12 a person's heart consists of... Features of the structure and function of the human heart. Systemic circulation

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

Perhaps everyone is familiar with the location of a person’s heart, 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 it is not so simple. Most people will only say 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 actually located in the chest cavity, and in such a way that most of this organ is localized on the left, and the smaller part is on the right. Those. its location can be called asymmetrical with respect to the general space of the chest.

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

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

The lungs are adjacent to this organ on the sides. They also partially cover its anterior surface, which is called the sternocostal surface, and with which the organ is adjacent to the anterior wall of the chest cavity. The lower surface is in contact with the diaphragm, and therefore is called 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.

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 faces upward, backward and to the right, and the apex faces downward, 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, the average length of the organ is usually in the range of 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 the organ reaches 300 g in men. Women have a slightly lighter heart – an average of 250 g.

Anatomy of the heart: lining of the heart wall

In addition to knowing where a person’s heart is located, it is also necessary to have an idea of ​​the structure of this organ. Since it is classified as hollow, it has walls and a cavity divided into chambers. 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 a thin film. Its name is endocardium.

The thickest middle layer is called the myocardium or heart 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 has two layers: a longitudinal inner layer and a circular outer layer. This fact determines the greater thickness of the wall of the ventricles compared to the atria. It is worth noting that the wall of the left ventricle is much thicker than that of the right. This anatomy of the human heart is explained by the need for greater effort to push blood into the systemic circulation.

The outer layer is known as the epicardium, which, at the level of the large blood-carrying vessels, becomes 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 in 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 inferior 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 there is the so-called coronary groove. In these grooves are located the branches of the right and left coronary arteries, which directly supply the organ in question with blood.

In addition to the coronary vessels of the heart, anatomy also distinguishes large arterial and venous trunks entering and exiting this organ.

In particular, the vena cava (among which the superior and inferior are distinguished), entering the 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 from the left ventricle a large circle of blood flow begins.

Another interesting topic covered by the anatomy of the heart is the valves, the attachment point of which is the so-called heart skeleton, 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 blood from flowing back 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 to prevent blood from flowing from the left atrium to the left ventricle.

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

Conduction system of the heart

When studying the structure of the heart, anatomy does not ignore the structures that provide one of the main functions of this organ. It contains a so-called conductive system that promotes contraction 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 the branches extending from these legs.

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

Localization of the atrioventricular node in the lower part of the interatrial septum. Next comes the bundle, which divides into right and left legs, giving rise to numerous branches going to different parts of the 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 of all cells of the muscular layer of the ventricles in the contractile process (which leads to an increase in the efficiency of contractions).

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The heart has a complex structure and performs an equally complex and important job. 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.

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. A transverse coronary groove runs along it, which separates the ventricles from the atria and thereby divides the heart into an upper part, formed by the atria, and a lower part, 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 landmarks are the grooves in which the blood vessels of the heart are located, 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. The endocardium is the inner layer of epithelial tissue that lines the cavities of the heart chambers from the inside, exactly repeating their relief.
2. The myocardium is a thick layer formed by muscle tissue (striated). 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. The epicardium is the outer layer, which is the visceral petal of the heart sac (pericardium), which is a serous membrane. 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

It is shaped like an irregular cube, with an additional cavity in front 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. The medial is the 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 varies from person to person. 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. Under stress or physical exertion, its work immediately changes: it increases the number of contractions.

The work of the heart muscle can be described as follows: its right part (venous heart) receives waste blood saturated with carbon dioxide from the veins and gives it to the lungs to be saturated with oxygen. From the lungs, O2-enriched blood is directed to the left side of the 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 lymphatic ones, they maintain the constancy of the 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. The arterial bed of the circulatory system transports necessary substances to the 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. There are superficial veins, located under the skin, and deep veins, located in the tissues next to the arteries. The main function of the venous section of the circulatory system is the outflow of blood saturated with metabolic products and carbon dioxide.

To assess the functional capabilities of the cardiovascular system and the permissibility of stress, special tests are carried out, which make it possible to assess the performance of the body and its compensatory capabilities. Functional tests of the cardiovascular system are included in the physical examination to determine the degree of fitness and general physical fitness. The assessment is based on such indicators of the heart and blood vessels as blood 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%. Over an average lifespan, it pumps about 6 million liters of blood. Another interesting fact: the heart supplies blood to 75 trillion cells in the human body, except for the cornea of ​​the eyes.

The heart is the main organ of our body. It is how it works and what condition it is in that determines human health. And the functions of the heart are a very broad topic with which everyone should be at least superficially familiar.

Structural features

So, the first thing to note is that this organ is located on the left side of the chest. Although there is a small group of completely unique people in our world - their heart is on the right side. Usually such individuals have a very unique body structure, that is, a mirror one. And, accordingly, the heart is also located opposite to its usual location.

In general, this organ consists of four cavities - the left and right atria, as well as the ventricles. These chambers are divided by partitions. The heart has a rather unique structure. The drawing of the organ shows exactly what it is. But cavities are not the most important thing. The valves responsible for blood flow deserve special attention.

Location of heart valves

The first thing worth saying about this part of the heart is that it goes into the left atrium and is hollow into the right atrium. From the right and left ventricles arises the ascending aorta, as well as the pulmonary trunk. So, this topic is worth considering in more detail. The left ventricle is divided with the atrium (located on the same side), which is also called bicuspid. And the right one is divided with the atrium. Even in the heart, the drawing of which allows us to examine in detail the structure of this organ, there are the aortic and pulmonary valves. They are responsible for the process of blood flowing out of the notorious ventricles.

Blood circulation process

What is the most important function of the heart? Naturally, blood circulation. Without this, the body would not be able to function fully. Everyone knows that the heart carries out two circles of blood circulation - small and large. The first of these begins in the right ventricle, and its end is in the left atrium. It is responsible for complete gas exchange in the alveoli of the lungs. Regarding the second, it is worth noting that the large circle begins in the left ventricle and ends, as you might guess, in the right atrium. It is responsible for supplying blood not only to the lungs, but also to other human organs. All this is fully realized only when

Valve mechanism in action

Much has been said about valves and the function of the heart. Their work must be clear and coordinated. After all, the pumping function of the heart depends precisely on the valves, which together form a whole mechanism. The tricuspid opens and blood passes into the right ventricle from the atrium. As soon as it fills with blood, the valve closes under the influence of muscle pressure. And then the blood can exit only through the pulmonary trunk, into which the pulmonary valve leads, which opens under blood pressure, which increases during contraction of the right ventricle. And blood can enter there only if it is open. The entrance to the aorta is closed by the aortic valve, consisting of three valves that resemble crescents in appearance. When the left ventricle is relaxed, it is closed, and so venous blood passes into the right atrium. This is how blood circulation occurs. Of course, in words this all takes a very long time, but in reality it only takes a moment. Our heart works so fast.

Facts worth knowing

The structure and functions of this organ are not only important, they are also interesting. For example, not everyone knows that blood circulation occurs about 100,000 times a day at a distance of about 100,000 kilometers! Amazingly, this is exactly the length of all the vessels in our body. And if we talk about how many times a year our heart contracts, then the figures are simply astronomical - more than 34 million! And finally, the latest data - during this time period the heart pumps three million liters of blood. This is an incredible amount. So, if you ask a question about what function the heart performs, then we can definitely say - vital. And he does a tremendous amount of work for this. It is worth noting one more nuance: one single contraction requires the amount of energy that would be enough to lift a load of 400 grams of weight to a height of 1 meter. And this is also taking into account the fact that the heart, being in a calm state, spends only 15 percent of the amount of its reserves that it has. But if the organ does hard work, then it spends 35% of its energy. This is our heart, the structure and functions of which are truly special and unique.

Myocardium and its specifics

Here we can talk for a long time and quite a lot. Take, for example, the contractile cells of the myocardium. When discussing the functions of the heart, one cannot help but touch upon this point. The fact is that they have been working non-stop for many years. Therefore, it is very important that they are constantly supplied with air. The lack of oxygen and other nutrients negatively affects the functions of the human heart. If they do not arrive, the cells will begin to die, and instantly. After all, they do not make supplies that could be useful in such cases. The life of heart cells is a relentless circulation of blood. Moreover, a muscle that is saturated with blood can starve. After all, the myocardium is not fed with blood, which fills its cavities. Oxygen and all nutrients pass through the vessels extending from the aorta.

Pressure function

Is one of the main ones. And it consists in alternating diastole and systole of the cardiac ventricles - this is their alternate relaxation and contraction. When diastole occurs, the ventricles fill with blood. If systole occurs, then they transfer blood to the pulmonary trunk and to the aorta, i.e., to the large arteries. As you can remember, next to the ventricles there are heart valves, which are an obstacle to the return flow of blood into the heart from the artery. After all, blood, before filling the ventricles, passes through large veins straight into the atria. Contractions are a precursor to ventricular systole. We can say that the atria are a kind of auxiliary pump that helps fill the ventricles.

Functional elements of the heart

Their importance is as important as the work performed by the valves. Muscle fiber is just one of the functional components. This is a chain made up of myocardial cells, which are connected to one another and enclosed in a single sarcoplasmic membrane. It should be noted that fibers are divided into several types. It all depends on their functional as well as morphological individual characteristics. The first type is the fibers of the myocardium of the ventricles and atria. They make up the main muscle mass and are the ones that provide the pumping function. And the second type is the muscle fibers of the so-called conduction system. They are responsible for the appearance of excitation, as well as for its transmission to myocardial cells. So an increased heart rate is a consequence of a disturbance in the functional components of the human central organ.

Consequences of cardiac dysfunction

His health depends on how well the functions of a person’s heart are performed; this has already been discussed. Unfortunately, today many suffer from diseases associated with this organ. Elderly and elderly people are actively affected by them. And this is due to what was mentioned - this organ works non-stop throughout life, and it is not surprising that after 50-60 years of continuous work it gets tired. Three out of five people die due to heart disease, mainly from heart attacks.

Diseases include three main groups of ailments that affect blood vessels, valves and lining tissues. For example, atherosclerosis is a disease that affects the heart vessels. By the way, the most common disease. Or heart failure, many also suffer from it. Vice should also be considered a serious illness. The essence of the disease lies in the disruption of any function of the heart valves. Moreover, the defect can be either acquired or congenital. Arrhythmia also occurs if a person's heart functions are impaired. Most often it appears due to a broken sequence, frequency or rhythm of the heartbeat. Some people suffer from angina pectoris (oxygen starvation). And finally, attention should be paid to such a disorder as myocardial infarction. A type of ischemic disease - when this disease occurs, an area of ​​the myocardium ceases to be saturated with blood, or this does not occur as intensely as usual.

Cardiopalmus

Based on all of the above, we can understand that if any changes occur in our main organ, then this is definitely a violation of any function of the heart. Perhaps the most common and most commonly observed ailment is heart palpitations. This may be tachycardia, which occurs due to ischemic disease, myocarditis, myocardial dystrophy, or due to a defect. But sometimes this ailment is not associated with the heart - it may be due to a disease of the thyroid gland, menopause, or a tumor that has manifested itself. Many people simply do not pay attention to periodic pain or strange sensations. And in vain, because our heart is under enormous stress. You should pay particular attention to this if your own activities are associated with nervous work, stress and breakdowns.

Additional functions

In addition to carrying out blood circulation, this important organ has other capabilities. What other main functions of the heart should be highlighted? Perhaps the so-called automatism is its ability to generate impulses that provoke excitement. The sinus node is characterized by the greatest automaticity. We must also not forget about conductivity - the function of the myocardium, or rather its ability to transmit impulses directly to the contractile part of the heart. Actually, excitability is the process of increased heart rate under the influence of impulses. And, of course, refractoriness, which consists in the inability to activate excited myocardial cells if additional signals begin to arrive at them. It is divided into absolute (when the heart is absolutely apathetic in relation to any excitation), as well as relative (the organ reacts to a very strong manifestation). So the functions of the human heart are limitless.

The only thing I would like to note is that it needs to be looked after. After all, this organ is very important, and the length of a person’s life depends on its condition. Thus, based on all of the above, we can confidently say that the heart, the structure and functions of which have been examined in detail, is a mechanism consisting of a mass of vessels, cavities and valves interconnected by one goal - to ensure complete blood circulation. After all, it is necessary for the life of any living creature. So these are the main functions of the heart.

The heart is called the “motor” of our body. Its correct and healthy work as part of the system that it forms together with the vessels is life.

We receive the basic part of knowledge about all this back in school, when such a subject as biology appears. The structure of the heart, information about its functions, mechanism of operation, diseases and pathologies, as well as much more - this is something that can be useful in everyday life, and not just for future doctors.

Human heart and vascular system: meaning

The vital activity of the body is possible only with the continuous supply of oxygen, nutrients, water to the body tissues and the subsequent removal of metabolic products. Blood circulating through the vessels promotes the movement of various compounds from one organ to another. Its second important function is thermoregulation of the body. In order for the latter to work smoothly, nature has provided a special system - the cardiovascular system. Its main function is to constantly move blood through a closed system of blood vessels. This is mainly ensured by the work of the heart. Next, we will consider in more detail the structure of this muscular organ and its components: the atria and ventricles, as well as the heart wall (myocardium, epicardium, endocardium).

General anatomy of the heart

The science that studies the shape and structure of the human body in connection with its phylogenetic and ontogenetic development, function and influence of environmental conditions is called anatomy. The human heart is a muscular organ, hollow from the inside, divided into four chambers (right and left ventricles and atria). In a healthy person, his weight ranges from 250 to 360 grams and directly depends on body size, age and the level of physical activity experienced. With its rhythmic contractions (systole), the heart “pumps” blood into the arteries. In a calm state, their frequency is 60-80 per minute. With further relaxation (diastole), it draws blood from the veins. The structure and function of the heart are such that the organ is often called a pump. Its shape is more like a cone. Its widened upper part is usually called the base, and its lower narrowed part is called the apex. The surface is divided into two parts:

• slightly convex anterior (sternocostal);
• flattened posterior (diaphragmatic).

There are also two edges: a pointed right one and a blunter left one. There are grooves on the surface of the heart that coincide with the outlines of its internal cavities. They contain fatty tissue. Closer to the base runs the so-called coronary groove, which marks the boundaries between the ventricles and atria. It also contains blood vessels that receive the same name (coronoid).

Topography of the heart

The heart is located behind the sternum and belongs to the organs of the middle mediastinum. It is surrounded by a pericardial sac (pericardium), the visceral layer (epicardium) of which passes into the parietal layer through large vessels. Between them there is a closed cavity that contains a certain amount of serous fluid (about 20 ml). The pericardium is a practically inextensible membrane, which is formed from intertwining elastic and collagen fibers.

Its inner surface is lined with single-layer squamous epithelium (mesothelium). It facilitates the sliding of the epicardium and pericardium relative to each other. The pericardial sac, in turn, is connected in front with the sternum and cartilage of the ribs, and on the sides with parts of the parietal pleura; it comes into contact with the descending aorta, esophagus, and azygos vein at the back, and below it tightly fuses with the diaphragm. The anatomy of the heart and blood vessels is a single whole. First of all, this can be seen from the structure. Thus, the pericardium envelops not only the heart, but also the initial sections of large vessels extending from it (aorta, pulmonary trunk, parts of the inferior and superior vena cava, as well as the pulmonary veins). He strengthens it on them.

In an adult, the halves of the heart are separated by a continuous longitudinal septum. It is customary to distinguish two parts - interatrial and interventricular.

Right atrium

It has a shape similar to a cube, and an additional, fairly large cavity (also called the right ear) in the form of a triangular protrusion. On the septum separating it from the left atrium, the oval fossa is clearly visible. It is covered with a thin membrane. This is what remains of the overgrown foramen ovale, through which the two atria of the fetus communicate. His heart anatomy is somewhat different from that of an adult. In addition, the right atrium has two openings: the inferior and superior vena cava. The first has a semilunar fold (flap) along the lower edge; it is small and unstable. In the fetus (embryo), it directs blood through the foramen ovale into the left atrium from the right.

Right ventricle

It is located slightly anterior and to the right of the left ventricle. The shape is similar to a pyramid with three sides, the top facing down. The slightly convex medial wall is formed by a septum called the interventricular septum. Most of it is muscular, and the smaller part is membranous. The right ventricle has two openings in the upper, widest part:

• atrioventricular (venous blood flows through it from the right atrium), it is closed by semilunar valves, there are three in total; when blood passes into the ventricle from the atrium, their valves open; when contracting, they, on the contrary, close; This is a peculiar anatomy, the human heart has cavities completely separated from each other;
• the opening of the pulmonary trunk (the area from which it emerges is called the conus arteriosus).

Left atrium

It has an irregular cuboid shape, delimited from the right atrium by the interatrial septum. Above and behind are the openings of the pulmonary veins (there are four of them) and one atrioventricular. On the front wall there is a cone-shaped extension - this is the left ear. On the inside it is covered with numerous pectineal muscles. Inside, the wall of the left atrium is mostly smooth, and only on the interatrial septum is an oval depression visible.

Left ventricle

It has a cone shape with the base facing upward. The internal cavity is covered with fleshy crossbars forming a complex network. It communicates with the left atrium through the atrioventricular orifice, and the mitral valve leaflets are attached to its edges. The anterior part of the ventricle forms the conus arteriosus. It connects to the opening of the aorta, and three semilunar valves limit it.

The anatomy of the heart also includes knowledge about the structure of its wall, which has three layers: the inner, otherwise endocardium, the thick muscular layer - the myocardium, and the outer (visceral layer of the membrane) - the endocardium. Let's study them in more detail.

Epicardium and endocardium: structural features

The epicardium (indicated by an arrow in the photo) is formed by the inner layer of the pericardial serous sac (pericardium). The fabric that makes up its base contains a large number of fibers (elastic and collagen). It contains a large number of blood and lymphatic capillaries and nerve endings.

The surface of the heart is lined from the inside by the endocardium. It is formed by a layer of flat, polygonal endothelocytes, which are located on a thin basement membrane. They are connected to each other by intercellular contacts, including nexuses. Heart valves are nothing more than folds of the endocardium; they have a connective tissue base with many collagen and elastic fibers.

The structure of the myocardium

This is the most powerful shell with a specific structure. And the work of the heart as a “pump” is carried out mainly by the myocardium. It is characterized by its greatest thickness in the left ventricle, and its smallest thickness in the atria. It is formed by striated muscle, consisting of cardiomyocytes, and they are connected into chains (fibers). This muscle network ensures the functioning of the heart, contraction of the ventricles and atria. Cells are very tightly connected to each other using desmos (intercellular contacts). Thin layers of connective tissue and a developed network of lymphatic and blood vessels lie between the fibers.

The anatomy of the heart has its own characteristics. In the thickness of the myocardium is its so-called skeleton. It is formed mainly by fibrous rings and gives rise to muscle fibers, which are divided into two types:

1. Atrial musculature. It clearly shows two layers: superficial and deep. The first is formed by transverse fibers, common to both atria, and the second by vertical fibers (each with its own).
2. Musculature of the ventricles. It is more powerful, especially on the left, and consists of three layers. Just like the atria, there is a division. The superficial and deep layers of both ventricles are common, and each has its own middle layer.

Myocardial diseases occupy a leading place among pathological processes in the heart. These include primarily atherosclerotic damage, damage due to hypertension, pulmonary-heart syndrome, inflammatory processes (myocarditis), and muscle dystrophy.

All diseases, as we know, are better to prevent than to treat. That is why the anatomy (structure) of the heart and its further study from a medical point of view are so important.

Heartperson- this is a cone-shaped hollow muscular organ that receives blood from the venous trunks flowing into it and pumps it into the arteries that are adjacent to the heart. The heart cavity is divided into 2 atria and 2 ventricles. The left atrium and left ventricle together form the “arterial heart,” named for the type of blood passing through it; the right ventricle and right atrium combine to form the “venous heart,” named for the same principle. Contraction of the heart is called systole, relaxation is called diastole.

The shape of the heart is not the same from person to person. It is determined by age, gender, physique, health, and other factors. In simplified models, it is described by a sphere, ellipsoids, and the 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 one, and with an asthenic body type, it is about 1.5. The length of the heart of an adult varies from 10 to 15 cm (usually 12-13 cm), width at the base 8-11 cm (usually 9-10 cm) and anteroposterior size 6-8.5 cm (usually 6.5-7 cm) . The average heart weight in men is 332 g (from 274 to 385 g), in women - 253 g (from 203 to 302 g).

Heart human is a romantic organ. In our country it is considered the seat of the soul. “I feel it in my heart,” people say. Among African aborigines it is considered the organ of the mind.

A healthy heart is a strong, continuously working organ, about the size of a fist and weighing about half a kilogram.

Consists of 4 chambers. A muscular wall called the septum divides the heart into left and right halves. Each half has 2 chambers.

The upper chambers are called atria, the lower chambers are called ventricles. The two atria are separated by the interatrial septum, and the two ventricles are separated by the interventricular septum. The atrium and ventricle of each side of the heart are connected by the atrioventricular orifice. This opening opens and closes the atrioventricular valve. The left atrioventricular valve is also known as the mitral valve, and the right atrioventricular valve is also known as the tricuspid valve. The right atrium receives all the blood returning from the upper and lower parts of the body. Then, through the tricuspid valve, it sends it to the right ventricle, which in turn pumps blood through the pulmonary valve to the lungs.

In the lungs, the blood is enriched with oxygen and returns to the left atrium, which sends it through the mitral valve to the left ventricle.

The left ventricle pumps blood through the arteries through the aortic valve throughout the body, where it supplies the tissues with oxygen. Oxygen-depleted blood returns through the veins to the right atrium.

The blood supply to the heart is carried out by two arteries: the right coronary artery and the left coronary artery, which are the first branches of the aorta. Each of the coronary arteries emerges from the corresponding right and left aortic sinuses. Valves are used to prevent blood flow in the opposite direction.

Types of valves: bicuspid, tricuspid and semilunar.

Semilunar valves have wedge-shaped leaflets that prevent blood from returning as it leaves the heart. There are two semilunar valves in the heart. One of these valves prevents backflow in the pulmonary artery, the other valve is located in the aorta and serves a similar purpose.

Other valves prevent blood from flowing from the lower chambers of the heart to the upper chambers. The bicuspid valve is located in the left side of the heart, the tricuspid valve is in the right. These valves have a similar structure, but one of them has two leaflets, and the other, respectively, three.

To pump blood through the heart, alternating relaxations (diastole) and contractions (systole) occur in its chambers, during which the chambers fill with blood and push it out accordingly.

The natural pacemaker, called the sinus node or Kis-Flyak node, is located in the upper part of the right atrium. This is an anatomical formation that controls and regulates heart rate in accordance with the activity of the body, time of day and many other factors affecting a person. The heart's natural pacemaker produces electrical impulses that pass through the atria, causing them to contract, to the atrioventricular (that is, atrioventricular) node, located at the border of the atria and ventricles. Then the excitation spreads through the conducting tissues into the ventricles, causing them to contract. After this, the heart rests until the next impulse, which begins a new cycle.

Basic heart function is to ensure blood circulation by communicating kinetic energy to the blood. To ensure the normal existence of the body in various conditions, the heart can operate in a fairly wide range of frequencies. This is possible due to some properties, such as:

Automaticity of the heart- this is the ability of the heart to contract rhythmically under the influence of impulses originating in itself. Described above.

Excitability of the heart- this is the ability of the heart muscle to be excited by various stimuli of a physical or chemical nature, accompanied by changes in the physical and chemical properties of the tissue.

Cardiac conductivity- carried out in the heart electrically due to the formation of an action potential in pacemaker cells. The place where excitation transfers from one cell to another is the nexus.

Cardiac contractility– The force of contraction of the heart muscle is directly proportional to the initial length of the muscle fibers

Myocardial refractoriness- a temporary state of non-excitability of tissues

When the heart rhythm fails, fibrillation occurs - rapid asynchronous contractions of the heart, which can lead to death.

Blood pumping is achieved through alternating contraction (systole) and relaxation (diastole) of the myocardium. The fibers of the heart muscle contract due to electrical impulses (excitation processes) formed in the membrane (shell) of the cells. These impulses appear rhythmically in the very heart. The ability of the heart muscle to independently generate periodic excitation impulses is called automaticity.

Muscle contraction in the heart is a well-organized periodic process. The function of periodic (chronotropic) organization of this process is provided by the conduction system.

As a result of the rhythmic contraction of the heart muscle, the periodic expulsion of blood into the vascular system is ensured. The period of contraction and relaxation of the heart constitutes the cardiac cycle. It consists of atrial systole, ventricular systole and a general pause. During atrial systole, the pressure in them increases from 1-2 mm Hg. Art. up to 6-9 mm Hg. Art. in the right and up to 8-9 mm Hg. Art. in the left. As a result, blood is pumped through the atrioventricular openings into the ventricles. In humans, blood is expelled when the pressure in the left ventricle reaches 65-75 mmHg. Art., and in the right - 5-12 mm Hg. Art. After this, ventricular diastole begins, the pressure in them quickly drops, as a result of which the pressure in large vessels becomes higher and the semilunar valves slam shut. As soon as the pressure in the ventricles drops to 0, the leaflet valves open and the ventricular filling phase begins. Ventricular diastole ends with the filling phase caused by atrial systole.

The duration of the phases of the cardiac cycle is not constant and depends on the heart rate. With a constant rhythm, the duration of the phases may be disrupted due to cardiac dysfunction.

The strength and frequency of heart contractions can change in accordance with the needs of the body, its organs and tissues for oxygen and nutrients. Regulation of heart activity is carried out by neurohumoral regulatory mechanisms.

The heart also has its own regulatory mechanisms. Some of them are related to the properties of the myocardial fibers themselves - the relationship between the magnitude of the heart rhythm and the force of contraction of its fiber, as well as the dependence of the energy of contraction of the fiber on the degree of its stretching during diastole.

The elastic properties of the myocardial material, manifested outside the process of active coupling, are called passive. The most likely carriers of elastic properties are the supporting-trophic skeleton (especially collagen fibers) and actomyosin bridges, which are present in a certain amount in passive muscle. The contribution of the supporting-trophic skeleton to the elastic properties of the myocardium increases during sclerotic processes. The bridging component of stiffness increases with ischemic contracture and inflammatory diseases of the myocardium.

TICKET 34 (LARGE AND SMALL CIRCULATION)