Heart anatomy drawing step by step. Blood supply and innervation of the heart

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

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

Systemic circulation

From the left atrium, blood moves into the left ventricle, from where it is subsequently pumped through the aorta to big circle blood circulation
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's called transposition 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 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. With growing up the pulse ordinary person 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 against the background 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.

Do read this great article turning point in your life - give up bad habits and change your lifestyle.

Many of us took up a pen or pencil not only to pass homework in drawing at school. Sometimes, for one reason or another, an inexplicable urge to draw appears in the life of a teenager or an adult. How I want to pick up a pencil and simply start creating small masterpieces, even if only for myself or for a close circle of people without pretensions to global recognition and glory. It may seem that those performing simple pencil movements in the video or in front of you are putting in little to no effort, but in reality this is not the case. Professionalism in drawing, as in any other craft, comes only with experience. Even in the simplest drawings you can highlight subtleties and details that you had never even thought about before. Now we will look at one of the most simple drawings- heart. Remember school years or those moments when we all drew it to each other. This time we will learn how to draw a regular heart, with an arrow or wings. Also recommends subscribing. This way you will see new materials first.

Simple ways

And so, let's figure out how to beautifully draw a heart with a pencil step by step for beginners. All we need is a sheet of paper, a simple pencil, and, of course, due perseverance in this endeavor. To make the heart cute, you need to make it symmetrical, and to do this, do a couple of simple steps:

Draw two identical circles on a piece of paper in the same horizontal plane so that both circles intersect slightly. Let’s immediately say that the upper halves of the circles will help create beautiful symmetrical edges of the heart. Accordingly, those parts that make up the main drawing can be drawn boldly, and those that need to be removed can be made weaker. It is advisable to draw circles by hand, it’s okay if at first the circle doesn’t turn out very round, this will improve with practice. But if you are not initially satisfied with the quality of the circles, you can resort to auxiliary means.

The next figure in the figure is a cross. The vertical line of the cross should pass along the intersection of the circles; to form it, it is enough to draw a line through two points at which the circles from the first point intersected. It doesn’t make sense to raise the vertical line high in length; its lower part is more useful for the drawing, so don’t skimp and lower it down. In order to understand how low you should go, ask yourself: how to draw a heart beautifully, what proportions in height will be optimal for you so that the drawing turns out beautiful. The horizontal line is drawn perpendicular to the vertical in the middle of both circles.

From extreme points At the intersection of the circles with a horizontal line, lower two smooth symmetrical lines to the bottom point of the heart. You should determine the position of this lowest point yourself, because because of this
parameter the heart will turn out to be more elongated or more flattened.

Point thick line semicircles of each circle upward from horizontal line and to the first intersection point.

At this stage, drawing the heart is complete. All that remains is to remove the extra lines used in the construction and create the resulting drawing.

The perfect heart in terms of symmetry and shape is already in front of you. Of course it's not the only way, allowing you to draw a heart.

An easier option for advanced artists

If the previous version seemed boring and unattractive to you due to the presence large quantity additional constructions, if you need to complete the drawing much faster and there is no way to build circles, if you feel you have a sufficient level and skills, we bring to your attention the second method of how to draw a heart with a pencil step by step. But let’s make a reservation right away: you must be good at drawing symmetrical circles, otherwise the heart will turn out to be asymmetrical.

Divide the sheet into four parts with two perpendicular lines, in other words, draw the same cross.
Mark on vertical line the position of the upper and lower points of the heart, and on the horizontal the same segment to the left and right of the intersection point.
Connect the top point with a smooth semicircular line to the leftmost point on the horizontal axis and the same smooth semicircular line with the right point.
From the extreme left and right points, lower two smooth symmetrical lines to the bottom edge.

For more experienced artists

The next method of depicting a heart is even simpler; it will help to depict a heart in just a couple of steps and with the effect of rotation around its axis. But this method is only suitable for experienced specialists who can easily draw symmetrical semicircular lines by hand, without using additional constructions.

draw the most ordinary oval, the edges of which are elongated in a horizontal plane.
divide the oval with a line in the middle; if the heart should turn out at an angle, the line should be curved in the desired direction. This frame will show you how to draw a heart step by step and quickly.
select a point just below top point oval on a vertical line and, starting from this position, draw two lines on the upper part of the heart. These lines can completely fit into the oval, or they can protrude beyond its limits, it all depends on your wishes and vision perfect shape for drawing.
repeat the previous point with the bottom of the heart - lower two symmetrical lines to the bottom point.
add Cupid's arrow.

As a result, we get the following picture:

Let's add details

The drawing can be equipped with additional effects, such as wings, horns, halos, inscriptions, fire and similar additions that give additional effects and allow you to harmoniously include the image in one or another motif of the drawing, depending on your ideas. Today we will look at several options for drawing hearts with wings, as the most romantic version of this image. Wings give the hearts a special romanticism and sublime tones. It should be noted that the position of the wings in relation to the heart determines the nature of what the author wants to convey: raised, spread wings show strong intentions, pure feelings, desire for a loved one. On the contrary, the more the wings go down (and possibly connect downwards), the more this shows the heart’s attempt to close itself off from some external factors and problems, an attempt to hide something under its care and care.

Wings on the heart will tell you a lot

So, let's look at how to draw a heart with wings step by step with a pencil. Such a drawing will require you to first study the topic of how to draw a heart or ready-made template with the image of a heart. So, to begin with, we start from the fact that we already have a ready-made drawing. It is clear that the simplest and most uncomplicated way is to draw the wings by hand without any frames or additional constructions. This method may seem to be the most common of the above, but at the same time the most difficult, since it will require the author to have practical skills in drawing symmetrical lines and curvilinear figures by hand. Several options for depicting wings from the heart should be highlighted. Wings can be depicted from the sides or from the top. The position of the wings themselves in this case does not matter at all; what matters is from which part they grow, so to speak.

Wings with feathers in one row

If you decide to depict wings growing from the top of the heart, then it is better to depict them as small, decorative, this gives a certain sophistication and sophistication when in visual contact with the picture. When depicting wings on the sides of the heart, excellent option there will be wings spread to the sides. We do the following:

Chic wings with feathers in several rows

If you want to get a heart effect with huge wings, a span reminiscent of a flying eagle, then it is better to use a multi-level version of the wings rather than a single-level one. The more rows of feathers there are on the wings, the more spectacular the design will seem and the nobler the impulse of the heart itself, as if an eagle’s wings are carrying it towards its lover. So, let's figure out step by step how to draw a heart with wings with a pencil, depicting a rich pattern of feathers or other additional effects on the wings.

As in previous cases, we begin the drawing with the most ordinary frame of the future heart. He can be portrayed as different ways, but it is better to choose one of the above.
To the frame of the heart itself or its finished drawing we add the frame of future wings. There is no need to skimp on space here; the span and size of the wings themselves should be truly royal. Don’t skimp on space; it’s better to draw a smaller heart. Form the frame with several levels at once: the smallest is closest to the heart, the largest is the farthest.

Then start drawing each feather, starting with the smallest at the base and ending with the longest and largest at the edges. In principle, you can start applying layers, gradually depicting each row of feathers separately, superimposing the next one on top of it without a frame. Repeat the steps described with the second wing.

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.

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.

This is what a human heart looks like

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. Wide part(base) is located on top, closer to the collarbones, and is projected at the level of the 3rd rib.

Human heart shape

Heart shaped healthy person looks 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 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:

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.
Ventricular systole - the valves of the blood vessels open, blood flows into the aorta and pulmonary artery.
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:

Diagram of the structure of the heart

The heart is an organ consisting of to a greater extent from muscle tissue, it provides blood supply to all organs and tissues and has the following anatomy. Located in the left half of the chest at the level of the second to fifth rib, the average weight is 350 grams. The base of the heart is formed by the atria, pulmonary trunk and aorta, turned towards the spine, and the vessels that make up the base fix the heart in the chest cavity. The apex is formed by the left ventricle and is a rounded area facing down and to the left towards the ribs.

In addition, the heart has four surfaces:

Anterior or sternocostal.
Lower or diaphragmatic.
And two pulmonary: right and left.

The structure of the human heart is quite complex, but it can be described schematically as follows. Functionally, it is divided into two sections: right and left or venous and arterial. The four-chamber structure ensures the division of blood supply into a small and large circle. The atria are separated from the ventricles by valves that open only in the direction of blood flow. The right and left ventricles are separated by the interventricular septum, and the interatrial septum is located between the atria.

The heart wall has three layers:

The epicardium is the outer shell, tightly fused with the myocardium, and covered on top by the pericardial sac - the pericardium, which separates the heart from other organs and, due to the content of a small amount of fluid between its leaves, ensures a reduction in friction during contraction.
Myocardium - consists of muscle tissue, which is unique in its structure; it provides contraction and carries out excitation and conduction of impulses. In addition, some cells have automatism, that is, they are able to independently generate impulses that are transmitted along pathways throughout the myocardium. Muscle contraction occurs - systole.
Endocardium - covers the inner surface of the atria and ventricles and forms the heart valves, which are folds of the endocardium, consisting of connective tissue with a high content of elastic and collagen fibers.

The structure of the myocardium

The thickest layer of the heart is the muscular layer; in the area of the left ventricle it reaches a thickness of 11 to 14 mm, which is 2 times greater than the wall of the right ventricle (4 to 6 mm). In the area of the atria, the muscle layer is even smaller - 2–3 mm. The myocardium of the atria and ventricles is separated by a fibrous ring; it surrounds the right and left atrioventricular orifices. The structure of the myocardium of the atria and ventricles is also different; the former have two muscle layers, and the latter three. This indicates a greater functional load on the lower parts of the heart.

The muscle fibers of the atria form the so-called ears, which are a continuation of the chambers of the upper parts of the heart. The right and left ears are distinguished. The ventricular myocardium forms papillary muscles, from which chords extend to the mitral and tricuspid valves. They are needed so that the high pressure of the ventricles does not bend the valve leaflets into the atria and does not push blood in the opposite direction.

The interatrial and interventricular septum are formed by muscle tissue. Only the latter has a membranous part, in which there are practically no muscle fibers; it occupies 1/5 of the entire surface, the remaining 4/5 of the surface is the muscular section, reaching a thickness of up to 11 mm.

Heart valves and hemodynamics

Diagram of blood flow through the chambers of the heart

To ensure the correct sequence of blood flow, valves are placed between the chambers. The right atrium and ventricle are separated by the tricuspid valve (tricuspid), and the left by the mitral valve (bicuspid). In addition, there are valves in both the pulmonary trunk and the aorta, their function is the same - to prevent the reverse flow of blood from the arteries to the heart.

When the atria contract, blood is pushed into the ventricles, after which the tricuspid and mitral valves close, and the latter begin to contract, carrying blood into the pulmonary trunk and aorta. This is how the large and small circles of blood circulation begin, the hemodynamic mechanism for them looks as follows.

The pulmonary trunk emerges from the right ventricle, it divides into the right and left pulmonary arteries, they carry venous blood to the lungs for oxygenation. The oxygenated blood then returns through the four pulmonary veins to the left atrium. This is what the pulmonary circulation looks like.

The division of vessels into arteries and veins depends not on what kind of blood they carry, but on the direction relative to the heart. An artery is any vessel coming from the heart, and a vein is called any vessel leading to it. Therefore, in the pulmonary circulation, arteries carry venous blood, and veins carry arterial blood.

Then from the left atrium the blood enters the left ventricle, and from it into the aorta - the beginning of the great circle. Blood carries oxygen and nutrients through the arteries to the tissues; as it approaches the periphery, the diameter of the vessels decreases and gas exchange and release of nutrients occur at the capillary level. After these processes, the blood becomes venous and is directed through the veins to the heart. Two vena cava flow into the right atrium - superior and inferior. And the big circle ends.

The heart has about 60–80 such cycles per minute, with a volume of about 5–6 liters. During its entire life, it carries about 6 million liters of blood. This is a colossal work performed every second to ensure the normal life of the body.

Conducting system

Conduction system of the heart

The conduction system is responsible for the correct and consistent contraction of the myocardium by transmitting excitation along muscle fibers. It consists of a complex of formations consisting of atypical muscle cells capable of automaticity, conduction and excitation. Includes the following entities:

Sinus node (Kisa-Flaca) - it is located in the right atrium at the mouth of the vena cava, and is the main pacemaker of the human heart. It consists of specialized muscle cells (Pacemakers) capable of generating impulses at a frequency of 60–80 per minute.
Three internodal tracts and one interatrial tract arise from the sinus node (SU). The first ones transmit the impulse from the suture block to the atrioventricular one, and the second one ensures its conduction to the left atrium.
Atrioventricular node (AVN) - its task is to transmit excitation to the ventricles, but it does not do this immediately, but after such a phenomenon as atrioventricular delay. It is necessary so that the atria and ventricles do not contract at the same time, since the latter simply will not have anything to pump into the vessels.
The Hiss bundles are divided into right and left according to their location in the heart. The first innervates the right ventricle, and the left is divided into two branches - anterior and posterior and is responsible for excitation of the left ventricle.
The latest and greatest small elements The conduction system is Purkinje fibers - they are diffusely separated in the thickness of the myocardium and directly transmit the impulse to the muscle fiber.

The existence of such a clear sequence ensures normal cardiac cycle and blood supply to tissues.

Blood supply to the myocardium

Coronary arteries

The heart is an organ like others, and it also needs blood, the myocardium does not feed on blood from the cavities of the heart, for this there is a separate circulatory system, which some authors even call the third circle of blood circulation. At the beginning of the aorta, two coronary (coronary) arteries branch off to the heart: the right and left. They divide dichotomously and give off smaller branches to the myocardium. The left coronary artery supplies the anterior wall of the heart, the interventricular septum and the apex, while the right one supplies the posterolateral part of the myocardium. The outflow of blood occurs through the capillaries and then through the coronary veins to the right atrium.

A feature of the coronary circulation is that the arteries fill at the moment the myocardium relaxes, so during diastole the heart not only “rests”, but also nourishes. Disturbances in the blood flow of the heart lead to diseases such as coronary heart disease, angina pectoris and myocardial infarction.

Work of the heart

The cardiac cycle (CC) is the successive phases of systole (contraction), diastole (relaxation) and the subsequent general pause. During diastole, the heart fills with blood, first the atria and then the ventricles. After which myocardial contraction occurs, and the chambers are freed of blood. On average, the duration of atrial systole is from 0.1 to 0.17 seconds, and ventricular systole is 0.33–0.47 seconds.

Phases cardiac cycle

The ventricles account for more hard work, since they must push blood into vessels of smaller diameter and with such force that it reaches the periphery. Therefore, the muscle wall in them is much thicker.

The duration of the cardiac cycle depends on the number of heartbeats. So at rest it will be larger, but at physical activity less. On average, one SP lasts 0.8 seconds if the heart rate is 75 beats per minute.

Schematically, this process can be described as follows: from the superior and inferior vena cava and pulmonary veins, blood enters the atria, where pressure begins to increase and the myocardium stretches. Under the influence of these factors, atrial systole occurs. Next, the blood enters the ventricles and, according to the same principle, is pushed into the pulmonary trunk and aorta.

When the ventricles contract, the atrium is in diastole, and vice versa. But there is also certain time, in which both the ventricles and atria are simultaneously in the relaxation phase, and then in a general pause.