Average heart mass in men. The structure and principle of the heart

16.08.2023

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. Such a complex structure is best suited for the separation of arterial and venous blood flows. In addition, the anatomy of the human heart implies many tiny 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 performs the motor function. The heart is located in the chest behind the sternum, more on the left, and its longitudinal axis is directed anteriorly, to the left and down. In front, the heart borders on the lungs, almost completely covered by 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 the chest wall ().

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

heart position

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

external structure of the heart

Age features

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 childbirth. It is in the first two months that the heart of the embryo is most vulnerable to the negative influence of certain factors on the expectant mother.

The heart of the fetus is involved in the blood flow through his body, but differs in the circles of blood circulation - the fetus does not yet have its own breathing with the lungs, but it “breathes” through the placental blood. There are some openings in the fetal heart that allow the pulmonary blood flow to be "switched off" from circulation prior to birth. During childbirth, accompanied by the first cry of the newborn, and, therefore, at the time of increased intrathoracic pressure and pressure in the heart of the child, these openings are closed. But this does not always happen, and they may remain in a child, for example, (not to be confused with such a defect as an atrial septal defect). An open window is not a heart defect, and subsequently, as the child grows, it overgrows.

hemodynamics in the heart before and after birth

The heart of a newborn child has a rounded 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, and more in length than in width. The mass of the heart of a newborn child is about 25-30 grams.

As the baby grows and develops, the heart also grows, sometimes significantly outpacing the development of the body itself according to age. By the age of 15, the mass of the heart increases by almost ten times, and its volume increases by more than five times. The heart grows most intensively up to five years, and then during puberty.

In an adult, the heart is about 11-14 cm long and 8-10 cm wide. Many rightly believe that the size of the heart of each person corresponds to the size of his clenched fist. The mass of the heart in women is about 200 grams, and in men - about 300-350 grams.

After 25 years, 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 up, and then aging, changes occur in all structures of the heart, as well as in the vessels that feed it (in 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 by partitions and valves into four chambers. The “upper” two are called the atria (atrium), and the “lower” two are called the ventricles (ventriculum). Between the right and left atria is the interatrial septum, and between the ventricles is the interventricular septum. Normally, these partitions 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 refer to.

basic structure of the chambers of the heart

The boundaries between the upper and lower chambers are atrioventricular openings - the left, covered by the leaflets of the mitral valve, and the right, covered by the leaflets of the tricuspid valve. The integrity of the septa and the proper functioning of the valvular leaflets prevent mixing of blood flows in the heart, and promote a clear unidirectional flow of blood.

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

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

structure of the heart and its vessels

From the inside, the upper and lower chambers of the heart also differ and have their own characteristics. The surface of the atria is smoother than that of the ventricles. From the valve ring between the atrium and the ventricle, thin connective tissue valves originate - bicuspid (mitral) on the left and tricuspid (tricuspid) on the right. The other edge of the leaflet faces the inside of the ventricles. But in order for them not to hang freely, they are, as it were, supported by thin tendon threads called chords. They are like springs, stretch when the valve flaps close and contract when the flaps open. Chords 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 bumpy 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 less resistance to muscle tissue to overcome, so 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 the pulmonary artery (right). Conventionally, the heart is divided into right and left halves. 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" in red. Normally, these streams never mix.

hemodynamics in the heart

One cardiac cycle lasts about 1 second and is carried out as follows. At the moment of filling with blood, the walls of the atria relax - atrial diastole occurs. The valves of the hollow veins and pulmonary veins are open. The tricuspid and mitral valves are closed. Then the atrial walls tighten and push blood into the ventricles, the tricuspid and mitral valves open. At this point, there is systole (contraction) of the atria and diastole (relaxation) of the ventricles. After the ventricles have taken in blood, the tricuspid and mitral valves close, and the aortic and pulmonary valves open. Then the ventricles contract (ventricular systole), and the atria fill with blood again. There comes a general diastole of the heart.

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 with a high content of oxygen and nutrients is pushed into the aorta, which enters the left half of the heart from the vessels of the lungs (flows to the heart through the pulmonary veins).

Venous blood, with a low content of oxygen and other substances, is collected from all cells and organs from the vena cava system, and flows into the right half of the heart from the superior and inferior vena cava. Further, venous blood is pushed out of 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 to enrich it with oxygen. In the lungs, arterial blood collects in the pulmonary venules and veins, and again flows into the left half of the heart (into the left atrium). And so regularly the heart pumps blood around the body at a frequency of 60-80 beats per minute. These processes are denoted by the concept "Circulation of blood". 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 arteries of the lungs - oxygenation of blood in the pulmonary alveoli - the flow of 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 to 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 a high content of carbon dioxide instead of oxygen) - further into the venous bed of organs - into the system of hollow veins - in the right atrium.

circles of blood circulation

Video: heart anatomy and cardiac cycle briefly

Morphological features of the heart

If you look at sections of the heart under a microscope, you can see a special type of musculature that is no longer found in any organ. This is a type of striated muscle, but with significant histological differences from ordinary skeletal muscles and from the muscles lining the internal organs. The main function of the heart muscle, or myocardium, is to provide the most important ability of the heart, which forms the basis of the vital activity of the whole organism as a whole. Is it the ability to shrink, or contractility.

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

Conductivity and contractility are possible due to the fact that the heart autonomously generates electricity in itself. Function Data (automatism and excitability) are provided with special fibers that are an integral part of the conductive system. The latter is represented by electrically active cells of the sinus node, the atrioventricular node, the His bundle (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, an electrical impulse originates in the cells of the sinus node, which is located in the zone of the right atrial appendage. In a short period of time (about half a millisecond), the impulse propagates through the atrial myocardium, and then enters the cells of the atrioventricular junction. Usually, signals are transmitted to the AV node through three main tracts - the Wenckenbach, Thorel and Bachmann bundles. In the cells of the AV node, the time of impulse transmission is extended to 20-80 milliseconds, and then the impulses enter through the right and left legs (as well as the anterior and posterior branches of the left leg) of the His bundle to the Purkinje fibers, and eventually 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 membrane 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 sheet of the pericardium and the epicardium, a cavity is formed, filled with a very small amount of fluid, to ensure better sliding of the sheets of the pericardium at the moments of heart contractions. Normally, the volume of fluid is up to 50 ml, an excess of 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 provide the whole 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 a branching of the coronary (coronary) arteries. The mouths of the right and left coronary arteries depart from the aortic root and are divided into branches penetrating 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 in full.

the location of the coronary arteries that supply 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 frequency of the rhythm, 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 some deviations in individual patients, therefore, only a doctor is able to determine the norm or pathology in a person after conducting an examination that can most informatively visualize the cardiovascular system.

Video: lecture on the anatomy of the heart

The dimensions of the fetal heart can be examined starting from the 20th week of pregnancy. After birth, it has the shape of a ball, and then by adolescence acquires an anatomical structure, as in adults. In diseases of the nervous, endocrine and digestive systems, body weight and, accordingly, the size of the heart may decrease. Microcardia is also a congenital pathology.

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What is the size of the heart, valves and chambers in a person is normal

You can study the structure of the heart using ultrasound. Its size is determined by age, physique. With malformations, there are violations - a deviation up or down. The data obtained during the instrumental study are needed to make a diagnosis and choose the tactics of treating the patient.

In the fetus

You can hear the work of the heart at week 8, but it is possible to detect the atria and ventricles in it only closer to the twentieth. It is usually recommended to have an ultrasound to measure the fetal heart by 24 weeks of gestation. The organ itself is easily detected in the chest cavity, but the study of its structure and volume can be difficult, especially with high fetal mobility or a decrease in the amount of amniotic fluid.

With the normal development of the heart, its characteristics are:

location in the left half of the chest;
the shape of a hollow ball;
detection of four chambers, valves between them, septum, aortic arch.

Ultrasound of the fetal heart (color doppler)

Since the heart of the fetus resembles a ball, the main measurements are taken in any of the directions. The diameter at week 24 is 2.5 cm, and by birth it increases to 4.5. All these indicators are average, they depend on the weight of the child. The valves are visualized, their range of motion can be assessed.

The thickness of the heart muscle is also considered an important parameter - during contraction it is 4 mm, and in the relaxation phase - 2.9 mm. An essential feature of the fetal heart is the equal size of the ventricles.

In children and adolescents

As the child grows, the heart gradually acquires the features of an adult. Finally, this process is completed only by 11-14 years. In one-year-old children, the weight of the organ increases by 2 times compared with the parameters after childbirth, and by the age of three it is 3 times higher. By the age of 5-6, growth slows down a little, and in adolescents it accelerates again. In a 17-year-old young man or girl, the size of the myocardium is 10 times larger than in newborns.

Initially, the left ventricle increases, since it bears the main burden of pumping blood. Its dimensions in a four-month-old baby are 2 times larger than in the right one. The thickness of the myocardium from 5 mm reaches 12 (left) and 6 mm (right). The relative volume of the heart (compared to the chest) is greater in children than in adults.

The heart of boys up to 10 years is larger than that of girls, then increased development by the age of 16 allows girls to get ahead of boys, then growth slows down again.

In one year, the heart has the following average parameters (diameter in cm):

ventricular diameter - left 3.2 and right 1.4 (at maximum filling);
atrium - left 2.4 and right 1.1;
partition - 0.5.

For adolescents 15 years old, the left half of the heart normally has the following dimensions:

end diastolic diameter of the ventricle 4.3 cm, systolic - 3.5 cm;
left atrium - 3 cm;
aortic diameter - from 2 to 3 cm.

The right ventricle at the same time reaches only 1.8 cm.

In an adult

The length of the heart varies from 9 to 16 cm. Most often it is close to 12.5 cm. The base of the heart is about 10.5 cm wide, and the size from the front to the back wall is 6 - 7.5. Heart chamber parameters (cm):

diameters - left ventricle about 4.6, right 1.95, left atrium 2.9 - 3.1, right 1.9 - 2.5;
valve circles - aorta 0.8 - 0.85 and pulmonary artery 0.57 - 0.98, and atrioventricular averages are about 1 cm;
the thickness of the wall of the ventricles - right up to 0.5, and left up to 1.5.

Expert opinion

Alena Ariko

Expert in cardiology

At the same time, in well-trained athletes, the heart may be larger than normal, and in short, thin women, its size is lower. If there are no functional impairments, then such deviations can be neglected. Diagnosis is not made on the basis of echocardiographic or radiographic measurements alone. Clinical symptoms, laboratory data, are taken into account.

If they put small sizes - is it bad?

A decrease in the anatomical parameters of the chambers of the heart or the entire organ can be in the following conditions:

Malformations- a severe form of cardiac hypoplasia. The left or right ventricle may be smaller. Usually associated with other congenital anomalies. If the entire left half of the heart is underdeveloped, it rapidly progresses with a fatal outcome.
With a decrease in the right half, breathing is disturbed, cyanosis of the skin is noted, the main load falls on the left ventricle, with its weakening, stagnant processes in the internal organs increase.

Exhaustion, protein-energy starvation- occurs with prolonged and severe infections, disruption of the digestive system, endocrine system, brain damage, malignant neoplasms. Against the background of weight loss, the size of the heart decreases.
- less than the norm can only be the capacity of the chambers of the heart due to the excessive growth of the inner shell. It occurs with a genetic predisposition, diabetes, sarcoidosis, tumor processes, radiation therapy. Due to low cardiac output, circulatory failure occurs.
- compaction of the sheets of the pericardial sac during inflammation compresses the heart from the outside. After the deposition of calcium salts, a strong shell is formed - a shell-like heart. This condition disrupts the filling of the ventricles, leads to exhaustion, disruption of the liver, edema, atrophy of muscle fibers, and arrhythmias.

For children, insufficient heart size compared to age norms is one of the signs of a lag in growth and development. This happens if:

both parents or one of them is short;
There is ;
the child is diagnosed with a disease of the respiratory system;
impaired function of the liver, digestive organs;
there is a genetic anomaly;
the pituitary gland, hypothalamus, thyroid gland are affected;
has diabetes.

In elderly patients, as well as in old age, involutional processes are observed, the outcome of which may be atrophy of the heart muscle. This condition is an extreme manifestation of myocardial malnutrition (), which increases with aging of the body. Myocardial dystrophy can also accompany:

The size of the heart is determined by age, body type and the presence of diseases. A decrease occurs with congenital malformations of the structure, protein starvation, lagging behind children in growth and development. Restrictive cardiomyopathy or constrictive pericarditis can also cause such a change. In elderly patients, a possible cause is myocardial dystrophy or atrophy of the heart with sudden weight loss, metabolic disorders.

Useful video

Watch the video on how the human heart works:

The principle of the heart

The laying of the heart tissue begins in the embryonic stage of fetal development. The baby receives nutrition through the mother's placenta, but in order for its own organs to grow and develop, nutrients must be delivered to every cell of the body. Therefore, the heart is the very first functional organ that begins to grow and form in a tiny organism. By the 22nd day of pregnancy, the first heartbeat appears in the embryo, by the 26th day, its own circulation circle is formed in the growing body. At birth, a baby's heart is no larger than a strawberry.

The baby's heart becomes similar to the heart of an adult by the tenth week of development: at this point, partitions and heart valves appear in it.

After the tiny "motor" begins its responsible work, the heart rate is almost the same as in an adult: 75-80 beats per minute. By the seventh week of development, the heart "accelerates" to 165-185 beats, and when conducting a CTG study, the expectant mother hears his quick knock. At birth, the pulse "calms down" to the norm of 120-170 beats per minute.

The entire cycle of the heart muscle consists of two phases: systole and diastole. At the moment of relaxation of the heart muscle, the atria and partially the ventricles are filled with blood. Then there is a contraction of the atria and the expulsion of the liquid medium into the ventricles, while the veins are compressed into the mouths, which prevents blood from flowing into them. After that, the atria relax, the ventricles contract and blood is pushed out into the aorta through the left ventricle and into the pulmonary artery through the right. The mitral and tricuspid valves at this moment block the return of blood to the atrium. After that, the cycle repeats again and so constantly throughout a person's life.

The heart rate is set by the sympathetic nervous system. The release of adrenaline into the blood, produced by the adrenal glands, increases the strength and number of heart contractions, and the production of acetycholine has the opposite effect.

What a person hears as a heartbeat is one of the periods of contraction of the heart muscle, namely, the closing of the valves.

Listening to heart tones is performed using a stethoscope invented by the French doctor Rene Laennec (the doctor was guided by the fact that it is quite difficult to hear the heart of ladies with a magnificent bust, simply by pressing his ear to his chest). Another invention associated with the human heart is the second hand on the clock, the patent belongs to the English doctor John Flower, he introduced an innovation in order to make it convenient to read the human pulse.

The heart rate in women is more frequent than in men, with an average of 78 beats per minute. In men, it is 74-75 beats per minute. Although it is believed that the heart beats smoothly, this is not entirely true. The period when the heart works is the contraction of the heart muscle, in a relaxed state, the heart begins a period of rest.

This explains the working capacity of the human motor, nature arranged its activity so that the heart has the opportunity to rest from its hard and constant work.

It is known that not a single engine will work without fuel. Oxygen is the fuel for the heart. In order to work out for a day, the heart muscle will need 130 liters of pure oxygen, its average consumption per minute is 2.5 liters. One heartbeat is equal to the amount of energy it takes to lift an object weighing 200 grams to a height of one meter. The energy generated by a human motor in a day would be enough for a passenger car to travel 32 kilometers, and in a month the heart can produce such an amount of energy that if you use it, then a person of average weight can easily be lifted to the top of the highest mountain - Chomolungmy. In a lifetime, a person could travel to the moon and back, using the resources of his own heart!

The heart is not just an important organ in the human body, it is a symbol of love. The ancient Egyptians believed that the ring finger was connected by a special channel to the heart muscle, hence the custom of putting a wedding ring on it. A monument to the heart has been erected in Russia, it is located in the city of Perm in the courtyard of the Heart Institute. The granite giant, weighing about four tons, symbolizes the fiery red, like a steppe poppy, the human heart. The weight of the human heart determines its age, height, physical form. And yet, it is not only a muscle that starts physiological processes in the human body, it is a small and roomy place where human feelings, experiences and secrets are stored.

The size of the heart varies from person to person. Usually, the size of the heart is compared with the size of the fist of a given person (length 10-15 cm, transverse size - 9-11 cm, anteroposterior size - 6-8 cm). the wall thickness of the right atrium is slightly less than the thickness of the left atrium (2-3 mm), the right ventricle (4-6 mm), the left 9-11 mm). The mass of the heart of an adult is 0.4-0.5% of body weight, or an average of 250-350 g. The volume of the heart of adults ranges from 250 to 350 ml.

Chambers of the heart.

The human heart has 4 chambers (cavities): two atria and two ventricles (right and left). One chamber is separated from the other by partitions. The longitudinal septum of the heart has no holes, i.e. its right half does not communicate with the left. The transverse septum divides the heart into atria and ventricles. It has atrioventricular orifices, equipped with flap valves. The valve between the left atrium and ventricle is bicuspid (mitral), and between the right atrium and ventricle is tricuspid. The valves open towards the ventricles and allow blood to flow only in that direction. The pulmonary trunk and aorta at their beginning have semilunar valves, consisting of three semilunar valves and opening in the direction of blood flow in these vessels.

Wall of the heart.

The wall of the heart consists of three layers: the inner one - the endocardium, the middle, thickest one - the myocardium and the outer one - the pericardium.

1) The endocardium lines all the cavities of the heart from the inside, is tightly fused with the underlying muscle layer, covering the papillary muscles with their tendon chords (threads). Consists of connective tissue with elastic fibers and smooth muscle cells, as well as endothelium. The endocardium forms the atrioventricular valves, the valves of the aorta, the pulmonary trunk, as well as the valves of the inferior vena cava and coronary sinus.

2) Myocardium (muscle layer) is the contractile apparatus of the heart. formed by striated cardiac muscle tissue. Unlike skeletal striated muscle tissue, in cardiac muscle tissue there are jumpers between muscle fibers that unite them into a single system. In this case, the muscles of the atria are completely separated from the muscles of the ventricles with the help of the right and left fibrous rings located around the corresponding atrioventricular openings. Accumulations of fibrous tissue are also found around the openings of the pulmonary trunk, the aorta, and in the upper membranous part of the interventricular septum. Fibrous rings, together with other accumulations of fibrous tissue, make up a kind of skeleton of the heart, which serves as a support for the muscles and valvular apparatus. The muscular layer of the atria consists of two layers: superficial and deep. It is thinner than the muscular membrane of the ventricles, consisting of three layers: inner, middle and outer. In this case, the muscle fibers of the atria do not pass into the muscle fibers of the ventricles; the atria and ventricles do not contract simultaneously.

3) The epicardium is part of the fibrous-serous membrane covering the heart (pericardium). The serous pericardium consists of an internal visceral plate (epicardium), which directly covers the heart and is tightly connected with it, and an external parietal (parietal) plate, lining the fibrous pericardium from the inside and passing into the epicardium at the place where large vessels leave the heart. Fibrous pericardium at the base of the heart passes into the adventitia (outer membrane) of large vessels; pleural sacs are adjacent to the pericardium on the side, from below it fuses with the tendon center of the diaphragm, and in front it is connected by connective tissue fibers to the sternum. Between the two plates of the serous pericardium - the parietal and the epicardium, there is a slit-like space - the pericardial cavity lined with mesothelium, which contains a small amount (up to 50 ml) of serous fluid. The pericardium isolates the heart from surrounding organs, prevents the heart from overstretching, and the serous fluid between its plates reduces friction during heart contractions.

The shape of the heart is not the same in different people. It is determined by age, gender, physique, health, and other factors. In simplified models, it is described by a sphere, ellipsoids, intersection figures of an elliptical paraboloid and a triaxial ellipsoid. The measure of elongation (factor) of the shape is the ratio of the largest longitudinal and transverse linear dimensions of the heart. With a hypersthenic body type, the ratio is close to unity and asthenic - about 1.5. The length of the heart 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 the heart in men is 332 g (from 274 to 385 g), in women - 253 g (from 203 to 302 g).

In relation to the midline of the body, 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, a transverse, oblique and vertical position of the heart is distinguished. The vertical position is more common in people with a narrow and long chest, the transverse position is more common in people with a wide and short chest. The heart can independently provide venous return only in the vessels located at the moment above the top of the atria, that is, by gravity, by gravity. Performing pumping functions in the circulatory system, the heart constantly pumps blood into the arteries. Simple calculations show that within 70 years the heart of an ordinary person performs more than 2.5 billion beats and pumps 250 million liters of blood.

The structure of the heart

The heart is located on the left side of the chest in the so-called pericardial sac - pericardium, which separates the heart from other organs. The wall of the heart consists of three layers - epicardium, myocardium and endocardium. The epicardium consists of a thin (not more than 0.3-0.4 mm) plate of connective tissue, the endocardium consists of epithelial tissue, and the myocardium consists of cardiac striated muscle tissue.

The heart is made up of four separate cavities called chambers: left atrium, right atrium, left ventricle, right ventricle. They are separated by partitions. The pulmonary veins enter the right atrium, and the pulmonary veins enter the left atrium. From the right ventricle and left ventricle, respectively, the pulmonary artery (pulmonary trunk) and the ascending aorta emerge. The right ventricle and left atrium close the pulmonary circulation, the left ventricle and right atrium close the large circle. The heart is located in the lower part of the anterior mediastinum, most of its anterior surface is covered by the lungs with inflowing sections of the caval and pulmonary veins, as well as outgoing aorta and pulmonary trunk. The pericardial cavity contains a small amount of serous fluid.

The wall of the left ventricle is approximately three times thicker than the wall of the right ventricle, since the left must be strong enough to push blood into the systemic circulation for the whole body (blood resistance in the systemic circulation is several times greater, and blood pressure is several times higher than in the pulmonary circulation).

There is a need to maintain blood flow in one direction, otherwise the heart could be filled with the same blood that was previously sent to the arteries. Responsible for the flow of blood in one direction are the valves, which at the appropriate moment open and close, passing the blood or blocking it. The valve between the left atrium and the left ventricle is called the mitral valve or bicuspid valve, as it consists of two petals. The valve between the right atrium and the right ventricle is called the tricuspid valve - it consists of three petals. The heart also contains the aortic and pulmonary valves. They control the flow of blood from both ventricles.

Circulation

coronary circulation

Each cell of the heart muscle must have a secure constant supply of oxygen and nutrients. The heart's own blood circulation, that is, the coronary circulation, is responsible for this process. The name comes from 2 arteries, which, like a crown, braid the heart. The coronary arteries arise directly from the aorta. Up to 20% of the blood ejected by the heart passes through the coronary system. Only such a powerful portion of oxygen-enriched blood ensures the continuous operation of the life-giving pump of the human body.

The cycle of the heart

The work of the heart

A healthy heart contracts and unclenches rhythmically and without interruption. In one cycle of the heart, three phases are distinguished:

The blood-filled atria contract. In this case, blood is pumped through the open valves into the ventricles of the heart (at this time they remain in a state of relaxation). The contraction of the atria begins from the place where the veins flow into it, therefore their mouths are compressed and blood cannot get back into the veins.
There is a contraction of the ventricles with simultaneous relaxation of the atria. The tricuspid and bicuspid valves that separate the atria from the ventricles rise, close, and prevent blood from returning to the atria, while the aortic and pulmonic valves open. Contraction of the ventricles pumps blood into the aorta and pulmonary artery.
A pause (diastole) is a relaxation of the whole heart, or a short period of rest for this organ. During a pause, blood from the veins enters the atria and partially drains into the ventricles. When a new cycle begins, the remaining blood in the atria will be pushed into the ventricles - the cycle will repeat.

One cycle of the heart lasts about 0.85 seconds, of which only 0.11 seconds fall on the time of atrial contraction, 0.32 seconds on the time of ventricular contraction, and the longest is the rest period, lasting 0.4 seconds. The heart of an adult at rest works in the system at about 70 cycles per minute.

Automatic heart

A certain part of the heart muscle is specialized in issuing control signals to the rest of the heart in the form of appropriate electrical impulses. These parts of the muscle tissue are called the excitatory-conducting system. Its main part is the sinoatrial node, called the pacemaker, placed on the fornix of the right atrium. It controls the heart rate by sending out regular electrical impulses. The electrical impulse through the paths in the atrial muscle enters the atriogastric node. The excited node sends an impulse further, to individual muscle cells, causing them to contract. The excitatory-conduction system ensures the rhythmic work of the heart with the help of synchronized contraction of the atria and ventricles.

Regulation of the heart

The work of the heart is regulated by the nervous and endocrine systems, as well as Ca and K ions, which are contained in the blood. The work of the nervous system on the heart is to regulate the frequency and strength of heart contractions (the sympathetic nervous system causes an increase in contractions, the parasympathetic one weakens). The work of the endocrine system on the heart is to release hormones that increase or decrease heart contractions. The main gland for secreting hormones that regulate the functioning of the heart are the adrenal glands. They secrete the hormones adrenaline and acetylcholine, whose functions in relation to the heart correspond to those of the sympathetic and parasympathetic systems. The same work is performed by Ca and K ions, respectively.

Electrical and acoustic phenomena

When the heart (like any muscle) works, electrical phenomena occur that cause the appearance of an electromagnetic field around the working organ. The electrical activity of the heart can be recorded using special electrodes applied to certain parts of the body. With the help of an electrocardiograph, an electrocardiogram (ECG) is obtained - a picture of changes over time in the potential difference on the surface of the body. ECG plays an important role in the diagnosis of heart attack and other diseases of the cardiovascular system.

Acoustic phenomena called heart sounds can be heard by placing an ear or a stethoscope against the chest. Each cardiac cycle is normally divided into 4 tones. With each contraction, the first 2 are heard with the ear. A longer and lower one is associated with the closure of the bi- and tricuspid valves, a shorter and higher one is associated with the closing of the aortic and pulmonary artery valves. Between one and the second tone there is a phase of contraction of the ventricles.

Notes

Links

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See what the "Heart of a Man" is in other dictionaries:

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