocardium are separated by fibrous rings. The conduction system that provides rhythmic contraction of the myocardium is one for the ventricles and atria.
3. Epicardium is the outer layer, which is the visceral lobe of the heart sac (pericardium), which is serosa. It covers not only the heart, but also the initial parts of the pulmonary trunk and aorta, as well as the final parts of the pulmonary and vena cava.

Anatomy of the atria and ventricles

The cardiac cavity is divided by a septum into two parts - right and left, which do not communicate with each other. Each of these parts consists of two chambers - the ventricle and the atrium. The septum between the atria is called the interatrial septum, and the septum between the ventricles is called the interventricular septum. Thus, the heart consists of four chambers - two atria and two ventricles.

Right atrium

In shape it looks like an irregular cube, in front there is additional cavity, called the right ear. The atrium has a volume of 100 to 180 cubic meters. cm. It has five walls, 2 to 3 mm thick: anterior, posterior, superior, lateral, medial.

The inferior vena cava (below) also flows into the right atrium (from above, from behind). On the lower right is the coronary sinus, where the blood of all the cardiac veins drains. Between the openings of the superior and inferior vena cava there is an intervenous tubercle. In the place where the inferior vena cava flows into the right atrium, there is a fold of the inner layer of the heart - the valve of this vein. The sinus of the vena cava is the posterior dilated section of the right atrium, into which both of these veins flow.

The chamber of the right atrium has a smooth internal surface, and only in the right appendage with the adjacent anterior wall the surface is uneven.

Many pinpoint openings of the small veins of the heart open into the right atrium.

Right ventricle

It consists of a cavity and an arterial cone, which is a funnel directed upward. The right ventricle has the shape of a triangular pyramid, the base of which faces upward and the apex faces downward. The right ventricle has three walls: anterior, posterior, medial.

The front is convex, the back is flatter. Medial is interventricular septum, consisting of two parts. The larger one, the muscular one, is located at the bottom, the smaller one, the membranous one, is at the top. The pyramid faces the atrium with its base and has two openings: posterior and anterior. The first is between the cavity of the right atrium and the ventricle. The second goes into the pulmonary trunk.

Left atrium

It has the appearance of an irregular cube, is located behind and adjacent to the esophagus and the descending aorta. Its volume is 100-130 cubic meters. cm, wall thickness – from 2 to 3 mm. Like the right atrium, it has five walls: anterior, posterior, superior, literal, medial. The left atrium continues anteriorly into an additional cavity called the left appendage, which is directed towards the pulmonary trunk. Four pulmonary veins flow into the atrium (back and above), in the openings of which there are no valves. The medial wall is the interatrial septum. The inner surface of the atrium is smooth, the pectineus muscles are present only in the left appendage, which is longer and narrower than the right one, and is noticeably separated from the ventricle by an interception. It communicates with the left ventricle via the atrioventricular orifice.

Left ventricle

It is shaped like a cone, the base of which faces upward. The walls of this chamber of the heart (anterior, posterior, medial) have the greatest thickness - from 10 to 15 mm. There is no clear boundary between the front and back. At the base of the cone are the openings of the aorta and the left atrioventricular opening.

The round opening of the aorta is located in front. Its valve consists of three valves.

Heart size

The size and weight of the heart differs among different people. The average values ​​are as follows:

• length is from 12 to 13 cm;
• greatest width – from 9 to 10.5 cm;
• anteroposterior size – from 6 to 7 cm;
• weight in men - about 300 g;
• weight in women is about 220 g.

Functions of the cardiovascular system and heart

The heart and blood vessels make up the cardiovascular system, the main function of which is transport. It consists of supplying tissues and organs with nutrition and oxygen and returning metabolic products.

The heart acts as a pump - it ensures continuous circulation of blood in the circulatory system and delivery of nutrients and oxygen to organs and tissues. When stressed or physical activity his work is immediately restructured: the number of layoffs increases.

The work of the heart muscle can be described as follows: its right part(venous heart) receives waste blood from the veins, saturated carbon dioxide and gives it to the lungs for oxygen saturation. From the lungs, O2-enriched blood is sent to left side heart (arterial) and from there is forcefully pushed into the bloodstream.

The heart produces two circles of blood circulation - large and small.

The large one supplies blood to all organs and tissues, including the lungs. It begins in the left ventricle and ends in the right atrium.

The pulmonary circulation produces gas exchange in the alveoli of the lungs. It begins in the right ventricle and ends in the left atrium.

Blood flow is regulated by valves: they prevent it from flowing in the opposite direction.

The heart has such properties as excitability, conductivity, contractility and automaticity (excitation without external stimuli under the influence of internal impulses).

Thanks to the conduction system, sequential contraction of the ventricles and atria occurs, and the synchronous inclusion of myocardial cells in the contraction process.

Rhythmic contractions of the heart ensure a portioned flow of blood into the circulatory system, but its movement in the vessels occurs without interruption, which is due to the elasticity of the walls and the resistance to blood flow that occurs in small vessels.

The circulatory system has a complex structure and consists of a network of vessels for different purposes: transport, shunting, exchange, distribution, capacitance. There are veins, arteries, venules, arterioles, capillaries. Together with the lymphatics, they maintain the constancy internal environment in the body (pressure, body temperature, etc.).

Arteries move blood from the heart to the tissues. As they move away from the center, they become thinner, forming arterioles and capillaries. Arterial bed circulatory system carries out transportation necessary substances to organs and maintains constant pressure in the vessels.

The venous bed is more extensive than the arterial bed. Veins move blood from tissues to the heart. Veins are formed from venous capillaries, which, merging, first become venules, then veins. They form large trunks near the heart. Distinguish superficial veins, located under the skin, and deep, located in the tissues near the arteries. The main function of the venous part of the circulatory system is the outflow of blood, rich in products metabolism and carbon dioxide.

To evaluate functionality of cardio-vascular system and the permissibility of loads, special tests are carried out, which make it possible to assess the performance of the body and its compensatory capabilities. Functional tests cardiovascular system are included in the physical examination to determine the degree of fitness and general physical training. The assessment is given based on such indicators of the functioning of the heart and blood vessels as arterial pressure, pulse pressure, blood flow speed, minute and stroke volumes of blood. Such tests include Letunov's tests, step tests, Martinet's test, Kotov's - Demin's test.

The heart begins to beat from the fourth week after conception and does not stop until the end of life. It does a gigantic job: per year it pumps about three million liters of blood and makes about 35 million heartbeats. At rest, the heart uses only 15% of its resource, and under load – up to 35%. Behind average duration During its lifetime it pumps about 6 million liters of blood. Another interesting fact: The heart supplies blood to 75 trillion cells human body except the cornea of ​​the eyes.

Heart is a part. This organ is located in anterior section mediastinum (the space between the lungs, spine, sternum and diaphragm). Contractions of the heart cause blood to move through the vessels. Latin name hearts – cor, Greek – kardia. From these words came terms such as “coronary”, “cardiology”, “cardiac” and others.

Structure of the heart

The heart in the chest cavity is slightly displaced relative to midline. About a third of it is located on the right, and two thirds - on the left half of the body. The lower surface of the organ is in contact with the diaphragm. The esophagus and large vessels (aorta, inferior vena cava) are adjacent to the heart from behind. The front of the heart is covered by the lungs, and only a small part of its wall directly touches the chest wall. According to the frome, the heart is close to a cone with a rounded top and base. The mass of the organ averages 300 - 350 grams.

Heart chambers

The heart is made up of cavities, or chambers. The two smaller ones are called atria, the two larger chambers are called ventricles. The right and left atria are separated by the interatrial septum. The right and left ventricles are separated from each other by the interventricular septum. As a result, there is no mixing of venous and aortic blood inside the heart.
Each of the atria communicates with the corresponding ventricle, but the opening between them has a valve. The valve between the right atrium and the ventricle is called tricuspid, or tricuspid, because it consists of three leaflets. The valve between the left atrium and the ventricle consists of two valves, its shape resembles the headdress of the Pope - the miter, and is therefore called bicuspid, or mitral. Atrioventricular valves allow unidirectional blood flow from the atrium to the ventricle, but not vice versa.
Blood from the entire body, rich in carbon dioxide (venous), is collected in large vessels: the superior and inferior vena cava. Their mouths open in the wall of the right atrium. From this camera blood is flowing into the cavity of the right ventricle. The pulmonary trunk delivers blood to the lungs, where it becomes arterial. It goes through the pulmonary veins to the left atrium, and from there to the left ventricle. The aorta begins from the latter: the most large vessel in the human body, through which blood enters smaller ones and enters the body. The pulmonary trunk and aorta are separated from the ventricles by corresponding valves that prevent retrograde (reverse) blood flow.

Structure of the heart wall

Cardiac muscle (myocardium) is the bulk of the heart. The myocardium has a complex layered structure. The thickness of the heart wall varies from 6 to 11 mm in its different parts.
Deep in the heart wall is the conduction system of the heart. It is formed by a special tissue that produces and conducts electrical impulses. Electrical signals excite the heart muscle, causing it to contract. There are large formations in the conducting system nerve tissue: nodes. The sinus node is located in the upper part of the myocardium of the right atrium. It produces impulses responsible for the functioning of the heart. The atrioventricular node is located in the lower segment of the interatrial septum. The so-called bundle of His departs from it, dividing into the right and left leg, which split into smaller and smaller branches. The smallest branches of the conduction system are called “Purkinje fibers” and are in direct contact with muscle cells in the wall of the ventricles.
The chambers of the heart are lined with endocardium. Its folds form the heart valves, which we discussed above. Outer shell heart - pericardium, consisting of two layers: parietal (external) and visceral (internal). The visceral layer of the pericardium is called the epicardium. In the interval between external and inner layers(leaves) of the pericardium there are about 15 ml serous fluid, ensuring their sliding relative to each other.

Blood supply, lymphatic system and innervation

The blood supply to the heart muscle is carried out through the coronary arteries. The large trunks of the right and left coronary arteries begin from the aorta. Then they break up into smaller branches that supply blood to the myocardium.
The lymphatic system consists of mesh layers of vessels that drain lymph into collectors and then into the thoracic duct.
The work of the heart is controlled by the autonomic nervous system regardless of human consciousness. Nervus vagus has a parasympathetic effect, including slowing down the heart rate. Sympathetic nerves accelerate and strengthen the work of the heart.

Physiology of cardiac activity

The main function of the heart is contractile. This organ is a kind of pump that ensures a constant flow of blood through the vessels.
The cardiac cycle is a period of repeated periods of contraction (systole) and relaxation (diastole) of the heart muscle.
Systole ensures the ejection of blood from the chambers of the heart. During diastole, the energy potential of the heart cells is restored.
During systole, the left ventricle pumps about 50–70 ml of blood into the aorta. The heart pumps 4–5 liters of blood per minute. Under load, this volume can reach 30 liters or more.
Contraction of the atria is accompanied by an increase in pressure in them, and the mouths of the vena cava flowing into them close. Blood from the atrial chambers is “squeezed out” into the ventricles. Then atrial diastole occurs, the pressure in them drops, and the cusps of the tricuspid and mitral valves. The contraction of the ventricles begins, as a result of which blood enters the pulmonary trunk and aorta. When systole ends, the pressure in the ventricles decreases, the valves of the pulmonary trunk and aorta close. This ensures unidirectional blood flow through the heart.
For valve defects, endocarditis and others pathological conditions valve apparatus cannot ensure the tightness of the heart chambers. Blood begins to flow retrograde, disrupting myocardial contractility.
provided by electrical impulses arising in sinus node. These impulses arise without external influence, that is, automatically. They are then conducted through the conduction system and excite muscle cells, causing them to contract.
The heart also has intrasecretory activity. It releases biologically into the blood active substances, in particular, atrial natriuretic peptide, which promotes the excretion of water and sodium ions through the kidneys.

Medical animation on the topic “How the human heart works”:

Educational video on the topic “The Human Heart: internal structure" (English):

Departments of the heart

The human heart is divided by partitions into four chambers, which different time filled with blood. The lower thick-walled chambers of the heart are called ventricles. They act as a pump and, after receiving blood from the upper chambers, send it into the arteries by contraction. The process of contraction of the ventricles is the heartbeat. The upper chambers are called atria, which, thanks to the elastic walls, easily stretch and accommodate the blood coming from the veins between contractions.

The left and right chambers of the heart are separate from each other, each consisting of an atrium and a ventricle. Oxygen-poor blood flowing from the body’s tissues first enters the right side and then goes to the lungs. On the contrary, the left section receives oxygenated blood from the lungs and is redirected to all tissues of the body. Due to the fact that the left ventricle performs the most difficult work, which is to pump blood through big circle blood circulation, it differs from other chambers of the heart in its massiveness and greater wall thickness - almost 1.5 cm.

In each half of the heart, the atria and ventricles are connected to each other by an opening closed by a valve. The valves open exclusively towards the ventricles. This process is assisted by tendon threads, which are attached at one end to the valve leaflets, and at the opposite end to the papillary muscles located on the walls of the ventricles. Such muscles are outgrowths of the wall of the ventricles and contract simultaneously with them, putting the tendon threads under tension and preventing blood from flowing back into the atrium. Tendon threads prevent the valves from turning toward the atria during the ventricles.

In the places where the aorta leaves the left ventricle and the pulmonary artery leaves the right ventricle, semilunar valves are placed in the form of pockets. Through them, blood passes into the aorta and pulmonary artery, but movement back into the ventricles is impossible due to the fact that the semilunar valves straighten and close when filled with blood.