Where are the coronary vessels located? common truncus arteriosus

The arteries of the heart depart from the aortic bulb, and, like a crown, surround the heart, in connection with which they are called coronary arteries.

Right coronary artery goes to the right under the ear of the right atrium, lies in the coronary sulcus and goes around the right surface of the heart. The branches of the right coronary artery supply the walls of the right ventricle and atrium, the back of the interventricular septum, the papillary muscles of the left ventricle, the sinoatrial and atrioventricular nodes of the cardiac conduction system.

Left coronary artery thicker than the right one and is located between the beginning of the pulmonary trunk and the auricle of the left atrium. The branches of the left coronary artery supply the walls of the left ventricle, papillary muscles, most of the interventricular septum, the anterior wall of the right ventricle, and the walls of the left atrium.

The branches of the right and left coronary arteries form two arterial rings around the heart: transverse and longitudinal. They provide blood supply to all layers of the walls of the heart.

There are several types of blood supply to the heart:

right coronary type - most parts of the heart are supplied with blood by the branches of the right coronary artery;
left coronary type - most of the heart receives blood from the branches of the left coronary artery;
uniform type - blood is evenly distributed through the arteries;
middle right type - transitional type of blood supply;
middle left type - transitional type of blood supply.

It is believed that among all types of blood supply, the middle right type is predominant.

Veins of the heart more numerous than arteries. Most of the major veins of the heart are collected in coronary sinus- one common wide venous vessel. The coronary sinus is located in the coronary groove on the posterior surface of the heart and opens into the right atrium. The tributaries of the coronary sinus are 5 veins:

large vein of the heart;
middle vein of the heart;
small vein of the heart;
posterior vein of the left ventricle;
oblique vein of the left atrium.

In addition to these five veins that flow into the coronary sinus, the heart has veins that open directly into the right atrium: anterior veins of the heart, and smallest veins of the heart.

Vegetative innervation of the heart.

Parasympathetic innervation of the heart

Preganglionic parasympathetic cardiac fibers are part of the branches extending from the vagus nerves on both sides in the neck. Fibers from the right vagus nerve predominantly innervate the right atrium and especially abundantly the sinoatrial node. The fibers from the left vagus nerve are mainly suitable for the atrioventricular node. As a result, the right vagus nerve mainly affects the heart rate, and the left one on atrioventricular conduction. The parasympathetic innervation of the ventricles is weakly expressed and exerts its influence indirectly, due to the inhibition of sympathetic effects.

Sympathetic innervation of the heart

Sympathetic nerves, in contrast to the vagus, are almost evenly distributed throughout all parts of the heart. Preganglionic sympathetic cardiac fibers originate in the lateral horns of the upper thoracic segments of the spinal cord. In the cervical and upper thoracic ganglia of the sympathetic trunk, in particular in the stellate ganglion, these fibers switch to postganglionic neurons. The processes of the latter approach the heart as part of several cardiac nerves.

In most mammals, including humans, ventricular activity is controlled predominantly by sympathetic nerves. As for the atria and, especially, the sinoatrial node, they are under constant antagonistic influences from the vagus and sympathetic nerves.

Afferent nerves of the heart

The heart is innervated not only by efferent, but also by a large number of afferent fibers that go as part of the vagus and sympathetic nerves. Most of the afferent pathways belonging to the vagus nerves are myelinated fibers with sensory endings in the atria and left ventricle. When recording the activity of single atrial fibers, two types of mechanoreceptors were identified: B receptors that respond to passive stretch, and A receptors that respond to active tension.

Along with these myelinated fibers from specialized receptors, there is another large group of sensory nerves extending from the free endings of the dense subendocardial plexus of amyelinous fibers. This group of afferent pathways is part of the sympathetic nerves. It is believed that these fibers are responsible for the sharp pains with segmental irradiation observed in coronary heart disease (angina pectoris and myocardial infarction).

Development of the heart. Anomalies of the position and structure of the heart.

Development of the heart

The complex and peculiar structure of the heart, which corresponds to its role as a biological engine, develops in the embryonic period. In the embryo, the heart goes through stages when its structure is similar to the two-chambered heart of fish and the incompletely blocked heart of reptiles. The rudiment of the heart appears during the period of the neural tube in an embryo of 2.5 weeks, having a length of only 1.5 mm. It is formed from the cardiogenic mesenchyme ventrally from the head end of the foregut in the form of paired longitudinal cell strands, in which thin endothelial tubes are formed. In the middle of the 3rd week, in an embryo 2.5 mm long, both tubes merge with each other, forming a simple tubular heart. At this stage, the rudiment of the heart consists of two layers. The inner, thinner layer represents the primary endocardium. Outside is a thicker layer, consisting of the primary myocardium and epicardium. At the same time, there is an expansion of the pericardial cavity, which surrounds the heart. At the end of the 3rd week, the heart begins to contract.

Due to its rapid growth, the heart tube begins to bend to the right, forming a loop, and then takes on an S-shape. This stage is called the sigmoid heart. At the 4th week, in an embryo 5 mm long, several parts can be distinguished in the heart. The primary atrium receives blood from the veins converging to the heart. At the confluence of the veins, an expansion is formed, called the venous sinus. From the atrium, through a relatively narrow atrioventricular canal, blood enters the primary ventricle. The ventricle continues into the bulb of the heart, followed by the truncus arteriosus. In places where the ventricle passes into the bulb and the bulb into the arterial trunk, as well as on the sides of the atrioventricular canal, there are endocardial tubercles, from which the heart valves develop. In its structure, the embryonic heart is similar to the two-chambered heart of an adult fish, the function of which is to supply venous blood to the gills.

During the 5th and 6th weeks there are significant changes in the relative position of the heart. Its venous end moves cranially and dorsally, while the ventricle and bulb move caudally and ventrally. Coronal and interventricular grooves appear on the surface of the heart, and it acquires a definitive external form in general terms. In the same period, internal transformations begin, which lead to the formation of a four-chambered heart, characteristic of higher vertebrates. Partitions and valves develop in the heart. Atrial division begins in an embryo 6 mm long. In the middle of its posterior wall, a primary septum appears, it reaches the atrioventricular canal and merges with the endocardial tubercles, which by this time increase and divide the canal into the right and left parts. The primary septum is not complete; first, the primary and then the secondary interatrial openings are formed in it. Later, a secondary septum is formed, in which there is an oval opening. Through the foramen ovale, blood passes from the right atrium to the left. The hole is covered by the edge of the primary septum, which forms a damper that prevents the reverse flow of blood. Complete fusion of the primary and secondary septa occurs at the end of the intrauterine period.

At the 7th and 8th weeks of embryonic development, a partial reduction of the venous sinus occurs. Its transverse part is transformed into the coronary sinus, the left horn is reduced to a small vessel - the oblique vein of the left atrium, and the right horn forms part of the wall of the right atrium between the confluence of the superior and inferior vena cava. The common pulmonary vein and the trunks of the right and left pulmonary veins are drawn into the left atrium, as a result of which two veins from each lung open into the atrium.

The bulb of the heart in the embryo of 5 weeks merges with the ventricle, forming an arterial cone belonging to the right ventricle. The arterial trunk is divided by the spiral septum developing in it into the pulmonary trunk and the aorta. From below, the spiral septum continues towards the interventricular septum in such a way that the pulmonary trunk opens into the right, and the beginning of the aorta into the left ventricle. The endocardial tubercles located in the bulb of the heart take part in the formation of the spiral septum; at their expense, the valves of the aorta and pulmonary trunk are also formed.

The interventricular septum begins to develop on the 4th week, its growth occurs from the bottom up, but until the 7th week the septum remains incomplete. In its upper part is the interventricular opening. The latter is closed by growing endocardial tubercles, in this place the membranous part of the septum is formed. The atrioventricular valves form from the endocardial tubercles.

As the chambers of the heart separate and valves form, the tissues that make up the wall of the heart differentiate. The atrioventricular conduction system is secreted in the myocardium. The pericardial cavity is separated from the general body cavity. The heart moves from the neck to the chest cavity. The heart of the embryo and fetus is relatively large, since it provides not only the movement of blood through the vessels of the body of the embryo, but also the placental circulation.

Throughout the prenatal period, a message is maintained between the right and left halves of the heart through the oval hole. Blood entering the right atrium through the inferior vena cava is directed by the valves of this vein and the coronary sinus to the foramen ovale and through it into the left atrium. From the superior vena cava, blood flows into the right ventricle and is ejected into the pulmonary trunk. The small circle of blood circulation in the fetus does not function, since the narrow pulmonary vessels provide great resistance to blood flow. Only 5-10% of the blood entering the pulmonary trunk passes through the lungs of the fetus. The rest of the blood is discharged through the ductus arteriosus into the aorta and enters the systemic circulation, bypassing the lungs. Thanks to the foramen ovale and ductus arteriosus, the balance of blood flow through the right and left halves of the heart is maintained.

The heart is the most important organ for maintaining the life of the human body. Through its rhythmic contractions, it carries the blood throughout the body, providing nourishment to all the elements.

The coronary arteries are responsible for supplying oxygen to the heart.. Another common name for them is coronary vessels.

The cyclical repetition of this process ensures uninterrupted blood supply, which keeps the heart in working condition.

Coronaries are a whole group of vessels that supply blood to the heart muscle (myocardium). They carry oxygen-rich blood to all parts of the heart.

The outflow, depleted of its content (venous) blood, is carried out by 2/3 of the large vein, medium and small, which are woven into a single extensive vessel - the coronary sinus. The remainder is excreted by the anterior and Tebezian veins.

When the heart ventricles contract, the shutter closes off the arterial valve. The coronary artery at this point is almost completely blocked and blood circulation in this area stops.

The flow of blood resumes after the opening of the entrances to the arteries. The filling of the sinuses of the aorta occurs due to the impossibility of returning blood to the cavity of the left ventricle, after its relaxation, because. at this time, the dampers are closed.

Important! The coronary arteries are the only possible source of blood supply for the myocardium, so any violation of their integrity or mechanism of operation is very dangerous.

Scheme of the structure of the vessels of the coronary bed

The structure of the coronary network has a branched structure: several large branches and many smaller ones.

Arterial branches originate from the aortic bulb, immediately after the valve of the aortic valve and, bending around the surface of the heart, carry out blood supply to its different departments.

These vessels of the heart consist of three layers:

Initial - endothelium;
Muscular fibrous layer;
Adventitia.

This layering makes the walls of the vessels very elastic and durable.. This contributes to proper blood flow even under conditions of high stress on the cardiovascular system, including during intense sports, which increase the speed of blood movement up to five times.

Types of coronary arteries

All vessels that make up a single arterial network, based on the anatomical details of their location, are divided into:

Basic (epicardial)
Adnexal (other branches):

Right coronary artery. Its main duty is to feed the right heart ventricle. Partially supplies oxygen to the wall of the left heart ventricle and the common septum.
Left coronary artery. Provides blood flow to all other cardiac departments. It is a branching into several parts, the number of which depends on the personal characteristics of a particular organism.
envelope branch. It is a branch from the left side and feeds the septum of the corresponding ventricle. It is subject to increased thinning in the presence of the slightest damage.
Anterior descending(large interventricular) branch. It also comes from the left artery. It forms the basis for the supply of nutrients to the heart and the septum between the ventricles.
subendocardial arteries. They are considered part of the overall coronary system, but run deep within the heart muscle (myocardium) rather than on the surface itself.

All arteries are located directly on the surface of the heart itself (except for subendocardial vessels). Their work is regulated by their own internal processes, which also control the exact volume of blood supplied to the myocardium.

Variants of dominant blood supply

Dominant, feeding the posterior descending branch of the artery, which can be either right or left.

Determine the general type of blood supply to the heart:

The right blood supply is dominant if this branch departs from the corresponding vessel;
The left type of nutrition is possible if the posterior artery is a branch from the circumflex vessel;
The blood flow can be considered balanced if it comes simultaneously from the right trunk and from the circumflex branch of the left coronary artery.

Reference. The predominant source of nutrition is determined on the basis of the total flow of blood flow to the atrioventricular node.

In the vast majority of cases (about 70%), a dominant right blood supply is observed in a person. Equivalent work of both arteries is present in 20% of people. Left dominant nutrition through the blood is manifested only in the remaining 10% of cases.

What is coronary heart disease?

Ischemic heart disease (CHD), also called coronary heart disease (CHD), is any disease associated with a sharp deterioration in the blood supply to the heart, due to insufficient activity of the coronary system.

IHD can be either acute or chronic.

Most often, it manifests itself against the background of atherosclerosis of the arteries, which occurs due to a general thinning or violation of the integrity of the vessel.

A plaque is formed at the site of damage, which gradually increases in size, narrows the lumen and thereby prevents the normal flow of blood.

The list of coronary diseases includes:

angina;
Arrhythmia;
Embolism;
Arteritis;
heart attack;
Distortion of the coronary arteries;
Death due to cardiac arrest.

Coronary disease is characterized by undulating jumps in the general condition, in which the chronic phase rapidly passes into the acute phase and vice versa.

How pathologies are determined

Coronary diseases are manifested by severe pathologies, the initial form of which is angina pectoris. Subsequently, it develops into more serious diseases, and strong nervous or physical stress is no longer required for the onset of attacks.

angina pectoris

Scheme of changes in the coronary artery

In everyday life, such a manifestation of IHD is sometimes called "toad on the chest." This is due to the occurrence of asthma attacks, which are accompanied by pain.

Initially, symptoms begin in the chest area, after which they spread to the left back, shoulder blade, collarbone and lower jaw (rarely).

Pain is the result of oxygen starvation of the myocardium, the aggravation of which occurs in the process of physical, mental work, excitement or overeating.

myocardial infarction

Cardiac infarction is a very serious condition, accompanied by the death of certain parts of the myocardium (necrosis). This is due to a continuous cessation or incomplete flow of blood into the organ, which, most often, occurs against the background of the formation of a blood clot in the coronary vessels.

blockage of a coronary artery

Sharp pain in the chest, which is given to neighboring areas;
Heaviness, tightness of breath;
Trembling, muscle weakness, sweating;
Coronary pressure is greatly reduced;
Attacks of nausea, vomiting;
Fear, sudden panic attacks.

The part of the heart that has undergone necrosis does not perform its functions, and the remaining half continues its work in the same mode. This can cause the dead section to rupture. If a person is not provided with urgent medical care, then the risk of death is high.

Heart rhythm disorder

It is provoked by a spasmodic artery or untimely impulses that arose against the background of impaired conduction of the coronary vessels.

The main symptoms of manifestation:

Sensation of tremors in the region of the heart;
A sharp fading of contractions of the heart muscle;
dizziness, blurriness, darkness in the eyes;
The severity of breathing;
Unusual manifestation of passivity (in children);
Lethargy in the body, constant fatigue;
Pressing and prolonged (sometimes sharp) pain in the heart.

Rhythm failure often manifests itself due to a slowdown in metabolic processes if the endocrine system is out of order. It can also be a catalyst for long-term use of many drugs.

This concept is the definition of insufficient activity of the heart, which is why there is a shortage of blood supply to the whole organism.

Pathology can develop as a chronic complication of arrhythmia, heart attack, weakening of the heart muscle.

Acute manifestation is most often associated with the intake of toxic substances, injuries and a sharp deterioration in the course of other heart diseases.

This condition needs urgent treatment, otherwise the likelihood of death is high.

Against the background of diseases of the coronary vessels, the development of heart failure is often diagnosed.

The main symptoms of manifestation:

Violation of the heart rhythm;
Difficulty breathing;
Coughing fits;
Blurring and darkening in the eyes;
Swelling of the veins in the neck;
Swelling of the legs, accompanied by painful sensations;
Disconnection of consciousness;
Strong fatigue.

Often this condition is accompanied by ascites (accumulation of water in the abdominal cavity) and an enlarged liver. If a patient has persistent hypertension or diabetes mellitus, it is impossible to make a diagnosis.

coronary insufficiency

Heart failure is the most common type of ischemic disease. It is diagnosed if the circulatory system has partially or completely stopped supplying blood to the coronary arteries.

The main symptoms of manifestation:

Severe pain in the region of the heart;
Feeling of "lack of space" in the chest;
Discoloration of urine and its increased excretion;
Paleness of the skin, a change in its shade;
The severity of the work of the lungs;
Sialorrhoea (intense salivation);
Nausea, vomiting, rejection of the usual food.

In the acute form, the disease is manifested by an attack of sudden cardiac hypoxia due to arterial spasm. Chronic course is possible due to angina pectoris against the background of accumulation of atherosclerotic plaques.

There are three stages in the course of the disease:

Initial (mild);
Expressed;
A severe stage that, if not properly treated, can lead to death.

Causes of vascular problems

There are several factors contributing to the development of CHD. Many of them are a manifestation of insufficient care for one's health.

Important! Today, according to medical statistics, cardiovascular diseases are the number 1 cause of death in the world.

Every year, more than two million people die from coronary artery disease, most of whom are part of the population of "prosperous" countries, with a comfortable sedentary lifestyle.

The main causes of ischemic disease can be considered:

Tobacco smoking, incl. passive inhalation of smoke;
Eating foods high in cholesterol
Excess weight (obesity);
Hypodynamia, as a consequence of a systematic lack of movement;
Exceeding the norm of sugar in the blood;
Frequent nervous tension;
Arterial hypertension.

There are also factors independent of a person that affect the state of blood vessels: age, heredity and gender.

Women are more resistant to such ailments and therefore they are characterized by a long course of the disease. And men more often suffer precisely from the acute form of pathologies that end in death. Surgical intervention is prescribed in case of ineffectiveness of traditional therapy. To better nourish the myocardium, coronary bypass surgery is used - they connect the coronary and external veins where the intact portion of the vessels is located. Dilation can be performed if the disease is associated with hyperproduction of the artery wall layer. This intervention involves the introduction of a special balloon into the lumen of the vessel, expanding it in places of a thickened or damaged shell.

Heart before and after chamber dilatation
Reducing the risk of complications
Own preventive measures reduce the risk of coronary artery disease. They also minimize the negative consequences during the rehabilitation period after treatment or surgery.
The simplest advice available to everyone:
Rejection of bad habits;
Balanced diet (special attention to Mg and K);
Daily walks in the fresh air;
Physical activity;
Control of blood sugar and cholesterol;
Hardening and sound sleep.

The coronary system is a very complex mechanism that needs to be treated with care. The pathology that has manifested once is steadily progressing, accumulating more and more new symptoms and worsening the quality of life, therefore, the recommendations of specialists and the observance of elementary health standards should not be neglected.
Systematic strengthening of the cardiovascular system will allow you to keep the vigor of the body and soul for many years.
Video. Angina. Myocardial infarction. Heart failure. How to protect your heart.

coronary arteries

stomach and heart. - B. arteries of the stomach(arteriae coronariae ventriculi) depart from the celiac artery (art. coeliaca) or its branches (hepatic artery, splenic, etc.). There are four of them; of these, two are connected at the lesser curvature of the stomach and thus form the upper arterial arch of the stomach (arcus arteriosus ventriculi superior); the other two, merging at the greater curvature, form the lower arterial arch of the stomach. A mass of small branches depart from both arterial arches, which enter the wall of the stomach and here break up into the smallest blood stems. B. artery heart (arteria coronaria cordis) - a branch that gives the main vascular trunk of the body (see Aorta), while still in the cavity of the pericardial sac. Starting with two openings lying approximately at the same height as the free edge of the aortic semilunar valves, two V. arteries depart from the expanded part of the latter, called the bulb, and go to the anterior surface of the heart, to its transverse groove. Here, both V. arteries diverge: the right one goes to the right edge of the heart, bends around it, passes to the back surface and along the posterior longitudinal groove reaches the apex of the heart, into the tissue of which it enters; the left gives first a large branch, reaching along the anterior longitudinal groove to the apex of the heart, then goes to the left edge of the heart, passes to the back and here, at the height of the transverse groove, enters the muscles of the heart. Throughout its length, both V. arteries give small branches that penetrate into the thickness of the wall of the heart. The right V. artery supplies blood to the walls of the right atrium, the right ventricle, the apex of the heart, and, in part, the left ventricle; left - apex of the heart, left atrium, left ventricle, ventricular septum. If an animal artificially closes or even only narrows the lumen of the V. artery, then after a while the heart stops contracting (cardiac paralysis), since the heart muscle can work correctly only as long as the V. arteries supply it with sufficient blood necessary for nourishment. quantity. On V. arteries of the human heart, there are pathological changes that affect in a similar way, that is, they completely stop or significantly reduce the flow of blood to the walls of the heart (see Arteriosclerosis, Thrombosis, Embolism) and thereby entail instant death or very painful suffering - myocarditis with its consequences (aneurysm, rupture, heart attack), often angina pectoris, and so on.

Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron. - St. Petersburg: Brockhaus-Efron. 1890-1907 .

See what "Coronary arteries" are in other dictionaries:

Trunk arteries - … Atlas of human anatomy

- (Greek, singular artēría), blood vessels that carry oxygenated (arterial) blood from the heart to all organs and tissues of the body (only the pulmonary artery carries venous blood from the heart to the lungs). * * * ARTERIES ARTERIES (Greek, singular… … encyclopedic Dictionary

Arteries that supply blood to the heart muscle. The right and left coronary arteries (right and left coronary arteries) depart from the bulb and give off branches that supply the heart. See Coronary angioplasty. Bypass vascular shunt. Source:… … medical terms

CORONARY ARTERIES, CORONARY ARTERIES- (coronary arteries) arteries supplying blood to the heart muscle. The right and left coronary arteries (right and left coronary arteries) depart from the bulb and give off branches that supply the heart. See Coronary angioplasty. Bypass shunt ... ... Explanatory Dictionary of Medicine

Vessels of the heart- Arteries. The blood supply to the heart is carried out by two arteries: the right coronary artery, a. coronaria dextra, and the left coronary artery, a. coronaria sinistra, which are the first branches of the aorta. Each of the coronary arteries comes out of ... ... Atlas of human anatomy

HEART- HEART. Contents: I. Comparative anatomy........... 162 II. Anatomy and histology ........... 167 III. Comparative physiology .......... 183 IV. Physiology .................. 188 V. Pathophysiology ................. 207 VI. Physiology, pat. ... ...

ANGINA PECTORIS- Angina pectoris, (angina pectoris, synonymous with Heberden's asthma), in its essence, is primarily a subjective syndrome, manifesting itself in the form of severe retrosternal pain, accompanied by a sense of fear and a sense of the immediate proximity of death. Story. 21… Big Medical Encyclopedia

In the diagram, the Aorta (lat..arteria ortha, a.ortha direct artery [source not specified 356 days]) is the largest unpaired arterial vessel of the great circle ... Wikipedia

LICHTENBERG- Alexander (Alexander Lich tenberg, born in 1880), an outstanding contemporary German. urologist. He was an assistant to Czerny and Narath. In 1924, he received the head of the urological department in the Catholic church of St. Hedwigs in Berlin, to a swarm in ... ... Big Medical Encyclopedia

The science that studies the structure of the body, individual organs, tissues and their relationships in the body. All living things are characterized by four features: growth, metabolism, irritability and the ability to reproduce themselves. The combination of these signs ... ... Collier Encyclopedia

The arteries of the heart depart from the aortic bulb - the initial expanded section of the ascending aorta and, like a crown, surround the heart, in connection with which they are called coronary arteries. The right coronary artery begins at the level of the right sinus of the aorta, and the left coronary artery - at the level of its left sinus. Both arteries depart from the aorta below the free (upper) edges of the semilunar valves, therefore, during contraction (systole) of the ventricles, the valves cover the openings of the arteries and almost do not let blood flow to the heart. With relaxation (diastole) of the ventricles, the sinuses fill with blood, blocking its path from the aorta back to the left ventricle, and at the same time open the access of blood to the vessels of the heart.

Right coronary artery

It leaves to the right under the ear of the right atrium, lies in the coronary sulcus, goes around the right pulmonary surface of the heart, then follows its posterior surface to the left, where it anastomoses with its end with the circumflex branch of the left coronary artery. The largest branch of the right coronary artery is the posterior interventricular branch, which is directed along the sulcus of the same name towards the apex of the heart. The branches of the right coronary artery supply the wall of the right ventricle and atrium, the posterior part of the interventricular septum, the papillary muscles of the right ventricle, the posterior papillary muscle of the left ventricle, the sinoatrial and atrioventricular nodes of the cardiac conduction system.

Left coronary artery

A little thicker than the right. Located between the beginning of the pulmonary trunk and the left atrial appendage, it is divided into two branches: the anterior interventricular branch and the circumflex branch. The latter, which is a continuation of the main trunk of the coronary artery, goes around the heart on the left, located in its coronary sulcus, where it anastomoses with the right coronary artery on the posterior surface of the organ. The anterior interventricular branch follows the sulcus of the same name towards the apex of the heart. In the region of the cardiac notch, it sometimes passes to the diaphragmatic surface of the heart, where it anastomoses with the terminal section of the posterior interventricular branch of the right coronary artery. Branches of the left coronary artery supply the wall of the left ventricle, including the papillary muscles, most of the interventricular septum, the anterior wall of the right ventricle, and the wall of the left atrium.

The branches of the right and left coronary arteries, connecting, form two arterial rings in the heart: a transverse one, located in the coronary sulcus, and a longitudinal one, the vessels of which are located in the anterior and posterior interventricular sulci.

Branches of the coronary arteries provide blood supply to all layers of the walls of the heart. In the myocardium, where the level of oxidative processes is the highest, microvessels anastomosing with each other repeat the course of the bundles of muscle fibers of its layers.

There are various options for the distribution of branches of the coronary arteries, which are called types of blood supply to the heart. The main ones are as follows: right coronary, when most parts of the heart are supplied with blood by the branches of the right coronary artery; left coronary, when most of the heart receives blood from the branches of the left coronary artery, and medium, or uniform, in which both coronary arteries evenly participate in the blood supply to the walls of the heart. There are also transitional types of blood supply to the heart - middle right and middle left. It is generally accepted that among all types of blood supply to the heart, the middle right type is predominant.

Variants and anomalies of the position and branching of the coronary arteries are possible. They are manifested in changes in the places of origin and the number of coronary arteries. So, the latter can depart from the aopta directly above the semilunar valves or much higher - from the left subclavian artery, and not from the aorta. The coronary artery may be the only one, that is, unpaired, there may be 3-4 coronary arteries, and not two: two arteries depart to the right and left of the aorta, or two from the aorta and two from the left subclavian artery.

Along with the coronary arteries, non-permanent (additional) arteries go to the heart (especially to the pericardium). These can be mediastinal-pericardial branches (upper, middle and lower) of the internal thoracic artery, branches of the pericardial phrenic artery, branches extending from the concave surface of the aortic arches, etc.

Coronary arteries of the heart

In this section, you will get acquainted with the anatomical location of the coronary vessels of the heart. To get acquainted with the anatomy and physiology of the cardiovascular system, you need to visit the section "Heart Diseases".

Left coronary artery.
Right coronary artery

The blood supply to the heart is carried out through two main vessels - the right and left coronary arteries, starting from the aorta immediately above the semilunar valves.

Left coronary artery.

The left coronary artery starts from the left posterior sinus of Wilsalva, goes down to the anterior longitudinal groove, leaving the pulmonary artery to the right of itself, and the left atrium and the ear surrounded by adipose tissue, which usually covers it, to the left. It is a wide, but short trunk, usually no more than 10-11 mm long.

The left coronary artery is divided into two, three, in rare cases, four arteries, of which the anterior descending (LAD) and circumflex branch (OB), or arteries, are of the greatest importance for pathology.

The anterior descending artery is a direct continuation of the left coronary artery.

Along the anterior longitudinal cardiac sulcus, it goes to the region of the apex of the heart, usually reaches it, sometimes bends over it and passes to the back surface of the heart.

Several smaller lateral branches depart from the descending artery at an acute angle, which are directed along the anterior surface of the left ventricle and can reach the blunt edge; in addition, numerous septal branches depart from it, perforating the myocardium and branching in the anterior 2/3 of the interventricular septum. Lateral branches feed the anterior wall of the left ventricle and give branches to the anterior papillary muscle of the left ventricle. The superior septal artery gives a branch to the anterior wall of the right ventricle and sometimes to the anterior papillary muscle of the right ventricle.

Throughout the entire length of the anterior descending branch lies on the myocardium, sometimes plunging into it with the formation of muscle bridges 1-2 cm long. The rest of its anterior surface is covered with fatty tissue of the epicardium.

The envelope branch of the left coronary artery usually departs from the latter at the very beginning (the first 0.5-2 cm) at an angle close to a right one, passes in the transverse groove, reaches the blunt edge of the heart, goes around it, passes to the posterior wall of the left ventricle, sometimes reaches the posterior interventricular sulcus and in the form of the posterior descending artery goes to the apex. Numerous branches depart from it to the anterior and posterior papillary muscles, the anterior and posterior walls of the left ventricle. One of the arteries that feed the sinoauricular node also departs from it.

Right coronary artery.

The right coronary artery originates in the anterior sinus of Vilsalva. First, it is located deep in the adipose tissue to the right of the pulmonary artery, goes around the heart along the right atrioventricular sulcus, passes to the posterior wall, reaches the posterior longitudinal sulcus, and then, in the form of a posterior descending branch, descends to the apex of the heart.

The artery gives 1-2 branches to the anterior wall of the right ventricle, partly to the anterior septum, both papillary muscles of the right ventricle, the posterior wall of the right ventricle and the posterior interventricular septum; the second branch also departs from it to the sinoauricular node.

There are three main types of myocardial blood supply: middle, left and right. This subdivision is based mainly on variations in the blood supply to the posterior or diaphragmatic surface of the heart, since the blood supply to the anterior and lateral regions is fairly stable and not subject to significant deviations.

At middle type all three main coronary arteries are well developed and fairly evenly developed. The blood supply to the entire left ventricle, including both papillary muscles, and the anterior 1/2 and 2/3 of the interventricular septum is carried out through the system of the left coronary artery. The right ventricle, including both right papillary muscles and the posterior 1/2-1/3 septum, receives blood from the right coronary artery. This appears to be the most common type of blood supply to the heart.

At left type blood supply to the entire left ventricle and, in addition, to the entire septum and partly the posterior wall of the right ventricle is carried out due to the developed circumflex branch of the left coronary artery, which reaches the posterior longitudinal groove and ends here in the form of the posterior descending artery, giving part of the branches to the posterior surface of the right ventricle .

Right type observed with a weak development of the circumflex branch, which either ends without reaching the obtuse edge, or passes into the coronary artery of the obtuse edge, not spreading to the posterior surface of the left ventricle. In such cases, the right coronary artery, after leaving the posterior descending artery, usually gives a few more branches to the posterior wall of the left ventricle. In this case, the entire right ventricle, the posterior wall of the left ventricle, the posterior left papillary muscle and partly the apex of the heart receive blood from the right coronary arteriole.

Myocardial blood supply is carried out directly :

a) capillaries lying between muscle fibers, braiding them and receiving blood from the system of coronary arteries through arterioles;

b) a rich network of myocardial sinusoids;

c) Viessant-Tebesia vessels.

With an increase in pressure in the coronary arteries and an increase in the work of the heart, the blood flow in the coronary arteries increases. The lack of oxygen also leads to a sharp increase in coronary blood flow. The sympathetic and parasympathetic nerves seem to have little effect on the coronary arteries, with their main action directly on the heart muscle.

Outflow occurs through the veins, which are collected in the coronary sinus

Venous blood in the coronary system is collected in large vessels, usually located near the coronary arteries. Some of them merge, forming a large venous canal - the coronary sinus, which runs along the back surface of the heart in the groove between the atria and ventricles and opens into the right atrium.

Intercoronary anastomoses play an important role in coronary circulation, especially in pathological conditions. There are more anastomoses in the hearts of people suffering from ischemic disease, so the closure of one of the coronary arteries is not always accompanied by necrosis in the myocardium.

In normal hearts, anastomoses are found only in 10-20% of cases, and they are of small diameter. However, their number and magnitude increase not only in coronary atherosclerosis, but also in valvular heart disease. Age and gender by themselves have no effect on the presence and degree of development of anastomoses.

Heart (cor)

The circulatory system consists of a huge number of elastic vessels of various structures and sizes - arteries, capillaries, veins. At the center of the circulatory system is the heart, a living suction-suction pump.

The structure of the heart. The heart is the central apparatus of the vascular system, highly capable of automatic action. In humans, it is located in the chest behind the sternum, for the most part (2 / 3) in the left half.

The heart lies (Fig. 222) on the tendon center of the diaphragm almost horizontally, located between the lungs in the anterior mediastinum. It occupies an oblique position and faces its wide part (base) up, back and to the right, and its narrower cone-shaped part (top) forward, down and to the left. The upper border of the heart is located in the second intercostal space; the right border protrudes approximately 2 cm beyond the right edge of the sternum; the left border passes, not reaching the mid-clavicular line (passing through the nipple in men) by 1 cm. The tip of the cardiac cone (the junction of the right and left contour lines of the heart) is placed in the fifth left intercostal space down from the nipple. In this place, at the moment of contraction of the heart, a cardiac impulse is felt.

Rice. 222. Position of the heart and lungs. 1 - heart in a heart shirt; 2 - diaphragm; 3 - tendon center of the diaphragm; 4 - thymus gland; 5 - lung; 6 - liver; 7 - crescent ligament; 8 - stomach; 9 - nameless artery; 10 - subclavian artery; 11 - common carotid arteries; 12 - thyroid gland; 13 - thyroid cartilage; 14 - superior vena cava

In shape (Fig. 223), the heart resembles a cone, with its base up and its top down. Large blood vessels enter and leave the wide part of the heart - the base. The weight of the heart in healthy adults ranges from 250 to 350 g (0.4-0.5% of body weight). By the age of 16, the weight of the heart increases 11 times compared to the weight of the heart of a newborn (V.P. Vorobyov). The average size of the heart: length 13 cm, width 10 cm, thickness (anteroposterior diameter) 7-8 cm. In terms of volume, the heart is approximately equal to the clenched fist of the person to whom it belongs. Of all vertebrates, birds have the largest relative heart size, requiring a particularly powerful motor to move blood.

Rice. 223. Heart (front view). 1 - nameless artery; 2 - superior vena cava; 3 - ascending aorta; 4 — a coronal furrow with the right coronal artery; 5 - right ear; 6 - right atrium; 7 - right ventricle; 8 - apex of the heart; 9 - left ventricle; 10 - anterior longitudinal furrow; 11 - left ear; 12 - left pulmonary veins; 13 - pulmonary artery; 14 - aortic arch; 15 - left subclavian artery; 16 - left common carotid artery

In higher animals and humans, the heart is four-chambered, that is, it consists of four cavities - two atria and two ventricles; its walls consist of three layers. The most powerful and functionally important layer is the muscular layer, the myocardium. Muscular tissue of the heart is different from skeletal muscle; it also has transverse banding, but the ratio of cell fibers is different than in the muscles of the skeleton. The muscle bundles of the heart muscle have a very complex arrangement (Fig. 224). In the walls of the ventricles, it is possible to trace three muscle layers: the outer longitudinal, the middle annular and the inner longitudinal. Between the layers there are transitional fibers that make up the predominant mass. The outer longitudinal fibers, deepening obliquely, gradually pass into the annular, which also obliquely gradually pass into the internal longitudinal; the papillary muscles of the valves are also formed from the latter. On the very surface of the ventricles lie fibers covering both ventricles together. Such a complex course of muscle bundles provides the most complete contraction and emptying of the heart cavities. The muscular layer of the walls of the ventricles, especially in the left, which drives the blood in a large circle, is much thicker. The muscle fibers that form the walls of the ventricles are assembled from the inside into numerous bundles, which are located in different directions, forming fleshy crossbars (trabeculae) and muscle protrusions - papillary muscles; tendon cords go from them to the free edge of the valves, which stretch when the ventricles contract and do not allow the valves to open in the atrial cavity under the pressure of blood.

Rice. 224. The course of the muscle fibers of the heart (semi-schematically)

The muscle layer of the walls of the atria is thin, since they have a small load - they only drive blood into the ventricles. Superficial muscle pins, facing inside the atrial cavity, form the pectinate muscles.

From the outer surface on the heart (Fig. 225, 226) two grooves are noticeable: longitudinal, covering the heart in front and behind, and transverse (coronal), located annularly; along them are the own arteries and veins of the heart. These grooves inside correspond to the partitions that divide the heart into four cavities. The longitudinal interatrial and interventricular septum divides the heart into two halves completely isolated from one another - the right and left hearts. The transverse septum divides each of these halves into an upper chamber - the atrium (atrium) and a lower one - the ventricle (ventriculus). Thus, two non-communicating atria and two separate ventricles are obtained. The superior vena cava, inferior vena cava and coronary sinus flow into the right atrium; the pulmonary artery departs from the right ventricle. The right and left pulmonary veins flow into the left atrium; the aorta departs from the left ventricle.

Rice. 225. Heart and large vessels (front view). 1 - left common carotid artery; 2 - left subclavian artery; 3 - aortic arch; 4 - left pulmonary veins; 5 - left ear; 6 - left coronary artery; 7 - pulmonary artery (cut off); 8 - left ventricle; 9 - apex of the heart; 10 - descending aorta; 11 - inferior vena cava; 12 - right ventricle; 13 - right coronary artery; 14 - right ear; 15 - ascending aorta; 16 - superior vena cava; 17 - unnamed artery

Rice. 226. Heart (rear view). 1 - aortic arch; 2 - left subclavian artery; 3 - left common carotid artery; 4 - unpaired vein; 5 - superior vena cava; 6 - right pulmonary veins; 7 - inferior vena cava; 8 - right atrium; 9 - right coronary artery; 10 - middle vein of the heart; 11 - descending branch of the right coronary artery; 12 - right ventricle; 13 - apex of the heart; 14 - diaphragmatic surface of the heart; 15 - left ventricle; 16-17 - common drain of the cardiac veins (coronary sinus); 18 - left atrium; 19 - left pulmonary veins; 20 - branches of the pulmonary artery

The right atrium communicates with the right ventricle through the right atrioventricular orifice (ostium atrioventriculare dextrum); and the left atrium with the left ventricle through the left atrioventricular orifice (ostium atrioventriculare sinistrum).

The upper part of the right atrium is the right ear of the heart (auricula cordis dextra), which looks like a flattened cone and is located on the anterior surface of the heart, covering the aortic root. In the cavity of the right ear, the muscle fibers of the atrial wall form parallel muscle rollers.

The left heart auricle (auricula cordis sinistra) departs from the anterior wall of the left atrium, in the cavity of which there are also muscle rollers. The walls in the left atrium are smoother from the inside than in the right.

The inner shell (Fig. 227), lining the inside of the heart cavity, is called the endocardium (endocardium); it is covered with a layer of endothelium (a derivative of the mesenchyme), which also extends to the inner lining of the vessels extending from the heart. On the border between the atria and ventricles there are thin lamellar outgrowths of the endocardium; here the endocardium, as if folded in half, forms strongly protruding folds, also covered with endothelium on both sides - these are the heart valves (Fig. 228) that close the atrioventricular openings. In the right atrioventricular opening there is a tricuspid valve (valvula tricuspidalis), consisting of three parts - thin fibrous elastic plates, and in the left - a bicuspid valve (valvula bicuspidalis, s. mytralis), consisting of two of the same plates. These flap valves open during atrial systole only towards the ventricles.

Rice. 227. The heart of an adult with the ventricles opened in front. 1 - ascending aorta; 2 - arterial ligament (overgrown ductus arteriosus); 3 - pulmonary artery; 4 - semilunar valves of the pulmonary artery; 5 - left ear of the heart; 6 - anterior cusp of a bicuspid valve; 7 - anterior papillary muscle; 8 — a back leaflet of the bicuspid valve; 9 - tendon threads; 10 - posterior papillary muscle; 11 - left ventricle of the heart; 12 - right ventricle of the heart; 13 - rear cusp of the tricuspid valve; 14 - medial cusp of the tricuspid valve; 15 - right atrium; 16 - anterior cusp of the tricuspid valve, 17 - arterial cone; 18 - right ear

Rice. 228. Heart valves. Opened heart. The direction of blood flow is shown by arrows. 1 - bicuspid valve of the left ventricle; 2 - papillary muscles; 3 - semilunar valves; 4 - tricuspid valve of the right ventricle; 5 - papillary muscles; 6 - aorta; 7 - superior vena cava; 8 - pulmonary artery; 9 - pulmonary veins; 10 - coronary vessels

At the exit site of the aorta from the left ventricle and the pulmonary artery from the right ventricle, the endocardium also forms very thin folds in the form of concave (into the ventricular cavity) semicircular pockets, three in each hole. In their form, these valves are called semilunar (valvulae semilunares). They open only upward towards the vessels during ventricular contraction. During the relaxation (expansion) of the ventricles, they automatically close and do not allow the reverse flow of blood from the vessels to the ventricles; when the ventricles are compressed, they reopen with a current of ejected blood. The semilunar valves are devoid of musculature.

It can be seen from the foregoing that in humans, as in other mammals, the heart has four valve systems: two of them, valvular, separate the ventricles from the atria, and two, semilunar, separate the ventricles from the arterial system. There are no valves at the place where the pulmonary veins enter the left atrium; but the veins approach the heart at an acute angle in such a way that the thin wall of the atrium forms a fold, partly acting as a valve or damper. In addition, there are thickenings of annular muscle fibers of the adjacent part of the atrial wall. These thickenings of muscle tissue during atrial contraction compress the mouths of the veins and thus prevent the reverse flow of blood into the veins, so that it enters only the ventricles.

In an organ that performs such a big job as the heart, support structures naturally develop, to which the muscle fibers of the heart muscle are attached. This soft cardiac "skeleton" includes: tendon rings around its openings equipped with valves, fibrous triangles located at the aortic root and the membranous part of the ventricular septum; they all consist of bundles of collagen fibrils with an admixture of elastic fibers.

The heart valves are composed of dense and elastic connective tissue (doubling of the endocardium - duplication). When the ventricles contract, the cusp valves, under pressure from the blood in the cavity of the ventricles, straighten out, like stretched sails, and touch so tightly that they completely close the openings between the atrial cavities and the ventricular cavities. At this time, the tendon threads mentioned above support them and prevent them from turning inside out. Therefore, blood from the ventricles cannot get back into the atria; under the pressure of the contracting ventricles, it is pushed out of the left ventricle into the aorta, and from the right into the pulmonary artery. Thus, all the valves of the heart open only in one direction - in the direction of blood flow.

The size of the cavities of the heart, depending on the degree of filling with blood and the intensity of its work, varies. So, the capacity of the right atrium ranges from 110-185 cm 3, the right ventricle - from 160 to 230 cm 3, the left atrium - from 100 to 130 cm 3 and the left ventricle - from 143 to 212 cm 3.

The heart is covered with a thin serous membrane, forming two sheets, passing one into the other at the place where large vessels leave the heart. The inner, or visceral, leaf of this sac, directly covering the heart and tightly soldered to it, is called the epicardium (epieardium), the outer, or parietal, leaf is called the pericardium (pericardium). The parietal sheet forms a bag covering the heart - this is a heart bag, or a heart shirt. The pericardium is adjacent to the sheets of the mediastinal pleura from the sides, adheres to the tendon center of the diaphragm from below, and is attached in front by connective tissue fibers to the posterior surface of the sternum. A slit-like hermetically closed cavity is formed between both sheets of the heart sac around the heart, always containing a certain amount (about 20 g) of serous fluid. The pericardium insulates the heart from its surrounding organs, and the fluid moistens the surface of the heart, reducing friction and making its movements slip during contractions. In addition, the strong fibrous tissue of the pericardium limits and prevents excessive stretching of the muscle fibers of the heart; if there were no pericardium, which anatomically limits the volume of the heart, it would be in danger of overstretching, especially during periods of its most intense and unusual activity.

Incoming and outgoing vessels of the heart. The superior and inferior vena cava join the right atrium. At the confluence of these veins, a wave of contraction of the heart muscle arises, quickly covering both atria and then passing to the ventricles. In addition to the large vena cava, the coronary sinus of the heart (sinus eoronarius cordis) also flows into the right atrium, through which venous blood flows from the walls of the heart itself. The opening of the sinus closes with a small fold (thebesian valve).

Four years of intravenous veins flow into the left atrium. The largest artery in the body, the aorta, emerges from the left ventricle. It goes first to the right and up, then, bending back and to the left, it spreads through the left bronchus in the form of an arc. The pulmonary artery emerges from the right ventricle; it goes first to the left and up, then turns to the right and divides into two branches, heading towards both lungs.

In total, the heart has seven input - venous - openings and two output - arterial - openings.

Circles of blood circulation(Fig. 229). Due to the long and complex evolution of the development of the circulatory organs, a certain system of supplying the body with blood has been established, which is characteristic of humans and all mammals. As a rule, blood moves inside a closed system of tubes, which includes a permanently powerful muscular organ - the heart. The heart, as a result of its historical automatism and regulation by the central nervous system, continuously and rhythmically drives blood throughout the body.

Rice. 229. Scheme of blood circulation and lymph circulation. The red color indicates the vessels through which arterial blood flows; blue - vessels with venous blood; purple color shows the portal vein system; yellow - lymphatic vessels. 1 - right half of the heart; 2 - left half of the heart; 3 - aorta; 4 - pulmonary veins; superior and inferior vena cava; 6 - pulmonary artery; 7 - stomach; 8 - spleen; 9 - pancreas; 10 - intestines; 11 - portal vein; 12 - liver; 13 - kidney

Blood from the left ventricle of the heart through the aorta first enters large arteries, which gradually branch into smaller ones and then pass into arterioles and capillaries. Through the thinnest walls of the capillaries, there is a constant exchange of substances between the blood and body tissues. Passing through a dense and numerous network of capillaries, the blood gives oxygen and nutrients to the tissues, and in return receives carbon dioxide and cellular metabolic products. Changing in its composition, the blood further becomes unsuitable for maintaining respiration and nutrition of cells, it turns from arterial to venous. Capillaries begin to gradually merge first into venules, venules into small veins, and the latter into large venous vessels - the superior and inferior vena cava, through which blood returns to the right atrium of the heart, thus describing the so-called large, or bodily, circle of blood circulation.

The venous blood that has entered the right ventricle from the right atrium is sent to the lungs through the pulmonary artery, where it is released from carbon dioxide and saturated with oxygen in the smallest network of pulmonary capillaries, and then returns again through the pulmonary veins to the left atrium, and from there to the left ventricle of the heart, from where it again comes to supply the tissues of the body. The circulation of blood along the way from the heart through the lungs and back is a small circle of blood circulation. The heart not only performs the work of a motor, but also acts as an apparatus that controls the movement of blood. Switching blood from one circle to another is achieved (in mammals and birds) by complete separation of the right (venous) half of the heart from its left (arterial) half.

These phenomena in the circulatory system have become known to science since the time of Harvey, who discovered (1628) blood circulation, and Malpighi (1661), who established blood circulation in capillaries.

Blood supply to the heart(see fig. 226). The heart, carrying an exceptionally important service in the body and doing a great job, itself needs abundant nutrition. This is an organ that is in an active state throughout a person's life and never has a rest period that would last more than 0.4 seconds. Naturally, this organ must be supplied with a particularly abundant amount of blood. Therefore, its blood supply is arranged in such a way that it fully ensures the inflow and outflow of blood.

The heart muscle receives blood before all other organs through two coronary (coronary) arteries (a. eoronaria cordis dextra et sinistra), extending directly from the aorta just above the semilunar valves. About 5-10% of all blood ejected into the aorta enters the abundantly developed network of coronary vessels of the heart, even at rest. The right coronary artery runs along the transverse groove to the right to the posterior half of the heart. It supplies most of the right ventricle, the right atrium, and part of the posterior side of the left heart. Its branch feeds the conduction system of the heart - the Ashof-Tavar node, the bundle of His (see below). The left coronary artery divides into two branches. One of them goes along the longitudinal groove to the apex of the heart, giving numerous lateral branches, the other goes along the transverse groove to the left and posteriorly to the posterior longitudinal groove. The left coronary artery supplies most of the left heart and the anterior part of the right ventricle. The coronary arteries break up into a large number of branches, widely aiastomosing among themselves and crumbling into a very dense network of capillaries, penetrating everywhere, into all parts of the organ. There are 2 times more (thicker) capillaries in the heart than in skeletal muscle.

Venous blood flows from the heart through numerous channels, of which the most significant is the coronary sinus (or a special coronary vein - sinus coronarius cordis), which flows independently directly into the right atrium. All other veins that collect blood from individual sections of the heart muscle also open directly into the cavity of the heart: into the right atrium, into the right and even into the left ventricle. It turns out that 3/5 of all blood passing through the coronary vessels flows through the coronary sinus, while the remaining 2/5 of the blood is collected by other venous trunks.

The heart is also pierced by a rich network of lymphatic vessels. The entire space between the muscle fibers and blood vessels of the heart is a dense network of lymphatic vessels and crevices. Such an abundance of lymphatic vessels is necessary for the rapid removal of metabolic products, which is very important for the heart as an organ that works continuously.

From what has been said, it can be seen that the heart has its own third circle of blood circulation. Thus, the coronary circle is included in parallel to the entire systemic circulation.

The coronary circulation, in addition to nourishing the heart, also has a protective value for the body, greatly mitigating the harmful effects of excessively high blood pressure during a sudden contraction (spasm) of many peripheral vessels of the systemic circulation; in this case, a significant part of the blood is sent along a parallel short and widely branched coronary path.

Innervation of the heart(Fig. 230). Contractions of the heart are made automatically due to the properties of the heart muscle. But the regulation of its activity, depending on the needs of the body, is carried out by the central nervous system. IP Pavlov said that "four centrifugal nerves control the activity of the heart: slowing down, accelerating, weakening and strengthening." These nerves approach the heart as part of branches from the vagus nerve and from the nodes of the cervical and thoracic sympathetic trunk. The branches of these nerves form a plexus (plexus cardiacus) on the heart, the fibers of which spread along with the coronary vessels of the heart.

Rice. 230. Conducting system of the heart. Schematic diagram of the conduction system in the human heart. 1 - Kis-Flak node; 2 - Ashof-Tavar node; 3 - bundle of His; 4 - legs of the bundle of His; 5 - a network of Purkinje fibers; 6 - superior vena cava; 7 - inferior vena cava; 8 - atrium; 9 - ventricles

The coordination of the activity of the parts of the heart, atria, ventricles, the sequence of contractions, relaxations are carried out by a special conduction system peculiar only to the heart. The cardiac muscle has the peculiarity that impulses are conducted to the muscle fibers through special atypical muscle fibers, called Purkinje fibers, which form the conduction system of the heart. Purkinje fibers are similar in structure to muscle fibers and directly pass into them. They look like wide ribbons, are poor in myofibrils and very rich in sarcoplasm. Between the right ear and the superior vena cava, these fibers form a sinus node (Kis-Flak node), which is connected by a bundle of the same fibers to another node (Ashof-Tavar node), located on the border between the right atrium and ventricle. A large bundle of fibers (the bundle of His) departs from this node, which descends in the septum of the ventricles, dividing into two legs, and then crumbles in the walls of the right and left ventricles under the epicardium, ending in the papillary muscles.

The fibers of the nervous system everywhere come into close contact with the Purkinje fibers.

The bundle of His is the only muscular connection between the atrium and the ventricle; through it, the initial stimulus that occurs in the sinus node is transmitted to the ventricle and ensures the completeness of the heart contraction.