Drawing of the structure of the human heart. Heart valves and hemodynamics

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. Such a complex structure the best way adapted to separate arterial and venous blood flows. In addition, the anatomy of the human heart involves many the smallest details, each of which performs its strictly defined functions.

Heart as an organ

So, the heart is nothing more than a hollow organ consisting of specific muscle tissue, which carries out the motor function. The heart is located in 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 a large muscle mass) – 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 embryonic heart is most vulnerable to negative influence some factors on the expectant mother.

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

hemodynamics in the heart before and after birth

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

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

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

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

Anatomical and functional features of the heart

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

basic structure of the chambers of the heart

The boundaries between the upper and lower chambers are the atrioventricular openings - the left one, covered by the mitral valve leaflets, and the right one, covered by the tricuspid valve leaflets. The integrity of the 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 integral part conducting system. The latter is represented by electrically active cells of the sinus node, atrioventricular node, the bundle of His (with two legs - right and left), as well as Purkinje fibers. In the case when a patient’s myocardial damage affects these fibers, they develop, otherwise called.

cardiac cycle

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

So, the myocardium, or cardiac muscle, is the middle layer in the wall of the heart. The inner and outer 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

When there is eternal spring in the soul, there is no way to contain the high spirits: it is bursting from the chest to splash out with sweet creativity. How to draw, or better yet, both together? Take a simple pencil Blank sheet paper - now you will find out everything.

Lesson #1: How to draw a heart with a pencil

We will draw a heart of roses. Draw a regular circle and divide it in half with a line. Right on horizontal line draw an uneven oval, similar to a deflated balloon. Attach a couple of curves to it at the top and bottom, like the red lines shown in the example figure.

In the lesson explaining how to draw a heart, first of all, pay attention to the red lines of the sample - these are new fragments that need to be repeated on your version of the original heart.

Draw some kind of snail in the very center of the future masterpiece. First, simply divide the uneven oval almost in half with a convex curved line. Add a few strokes: in the form of the letter “P” and from its top regular line, limited by the same oval. Don't forget to add one more stroke, very small, in the upper petal. This inverted “comma” will add volume to the drawing.

A very easy step creative process entitled "How to Draw a Heart": draw two symmetrical petals, top part which he seems to repeat invisible lines heart.

All that's left is to add three petals at the bottom of the heart. If you didn't skip math classes at school, then you know how to draw curly braces. This acquired skill will help you easily cope with the task: a couple of curves on the left and right and another, final one, with an “arrow” down the center. By the way, if you look closely at the sample, you will see that the last petal you drew will be boring without a small detail - a convex stroke that adds volume.

Erase all auxiliary, erroneous and unnecessary lines. Lesson “How to draw a heart” is completed!

Lesson #2: Heart surrounded by roses

Let’s complicate the task: let’s draw in a scarlet round dance:

Draw arbitrary contour hearts, for example, like this:

Make the first sketches of three buds at once, distributing them evenly. Start with curls, work from there lateral lines according to the example:

Each flower has its own individual uniform, which appears thanks to simple curved lines. Take a closer look and repeat them in your drawing, there is nothing complicated about it:

Let's complete the drawing of the roses by adding three or four graceful outlines to each bud.

The heart means a lot to a person. A real heart is the basis of our body, and valentines or simple drawn hearts help us express our feelings. This is a manifestation of warmth, love and tender feelings to a person. Below we will give a few simple tips how to draw a heart. There are several drawing options, you can use them or come up with your own.

Simplified version

Before you draw a heart with a pencil (or rather, start), prepare all the tools (paper, eraser, pencils). Place a piece of paper in front of you. First you need to think through the details if you want to add something to the heart. Make sure that all parts of the drawing fit on the sheet. It is better to draw all the main elements schematically (in squares, circles). Now take a pencil and get started. There are three options for how to draw a Valentine heart

First way

Place a dot in the center of the sheet, it will be the base of the heart. Draw a semicircular line, directing it first up to the right and then down. The end point of the arc should be under the base point. You should end up with something that looks like a question mark. Repeat the steps on the left half of the sheet. The lines should converge at one point.

Second way

Draw upside down isosceles triangle(the base should be at the top). Draw a bisector from the bottom vertex. Then “write” half a heart into each of the resulting triangles. Use an eraser to remove unnecessary lines.

Third way

Draw two intersecting circles (you can use stencils) and draw a heart based on them. If it turns out to be asymmetrical, then fold a sheet of paper in half and draw one half at the fold line, then cut it out. Now you know how to draw beautiful heart in its simplified version. When you have the base ready, you can use your imagination: pierce the heart with arrows, thorns, draw roses or wings around it. You can color it or outline it with a marker, leaving it in black and white. Do not overload the drawing with many unnecessary details.

How to draw a human heart

You will also need tools, prepare yourself a space. It is better to use a vertically oriented sheet. In this matter, you need to thoroughly study the anatomy of the human heart. You can copy it from a textbook or medical reference book.

Brief description of the process:

You need to draw an oval that tapers downwards. It should be slightly tilted. Then draw the right atrium. An important part of the heart is the aorta, don’t forget about it. This is a large “tube” that will be located at the top of the picture, with three more vessels coming out of it. Add the veins, don't forget the left atrium. Also trace the drawing and color it if desired. Don't forget to erase extra lines.

Conclusion

Now you know several ways to draw a heart. If you don't get the drawing, don't give up. When everything starts to work out for you, you can please your loved one with a beautiful handmade valentine.

To ensure adequate nutrition 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.

Read in this article

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 it has an angle of inclination, but for fat 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- the top. 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 connecting to 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 body type and total weight body 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. Cardiac cycle consists of a systolic and 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.

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

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

Our blood provides the entire body with oxygen and nutrients. In addition, it also has a cleansing function, helping in the removal of metabolic waste.

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

How much blood does the human heart pump?

The human heart pumps from 7,000 to 10,000 liters of blood in one day. This amounts to approximately 3 million liters per year. That works out to 200 million liters over a lifetime!

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

The circulatory system consists of about 65 thousand vessels, their total length is about 100 thousand kilometers! Yes, we didn't make a mistake.

Circulatory system

The human cardiovascular system is formed by two circles of blood circulation. With each heartbeat, blood moves in both circles at once.

Pulmonary circulation

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

Systemic circulation

1. From the left atrium, blood moves into the left ventricle, from where it is subsequently pumped through the aorta to big circle blood circulation
2. After going through a difficult path, the blood again arrives through the vena cava to the right atrium of the heart.

Normally, the amount of blood pushed out of the ventricles of the heart is the same with each contraction. Thus, an equal volume of blood simultaneously enters the greater and lesser circulation.

What is the difference between veins and arteries?

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

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

Anatomical structure

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

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

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

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

• two upper ones - the left and right atria;
• and two lower ones - the left and right ventricles.

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

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

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

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

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

The device of heart valves

Special heart valves allow you to constantly maintain blood flow in the correct (unidirectional) direction. The valves alternately open and close, either letting blood through or blocking its path. Interestingly, all four valves are located along the same plane.

Between the right atrium and the right ventricle is located tricuspid (tricuspid) valve. It contains three special leaflet plates that, during contraction of the right ventricle, can provide protection from the reverse flow (regurgitation) of blood into the atrium.

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

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

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

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

Cardiac vessels and coronary circulation

The human heart requires nutrition and oxygen, just like any other organ. The vessels that supply (nourish) the heart with blood are called coronary or coronary. These vessels branch from the base of the aorta.

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

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

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

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

How does the heart develop (form)?

Pulse path

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

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

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

Next, the atrioventricular node passes into His bundle(atrioventricular bundle divided into two legs). The right leg rushes towards the right ventricle. The left leg is divided into two more halves.

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

In case of weakness of the sinus node and atrioventricular block, the His bundle is capable of creating impulses at a speed of 30-40 per minute.

The conducting system deepens and further branches into smaller branches, eventually moving into Purkinje fibers, which penetrate the entire myocardium and serve as a transmission mechanism for contraction of the ventricular muscles. Purkinje fibers are capable of initiating impulses at a frequency of 15-20 per minute.

Exceptionally trained athletes can have normal resting heart rates down to the lowest recorded figure of just 28 beats per minute! However, for the average person, even one leading a very active lifestyle, a heart rate below 50 beats per minute may be a sign of bradycardia. If your heart rate is this low, you should be examined by a cardiologist.

Heartbeat

A newborn's heart rate may be around 120 beats per minute. As a person gets older, the pulse stabilizes between 60 and 100 beats per minute. Well trained athletes we're talking about about people with well-trained cardiovascular and respiratory systems) have a pulse of 40 to 100 beats per minute.

Controls heart rhythm nervous system- the sympathetic strengthens contractions, and the parasympathetic weakens.

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

In addition, the endocrine system can have a significant impact on the heart rhythm - both the frequency of contractions and their strength. For example, the release of the well-known adrenaline by the adrenal glands causes an increase in heart rate. The hormone with the opposite effect is acetylcholine.

Heart sounds

One of the most simple methods diagnosing heart disease is by listening to the chest using a stethoscope (auscultation).

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

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

Each sound consists of two components, but to the human ear they merge into one due to the very short period of time between them. If, under normal conditions of auscultation, additional tones become audible, this may indicate some kind of disease of the cardiovascular system.

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

Heart diseases

It is not surprising that the number of cardiovascular diseases. The heart is a complex organ that actually rests (if it can be called rest) only in the intervals between heartbeats. Any complex and constantly working mechanism itself requires as much as possible careful attitude and ongoing prevention.

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

The huge amounts of food consumed by the population of wealthy countries and the endless pursuit of money, as well as the associated stress, destroy our hearts. Another reason for the spread of cardiovascular diseases is physical inactivity - catastrophically low physical activity, destroying the entire body. Or, on the contrary, an illiterate passion for heavy physical exercise, often occurring in the background, the presence of which people do not even suspect and manage to die right during “health” activities.

Lifestyle and heart health

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

• Obesity.
• High blood pressure.
• Increased blood cholesterol levels.
• Physical inactivity or excessive physical activity.
• Abundant, low-quality food.
• Depressed emotional condition and stress.

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