Anatomical structure of the heart. Anatomy of the human heart: structure and main functions

The functioning of the body is impossible without the main organ - the heart. It performs an important job - it pumps blood in the body, ensuring its flow to all internal organs, while simultaneously delivering nutrients and oxygen to them through the bloodstream. Many people are very figuratively familiar with the work and structure of the heart, and cannot always even indicate its location with maximum accuracy; as a rule, this comes down to general knowledge that it is located “in the chest.” In order to know how the body functions and the heart works, what diseases it is susceptible to and how to treat them, it is necessary to know its structure, phases and blood pumping cycles. It is foolish to think that this information will be useful only to medical workers, it will be useful to ordinary people, and in some cases it may help save lives.

Location and functions of the heart

The heart is an important human organ, which is located in the center of the chest between the lungs, with a slight shift to the left. In exceptional cases, it may be located on the right, when a person has a mirror structure of the body. At its core, it is a muscle that, by contracting, maintains normal blood circulation in the body. The heart has a cone shape, the average weight of the organ is 250-300 grams, and its dimensions are 10-15 cm in height and 9-10 cm at the base.

Heart function

Pumping blood is the main function of the heart. This process must occur continuously to ensure that the internal organs are supplied with oxygen and nutritional components.
The work of the heart muscle consists of two stages:

• Diastole is relaxation of the heart. At this stage, blood enters the left atrium and flows through the mitral orifice into the ventricle.
• Systole is a contraction of the heart, during which blood flows into the aorta and spreads throughout the body, transporting oxygen to the internal organs.

The cardiac cycle includes the following stages: contraction of the atria, which lasts 0.1 seconds, and ventricles (duration 0.3 seconds) and their relaxation.

The heart carries out two circles of blood circulation:

• Small - begins in the right ventricle and ends in the left atrium. This circulation is responsible for normal gas exchange in the pulmonary alveoli.
• Large - the circle begins in the left ventricle and ends in the right atrium. The main role is to ensure the flow of blood to all internal organs.

How does blood circulate in the heart?

• Blood from the veins with a high carbon dioxide content enters the vena cava.
• From the mouth of the veins it flows into the right atrium, and then into the right ventricle.
• Blood enters the pulmonary trunk and is delivered through it to the lungs. Here it is enriched with oxygen and becomes arterial.
• Through the arteries, blood from the lungs returns to the heart - the left atrium and left ventricle.
• From the heart, blood enters the aorta (a large blood vessel), and from there it is distributed among small vessels and spread throughout the body.

Anatomical structure of the heart

The heart is a muscular organ that is surrounded on the outside by the pericardium. The cavity between the two components is filled with liquid, which performs an important function - it reduces friction of the heart muscle and ensures its hydration. The pericardium includes three layers: epicardium, myocardium and endocardium.

The heart itself consists of 4 sections: two atria and two ventricles. The left ventricle and atrium circulate arterial blood enriched with oxygen, the right side of the heart helps pump venous blood. Entering the heart, blood accumulates in the atria and, upon reaching the required volume, is redirected to the ventricles.

All sections are separated by valves - the mitral on the left and the tricuspid on the right. Their main purpose is to ensure the movement of blood in one direction - from the atria to the ventricles.

During normal functioning of the heart, the right and left parts do not communicate with each other. With the development of pathology (usually congenital heart defects), holes may remain in the septum. In this case, during contraction of the heart muscle, blood from one half can enter the other.

Heart diseases

Heart disease has increasingly affected people in recent decades. This is caused by a low quality of life, poor nutrition, a sedentary lifestyle and a large number of bad addictions that every second person on earth has. Older people are more likely to suffer from heart disease. This is due to physical fatigue of the muscle, thickening of the blood, slowdown of all processes in the body and the presence of other concomitant diseases. According to statistics, heart disease is the most common cause of death. All diseases are conventionally divided into three groups, depending on which part of the organ is affected - blood vessels, valves and membrane tissue.

Let's look at the most popular heart diseases:

Treatment of heart diseases

He treats heart diseases. Before starting therapy, the doctor conducts a thorough examination of the patient, which includes: general and Holter ECG and other studies.

Only after complete diagnosis and diagnosis is therapy prescribed. Basic methods of treating heart disease:

• Conservative treatment: maintaining physical and emotional peace, taking prescribed medications, regulating proper nutrition.
• Drug therapy is used for any disease. Most often, drugs are prescribed to reduce bad cholesterol, blood thinners (especially in old age), inhibitors and many others, depending on the diagnosis.
• Surgical intervention is performed if it is impossible to achieve the desired effect using conservative methods, for example, when a pacemaker is required, a hole between the parts of the heart needs to be repaired, or the patient needs an organ transplant.

Diagnosis and treatment of heart disease should be carried out exclusively by a doctor (general practitioner, cardiologist or cardiac surgeon). Self-medication is strictly forbidden - at best it will not bring the expected result, at worst it will aggravate the situation and lead to a number of complications.

Disease Prevention

A healthy heart is the key to excellent health and normal functioning of the body. It is extremely important to take proper care of it to reduce the risk of developing heart disease. To do this, just follow the doctor’s simple recommendations:

The heart is an important organ that circulates blood in the body. It is extremely important to maintain its health and normal functioning. By taking care of your heart, you will ensure a long and healthy life.

In order to ensure adequate nutrition of internal organs, the heart pumps an average of seven tons of blood per day. Its size is equal to a clenched fist. Throughout life, this organ makes approximately 2.55 billion beats. The final formation of the heart occurs by the 10th week of intrauterine development. After birth, the type of hemodynamics changes dramatically - from feeding on the mother’s placenta to independent, pulmonary breathing.

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Muscle fibers (myocardium) are the predominant type of heart cells. They make up its bulk and are located in the middle layer. The outside of the organ is covered with epicardium. It wraps at the level of the attachment of the aorta and pulmonary artery, heading downwards. In this way, the pericardial sac is formed. It contains about 20 - 40 ml of clear liquid, which prevents the leaves from sticking together and being injured during contractions.

The inner membrane (endocardium) folds in half at the transition of the atria into the ventricles, the mouths of the aortic and pulmonary trunk, forming valves. Their valves are attached to a ring of connective tissue, and the free part moves with the blood flow. In order to prevent the parts from everting into the atrium, threads (chords) are attached to them, extending from the papillary muscles of the ventricles.

The heart has the following structure:

• three membranes - endocardium, myocardium, epicardium;
• pericardial sac;
• chambers with arterial blood - left atrium (LA) and ventricle (LV);
• sections with venous blood - right atrium (RA) and ventricle (RV);
• valves between the LA and LV (mitral) and tricuspid on the right;
• two valves separate the ventricles and large vessels (aortic on the left and pulmonary artery on the right);
• the septum divides the heart into right and left halves;
• efferent vessels, arteries - pulmonary (venous blood from the pancreas), aorta (arterial from the left ventricle);
• afferent veins - pulmonary (with arterial blood) enter the LA, vena cava flow into the RA.

Internal anatomy and structural features of valves, atria, ventricles

Each part of the heart has its own function and anatomical features. In general, the LV is more powerful (compared to the right), as it forces blood into the arteries, overcoming the high resistance of the vascular walls. The PP is more developed than the left, it receives blood from the whole body, and the left one only from the lungs.

Which side of a person's heart is on?

In humans, the heart is located on the left side in the center of the chest. The main part is located in this area - 75% of the total volume. One third extends beyond the midline into the right half. In this case, the axis of the heart is inclined (oblique direction). This situation is considered classic, as it occurs in the vast majority of adults. But options are also possible:

• dextrocardia (right side);
• almost horizontal - with a wide, short chest;
• close to vertical - for thin people.

Where is a person's heart located?

The human heart is located in the chest between the lungs. It is adjacent to the sternum from the inside, and is limited below by the diaphragm. It is surrounded by the pericardium, the pericardium. Pain in the heart area appears on the left near the mammary gland. The top is projected there. But with angina, patients feel pain behind the sternum, and it spreads along the left side of the chest.

Where is the heart located in the human body?

The heart in the human body is located in the center of the chest, but its main part goes into the left half, and only one third is located on the right side. For most people it has an angle of inclination, but for overweight people its position is closer to horizontal, and for thin people it is closer to vertical.

Location of the heart in the human chest

In humans, the heart is located in the chest in such a way that its anterior and lateral surfaces are in contact with the lungs, and its posterior and inferior surfaces are in contact with the diaphragm. The base of the heart (from above) passes into large vessels - the aorta, pulmonary artery. The apex is the lowest part, it approximately corresponds to the 4-5 space between the ribs. It can be found in this area by lowering an imaginary perpendicular from the center of the left collarbone.

The external structure of the heart refers to its chambers; it contains two atria and two ventricles. They are separated by partitions. The pulmonary veins, the vena cava, enter the heart, and the arteries of the lungs, the aorta, carry the blood out. Between the large vessels, at the border of the atria and ventricles of the same name, there are valves:

• aortic;
• pulmonary artery;
• mitral (left);
• tricuspid (between the right parts).

The heart is surrounded by a cavity containing a small amount of fluid. It is formed by the pericardial layers.

If you clench your fist, you can imagine exactly the appearance of a heart. In this case, the part that is located at the wrist joint will be its base, and the acute angle between the first and thumb will be its apex. What is important is that its size is also very close to a clenched fist.

Borders of the heart and their projection onto the surface of the chest

The boundaries of the heart are found by percussion, by tapping; radiography or echocardiography helps to determine them more accurately. The projections of the cardiac contour onto the surface of the chest are:

• right – 10 mm to the right of the sternum;
• left – 2 cm inward from the perpendicular from the center of the collarbone;
• apex – 5th intercostal space;
• base (upper) – 3rd rib.

What tissues make up the heart?

The heart consists of the following types of tissue:

• muscle - the main one, is called the myocardium, and the cells are cardiomyocytes;
• connective – valves, chords (threads that hold the valves), outer (epicardial) layer;
• epithelium – inner lining (endocardium).

Surfaces of the human heart

The human heart has the following surfaces:

• ribs, sternum – anterior;
• pulmonary – lateral;
• diaphragmatic – lower.

Apex and base of the heart

The apex of the heart is directed down and to the left, its localization is the 5th intercostal space. It represents the top of the cone. The wide part (base) is located on top, closer to the collarbones, and is projected at the level of the 3rd rib.

Human heart shape

The shape of a healthy person's heart is like a cone. Its tip is directed at an acute angle down and to the left of the center of the sternum. The base contains the mouths of large vessels and is located at the level of the 3rd rib.

Right atrium

Receives blood from the vena cava. Next to them is the foramen ovale, which connects the RA and LA in the fetal heart. In a newborn, it closes after the pulmonary blood flow opens, and then completely heals. During systole (contraction), venous blood passes into the pancreas through the tricuspid valve. The RA has a fairly powerful myocardium and a cubic shape.

Left atrium

Arterial blood from the lungs passes into the LA through 4 pulmonary veins and then flows through the opening into the LV. The walls of the LA are 2 times thinner than those of the right one. The shape of the LP is similar to a cylinder.

Right ventricle

It looks like an inverted pyramid. The capacity of the pancreas is about 210 ml. It can be divided into two parts - the arterial (pulmonary) cone and the ventricular cavity itself. In the upper part there are two valves: the tricuspid and the pulmonary trunk.

Left ventricle

It looks like an inverted cone, its lower part forms the top of the heart. The thickness of the myocardium is the largest - 12 mm. There are two openings at the top - for connection with the aorta and LA. Both of them are covered by valves - the aortic and mitral.

Why are the walls of the atria thinner than the walls of the ventricles?

The thickness of the walls of the atrium is less, they are thinner, since they only need to push blood into the ventricles. The right ventricle follows them in strength; it throws its contents into the neighboring lungs, and the left one is the largest in terms of the size of its walls. It pumps blood to the aorta, where there is high pressure.

Tricuspid valve

The right atrioventricular valve consists of a sealed ring that limits the opening and leaflets; there may be not 3, but from 2 to 6.

Half of the people have a tricuspid configuration.

The function of this valve is to prevent the reflux of blood into the RA during RV systole.

Pulmonary valve

It prevents blood from passing back into the pancreas after it contracts. The composition contains valves similar in shape to a crescent. In the middle of each there is a knot that seals the closure.

Mitral valve

It has two doors, one is in the front and the other is in the back. When the valve is open, blood flows from the LA to the LV. When the ventricle contracts, its parts close together to allow blood to pass into the aorta.

Aortic valve

Formed by three semilunar-shaped flaps. Like the pulmonary one, it does not contain threads that hold the valves in place. In the area where the valve is located, the aorta expands and has depressions called sinuses.

Adult heart weight

Depending on the physique and total body weight, the weight of the heart in an adult varies from 200 to 330 g. In men, it is on average 30-50 g heavier than in women.

Diagram of blood circulation

Gas exchange occurs in the alveoli of the lungs. They receive venous blood from the pulmonary artery emerging from the pancreas. Despite the name, the pulmonary arteries carry venous blood. After the release of carbon dioxide and oxygen saturation through the pulmonary veins, the blood passes into the left atrium. This is how a small circle of blood flow, called pulmonary, is formed.

The large circle covers the entire body as a whole. From the LV, arterial blood spreads to all vessels, nourishing the tissues. Deprived of oxygen, venous blood flows from the vena cava into the RA, then into the RV. The circles close together, ensuring a continuous flow.

In order for blood to enter the myocardium, it must first pass into the aorta and then into the two coronary arteries. They are named so because of the shape of the branches, reminiscent of a crown (crown). Venous blood from the heart muscle predominantly enters the coronary sinus. It opens into the right atrium. This circle of blood circulation is considered the third, coronary.

Watch the video about the structure of the human heart:

What is special about the structure of a child’s heart?

Until the age of six, the heart is spherical due to the large atria. Its walls are easily stretched, they are much thinner than those of adults. A network of tendon threads is gradually formed, fixing the valve leaflets and papillary muscles. Full development of all heart structures ends by age 20.

The position of the newborn's heart in the chest is initially oblique, adjacent to the anterior surface. This is caused by an increase in the volume of lung tissue and a decrease in the mass of the thymus gland.

Until two years of age, the heart impulse forms the right ventricle, and then part of the left. The atria are the leaders in growth rate up to 2 years, and the ventricles after 10 years. Up to ten years, the LV is ahead of the right.

Basic functions of the myocardium

The heart muscle differs in structure from all others, as it has several unique properties:

• Automatism is excitation under the influence of one’s own bioelectric impulses. They first form in the sinus node. He is the main pacemaker, generating about 60 - 80 signals per minute. The underlying cells of the conducting system are nodes of the 2nd and 3rd order.
• Conduction - impulses from the site of formation can spread from the sinus node to the RA, LA, atrioventricular node, and along the ventricular myocardium.
• Excitability - in response to external and internal stimuli, the myocardium is activated.
• Contractility is the ability to contract when excited. This function creates the pumping capabilities of the heart. The force with which the myocardium reacts to an electrical stimulus depends on the pressure in the aorta, the degree of stretching of the fibers in diastole, and the volume of blood in the chambers.

The functioning of the heart goes through three stages:

1. Contraction of the RA, LA and relaxation of the RV and LV with the opening of the valves between them. Transition of blood into the ventricles.
2. Ventricular systole - the valves of the blood vessels open, blood flows into the aorta and pulmonary artery.
3. General relaxation (diastole) - blood fills the atria and presses on the valves (mitral and tricuspid) until they open.

During the period of contraction of the ventricles, the valves between them and the atria are closed by blood pressure. In diastole, the pressure in the ventricles drops, it becomes lower than in large vessels, then parts of the pulmonary and aortic valves close so that the blood flow does not return.

Heart cycle

There are 2 stages in the heart cycle: contraction and relaxation. The first is called systole and also includes 2 phases:

• compression of the atria to fill the ventricles (lasts 0.1 sec.);
• the work of the ventricular part and the release of blood into large vessels (about 0.5 sec.).

Then comes relaxation - diastole (0.36 sec). Cells change polarity to respond to the next impulse (repolarization), and the blood vessels of the myocardium bring nutrition. During this period, the atria begin to fill.

The heart ensures the movement of blood through the large and small circles thanks to the coordinated work of the atria, ventricles, great vessels and valves. The myocardium has the ability to generate an electrical impulse and conduct it from the nodes of automaticity to the cells of the ventricles. In response to the signal, muscle fibers become active and contract. The cardiac cycle consists of a systolic and a diastolic period.

Useful video

Watch the video about the work of the human heart:

Read also

Coronary circulation plays an important function. Its features, pattern of movement in a small circle, blood vessels, physiology and regulation are studied by cardiologists if problems are suspected.

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

Structure of the heart

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

Heart chambers

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

Structure of the heart wall

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

Blood supply, lymphatic system and innervation

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

Physiology of cardiac activity

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

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

Educational video on the topic “The human heart: internal structure” (English):

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

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

Heart as an organ

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

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

heart position

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

external structure of the heart

Age characteristics

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

development of the heart in utero

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

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

hemodynamics in the heart before and after birth

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

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

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

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

Anatomical and functional features of the heart

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

basic structure of the chambers of the heart

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

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

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

structure of the heart and its vessels

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

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

hemodynamics in the heart

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

cardiac cycle

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

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

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

circulation circles

Video: cardiac anatomy and cardiac cycle briefly

Morphological features of the heart

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

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

cardiac cycle

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

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

structure of the heart wall and membrane

Blood supply and innervation of the heart

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

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

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

innervation of the heart

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

Video: lecture on cardiac anatomy

The heart is the main organ of the blood supply and lymph formation system in the body. It is presented in the form of a large muscle with several hollow chambers. Thanks to its ability to contract, it moves the blood. There are three linings of the heart: epicardium, endocardium and myocardium. The structure, purpose and functions of each of them will be considered in this material.

The structure of the human heart - anatomy

The heart muscle consists of 4 chambers - 2 atria and 2 ventricles. The left ventricle and left atrium form the so-called arterial part of the organ, based on the nature of the blood found here. In contrast, the right ventricle and right atrium make up the venous part of the heart.

The circulatory organ is presented in the shape of a flattened cone. It has a base, apex, lower and anterosuperior surfaces, as well as two edges - left and right. The apex of the heart has a rounded shape and is formed entirely by the left ventricle. The atria are located in the base area, and the aorta lies in its anterior part.

Heart sizes

It is believed that in an adult, mature human individual, the size of the heart muscle is equal to the size of a clenched fist. In fact, the average length of this organ in a mature person is 12-13 cm. The diameter of the heart is 9-11 cm.

The weight of an adult man's heart is about 300 g. In women, the heart weighs on average about 220 g.

Phases of the heart

There are several separate phases of contraction of the heart muscle:

1. At the beginning, contraction of the atria occurs. Then, with some slowdown, ventricular contraction begins. During this process, blood naturally tends to fill the chambers with reduced pressure. Why doesn’t it flow back into the atria after this? The fact is that the blood is blocked by the gastric valves. Therefore, it can only move in the direction of the aorta, as well as the vessels of the pulmonary trunk.
2. The second phase is relaxation of the ventricles and atria. The process is characterized by a short-term decrease in the tone of the muscle structures from which these chambers are formed. The process causes a decrease in pressure in the ventricles. Thus, the blood begins to move in the opposite direction. However, this is prevented by the closing pulmonary and arterial valves. During relaxation, the ventricles fill with blood that comes from the atria. On the contrary, the atria are filled with bodily fluid from the large and

What is responsible for the work of the heart?

As you know, the functioning of the heart muscle is not a voluntary act. The organ remains active continuously, even when a person is in a state of deep sleep. There are hardly people who pay attention to their heart rate during activity. But this is achieved due to a special structure built into the heart muscle itself - a system for generating biological impulses. It is noteworthy that the formation of this mechanism occurs in the first weeks of intrauterine conception of the fetus. Subsequently, the impulse generation system does not allow the heart to stop throughout life.

In a calm state, the number of contractions of the heart muscle per minute is about 70 beats. Within one hour the number reaches 4200 beats. Considering that during one contraction the heart releases 70 ml of fluid into the circulatory system, it is easy to guess that up to 300 liters of blood passes through it in an hour. How much blood does this organ pump over its entire life? This figure averages 175 million liters. Therefore, it is not surprising that the heart is called an ideal engine that practically does not fail.

The membranes of the heart

In total, there are 3 separate membranes of the heart muscle:

1. Endocardium is the inner lining of the heart.
2. The myocardium is an internal muscle complex formed by a thick layer of thread-like fibers.
3. The epicardium is the thin outer layer of the heart.
4. The pericardium is an auxiliary cardiac membrane, which is a kind of bag that contains the entire heart.

Myocardium

The myocardium is a multi-tissue muscular layer of the heart that is formed by striated fibers, loose connective structures, nerve processes, and a branched network of capillaries. Here are P-cells that form and conduct nerve impulses. In addition, the myocardium contains myocytes and cardiomyocytes, which are responsible for the contraction of the blood organ.

The myocardium consists of several layers: inner, middle and outer. The internal structure consists of muscle bundles that are located longitudinally in relation to each other. In the outer layer, bundles of muscle tissue are located obliquely. The latter go to the very top of the heart, where they form the so-called curl. The middle layer consists of circular muscle bundles, separate for each of the ventricles of the heart.

Epicard

The presented membrane of the heart muscle has the smoothest, thinnest and somewhat transparent structure. The epicardium forms the outer tissue of the organ. In fact, the membrane acts as the inner layer of the pericardium - the so-called cardiac sac.

The surface of the epicardium is formed from mesothelial cells, under which there is a connective, loose structure represented by connective fibers. In the region of the apex of the heart and in its grooves, the lining in question includes adipose tissue. The epicardium fuses with the myocardium in the areas of least accumulation of fat cells.

Endocardium

Continuing to consider the membranes of the heart, let's talk about the endocardium. The presented structure is formed by elastic fibers, which consist of smooth muscle and connective cells. Endocardial tissue lines all hearts. The endocardial tissues move smoothly onto the elements extending from the blood organ: aorta, pulmonary veins, pulmonary trunk, without clearly distinguishable boundaries. In the thinnest parts of the atria, the endocardium fuses with the epicardium.

Pericardium

The pericardium is the outer layer of the heart, also called the pericardial sac. This structure is presented in the form of an obliquely cut cone. The inferior base of the pericardium is placed on the diaphragm. Toward the top, the shell goes more to the left than to the right. This peculiar bag surrounds not only the heart muscle, but also the aorta, the mouth of the pulmonary trunk and adjacent veins.

The pericardium forms in human individuals during the early stages of fetal development. This happens approximately 3-4 weeks after the formation of the embryo. Violations of the structure of this membrane, its partial or complete absence, often lead to congenital heart defects.

Finally

In the material presented, we examined the structure of the human heart, the anatomy of its chambers and membranes. As you can see, the heart muscle has an extremely complex structure. Surprisingly, despite its intricate structure, this organ functions continuously throughout life, malfunctioning only in the event of the development of serious pathologies.