The human heart is made up of The complex structure of the heart is the key to its effective work. Location and size of the heart

The anatomy of the heart is a very important and interesting section of the science of structure. human body. Thanks to this organ, blood flows through our vessels and, as a result, the life of the whole organism is supported. In addition, it is difficult to imagine a more famous organ, which is not only talked about at work and at home, at a doctor's appointment and on a walk in the park, but also written in stories, sung in poetry, and mentioned in songs.

Perhaps everyone is familiar with the location of the heart in a person, and since childhood. This is dictated by increased attention to the organ from various points of view, not necessarily only from the medical side. It would seem that stop any passerby and ask a question about the location of the main organ of love, which is often called the heart, and he will immediately give an answer. But in reality, not everything is so simple. Most people will say only one phrase: "in the chest." And formally they will be right. However, they have no idea where exactly the heart is.

Location of the heart in the chest

As anatomy says, the place where the heart is located is really located in chest cavity, and so that most of this organ is localized on the left, and the smaller one is on the right. Those. its location can be called asymmetric in relation to the general space of the chest.

It is worth noting here that in the global sense, a whole complex of organs is allocated in the chest cavity, located, as it were, between the lungs, called the mediastinum. The heart with large vessels almost completely occupies it middle part, taking in neighbors the trachea, lymph nodes and main bronchi.

Thus, the location of the heart is not just the chest cavity, but the mediastinum. In this case, it is necessary to know that two floors are distinguished in the mediastinum: upper and lower. In the lower mediastinum, in turn, there are anterior, middle and posterior sections. This division has different purposes, for example, it is very convenient when planning an operation or radiotherapy, and also helps in describing the localization pathological process and location of organs. Based on this, we can say that the location of the heart in the chest falls on the middle mediastinum.

From the sides to this body adjoining lungs. They also partially cover its front surface, which is called the sternocostal, and with which the organ is adjacent to the anterior wall of the chest cavity. bottom surface in contact with the diaphragm, and therefore has the name diaphragmatic.

To form a clear idea of where the human heart is, see the photo below:

On it you can observe the organ in question in all its glory. Of course, in reality, everything does not look as colorful as in the picture, but for a general understanding, perhaps nothing better can be found.

The shape and size of the human heart

In addition to the location of the heart, anatomy also describes its shape and size. It is a cone-shaped organ that has a base and an apex. The base is turned up, backwards and to the right, and the top is down, in front and to the left.

As for the size, we can say that in humans this organ is comparable to a hand clenched into a fist. In other words, the size of a healthy heart and the size of the entire body of a particular person correlate with each other.

In adults average length body, usually within 10-15 cm (most often 12-13). The width at the base is from 8 to 11, and mostly 9-10 cm. At the same time, the anteroposterior size is 6-8 cm (most often about 7 cm). The average weight of an organ reaches 300 g in men. In women, the heart is slightly lighter - an average of 250 g.

Anatomy of the heart: membranes of the heart wall

In addition to knowing where the human heart is located, it is also necessary to have an idea about the structure of this organ. Since it belongs to the hollow, walls and a cavity divided into chambers are distinguished in it. A person has 4 of them: 2 ventricles and atria (left and right, respectively).

The heart wall is formed by three membranes. The inner one is formed by flat cells and looks like thin film. Its name is endocardium.

The thickest middle layer is called the myocardium or cardiac muscle. This shell of the heart has the most interesting anatomy. In the ventricles, it consists of 3 layers, of which 2 are longitudinal (inner and outer) and 1 is circular (middle). In the atria, the heart muscle is two-layered: longitudinal internal and circular external. This fact determines the greater thickness of the wall of the ventricles compared to the atria. It should be noted that the wall of the left ventricle is much thicker than that of the right one. This anatomy of the human heart is explained by the need for more effort to push blood into big circle blood flow.

The outer shell is known as the epicardium, which is at the level of large carrying blood vessels passes into the so-called pericardial sac, known as the pericardium. Between the peri- and epicardium is the cavity of the pericardial sac.

Anatomy of the heart: vessels and valves

In the photo where the heart is located, its vessels are also clearly visible. Some pass through special grooves on the surface of the organ, others come out of the heart itself, and others enter it.

On the anterior, as well as on the lower ventricular surface, there are longitudinal interventricular grooves. There are two of them: front and back. They go towards the top. And between the upper (atria) and lower (ventricles) chambers of the organ is the so-called coronal sulcus. In these furrows are located the branches of the right and left coronary arteries that feed blood directly to the organ in question.

Except coronary vessels the anatomy of the heart also distinguishes large arterial and venous trunks entering and leaving this organ.

In particular vena cava(among which there are upper and lower), entering into right atrium; pulmonary trunk, emerging from the right ventricle and carrying venous blood to the lungs; pulmonary veins, bringing blood from the lungs to the left atrium; and finally, the aorta, with the exit of which a large circle of blood flow begins from the left ventricle.

Another one interesting topic, which illuminates the anatomy of the heart - valves, the place of attachment of which is the so-called skeleton of the heart, represented by two fibrous rings located between the upper and lower chambers.

There are 4 such valves in total. One of them is called tricuspid or right atrioventricular. It prevents the backflow of blood from the right ventricle.

Another valve covers the opening of the pulmonary trunk, preventing blood from flowing back from this vessel into the ventricle.

The third - the left atrioventricular valve - has only two leaflets and is therefore called bicuspid. Its other name is the mitral valve. It serves as a barrier against the flow of blood from the left atrium into the left ventricle.

The fourth valve is located at the exit site of the aorta. Its task is to prevent blood from flowing back into the heart.

conduction system of the heart

Studying the structure of the heart, anatomy does not ignore the structures that provide one of the main functions of this organ. The so-called conduction system is distinguished in it, which contributes to the reduction of its muscle layer, i.e. essentially creating a heartbeat.

The main components of this system are the sinoatrial and atrioventricular nodes, the atrioventricular bundle with its legs, as well as with the branches extending from these legs.

The sinoatrial node is called the pacemaker, because it is in it that an impulse is generated that gives the command to contract the heart muscle. It is located near the place where the superior vena cava passes into the right atrium.

Localization of the atrioventricular node in the lower part of the interatrial septum. Next comes the bundle, which is divided into right and left legs, giving rise to numerous branches going to different parts organ.

The presence of all these structures provides such physiological features of the heart as:

rhythmic generation of impulses;
coordination of atrial and ventricular contractions;
synchronous involvement in the contractile process of all cells of the muscular layer of the ventricles (which leads to an increase in the efficiency of contractions).

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The heart is a hollow, muscular organ shaped like a cone. The heart is located in the chest, behind the sternum. The extended part of it - the base - is turned up, back and to the right, and the narrow top is down, forward, to the left. Two-thirds of the heart is in the left half of the chest, one-third lies in its right half.

The structure of the human heart

The walls of the heart have three layers:

The outer layer covering the surface of the heart is represented by serous cells and is called epicardium;
the middle layer is formed by a special striated muscle tissue. The contraction of the heart muscle, although it is striated, occurs involuntarily. The thickness of the muscular wall of the atria is less pronounced than that of the muscular wall of the ventricles. middle layer called myocardium;
inner layer - endocardium- represented by endothelial cells. It lines the chambers of the heart from the inside and forms the heart valves.

The heart is located in the pericardial sac pericardium, which secretes a fluid that reduces the friction of the heart during contractions.

The heart is divided by a continuous longitudinal septum into two halves that do not communicate with each other - the right and left (heart chambers):

In the upper part of both halves are the right and left atria;
in the lower part - the right and left ventricles.

Thus, The human heart has four chambers.

human heart chambers

Due to the greater development of the myocardium (large load), the walls of the left ventricle are much thicker than the walls of the right one.

The right atrium receives blood from all parts of the body through the superior and inferior vena cava. The pulmonary trunk emerges from the right ventricle, deoxygenated blood enters the lungs.

Four pulmonary veins flow into the left atrium, carrying arterial blood from the lungs. The aorta emerges from the left ventricle, carrying arterial blood to the systemic circulation.

In its right half is venous blood;
in the left - arterial.

Heart valves

The atria and ventricles communicate with each other through atrioventricular orifices equipped with cuspid valves.

Between the right atrium and the right ventricle, the valve has three leaflets ( tricuspid) - tricuspid valve.
between the left atrium and left ventricle - two valves ( double leaf) - mitral valve.

Tendon filaments are attached to the free edges of the valves facing the ventricle. At their other end, they are attached to the wall of the ventricle. This does not allow them to turn out towards the atria and does not allow the reverse flow of blood from the ventricles to the atria.

In the aorta, on its border with the left ventricle and in the pulmonary trunk, on its border with the right ventricle, there are valves in the form of three pockets that open in the direction of blood flow in these vessels. Because of their shape, the valves are called semilunar. With a decrease in pressure in the ventricles, they fill with blood, their edges close, closing the lumen of the aorta and pulmonary trunk, and prevent the back penetration of blood into the heart.

In the process of cardiac activity, the heart muscle performs a huge job. Therefore, it needs a constant supply of nutrients, oxygen and the removal of decay products. The heart receives arterial blood from two arteries - the right and left, which start from the aorta under the leaflets of the semilunar valves. Located on the border between the atria and ventricles in the form of a crown, or wreath, these arteries are called coronary (coronary). From the heart muscle, blood is collected in the heart's own veins, which flow into the right atrium.

The reason for the movement of blood through the blood vessels is the pressure difference in the arteries and veins. This pressure difference is created and maintained by the rhythmic contractions of the heart. The human heart, at rest, makes about 70 rhythmic contractions per minute, pumping about 5 liters of blood. For 70 years of a person's life, his heart pumps about 150 thousand tons of blood - an amazing performance for an organ weighing 300 g! The reason for this performance is the rhythmic nature of heart contractions.

The cycle of cardiac activity consists of three phases: atrial contraction, ventricular contraction, and a general pause. The first phase lasts 0.1s, the second - 0.3 and the third - 0.4s. During a general pause, both the atria and the ventricles are relaxed.

During cardiac cycle the atria contract 0.1s and 0.7s are in a relaxed state; the ventricles contract for 0.3s and rest for 0.5s. This explains the ability of the heart muscle to work without fatigue throughout life.

Automatic heart

Unlike striated skeletal muscles fibers of the heart muscle are interconnected by processes, and therefore excitation from one part of the heart can spread to other muscle fibers.

Heart contractions are involuntary. A person cannot increase or change the heart rate. At the same time, the heart is automatic. This means that the impulses leading to contraction arise in him, while to skeletal muscles they come along centrifugal fibers from the central nervous system.

The frog's heart, placed in a solution that replaces blood, continues to contract rhythmically for a long time. The cause of the automatism of the heart was not fully elucidated. However, electrophysiological studies have shown that in the cells of the conducting system of the heart, changes in the potential of the cell membrane occur rhythmically, causing the appearance of excitation, which causes contraction of the heart muscle.

Nervous and humoral regulation of the activity of the human heart

The frequency and strength of heart contractions in the body are regulated by the nervous and endocrine systems. The heart is innervated by the vagus and sympathetic nerves. The vagus nerve slows down the frequency of contractions and reduces their strength. Sympathetic nerves, on the contrary, increase the frequency and strength of contractions.

Cardiac activity is influenced by certain substances secreted by various organs into the blood. Adrenal hormone - adrenaline sympathetic nerves, increases the frequency and strength of heart contractions. Therefore, neuro humoral regulation ensures the adaptation of the activity of the heart, and consequently, the intensity of blood circulation to the needs of the body and environmental conditions.

Pulse and its definition

At the moment of contractions of the heart, blood is ejected into the aorta and the pressure in the latter rises. Wave high blood pressure spreads through the arteries to the capillaries, causing wave-like vibrations of the walls of the arteries. These rhythmic oscillations of the wall of arterial vessels caused by the work of the heart are called the pulse.

The pulse can be easily felt on the arteries lying on the bone (radial, temporal, etc.); most often - on the radial artery. From the pulse, you can determine the frequency and strength of heart contractions, which in some cases can serve as diagnostic sign. In a healthy person, the pulse is rhythmic. In diseases of the heart, rhythm disturbances - arrhythmia - can be observed.

Despite the fact that the heart makes up only half a percent of the total body weight, it is the most important of the organs of the human body. It is the normal functioning of the heart muscle that makes possible the full work of all organs and systems. complex structure The heart is best suited for the distribution of arterial and venous blood flows. From the point of view of medicine, it is cardiac pathologies that occupy the first place among human diseases.

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Location

The heart is located in the chest cavity. In front of him is the sternum. The organ is displaced slightly to the left in relation to the sternum. It is located at the level of the sixth and eighth thoracic vertebrae.

On all sides, the heart is surrounded by a special serous membrane. This membrane is called the pericardium. It forms its own cavity called the pericardial. Being in this cavity makes it easier for the organ to slide in relation to other tissues and organs.

Position Options

From the point of view of radiological criteria, the following options for the position of the heart muscle are distinguished:

The most common is oblique.
As if suspended, with a shift of the left border to the median line - vertical.
Spread on the underlying diaphragm - horizontal.

Options for the position of the heart muscle depend on the morphological constitution of a person. In an asthenic, it is vertical. In a normosthenic, the heart is oblique, and in a hypersthenic, it is horizontal.

Structure and form

The heart muscle is cone shaped. The base of the organ is expanded and turned backwards and upwards. Suitable for the base of the organ main vessels. The structure and functions of the heart are inextricably linked.

The following surfaces are distinguished in the heart muscle:

anterior, facing the sternum;
lower, deployed to the diaphragm;
lateral, facing the lungs.

Furrows are visualized on the heart muscle, reflecting the location of its internal cavities:

Coronal furrow. It is located at the base of the heart muscle and is located on the border of the ventricles and atria.
Interventricular grooves. They go along the anterior and posterior surfaces of the organ, along the border between the ventricles.

Heart valves and chambers

The human heart muscle has four chambers. The transverse partition divides it into two cavities. Each cavity is divided into two chambers.

One chamber is atrial and the other is ventricular. Venous blood circulates in the left side of the heart muscle, and arterial blood circulates in the right side.

The right atrium is a muscular cavity into which the superior and inferior vena cava open. In the upper part of the atria, a protrusion is distinguished - the ear. The inner walls of the atrium are smooth, except for the surface of the protrusion. On the site of the transverse septum, which separates the atrial cavity from the ventricle, there is an oval fossa. It is completely closed. In the intrauterine period, a window opened in its place, through which a mixture of venous and arterial blood took place. In the lower part of the right atrium is the atrioventricular opening through which venous blood enters the right ventricle from the right atrium.

Blood enters the right ventricle from the right atrium at the time of its contraction and relaxation of the ventricle. At the moment of contraction of the left ventricle, blood is pushed into the pulmonary trunk.

The atrioventricular orifice is closed by a valve of the same name. This valve also has another name - tricuspid. The three leaflets of the valve are folds of the inner surface of the ventricle. Special muscles are attached to the valves, which prevent them from eversion into the atrial cavity at the time of contraction of the ventricles. On the inner surface of the ventricle is a large number of transverse muscle lines.

The opening of the pulmonary trunk is blocked by a special semilunar valve. When closed, it prevents the reverse flow of blood from the pulmonary trunk at the moment of relaxation of the ventricles.

Blood enters the left atrium through four pulmonary veins. It has a protrusion - an ear. The comb muscles are well developed in the ear. Blood from the left atrium enters the left ventricle through the left atrioventricular orifice.

The left ventricle has thicker walls than the right. On the inner surface of the ventricle, developed muscle crossbars and two papillary muscles are clearly visible. These muscles are attached to the bicuspid left atrioventricular valve with the help of elastic tendon filaments. They prevent eversion of the valve leaflets into the cavity of the left atrium at the time of contraction of the left ventricle.

The aorta originates from the left ventricle. The aorta is closed by the tricuspid semilunar valve. The valves prevent the return of blood from the aorta to the left ventricle when it relaxes.

Support system

In relation to other organs, the heart is in a certain position with the help of the following fixation formations:

large blood vessels;
ring-shaped accumulations of fibrous tissue;
fibrous triangles.

The wall of the heart muscle consists of three layers: inner, middle and outer:

1. The inner layer (endocardium) consists of a connective tissue plate and covers the entire inner surface of the heart. Tendon muscles and filaments attached to the endocardium form the heart valves. Beneath the endocardium is an additional basement membrane.
2. The middle layer (myocardium) consists of striated muscle fibers. Each muscle fiber is a cluster of cells - cardiomyocytes. Visually, dark stripes are visible between the fibers, which are inserts that play an important role in the transfer of electrical excitation between cardiomyocytes. Outside, muscle fibers are surrounded by connective tissue, which contains nerves and blood vessels that provide trophic function.
3. The outer layer (epicardium) is a serous sheet, tightly fused with the myocardium.

Conducting system

In the heart muscle there is a special conducting system of the organ. It is involved in the direct regulation of rhythmic contractions of muscle fibers and intercellular coordination. The cells of the conduction system of the heart muscle, myocytes, have a special structure and rich innervation.

The conduction system of the heart consists of a cluster of nodes and bundles organized in a special way. This system is localized under the endocardium. In the right atrium is the sinoatrial node, which is the main generator of cardiac excitation.

From this node, the interatrial bundle departs, which is involved in synchronous atrial contraction. Also, three bundles of conductive fibers depart from the sinoatrial node to the atrioventricular node, located in the region of the coronary sulcus. Large branches of the conducting system break up into smaller ones and then into the smallest ones, forming a single conducting network of the heart.

This system ensures the synchronous work of the myocardium and the coordinated work of all departments of the organ.

The pericardium is a membrane that forms a pericardial sac around the heart. This shell reliably separates the heart muscle from other organs. The pericardium consists of two layers. Dense fibrous and thin serous.

The serous layer consists of two sheets. A space is formed between the sheets, filled serous fluid. This circumstance allows the heart muscle to slide comfortably during contractions.

Physiology

Automatism is the main functional quality of the heart muscle to contract under the influence of impulses that are generated in it. The automatism of cardiac cells is directly related to the properties of the membrane of cardiomyocytes. The cell membrane is semi-permeable to sodium and potassium ions, which form an electric potential on its surface. The rapid movement of ions creates conditions for increasing the excitability of the heart muscle. At the moment of reaching electrochemical equilibrium, the heart muscle is unexcitable.

The energy supply of the myocardium occurs due to the formation of energy substrates ATP and ADP in the mitochondria of muscle fibers. For the full-fledged work of the myocardium, adequate blood supply is necessary, which is provided by the coronary arteries extending from the aortic arch. The activity of the heart muscle is directly related to the work of the central nervous system and the system of cardiac reflexes. Reflexes play a regulatory role, ensuring the optimal functioning of the heart in constantly changing conditions.

Features of nervous regulation:

adaptive and triggering effect on the work of the heart muscle;
balancing metabolic processes in the heart muscle
humoral regulation of organ activity.

General Functions

The functions of the heart are:

It is able to exert pressure on the blood flow and saturate organs and tissues with oxygen.
It can remove carbon dioxide and waste products from the body.
Each cardiomyocyte is capable of being excited under the influence of impulses.
The cardiac muscle is able to conduct an impulse between cardiomyocytes along a special conduction system.
After excitation, the heart muscle is able to contract with the atria or ventricles, pumping blood.

The heart is one of the most perfect organs of the human body. It has a set of amazing qualities: power, tirelessness and the ability to adapt to constantly changing conditions. environment. Thanks to the work of the heart, oxygen and nutrients enter all tissues and organs. It provides continuous blood flow throughout the body. Human body is a complex and coordinated system, where the heart is the main driving force.

Ensuring the movement of blood through the vessels.

Anatomy

Rice. 1-3. Human heart. Rice. 1. Opened heart. Rice. 2. Conducting system of the heart. Rice. 3. Vessels of the heart: 1-superior vena cava; 2-aorta; 3-left atrium; 4-aortic valve; 5-bivalve valve; 6-left ventricle; 7 - papillary muscles; 8 - interventricular septum; 9-right ventricle; 10-leaflet valve; 11 - right atrium; 12 - inferior vena cava; 13-sinus node; 14-atrioventricular node; 15-trunk of the atrioventricular bundle; 16-right and left leg of the atrioventricular bundle; 17-right coronary artery; 18-left coronary artery; 19-great vein of the heart.

The human heart is a four-chambered muscular sac. It is located in the anterior, mainly in the left half of the chest. back surface the heart is adjacent to the diaphragm. On all sides it is surrounded by lungs, with the exception of the part of the anterior surface directly adjacent to chest wall. In adults, the length of the heart is 12-15 cm, transverse dimension 8-11 cm, anterior-posterior size 5-8 cm. The weight of the heart is 270-320 g. The walls of the heart are formed mainly by muscle tissue - the myocardium. Inner surface The heart is lined with a thin membrane called the endocardium. The outer surface of the heart is covered with a serous membrane - the epicardium. Last on the level large vessels, departing from the heart, wraps outwards and down and forms a pericardial sac (pericardium). The expanded posterior-upper part of the heart is called the base, the narrow anterior-lower part is called the apex. The heart consists of two atria at the top and two ventricles at the bottom. The longitudinal septum divides the heart into two halves that do not communicate with each other - the right and left, each of which consists of an atrium and a ventricle (Fig. 1). The right atrium is connected to the right ventricle, and the left atrium is connected to the left ventricle by the atrioventricular orifices (right and left). Each atrium has a hollow process called an auricle. The superior and inferior vena cava, which carry venous blood from the systemic circulation, and the veins of the heart flow into the right atrium. The pulmonary trunk leaves the right ventricle, through which venous blood enters the lungs. Four pulmonary veins flow into the left atrium, carrying oxygenated arterial blood from the lungs. The aorta emerges from the left ventricle, through which arterial blood is directed to the systemic circulation. The heart has four valves that control the direction of blood flow. Two of them are located between the atria and ventricles, covering the atrioventricular openings. The valve between the right atrium and the right ventricle consists of three cusps (tricuspid valve), between the left atrium and the left ventricle - of two cusps (bicuspid, or mitral valve). The cusps of these valves are formed by a duplication inner shell hearts and are attached to the fibrous ring, limiting each atrioventricular opening. Tendon threads are attached to the free edge of the valves, connecting them with the papillary muscles located in the ventricles. The latter prevent the "inversion" of the valve leaflets into the atrial cavity at the time of contraction of the ventricles. The other two valves are located at the entrance to the aorta and pulmonary trunk. Each of them consists of three semilunar dampers. These valves, closing during relaxation of the ventricles, prevent the reverse flow of blood into the ventricles from the aorta and pulmonary trunk. The department of the right ventricle, from which the pulmonary trunk begins, and the left ventricle, where the aorta originates, is called the arterial cone. The thickness of the muscle layer in the left ventricle is 10-15 mm, in the right ventricle - 5-8 mm, and in the atria - 2-3 mm.

In the myocardium there is a complex of special muscle fibers that make up the conduction system of the heart (Fig. 2). In the wall of the right atrium, near the mouth of the superior vena cava, there is a sinus node (Kiss-Fleck). Part of the fibers of this node in the region of the base of the tricuspid valve forms another node - atrioventricular (Ashoff - Tavar). From it begins the atrioventricular bundle of His, which in the interventricular septum is divided into two legs - right and left, going to the corresponding ventricles and ending under the endocardium with individual fibers (Purkinje fibers).

The blood supply to the heart occurs through the coronary (coronary) arteries, right and left, which depart from the aortic bulb (Fig. 3). The right coronary artery supplies blood primarily to back wall hearts, back interventricular septum, right ventricle and atrium and partially left ventricle. The left coronary artery supplies the left ventricle, the anterior part of the interventricular septum, and the left atrium. The branches of the left and right coronary arteries, breaking up into tiny branches, form a capillary network.

Venous blood from the capillaries through the veins of the heart enters the right atrium.

The innervation of the heart is carried out by branches vagus nerve and branches of the sympathetic trunk.

Rice. 1. Section of the heart through the atria and ventricles (front view). Rice. 2. Arteries of the heart and coronary sinus (atria, pulmonary trunk and aorta removed, top view). Rice. 3. Cross sections of the heart. I - upper surface of the atria; II - the cavity of the right and left atria, the openings of the aorta and the pulmonary trunk; III - incision at the level of atrioventricular openings; IV, V and VI - sections of the right and left ventricles; VII - region of the apex of the heart. 1 - atrium sin.; 2-v. pulmonalis sin.; 3 - valva atrioventricularis sin.; 4 - ventriculus sin.; 5 - apex cordis; 6 - septum interventriculare (pars muscularis); 7 - m. papillaris; 8 - ventriculus dext.; 9 - valva atrioventricularis dext.; 10 - septum interventriculare (pars membranacea); 11 - valvula sinus coronarii; 12-mm. pectinati; 13-v. cava inf.; 14 - atrium dext.; 15 - fossa ovalis; 16 - septum interatriale; 17-vv. pulmonales dext.; 18 - truncus pulmonalis; 19 - auricula atrii sin.; 20 - aorta; 21 - auricula atrii dext.; 22-v. cava sup.; 23 - trabecula septomarginal; 24 - trabeculae carneae; 25 - chordae tendineae; 26 - sinus coronarius; 27 - cuspis ventralis; 28 - cuspis dorsalis; 29 - cuspis septalis; 30 - cuspis post.; 31-cuspis ant.; 32-a. coronaria sin.; 33-a. coronaria dext.

The heart is a muscular organ in humans and animals that pumps blood through the blood vessels.

Functions of the heart - why do we need a heart?

Our blood provides the whole body with oxygen and nutrients. In addition, it also has a cleansing function, helping to remove metabolic waste.

The function of the heart is to pump blood through the blood vessels.

How much blood does the human heart pump?

The human heart pumps between 7,000 and 10,000 liters of blood in one day. This is approximately 3 million liters per year. It turns out up to 200 million liters in a lifetime!

The amount of pumped blood per minute depends on the current physical and emotional load - the greater the load, the more blood the body needs. So the heart can carry through itself from 5 to 30 liters in one minute.

The circulatory system consists of about 65 thousand vessels, their total length is about 100 thousand kilometers! Yes, we are not sealed.

circulatory system

The human cardiovascular system is formed by two circles of blood circulation. At every heart contraction there is a movement of blood at once in both circles.

Small circle of blood circulation

Deoxygenated blood from the superior and inferior vena cava enters the right atrium and then into the right ventricle.
From the right ventricle, blood is pushed into the pulmonary trunk. The pulmonary arteries carry blood directly to the lungs (to the pulmonary capillaries), where it receives oxygen and releases carbon dioxide.
Having received enough oxygen, the blood returns to the left atrium of the heart through the pulmonary veins.

Systemic circulation

From the left atrium, blood moves into the left ventricle, from where it is subsequently pumped out through the aorta into the systemic circulation.
Having passed a difficult path, the blood through the vena cava again arrives in the right atrium of the heart.

Normally, the amount of blood ejected from the ventricles of the heart is the same with each contraction. Thus, an equal volume of blood simultaneously enters the large and small circles of blood circulation.

What is the difference between veins and arteries?

Veins are designed to transport blood to the heart, while the task of arteries is to supply blood in the opposite direction.
In veins, blood pressure is lower than in arteries. Accordingly, the walls of the arteries are more extensible and denser.
Arteries saturate "fresh" tissue, and veins take "waste" blood.
In case of vascular damage, arterial or venous bleeding can be distinguished by its intensity and color of the blood. Arterial - strong, pulsating, beating with a "fountain", the color of the blood is bright. Venous - bleeding of constant intensity (continuous flow), the color of the blood is dark.

The weight of the human heart is only about 300 grams (on average 250g for women and 330g for men). Despite the relatively low weight, it is undoubtedly the main muscle in the human body and the basis of its life activity. The size of a heart is indeed approximately equal to a human fist. In athletes, the heart can be one and a half times larger than in an ordinary person.

Anatomical structure

The heart is located in the middle of the chest at the level of 5-8 vertebrae.

Normally, the lower part of the heart is located mostly in the left side of the chest. There is a variant of congenital pathology in which all organs are mirrored. It's called transposition. internal organs. The lung, next to which the heart is located (normally the left one), has a smaller size relative to the other half.

The posterior surface of the heart is located near spinal column, and the front is securely protected by the sternum and ribs.

The human heart consists of four independent cavities (chambers) divided by partitions:

the top two - the left and right atria;
and two lower - left and right ventricles.

The right side of the heart includes the right atrium and ventricle. The left half of the heart is represented by the left ventricle and atrium, respectively.

The inferior and superior vena cava enter the right atrium, and the pulmonary veins enter the left atrium. From right ventricle the pulmonary arteries (also called the pulmonary trunk) exit. From left ventricle the ascending aorta rises.

The heart has protection from overstretching and other organs, which is called the pericardium or the pericardial sac (a kind of shell where the organ is enclosed). Has two layers: outer dense durable connective tissue, bearing the name fibrous membrane of the pericardium and internal ( serous pericardium).

Thus, the heart itself consists of three layers: epicardium, myocardium, endocardium. It is the contraction of the myocardium that pumps blood through the vessels of the body.

The walls of the left ventricle are about three times larger than the walls of the right! Explained given fact the fact that the function of the left ventricle is to push blood into the systemic circulation, where the resistance and pressure are much higher than in the small one.

Heart valve device

Special heart valves keep blood flowing in the correct (unidirectional) direction at all times. The valves alternately open and close, then passing the blood, then blocking its path. Interestingly, all four valves are located along the same plane.

Between the right atrium and the right ventricle is tricuspid (tricuspid) valve. It contains three special sash plates that can, during right ventricular contraction, protect against backflow (regurgitation) of blood into the atrium.

Works in a similar way mitral valve, only it is located on the left side of the heart and is bicuspid in structure.

aortic valve prevents backflow of blood from the aorta into the left ventricle. Interestingly, when the left ventricle contracts, the aortic valve opens as a result of blood pressure on it, as it moves into the aorta. Then, during diastole (the period of relaxation of the heart), the reverse flow of blood from the artery contributes to the closure of the valves.

Normally, the aortic valve has three leaflets. The most common congenital anomaly heart - bicuspid aortic valve. This pathology occurs in 2% of the human population.

Pulmonary (pulmonary) valve at the moment of contraction of the right ventricle, it allows blood to flow into the pulmonary trunk, and during diastole it does not allow it to flow in the opposite direction. Also consists of three wings.

Vessels of the heart and coronary circulation

The human heart needs food and oxygen, just like any other organ. Vessels that supply the heart with blood are called coronary or coronary. These vessels branch off from the base of the aorta.

The coronary arteries supply the heart with blood, while the coronary veins carry deoxygenated blood. Those arteries that are on the surface of the heart are called epicardial. Subendocardial are called coronary arteries hidden deep in the myocardium.

Most of the outflow of blood from the myocardium occurs through three cardiac veins: large, medium and small. Forming the coronary sinus, they flow into the right atrium. The anterior and small veins of the heart deliver blood directly to the right atrium.

Coronary arteries are divided into two types - right and left. The latter consists of the anterior interventricular and circumflex arteries. The great cardiac vein branches into the posterior, middle and small veins of the heart.

Even absolutely healthy people have their own unique features coronary circulation. In reality, the vessels may look and be located differently than shown in the picture.

How does the heart develop (form)?

Pulse path

This system ensures the automatism of the heart - the excitation of impulses that are born in cardiomyocytes without an external stimulus. In a healthy heart, the main source of impulses is the sinoatrial (sinus) node. He is the leader and blocks the impulses from all other pacemakers. But if there is any disease leading to weakness syndrome sinus node, then other parts of the heart take over its function. So the atrioventricular node (automatic center of the second order) and the His bundle (AC of the third order) are able to activate when the sinus node is weak. There are cases when secondary nodes increase their own automatism and normal operation sinus node.

sinus node located in the upper posterior wall of the right atrium in close proximity to the mouth of the superior vena cava. This node initiates pulses at a frequency of approximately 80-100 times per minute.

Atrioventricular node (AV) located in the lower part of the right atrium in the atrioventricular septum. This septum prevents the impulse from propagating directly into the ventricles, bypassing the AV node. If the sinus node is weakened, then the atrioventricular node will take over its function and begin to transmit impulses to the heart muscle at a frequency of 40-60 contractions per minute.

Then the atrioventricular node passes into bundle of His(atrioventricular bundle subdivided into two legs). Right leg rushes to the right ventricle. The left leg is further divided into two halves.

The situation with the left leg of the bundle of His has not been fully studied. It is believed that the left leg with the fibers of the anterior branch rushes to the anterior and lateral wall of the left ventricle, and the posterior branch supplies fibers to the posterior wall of the left ventricle, and the lower parts of the lateral wall.

In case of weakness of the sinus node and blockade of the atrioventricular node, the His bundle is able to create impulses at a speed of 30-40 per minute.

The conducting system deepens and further branching into more small branches eventually turning into Purkinje fibers, which permeate the entire myocardium and serve as a transmission mechanism for contraction of the muscles of the ventricles. Purkinje fibers are capable of initiating impulses at a frequency of 15-20 per minute.

Exceptionally trained athletes can have a normal resting heart rate down to the lowest recorded figure - as little as 28 heart beats per minute! However, for the average person, even if they lead a very active lifestyle, a heart rate below 50 beats per minute can be a sign of bradycardia. If you have such a low heart rate, then you should be examined by a cardiologist.

Heartbeat

The heart rate of a newborn can be about 120 beats per minute. With growing up, the pulse ordinary person stabilizes in the range of 60 to 100 beats per minute. Well-trained athletes (we are talking about people with well-trained cardiovascular and respiratory systems) have a pulse of 40 to 100 beats per minute.

The rhythm of the heart is controlled by the nervous system - the sympathetic strengthens contractions, and the parasympathetic weakens.

Cardiac activity, to a certain extent, depends on the content of calcium and potassium ions in the blood. Other biologically active substances also contribute to the regulation of the heart rhythm. Our heart can start to beat faster under the influence of endorphins and hormones released when listening to our favorite music or kissing.

Besides, endocrine system can have a significant impact on the heart rate - and the frequency of contractions and their strength. For example, the secretion of the adrenaline by the well-known adrenaline causes an increase in heart rate. The opposite hormone is acetylcholine.

Heart tones

One of the most simple methods diagnosing heart disease is listening to the chest with a stethophonendoscope (auscultation).

In a healthy heart, only two heart sounds are heard during standard auscultation - they are called S1 and S2:

S1 - the sound heard when the atrioventricular (mitral and tricuspid) valves close during systole (contraction) of the ventricles.
S2 - the sound heard when the semilunar (aortic and pulmonary) valves close during diastole (relaxation) of the ventricles.

Each sound consists of two components, but for the human ear they merge into one due to the very small time interval between them. If in normal conditions auscultation, additional tones become audible, then this may indicate any disease of the cardiovascular system.

Sometimes additional abnormal sounds, called heart murmurs, may be heard in the heart. As a rule, the presence of noise indicates any pathology of the heart. For example, noise can cause blood to flow backwards (regurgitation) due to wrong work or damage to any valve. However, noise is not always a symptom of the disease. To clarify the reasons for the appearance of additional sounds in the heart, it is worth doing an echocardiography (ultrasound of the heart).

Heart disease

Not surprisingly, the number of cardiovascular disease. The heart is a complex organ that actually rests (if it can be called rest) only between heartbeats. Any complex and constantly working mechanism in itself requires the most careful attitude and constant prevention.

Just imagine what a monstrous burden is placed on the heart, given our lifestyle and low-quality plentiful food. Interestingly, mortality from cardiovascular diseases is quite high in countries with high level income.

The huge amounts of food consumed by the population of wealthy countries and the endless pursuit of money, as well as the stresses associated with it, destroy our heart. Another reason for the spread of cardiovascular diseases is hypodynamia - catastrophically low physical activity that destroys the entire body. Or, on the contrary, an illiterate passion for heavy exercise, often taking place against the background, the presence of which people are not even aware of and manage to die right during “health” activities.

Lifestyle and heart health

The main factors that increase the risk of developing cardiovascular disease are:

Obesity.
High blood pressure.
Elevated blood cholesterol levels.
Hypodynamia or excessive physical activity.
Abundant poor quality food.
repressed emotional condition and stress.

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