Where are the coronary vessels located? Common truncus arteriosus

The arteries of the heart arise from the aortic bulb and surround the heart like a crown, which is why they are called coronary arteries.

Right coronary artery goes to the right under the appendage 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 blood to the walls of the right ventricle and atrium, back interventricular septum, papillary muscles of the left ventricle, sinoatrial and atrioventricular nodes of the conduction system of the heart.

Left coronary artery thicker than the right and located between the beginning pulmonary trunk and left atrial appendage. The branches of the left coronary artery supply blood to the walls of the left ventricle, the 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 large veins of the heart gather in coronary sinus- one common wide venous vessel. The coronary sinus is located in the coronary sulcus on the posterior surface of the heart and opens into the right atrium. The tributaries of the coronary sinus are 5 veins:

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

In addition to these five veins, which 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.

Autonomic innervation hearts.

Parasympathetic innervation of the heart

Preganglionic parasympathetic cardiac fibers are part of the branches that arise from the vagus nerves on both sides in the neck. Fibers from the right vagus nerve innervate predominantly the right atrium and especially abundantly the sinoatrial node. The atrioventricular node is approached mainly by fibers from the left vagus nerve. As a result, the right vagus nerve predominantly affects the heart rate, and the left one affects atrioventricular conduction. 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, unlike the vagus nerves, 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 superior thoracic ganglia 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 primarily 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 efferents, but also big amount afferent fibers running 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, responding to passive stretch, and A-receptors, responding to active tension.

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

Heart development. Anomalies of the position and structure of the heart.

Heart development

The complex and peculiar structure of the heart, which corresponds to its role as a biological engine, develops into embryonic period, In the embryo, the heart goes through stages when its structure is similar to the two-chamber 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 heart rudiment 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 an S-shape. This stage is called the sigmoid heart. At the 4th week, several parts can be distinguished in the heart of an embryo 5 mm long. The primary atrium receives blood from the veins converging to the heart. At the junction of the veins, an extension 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. The structure of the embryonic heart is similar to a two-chamber heart adult fish, whose function is to supply venous blood to the gills.

During the 5th and 6th weeks, significant changes occur in relative position parts of the heart. Its venous end moves cranially and dorsally, while the ventricle and bulb move caudally and ventrally. The coronary and interventricular grooves appear on the surface of the heart, and it acquires, in general terms, a definitive external shape. During this same period, internal transformations begin, which lead to the formation of a four-chambered heart, characteristic of higher vertebrates. The heart develops septa and valves. The division of the atria begins at an embryo of 6 mm in length. In the middle of its posterior wall, the 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 septum primum is not complete; first the primary and then the secondary interatrial foramina 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 septum primum, forming a valve that prevents the reverse flow of blood. Complete fusion of the primary and secondary septa occurs at the end prenatal period.

During the 7th and 8th weeks embryonic development partial reduction occurs venous sinus. 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 places where the superior and inferior vena cava flow into it. 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.

At 5 weeks old, the bulb of the heart merges with the ventricle in the embryo, forming the 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. Endocardial tubercles located in the bulb of the heart take part in the formation of the spiral septum; due to them, the valves of the aorta and pulmonary trunk are also formed.

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

As the heart chambers divide and valves form, the tissues that make up the heart wall begin to differentiate. The atrioventricular conduction system is distinguished in the myocardium. The pericardial cavity is separated from common cavity bodies. The heart moves from the neck to the chest cavity. The embryonic and fetal hearts have relatively big sizes, since it ensures not only the movement of blood through the vessels of the fetal body, but also placental blood circulation.

Throughout the prenatal period, communication is maintained between the right and left halves of the heart through the foramen ovale. Blood entering the right atrium through the inferior vena cava is directed through 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 fetal lungs. The rest of the blood is drained 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.

Heart - most important organ to maintain 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 saturating the heart with oxygen.. 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 of (venous) blood depleted of its content is carried out by 2/3 of the large, middle and small veins, which are woven into a single vast 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 moment 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. Filling of the aortic sinuses occurs due to the impossibility of blood returning 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 operating mechanism 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.

The arterial branches originate from the aortic bulb, immediately after the aortic valve valve and, bending around the surface of the heart, supply blood to its different parts.

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 in conditions high load on the cardiovascular system, including during intense sports, which increases 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 nourish the right cardiac ventricle. Partially supplies oxygen to the wall of the left cardiac 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.
Enveloping branch. It is a branch from the left side and supplies 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.

Options for dominant blood supply

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

Define general type blood supply to the heart:

The right blood supply is dominant if this branch departs from the corresponding vessel;
The left type of power supply is possible if posterior artery– this 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. Equal 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 have both an acute and chronic form.

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 coronary arteries;
Death due to cardiac arrest.

Ischemic disease is characterized by wave-like jumps general condition, in which the chronic phase rapidly turns into the acute phase and vice versa.

How are pathologies determined?

Coronary diseases manifest themselves as severe pathologies, the initial form of which is angina pectoris. Subsequently it develops into more serious illnesses and the onset of attacks no longer requires strong nervous or physical stress.

Angina pectoris

Scheme of changes in the coronary artery

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

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

Pain is the result oxygen starvation myocardium, 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 individual parts of the myocardium (necrosis). This occurs due to a complete 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.

Blocked coronary artery

Acute chest pain that radiates to neighboring areas;
Heaviness, difficulty breathing;
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 to function as before. This may cause the dead section to rupture. If a person is not provided with urgent medical assistance, then the risk of death is high.

Heart rhythm disturbance

It is provoked by a spasmodic artery or untimely impulses that arise against the background of impaired conductivity 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 disturbances often occur due to a slowdown in metabolic processes, if endocrine system not okay. Also, its catalyst can be long-term use of many medications.

This concept is a definition of insufficient activity of the heart, which causes a lack of blood supply to the entire body.

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

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

Such a state needs emergency treatment otherwise, the risk of death is high.

The development of heart failure is often diagnosed against the background of coronary vascular diseases.

The main symptoms of manifestation:

Heart rhythm disturbances;
Difficulty breathing;
Coughing attacks;
Clouding and darkening of the eyes;
Swelling of the veins in the neck;
Swelling of the legs, accompanied by painful sensations;
Blackout;
Severe fatigue.

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

Coronary insufficiency

Heart coronary insufficiency is the most common type 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:

Strong painful sensations in the region of the heart;
Feeling of “not enough space” in the chest;
Discoloration of urine and increased excretion;
Pallor of the skin, change in its shade;
The severity of the lungs;
Sialorrhea (intense salivation);
Nausea, vomiting, rejection of usual food.

In its acute form, the disease manifests itself as an attack of sudden cardiac hypoxia, which occurs due to spasm of the arteries. A chronic course is possible due to angina pectoris against the background of accumulation of atherosclerotic plaques.

There are three stages of the disease:

Initial (mild);
Expressed;
A severe stage, which without proper treatment can lead to death.

Causes of vascular problems

There are several contributing factors development of coronary artery disease. Many of them are a manifestation of insufficient care for one’s health.

Important! Today, according to medical statistics, cardiovascular diseases are the No. 1 cause of death in the world.

Every year, more than two million people die from ischemic heart 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 smoke inhalation;
Eating foods rich in cholesterol;
Availability overweight(obesity);
Physical inactivity, as a consequence of a systematic lack of movement;
Exceeding the normal blood sugar level;
Frequent nervous tension;
Arterial hypertension.

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

Women endure such ailments more steadfastly and therefore it is typical for them long course diseases. And men more often suffer from acute forms of pathologies that end in death. Surgical intervention is prescribed in case of ineffectiveness traditional therapy. To better nourish the myocardium, apply coronary bypass surgery– connect the coronary and external veins where the intact portion of the vessels is located. Dilatation can be performed if the disease is associated with overproduction of the layer of the arterial wall. This intervention involves the introduction of a special balloon into the lumen of the vessel, expanding it in places where the membrane is thickened or damaged.

Heart before and after chamber dilatation
Reducing the risk of complications
Own preventive measures reduce the risk of coronary artery disease. They also minimize negative consequences during the rehabilitation period after treatment or surgery.
The most simple tips, available to everyone:
Rejection of bad habits;
Balanced diet ( Special attention for 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 very complex mechanism, which needs careful handling. Once manifested, the pathology steadily progresses, accumulating new symptoms and worsening the quality of life, so the recommendations of specialists and compliance with basic health standards should not be neglected.
Systematic strengthening of cardio-vascular system will keep your body and soul energetic for many years.
Video. Angina pectoris. Myocardial infarction. Heart failure. How to protect your heart.

Coronary arteries

stomach and heart. - B. gastric artery(arteriae coronariae ventriculi) arise from the celiac artery (art. coeliaca) or its branches ( hepatic artery, splenic, etc.). There are four of them; two of them connect at the lesser curvature of the stomach and thus form the superior arterial arch of the stomach (arcus arteriosus ventriculi superior); the remaining 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 tiny blood stems. B. artery heart (arteria coronaria cordis) - a branch that gives rise to the main vascular trunk of the body (see Aorta), while still in the cavity of the pericardial sac. Beginning with two openings lying approximately at the same height with the free edge of the semilunar valves of the aorta, two V. arteries depart from the expanded part of the latter, called the bulb, and are directed 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, goes around it, passes to the posterior surface and along the posterior longitudinal groove reaches the apex of the heart, into the tissue of which it enters here; the left one first gives off 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 musculature of the heart. Along their entire length, both V. arteries give off small branches that penetrate into the thickness of the heart wall. The right V. artery supplies blood to the walls of the right atrium, right ventricle, apex of the heart and, partly, the left ventricle; left - apex of the heart, left atrium, left ventricle, ventricular septum. If the lumen of the V. artery is artificially closed or even narrowed in an animal, then after some time the heart stops contracting (heart paralysis), since the heart muscle can work correctly only as long as the V. arteries deliver it the blood necessary for nutrition in sufficient quantities. quantity. On V. arteries of a human heart meet pathological changes, which affect in a similar way, i.e., they completely stop or significantly reduce the blood flow 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, heartbeat), often angina pectoris and so on.

encyclopedic Dictionary F. Brockhaus and I.A. Efron. - S.-Pb.: Brockhaus-Efron. 1890-1907 .

See what "Coronary arteries" are in other dictionaries:

Arteries of the trunk - … Atlas of Human Anatomy

- (Greek, singular artēría), blood vessels carrying oxygen-rich (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 arise from the bulb and give off branches that supply blood to the heart. See Coronary angioplasty. Vascular bypass shunt. Source:… … Medical terms

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

Heart vessels- 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 emerges from... ... 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, syn. Heberden's asthma), in its essence, is primarily a subjective syndrome, manifested in the form of severe chest pain, accompanied by a feeling of fear and a feeling of the immediate proximity of death. Story. 21… Great Medical Encyclopedia

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

LICHTENBERG- Alexander (AlexanderLich tenberg, born in 1880), an outstanding modern German. urologist. He was an assistant to Cherny and Narath. In 1924, he received the management of the urological department at the Catholic Church of St. Hedwig in Berlin, to the swarm in... ... Great 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 characteristics: growth, metabolism, irritability and the ability to reproduce themselves. The combination of these characteristics... ... Collier's 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. Most large branch the right coronary artery is the posterior interventricular branch, which is directed along the groove of the heart of the same name towards its apex. The branches of the right coronary artery supply blood to 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 conduction system of the heart.

Left coronary artery

Slightly thicker than the right one. 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, bends around the heart on the left, located in its coronary sulcus, where on the posterior surface of the organ it anastomoses with the right coronary artery. The anterior interventricular branch follows the same groove of the heart towards its apex. In the area 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 groove, and a longitudinal one, the vessels of which are located in the anterior and posterior interventricular grooves.

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 originates from the left posterior sinus of Wilsalva, goes down to the anterior longitudinal groove, leaving to its right pulmonary artery, and on the left is the left atrium and the appendage, surrounded by fatty tissue, which usually covers it. It is a wide but short trunk, usually no more than 10-11 mm long.

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

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

Along the anterior longitudinal cardiac groove it is directed to the region of the apex of the heart, usually reaches it, sometimes bends over it and passes to the posterior surface of the heart.

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

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

The circumflex 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 straight line, passes in the transverse groove, reaches the obtuse edge of the heart, goes around it, passes to the posterior wall of the left ventricle, sometimes reaches posterior interventricular groove and in the form of the posterior descending artery goes to the apex. Numerous branches extend from it to the anterior and posterior papillary muscles, the anterior and posterior walls of the left ventricle. One of the arteries supplying 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, bends around the heart along the right atrioventricular groove, passes to the posterior wall, reaches the posterior longitudinal groove, 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, partially to anterior section septum, both papillary muscles of the right ventricle, the posterior wall of the right ventricle and the posterior part of the 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 division 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 sections is quite stable and is not subject to significant deviations.

At average 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 left coronary artery system. The right ventricle, including both right papillary muscles and the posterior 1/2-1/3 of the 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 coronary blood flow. The sympathetic and parasympathetic nerves seem to have little effect on the coronary arteries, exerting their main action directly on the heart muscle.

Outflow occurs through veins that collect in the coronary sinus

Venous blood in the coronary system collects 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 posterior 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 coronary disease, therefore, closure of one of the coronary arteries is not always accompanied by necrosis in the myocardium.

IN normal hearts anastomoses were found only in 10-20% of cases, and of small diameter. However, their number and magnitude increase not only with coronary atherosclerosis, but also at valvular defects hearts. Age and gender by themselves do not have any effect on the presence and degree of development of anastomoses.

Heart (cor)

The circulatory system consists of a huge number of elastic vessels different structure and sizes - arteries, capillaries, veins. In the center circulatory system there is a heart - a living suction-discharge pump.

The structure of the heart. The heart is the central apparatus of the vascular system, with a high degree of automatic action. In humans, it is located in the chest behind the sternum, most of it (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) upward, back and to the right, and its narrower cone-shaped part (top) forward, down and to the left. Upper limit 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 without reaching the midclavicular line (passing through the nipple in men) by 1 cm. The apex 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; 5 - lung; 6 - liver; 7 - falciform ligament; 8 - stomach; 9 - innominate 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 facing upward and its apex downward. 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). Average dimensions of the heart: length 13 cm, width 10 cm, thickness (antero-posterior diameter) 7-8 cm. The volume of 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 - innominate artery; 2 - superior vena cava; 3 - ascending aorta; 4 - coronary groove with the right coronary artery; 5 - right ear; 6 - right atrium; 7 - right ventricle; 8 - apex of the heart; 9 - left ventricle; 10 - anterior longitudinal groove; 11 - left ear; 12 - left pulmonary veins; 13 - pulmonary artery; 14 — aortic arch; 15 - left subclavian artery; 16 - left general 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 most important functionally is the muscle layer - the myocardium. The muscle tissue of the heart is different from skeletal muscle; it also has transverse striations, but the ratio of cell fibers is different than in skeletal muscles. 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 transition fibers that make up the predominant mass. The outer longitudinal fibers, deepening obliquely, gradually turn into annular fibers, which also gradually turn obliquely into internal longitudinal ones; The papillary muscles of the valves are also formed from the latter. On the very surface of the ventricles there are fibers that cover both ventricles together. Such a complex course of muscle bundles provides the most complete reduction and emptying of the cavities of the heart. The muscle layer of the walls of the ventricles, especially the left one, which drives blood in a large circle, is much thicker. The muscle fibers that form the walls of the ventricles are collected from the inside into numerous bundles, which are located in different directions, forming fleshy crossbars (trabeculae) and muscle protrusions - papillary muscles; From them, tendon cords go to the free edge of the valves, which stretch during contraction of the ventricles and do not allow the valves to open in the atrium cavity under the pressure of blood.

Rice. 224. Course of the muscle fibers of the heart (semi-schematic)

The muscle layer of the walls of the atria is thin, since their load is small - they only drive blood into the ventricles. Superficial muscle pikes facing the inside of the atrium cavity form the pectineus muscles.

From the outer surface of the heart (Fig. 225, 226), two grooves are noticeable: a longitudinal one, covering the heart from the front and back, and a transverse (coronal) groove, located in a ring shape; The heart's own arteries and veins run along them. These grooves inside correspond to partitions that divide the heart into four cavities. Longitudinal interatrial and interventricular septum divides the heart into two halves completely isolated from one another - the right and left heart. The transverse septum divides each of these halves into an upper chamber - the atrium (atrium) and a lower chamber - the ventricle (ventriculus). Thus, two atria and two separate ventricles are obtained that do not communicate with each other. 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 - innominate artery

Rice. 226. Heart (back view). 1 - aortic arch; 2 - left subclavian artery; 3 - left common carotid artery; 4 - azygos 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 drainage 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 has the shape of 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 atrium wall form parallel muscle ridges.

The left cardiac appendage (auricula cordis sinistra) extends from the anterior wall of the left atrium, in the cavity of which there are also muscle ridges. The walls in the left atrium are smoother from the inside than in the right.

The inner membrane (Fig. 227), lining the inside of the heart cavities, is called the endocardium; it is covered with a layer of endothelium (a derivative of mesenchyme), which extends to the inner lining of the vessels extending from the heart. At 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 on both sides with endothelium, these are the heart valves (Fig. 228), closing the atrioventricular openings. In the right atrioventricular orifice 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 leaflet valves open during atrial systole only towards the ventricles.

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

Rice. 228. Heart valves. Opened heart. The direction of blood flow is shown by arrows. 1 - bicuspid valve 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 site where the aorta exits the left ventricle and the pulmonary artery exits the right ventricle, the endocardium also forms very thin folds in the form of concave (into the ventricular cavity) semicircular pockets, three in each opening. Due to their shape, these valves are called semilunar valves (valvulae semilunares). They open only upward towards the vessels during contraction of the ventricles. During the relaxation (expansion) of the ventricles, they automatically close and do not allow the reverse flow of blood from the vessels into the ventricles; when the ventricles contract, they open again with the flow of expelled blood. The semilunar valves are devoid of muscle.

From the above it is clear that in humans, as in other mammals, the heart has four valve systems: two of them, cusp valves, separate the ventricles from the atria, and two, semilunar, separate the ventricles from the atria. arterial system. There are no valves at the point 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, acting in part as a valve or flap. In addition, there are thickenings of ring-shaped muscle fibers of the adjacent part of the atrial wall. These thickenings of muscle tissue, during contraction of the atria, compress the mouths of the veins and thereby prevent the blood from flowing back into the veins, so that it flows only into the ventricles.

In the body performing such great job As the heart naturally develops, supporting structures 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 root of the aorta and the membranous part of the ventricular septum; they all consist of bundles of collagen fibrils with an admixture of elastic fibers.

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

The size of the cavities of the heart varies depending on the degree of filling with blood and the intensity of its work. Thus, the capacity of the right atrium ranges from 110-185 cm3, the right ventricle - from 160 to 230 cm3, the left atrium - from 100 to 130 cm3 and the left ventricle - from 143 to 212 cm3.

The heart is covered with thin serosa, forming two leaves that pass into one another at the point of departure from the heart large vessels. The inner, or visceral, leaf of this sac, directly covering the heart and tightly fused to it, is called the epicardium (epieardium), the outer, or parietal, leaf is called the pericardium (pericardium). The parietal layer forms a sac that encloses the heart - this is the cardiac sac, or cardiac sac. The pericardium is adjacent to the layers of the mediastinal pleura on the lateral sides, grows from below to the tendon center of the diaphragm, and in front is attached by connective tissue fibers to the posterior surface of the sternum. Between both leaves of the cardiac sac, a slit-like hermetically closed cavity is formed around the heart, always containing a certain amount (about 20 g) of serous fluid. The pericardium insulates the heart from the surrounding organs, and the fluid moisturizes the surface of the heart, reducing friction and making its movements gliding during contractions. Moreover, it is strong fibrous tissue the pericardium limits and prevents excessive stretching of the muscle fibers of the heart; if there were no pericardium to anatomically limit the volume of the heart, it would be in danger of overextension, especially during periods of its most intense and unusual activity.

Incoming and outgoing vessels of the heart. The superior and inferior vena cava drain into the right atrium. At the confluence of these veins, a wave of contraction of the heart muscle occurs, quickly covering both atria and then moving 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 here from the walls of the heart itself. The sinus opening is closed by a small fold (tebesian valve).

The four-year-old veins drain into the left atrium. The largest artery in the body, the aorta, emerges from the left ventricle. It first goes to the right and up, then, bending back and to the left, it spreads over 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 to both lungs.

In total, the heart has seven inlet - venous - holes and two outlet - arterial - holes.

Circulation circles(Fig. 229). Thanks to the long and complex evolution of the development of the circulatory organs, a certain system of supplying the body with blood, characteristic of humans and all mammals, has been established. As a rule, blood moves inside a closed system of tubes, which includes a constantly operating powerful muscular organ - the heart. The heart, as a result of its historically established automatism and regulation by the central nervous system continuously and rhythmically pumps blood throughout the body.

Rice. 229. Scheme of blood circulation and lymph circulation. Vessels through which the flow flows are indicated in red. arterial blood; blue - vessels with venous blood; the portal vein system is shown in purple; yellow - lymphatic vessels. 1 - right half hearts; 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; eleven - portal vein; 12 - liver; 13 - kidney

Blood from the left ventricle of the heart first flows through the aorta into large arteries, which gradually branch into smaller ones and then pass into arterioles and capillaries. Through the thinnest walls capillaries constantly exchange substances between blood and body tissues. Passing through a dense and numerous network of capillaries, the blood gives oxygen to the tissues and nutrients, and takes in exchange carbon dioxide and products of cellular metabolism. 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 body tissues. 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 blood circulation (1628), and Malpighi (1661), who established blood circulation in the capillaries.

Blood supply to the heart(see Fig. 226). The heart, having an extremely important service in the body and performing enormous work, 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 lasts more than 0.4 seconds. Naturally, this organ must be especially equipped copious amounts blood. Therefore, its blood supply is designed in such a way that it completely ensures the inflow and outflow of blood.

The heart muscle receives blood first of all other organs through two coronary (coronary) arteries (a. eoronaria cordis dextra et sinistra), extending directly from the aorta just above the semilunar valves. Even at rest, the abundantly developed network of coronary vessels of the heart receives about 5-10% of all blood ejected into the aorta. The right coronary artery runs along the transverse groove to the right towards 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-Tavara node, the bundle of His (see below). The left coronary artery divides into two branches. One of them runs along the longitudinal groove to the apex of the heart, giving numerous lateral branches, the other runs 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 split into a large number of branches, widely interconnecting with each other and crumbling into a very dense network of capillaries, penetrating everywhere, into all parts of the organ. The heart has 2 times more (thicker) capillaries than 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 directly into the right atrium. All other veins that collect blood from individual areas cardiac 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 the 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 penetrated by a rich network of lymphatic vessels. The entire space between muscle fibers and blood vessels The heart is a dense network of lymphatic vessels and slits. 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 harmful effects excessively elevated blood pressure due to 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 tract.

Innervation of the heart(Fig. 230). Heart contractions occur 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. I. P. Pavlov said that “the activity of the heart is controlled by four centrifugal nerves: slowing down, accelerating, weakening and strengthening.” These nerves approach the heart as part of branches from the vagus nerve and from the cervical and thoracic sympathetic trunk. The branches of these nerves form a plexus on the heart (plexus cardiacus), the fibers of which spread along with the coronary vessels of the heart.

Rice. 230. Conducting system of the heart. Diagram of the location of the conduction system in the human heart. 1 - Kis-Flaka knot; 2 - Ashof-Tavara knot; 3 - bundle of His; 4 - bundle branches; 5 - network of Purkinje fibers; 6 - superior vena cava; 7 - inferior vena cava; 8 - atria; 9 - ventricles

Coordination of the activity of parts of the heart, atria, ventricles, the sequence of contractions and relaxations is 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 the sinus node (Kis-Flaka node), which is connected by a bundle of the same fibers to another node (Aschof-Tavara node), located on the border between the right atrium and the ventricle. A large bundle of fibers (bundle of His) departs from this node, which descends in the ventricular septum, dividing into two legs, and then scatters in the walls of the right and left ventricles under the epicardium, ending in the papillary muscles.

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

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