An important role in functions of atrioventricular valves the apparatus holding the valves plays - tendon threads attached, on the one hand, to the free edge of the valve cusps, on the other, to the tops of the papillary muscles. With endocarditis and myocarditis, these formations are involved in the process, undergo pathological changes, and therefore, to a greater or lesser extent, disrupt the function of also affected valves to a certain extent.
tendon threads like valves, they consist of fibrous, cell-poor tissue covered with a very thin layer of endocardium. Passing into the tissue of the valve leaflets, the fibrous tissue of the filaments is fan-shaped distributed in the fibrous plate of the leaflet. From each papillary muscle, one or more tendon threads depart, which are attached to the free edges of the valves or, less often, to their ventricular surface.
A bunch of threads from each papillary muscle is divided in the left ventricle into two parts, of which one goes to the posterior leaflet, the other to the anterior. The distribution of filament attachment to the valves in the right ventricle is not so clearly defined. A large number of thin tendon filaments start directly from the muscles of the ventricles and go to different parts of the valves. Tendon threads of the left ventricle are thicker and more numerous than the right one.
If all threads are the same tense, then the valve flaps are evenly stretched (A. M. Eliseeva, 1948).
Naturally, when endocarditis the inflammatory process can also pass to the tendon threads; valve leaflets undergo changes with their tendon filaments. As a result of the organization of thrombotic masses and sclerosis, thickening, shortening, coarsening and compaction of the tendon filaments occur. Sometimes adjacent tendon filaments are soldered together either due to the organization of thrombotic masses enveloping them, or due to the growth of connective tissue from the side of the valves.
In these cases, they may form connecting plates like the swimming membranes of a frog's foot. The process of sclerosis can also capture the tops of the papillary muscles. With ulcerative endocarditis, the process passes to the tendon threads, leads to their destruction, ruptures. Sometimes all the tendon threads of one valve are torn.
important role in ensuring normal The function of the atrioventricular valves belongs to the papillary (papillary) muscles. These muscles in the left ventricle are relatively large sizes, him in the right. With tension of the papillary muscles, the adjacent edges of the valves approach each other.
With inflammation myocardium the same processes are observed in the papillary muscles. The bases of the papillary muscles are affected first and most severely. Sclerosis and death of muscle tissue are also more pronounced in papillary muscles than in the rest of the myocardium. This is also confirmed by the data of M. A. Skvortsov (1950).
Spreading ulcerative endocarditis or purulent myocarditis can lead to the destruction of the papillary muscles, to their separation. The same pathology can cause a heart attack of the ventricular wall with the capture of the papillary muscle or with its limited necrosis. Most often this happens with the posterior papillary muscle of the left ventricle. At the autopsy, a piece of muscle is found, freely hanging on the tendon threads (EM Gelstein, 1951).
break or even full detachment of the valve, tendon filaments, and papillary muscles can also be observed without destructive processes in the endocardium or myocardium - due to significant physical stress, sharp bruises and compression of the chest, falling from a height, direct injuries of the heart. These same causes can cause rupture of the walls of the heart and large vessels. Traumatic rupture of the heart occurs especially easily with pathological changes in the myocardium on the basis of myocarditis, cardiosclerosis, aneurysms (V. N. Sirotinin, 1913; A. Foght, 1920).
Pathological processes leading to sclerosis (cusps, foramens, tendon filaments and their muscles) underlie the pathology that is commonly called heart defects or, more precisely, heart valve defects. Damage to the valves leads to a greater or lesser disruption of the heart, as a result of which a more or less pronounced circulatory failure develops.
Right atrium,atrium dextrum, shaped like a cube, has a rather large additional cavity - right ear,auricula dextra. The right atrium is separated from the left interatrial septum,septum intertridle (Fig. 33). On the septum, an oval depression is clearly visible - an oval fossa, fossa o. vdlis, within which the septum is thinner. This fossa, which is the remnant of an overgrown foramen ovale, is limited the edge of the oval fossa,limbus fossae ovdlis. In the right atrium there are opening of the superior vena cava,ostium Venae cavae superioris, And opening of the inferior vena cava,ostium Venae cdvae inferioris. Along the lower edge of the latter stretches a small non-permanent lunate fold, called valve of the inferior vena cava (eustachian valve),valvula Venae cdvae inferioris; in the embryo directs blood flow from the right atrium to the left through the foramen ovale. Sometimes the valve of the inferior vena cava has a mesh structure - it consists of several tendon filaments connected to each other. Between the holes of the vena cava, a small intervenous tubercle(lover's tubercle), tuberculum intervenosum, which is considered the remainder of the valve that directs the blood flow from the superior vena cava into the right atrioventricular opening in the embryo. The expanded posterior portion of the cavity of the right atrium, which receives both vena cava, is called sinus of the vena cava,sinus venarum cavarum.
On the inner surface of the right ear and the adjacent section of the anterior wall of the right atrium, longitudinal muscle ridges protruding into the atrial cavity are visible - comb muscles,mm. pectinati. At the top they end border ridge,crista terminalis, which separates the venous sinus from the cavity of the right atrium (in the embryo, there was a border between the common atrium and the venous sinus of the heart). The atrium communicates with the ventricle through ostium atrioventri- culare dextrum. Between the latter and the opening of the inferior vena cava is opening of the coronary sinus,ostium sinus coro narii. A thin sickle-shaped fold is visible at its mouth - coronary sinus valve(Tebezian damper), valvula sinus coronaria. Near the opening of the coronary sinus there are dot openings of the smallest veins of the heart,foramina venarum minimdrum, flowing into the right atrium on their own; their number may vary. Along the circumference of the coronary sinus, the pectinate muscles are absent.
right ventricle,ventriculus dexter, located to the right and in front of the left ventricle, shaped like a trihedral pyramid with the apex facing down. Its slightly convex medial (left) wall is interventricular septum,septum interventriculdre, separating the right ventricle from the left. Most of the septum is muscular, pars mwsculdris, and the smaller one, located in the uppermost section closer to the atria, is membranous, pars membranacea.
The lower wall of the ventricle, adjacent to the tendon center of the diaphragm, is flattened, and the anterior wall is convex anteriorly. In the upper, widest part of the ventricle, there are two openings: behind - right atrioventricular orifice,ostium atrioventriculdre dextrum, through which venous blood enters the ventricle from the right atrium, and in front - opening of the pulmonary trunk,ostium Trunci pulmonalis, through which blood is directed to the pulmonary trunk. The part of the ventricle from which the pulmonary trunk exits is called arterial cone (funnel),conus arteriosus (fundibulum). Small supraventricular ridge,crista supraventriculdris, delimits it from the inside from the rest of the right ventricle. The right atrioventricular orifice closes right atrioventricular(tricuspid) valve,vdlva atrio ventricularis dextra (vdlva tricuspiddlis) (Fig. 34), fixed on a dense connective tissue fibrous ring, the tissue of which continues into the valve leaflets. The latter resemble triangular tendon plates in appearance. Their bases are attached to the circumference of the atrioventricular orifice, and the free edges face the ventricular cavity. On the front semicircle of the hole, the front valve flap,cuspis anterior, on the posterolateral - back flap,cuspis posterior, and, finally, on the medial semicircle - the smallest of them - medial - partition wall,cuspis septalis. During atrial contraction, the valve leaflets are pressed by the blood flow against the walls of the ventricle and do not prevent its passage into the cavity of the latter. When the ventricles contract, the free edges of the valves close, but do not turn into the atrium, since they are held from the side of the ventricle by stretching dense connective tissue cords - tendon chords,chordae ien- dinae. The inner surface of the right ventricle (with the exception of the arterial cone) is uneven; fleshy trabeculae,trabecu- lae cdrneae, and conical papillary muscles,mm. papilldres. From the top of each of these muscles - the anterior (largest) and posterior (mm. papilldres anterior et posterior) most (10-12) tendon chords begin; sometimes some of them originate from the fleshy trabeculae of the interventricular septum (the so-called septal papillary muscles). These chords are attached simultaneously to the free edges of two adjacent valves, as well as to their surfaces facing the ventricular cavity.
Located directly at the beginning of the pulmonary trunk lapan of the pulmonary trunk,vdlva Trunci pulmonalis, consisting of three semi-lunar flaps located in a circle: front, left and right: valvula semilunaris anterior, valvula semilunaris dextra et valvula semilunaris sinistra. Their convex (lower) surface faces the cavity of the right ventricle, and the concave (upper) and free edge faces the lumen of the pulmonary trunk. The middle of the free edge of each of these valves is thickened due to the so-called semilunar valve knot, nodulus vdlvulae semi lunaris. These nodules contribute to a tighter closing of the semilunar valves when they are closed. Between the wall of the pulmonary trunk and each of the semilunar valves there is a small pocket - pulmonary sinus,sinus Trunci pulmondlis. When the muscles of the ventricle contract, the semilunar valves (valves) are pressed by the blood flow against the wall of the pulmonary trunk and do not prevent the passage of blood from the ventricle; during relaxation, when the pressure in the cavity of the ventricle drops, the return flow of blood fills the sinuses and opens the valves. Their edges close and do not let blood into the cavity of the right ventricle.
left atrium,atrium sinistrum, which has an irregular cuboid shape, delimited from the right by a smooth interatrial septum. The oval fossa located on it is more clearly expressed from the side of the right atrium. There are 5 holes in the left atrium, four of them are located above and behind. This openings of the pulmonary veins,ostia vena- rum pulmondlium. The pulmonary veins are devoid of valves. Fifth, largest, opening of the left atrium - left atrioventricular orifice,ostium atrioventriculare sinistrum, communicating atrium with the same ventricle. The anterior wall of the atrium has a cone-shaped extension facing anteriorly - left ear,auricula sinistra. On the side of the cavity, the wall of the left atrium is smooth, since the comb muscles are located only in the atrial appendage.
left ventricle,ventriculus sinister, cone-shaped, with the base turned upwards. In the upper, widest, section of the ventricle there are openings; behind and to the left is left atrioventricular orifice,ostium atrioventricu lare sinistrum, and to the right of it - aortic opening,ostium aortae. In the right there is left atrioventricular valve(mitral valve) vdlva atrioventriculdris sinistra (vdlva mitrd- lis), consisting of two wings of a triangular shape - the front leaf, ciispis anterior, which starts from the medial semicircle of the opening ^ (near the interventricular septum), and the posterior leaflet, cuspis posterior, smaller than the anterior, starting from the lateral-posterior semicircle of the opening.
On the inner surface of the ventricle (especially in the apex) there are many large fleshy trabeculae and two papillary muscles: anterior,m. papillaris anterior, And back, i.e.papillaris posterior, with their thick tendinous cords attached to the leaflets of the atrioventricular valve. Before entering the aortic opening, the surface of the ventricle is smooth. aortic valve,vdlva aortae, located at the very beginning, consists of three semilunar valves: back, vdlvula semilundris posterior; right, vdlvula semilundris dextra, and left vdlvula semilundris sinistra. Between each valve and the wall of the aorta there is sinus,sinus aortae. The aortic valves are thicker, and the nodules of the semilunar valves, located in the middle of the free edges, are larger than in the pulmonary trunk.
The structure of the wall of the heart. The wall of the heart consists of 3 layers: a thin inner layer - the endocardium, a thick muscle layer - the myocardium and a thin outer layer - the epicardium, which is a visceral sheet of the serous membrane of the heart - the pericardium (pericardial sac).
endocardium,endocardium, lines the cavity of the heart from the inside, repeating their complex relief and covering the papillary muscles with their tendon chords. The atrioventricular valves, the aortic valve and the pulmonary valve, as well as the valves of the inferior vena cava and the coronary sinus, are formed by duplications of the endocardium, inside which connective tissue fibers are located.
Middle layer of the heart wall myocardium,myocardium (Fig. 35), formed by cardiac striated muscle tissue and consists of cardiac myocytes (cardiomyocytes) interconnected big amount jumpers (intercalary disks), with the help of which they are connected into muscle complexes or fibers that form a narrow-loop network. This narrow-looped muscle network ensures complete rhythmic contraction of the atria and ventricles. The thickness of the myocardium is the smallest in the atria, and the largest - in the left ventricle.
The muscle fibers of the atria and ventricles begin from fibrous rings that completely separate the atrial myocardium from the ventricular myocardium. These fibrous rings, like a number of other connective tissue formations of the heart, are part of its soft skeleton. Skeleton.hearts include: interconnected right And left annulus,dnuli fibrosis dexter et sinister, which surround the right and left atrioventricular openings and constitute the support of the right and left atrioventricular valves (their projection from the outside corresponds to the coronary sulcus of the heart); right And left fibrous triangles,trigonum fibrosum dextrum et trigonum fibrosum sinistrum, - dense plates, which are adjacent to the posterior semicircle of the aorta on the right and left and are formed as a result of the fusion of the left fibrous ring with the connective tissue ring of the aortic opening. The right, most dense, fibrous triangle, which actually connects the left and right fibrous rings and the connective tissue ring of the aorta, is in turn connected to the membranous part of the interventricular septum. In the right fibrous triangle there is a small hole through which the fibers of the atrioventricular bundle of the conduction system of the heart pass.
The atrial myocardium is separated by fibrous rings from the ventricular myocardium. The synchrony of myocardial contractions is provided by the conduction system of the heart, which is the same for the atria and ventricles. In the atria, the myocardium consists of two layers: superficial, common to both atria, and deep, separate for each of them. The first contains muscle fibers located transversely, and the second contains two types of muscle bundles - longitudinal, which originate from the fibrous rings, and circular, loop-like covering the mouths of the veins that flow into the atria, like constrictors. Longitudinally lying beams muscle fibers protrude in the form of vertical strands inside the cavities of the auricles of the atria and form the comb muscles.
The myocardium of the ventricles consists of three different muscle layers: outer (superficial), middle and inner (deep). The outer layer is represented by muscle bundles of obliquely oriented fibers, which, starting from the fibrous rings, continue down to the top of the heart, where they form heart curl,vortex cordis, and pass into the inner (deep) layer of the myocardium, the fiber bundles of which are located longitudinally. Due to this layer, papillary muscles and fleshy trabeculae are formed. The outer and inner layers of the myocardium are common to both ventricles, and the middle layer located between them, formed by circular (circular) bundles of muscle fibers, is separate for each ventricle. The interventricular septum is formed in its greater part (its muscular part) by the myocardium and the endocardium covering it; the basis of the upper section of this septum (its membranous part) is a plate of fibrous tissue.
Outer shell of the heart epicardium,epicdrdium, adjacent to the myocardium from the outside, is a visceral sheet of the serous pericardium, built according to the type of serous membranes and consists of a thin plate of connective tissue covered with mesothelium. The epicardium covers the heart, the initial sections of the ascending aorta and pulmonary trunk, the final sections of the caval and pulmonary veins. Through these vessels, the epicardium passes into the parietal plate of the serous pericardium.
conduction system of the heart
The regulation and coordination of the contractile function of the heart is carried out by its conducting system. These are atypical muscle fibers (cardiac conductive muscle fibers), consisting of cardiac conductive myocytes, richly innervated, with a small number of myofibrils and an abundance of sarcoplasm, which have the ability to conduct irritation from the nerves of the heart to the atrial and ventricular myocardium. The centers of the conduction system of the heart are two nodes: 1) sinoatrial node(Kiss-Fleck knot), node si nuatrialis, located in the wall of the right atrium between the opening of the superior vena cava and the right ear and giving branches to the atrial myocardium, and 2) atrioventricular node(Ashoff-Tavary node), node atrioventricularis, lying in the thickness of the lower part of the interatrial septum (Fig. 36). From top to bottom, this node passes into atrioventricular bundle(bundle of His), fasciculus atrioventriculdris, which connects the atrial myocardium with the ventricular myocardium. In the muscular part of the interventricular septum, this bundle is divided into the right and left legs, crus dextrum et crus sinist- rum. The terminal branches of the fibers (Purkinje fibers) of the conduction system of the heart, into which these legs break up, end in the myocardium of the ventricles.
Pericardium (pericardium), pericardium (rice. 41), delimits the heart from neighboring organs, is a thin and at the same time dense, durable fibro-serous sac in which the heart is located. It consists of two layers having a different structure: outer - fibrous and inner - serous. outer layer - fibrous pericardium,pericardium fibrosum, near the large vessels of the heart (at its base) passes into their adventitia. serous pericardium,peri cardium serosum, has two plates - parietal, lamina parietalis, which lines the fibrous pericardium from the inside, and the visceral, lamina visceralls (epicdrdium), which covers the heart, being its outer shell - the epicardium. The parietal and visceral plates pass into each other in the region of the base of the heart, in the place where the fibrous pericardium is fused with the adventitia of large vessels: the aorta, pulmonary trunk, vena cava. Between the parietal plate of the serous pericardium on the outside and its visceral plate there is a slit-like space - pericardial cavity,cdvitas pericardidis, covering the heart from all sides and containing not a large number of serous fluid.
The pericardium resembles an irregular cone in shape, the base of which is tightly (lower section) fused with the tendon center of the diaphragm, and at the top (at the top of the cone) it covers the initial sections of large vessels: the ascending aorta, the pulmonary trunk, as well as the superior and inferior vena cava and pulmonary veins. The pericardium is divided into three sections: front- sternocostal, which is connected to the posterior surface of the anterior chest wall by sterno-pericardial ligaments and, ligamenta sternopericardidca, occupies the area between the right and left mediastinal pleura; lower - diaphragmatic, fused with the tendon center of the diaphragm; me-diastinal department (right and left) - the most significant in length. From the lateral sides and in front, this section of the pericardium is tightly fused with the mediastinal pleura. On the left and right, between the pericardium and the pleura, the phrenic nerve and blood vessels pass. Behind the mediastinal pericardium is adjacent to the esophagus, thoracic aorta, unpaired and semi-unpaired veins, surrounded by loose connective tissue.
In the cavity of the pericardium between it, the surface of the heart and large vessels, there are rather deep pockets - sinuses. First of all, this transverse sinus of the pericardium,sinus transver sus pericardii, located at the base of the heart. Anteriorly and superiorly, it is bounded by the initial section of the ascending aorta. And pulmonary trunk, and behind - the anterior surface of the right atrium and the superior vena cava. oblique sinus of the pericardium,sinus obliquus pericardii, located on the diaphragmatic surface of the heart, limited by the base of the left pulmonary veins on the left and the inferior vena cava on the right. The anterior wall of this sinus is formed by the posterior surface of the left atrium, the posterior by the pericardium.
Vessels and nerves of the pericardium. Pericardial branches of the thoracic aorta, branches of the pericardiodiaphragmatic artery, and branches of the superior phrenic arteries participate in the blood supply of the pericardium. The pericardial veins accompanying the arteries of the same name flow into the brachiocephalic, unpaired and semi-unpaired veins. The lymphatic vessels of the pericardium are sent to the lateral pericardial, prepericardial, anterior and posterior mediastinal lymph nodes. The pericardial nerves are branches of the phrenic and vagus nerves, as well as the cervical And thoracic cardiac nerves extending from the corresponding nodes of the right and left sympathetic trunks.
4. Parasympathetic part of the autonomic NS: central, peripheral.
parasympathetic part, pars parasympathetic ( parasympa thetica ), autonomous (vegetative) nervous system subdivided into head and sacral sections. To head office [ pars cranidlis] include autonomic nuclei and parasympathetic fibers of the oculomotor (III pair), facial (more precisely, intermediate, - VIII pair), glossopharyngeal (IX pair) and vagus (X pair) nerves, as well as the ciliary, pterygopalatine, submandibular, hyoid and ear nodes and their branches. sacral department [ pars pelvica] parasympathetic part is represented sacral parasympathetic nuclei,nuclei parasympathetics sacrales, II, III and IV sacral segments of the spinal cord, splanchnic pelvic nerves, pp.splanchnici pelvini, And parasympathetic pelvic nodes,ganglia pelvina, with their branches.
1. Parasympathetic part of the oculomotor nerve presented additional(parasympathetic) core,nucl. oculo- motorius accessorius, the so-called Yakubovich's nucleus, the ciliary node and processes of cells located in this nucleus and node. The axons of the cells of the accessory nucleus of the oculomotor nerve, which lies in the tegmentum of the midbrain, pass through the third pair of cranial nerves in the form of preganglionic fibers.
2. Parasympathetic part of the facial nerve consists of the upper and salivary nuclei, pterygopalatine, submandibular and sublingual vegetative nodes. The axons of the cells of the superior salivary nucleus, which lies in the tire of the bridge, pass as part of the facial (intermediate) nerve in the canal of the same name.
3. Parasympathetic part of the glossopharyngeal nerve formed by the lower salivary nucleus, the ear node and the processes of the cells lying in them. The axons of the cells of the lower salivary nucleus, located in the medulla oblongata, as part of the glossopharyngeal nerve, exit the cranial cavity through the jugular foramen.
4. Parasympathetic part of the vagus nerve consists of the posterior (parasympathetic) nucleus of the vagus nerve, numerous nodes that are part of the organ autonomic plexuses and processes of cells located in the nucleus and these nodes. The axons of the cells of the posterior nucleus of the vagus nerve, located in the medulla oblongata, go as part of the branches of the vagus nerve. They reach parasympathetic nodes,gang lia parasympathetic, periorganic and intraorganic vegetative plexuses.
5. The sacral division of the parasympathetic part of the autonomic (vegetative) nervous system is represented by sacral parasympathetic nuclei,nuclei parasympathetia sac- rales, located in the lateral intermediate substance of 11 sacral segments of the spinal cord, pelvic (parasympathetic) nodes,ganglia pelvina, and processes of the cells lying in them. The axons of the cells of the sacral parasympathetic nuclei exit the spinal cord as part of the anterior roots, then go as part of the anterior branches of the sacral spinal nerves, and after they exit through the pelvic sacral openings, branch off, form pelvic splanchnic nerves, pp.spldnchnici pelvini.
Ticket number 22
1. Muscles of the girdle of the upper limb.
Even though the heart is only half a percent of total mass body, it is the most important of the organs of the human body. It is the normal functioning of the heart muscle that makes possible the full work of all organs and systems. The complex structure of the heart is best adapted to the distribution of arterial and venous blood flows. From the point of view of medicine, it is cardiac pathologies that occupy the first place among human diseases.
- The most common is oblique.
- As if suspended, with a shift of the left border to the median line - vertical.
- Spread on the underlying diaphragm - horizontal.
- anterior, facing the sternum;
- lower, deployed to the diaphragm;
- lateral, facing the lungs.
- Coronal furrow. It is located at the base of the heart muscle and is located on the border of the ventricles and atria.
- Interventricular grooves. They go to the front and rear surface organ, along the border between the ventricles.
- large blood vessels;
- ring-shaped accumulations of fibrous tissue;
- fibrous triangles.
- 1. The inner layer (endocardium) consists of a connective tissue plate and covers the entire inner surface of the heart. Tendon muscles and filaments attached to the endocardium form the heart valves. Beneath the endocardium is an additional basement membrane.
- 2. The middle layer (myocardium) consists of striated muscle fibers. Each muscle fiber is a cluster of cells - cardiomyocytes. Visually, there are visible dark stripes between the fibers, which are inserts that play important role in the transmission of electrical excitation between cardiomyocytes. Outside, muscle fibers are surrounded by connective tissue, which contains nerves and blood vessels that provide trophic function.
- 3. The outer layer (epicardium) is a serous sheet, tightly fused with the myocardium.
- adaptive and triggering effect on the work of the heart muscle;
- balancing metabolic processes in the heart muscle;
- humoral regulation of organ activity.
- It is able to exert pressure on the blood flow and saturate organs and tissues with oxygen.
- It can remove carbon dioxide and waste products from the body.
- Each cardiomyocyte is capable of being excited under the influence of impulses.
- The cardiac muscle is able to conduct an impulse between cardiomyocytes along a special conduction system.
- After excitation, the heart muscle is able to contract with the atria or ventricles, pumping blood.
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Location
The heart is located in the chest cavity. In front of him is the sternum. The organ is displaced slightly to the left in relation to the sternum. It is located at the level of the sixth and eighth thoracic vertebrae.
On all sides, the heart is surrounded by a special serous membrane. This membrane is called the pericardium. It forms its own cavity called the pericardial. Being in this cavity makes it easier for the organ to slide in relation to other tissues and organs.
Position Options
From the point of view of radiological criteria, the following options for the position of the heart muscle are distinguished:
Options for the position of the heart muscle depend on the morphological constitution of a person. In an asthenic, it is vertical. In a normosthenic, the heart is oblique, and in a hypersthenic, it is horizontal.
Structure and form
The heart muscle is cone shaped. The base of the organ is expanded and turned backwards and upwards. The main vessels approach the base of the organ. The structure and functions of the heart are inextricably linked.
The following surfaces are distinguished in the heart muscle:
Furrows are visualized on the heart muscle, reflecting the location of its internal cavities:
Heart valves and chambers
The human heart muscle has four chambers. A transverse partition divides it into two cavities. Each cavity is divided into two chambers.
One chamber is atrial and the other is ventricular. Venous blood circulates in the left side of the heart muscle, and arterial blood circulates in the right side.
The right atrium is a muscular cavity into which the superior and inferior vena cava open. In the upper part of the atria, a protrusion is distinguished - the ear. The inner walls of the atrium are smooth, except for the surface of the protrusion. On the site of the transverse septum, which separates the atrial cavity from the ventricle, there is an oval fossa. It is completely closed. In the intrauterine period, a window opened in its place, through which a mixture of venous and arterial blood took place. In the lower part of the right atrium is the atrioventricular opening through which venous blood enters the right ventricle from the right atrium.
Blood enters the right ventricle from the right atrium at the time of its contraction and relaxation of the ventricle. At the moment of contraction of the left ventricle, blood is pushed into the pulmonary trunk.
The atrioventricular orifice is closed by the valve of the same name. This valve also has another name - tricuspid. The three leaflets of the valve are folds of the inner surface of the ventricle. Special muscles are attached to the valves, which prevent them from eversion into the atrial cavity at the time of contraction of the ventricles. On the inner surface of the ventricle is a large number of transverse muscle bars.
The opening of the pulmonary trunk is blocked by a special semilunar valve. When closed, it prevents the reverse flow of blood from the pulmonary trunk at the moment of relaxation of the ventricles.
Blood enters the left atrium through four pulmonary veins. It has a protrusion - an ear. The comb muscles are well developed in the ear. Blood from the left atrium enters the left ventricle through the left atrioventricular orifice.
The left ventricle has thicker walls than the right. On the inner surface of the ventricle, developed muscle crossbars and two papillary muscles are clearly visible. These muscles are attached to the bicuspid left atrioventricular valve with the help of elastic tendon filaments. They prevent eversion of the valve leaflets into the cavity of the left atrium at the time of contraction of the left ventricle.
The aorta originates from the left ventricle. The aorta is closed by the tricuspid semilunar valve. The valves prevent the return of blood from the aorta to the left ventricle when it relaxes.
Support system
In relation to other organs, the heart is in a certain position with the help of the following fixation formations:
The wall of the heart muscle consists of three layers: inner, middle and outer:
Conducting system
In the heart muscle there is a special conducting system of the organ. It is involved in the direct regulation of rhythmic contractions of muscle fibers and intercellular coordination. The cells of the conduction system of the heart muscle, myocytes, have a special structure and rich innervation.
The conduction system of the heart consists of a cluster of nodes and bundles organized in a special way. This system is localized under the endocardium. In the right atrium is the sinoatrial node, which is the main generator of cardiac excitation.
From this node, the interatrial bundle departs, which is involved in synchronous atrial contraction. Also, three bundles of conductive fibers depart from the sinoatrial node to the atrioventricular node, located in the region of the coronary sulcus. Large branches of the conducting system break up into smaller ones and then into the smallest ones, forming a single conducting network of the heart.
This system ensures the synchronous work of the myocardium and the coordinated work of all departments of the organ.
The pericardium is a membrane that forms a pericardial sac around the heart. This shell reliably separates the heart muscle from other organs. The pericardium consists of two layers. Dense fibrous and thin serous.
The serous layer consists of two sheets. A space filled with serous fluid forms between the sheets. This circumstance allows the heart muscle to slide comfortably during contractions.
Physiology
Automatism is the main functional quality of the heart muscle to contract under the influence of impulses that are generated in it. The automatism of cardiac cells is directly related to the properties of the membrane of cardiomyocytes. The cell membrane is semi-permeable to sodium and potassium ions, which form an electric potential on its surface. The rapid movement of ions creates conditions for increasing the excitability of the heart muscle. At the moment of reaching electrochemical equilibrium, the heart muscle is unexcitable.
The energy supply of the myocardium occurs due to the formation of energy substrates ATP and ADP in the mitochondria of muscle fibers. For the full-fledged work of the myocardium, adequate blood supply is necessary, which is provided by the coronary arteries extending from the aortic arch. The activity of the heart muscle is directly related to the work of the central nervous system and the system of cardiac reflexes. Reflexes play a regulatory role, ensuring the optimal functioning of the heart in constantly changing conditions.
Features of nervous regulation:
General Functions
The functions of the heart are:
The heart is one of the most perfect organs human body. It has a set of amazing qualities: power, tirelessness and the ability to adapt to constantly changing environmental conditions. Thanks to the work of the heart, oxygen and nutrients enter all tissues and organs. It provides continuous blood flow throughout the body. The human body is a complex and coordinated system, where the heart is the main driving force.
Right ventricle of the heart occupies most of the anterior surface of the organ. It has a thicker wall, because. three layers of myocardium are located here, and not two, as in the left and right atria. The cavity of this part of the heart has an interesting shape, which would be easy to study if you pour plaster into it and make an impression. It would turn out to be a kind of "cobblestone" with two spurs. Accordingly, three parts are distinguished in the ventricle (Fig. 1): entrance department(1) - has a short length, but very wide, originates from the atrioventricular opening (2), exit department(3), called in old manuals the "arterial sinus" and leading to the pulmonary trunk with its semilunar valve (4), and muscular department(5), which occupies the main volume. The inner surface of the muscular section is also smooth due to the endothelium, but not so smooth: from the side of the wall of the ventricle, fleshy crossbars protrude into the cavity (more often they are called trabeculae), from the largest of which - the transverse marginal trabeculae - the papillary muscles originate. Most often there are three of them: anterior (6), posterior (7) and septal (8), but it happens that there are more of them.
Fig.1. Scheme of the structure of the right ventricle
Very important element structures of the ventricles of the heart are chords - tendon threads(9), or in literal translation from Latin tendon strings. These are thin whitish threads originating from the tops of the papillary muscles and ending on the surfaces of the three cusps of the atrioventricular valves (also, by the way, anterior, posterior and septal). There is a kind of overlap in this. So the anterior papillary muscle “sends” the threads mainly to the anterior of the three valves and partly to the posterior, the posterior muscle mainly to the posterior valve and partly to the third, septal. Accordingly, from the septal papillary muscle, the tendon filaments approach the same leaf of the tricuspid valve and in several bundles to the anterior one. Output and input departments, divides supraventricular ridge, it flows into the cavity of the left ventricle. The exit and entrance sections are clearly distinguishable, more even from the inside, since the bulk of the trabeculae falls on the muscular section. Recall that the right ventricle has two openings: the atrioventricular and the opening of the pulmonary trunk.
The posterior section is presented left ventricle of the heart. The diaphragmatic surface, blunt edge and apex of the heart can serve as landmarks for the location of the left ventricle, as well as left side coronal and both interventricular sulci, which are the outer boundaries. Although left ventricle of the heart smaller than the right one, it does not differ much from it. There are also three layers of myocardium, however, the wall of the left ventricle is even thicker 1.2 cm due to the more developed muscle layer. It is worth noting that the wall of the right ventricle is 0.3 cm in size. The following departments are also distinguished in the left ventricle (Fig. 2): input(1), that is, closest to the atrioventricular opening (2), day off(3) continuing into the aorta (4), and muscular(5), but in the case of this cavity of the heart, there is no such pronounced boundary as the supraventricular crest between the inlet and outlet sections. This is another feature and difference in structure of the ventricles of the heart.
Fig.2. Scheme of the structure of the left ventricle
There is only a rather conditional delimiter between the inlet and outlet sections, and this is the anterior leaflet (6) of the mitral valve. This delimiter is conditional since it is such only during the opening of the valve (Fig. 2, a). If the valve is closed, then there is no anterior cusp in the cavity, the division of the ventricle into sections is not noticeable (Fig. 2b). go to the mitral valve tendon threads papillary muscles, two papillary muscles (or two groups of muscles) are most developed: anterior (7) and posterior (8), respectively tendon threads these muscles go to the anterior and posterior leaflets of the mitral valve. There are two holes: atrioventricular and aortic. The first with a bicuspid (mitral) valve. The second is covered with three semi-lunar wings. The left ventricle sends blood to the aorta through the aortic opening, and then the blood is distributed throughout the body.
The left atrioventricular (mitral) valve, valva atrioventricularis sinistra (v. mitralis), is attached along the circumference of the left atrioventricular orifice; the free edges of its valves protrude into the cavity of the ventricle. Like the tricuspid valve, they are formed by duplication of the innermost layer of the heart, the endocardium. This valve, when the left ventricle contracts, prevents the passage of blood from its cavity back into the cavity of the left atrium. In the valve, an anterior cusp, cuspis anterior, and a posterior cusp, cuspis posterior, are distinguished, between which two small teeth are sometimes located. The anterior cusp, being strengthened on the anterior parts of the circumference of the left atrioventricular orifice, as well as on the connective tissue basis of the aortic orifice closest to it, is located to the right and more anteriorly than the posterior one. The free edges of the anterior leaflet are fixed by tendon chords, chordae tendineae, to the anterior papillary muscle, m.. papillaris anterior, which starts from the anterior wall of the ventricle. The anterior fold is slightly larger than the posterior one. Due to the fact that it occupies the area between the left atrioventricular orifice and the aortic orifice, its free edges are adjacent to the aortic orifice. The back leaf is attached to the back section of the circumference of the specified hole. It is smaller than the anterior one and, in relation to the opening, is located somewhat posteriorly and to the left. Through the chordae tendineae, it is fixed mainly to the posterior papillary muscle, m .. papillaris posterior, which begins on the posterior wall of the ventricle. Small teeth, lying in the intervals between large ones, are fixed with the help of tendon chords either to the papillary muscles or directly to the wall of the ventricle. In the thickness of the teeth of the mitral valve, as well as in the thickness of the teeth of the tricuspid valve, there are connective tissue, elastic fibers and a small amount of muscle fibers associated with the muscle layer of the left atrium. The anterior and posterior papillary muscles can each be divided into several papillary muscles.
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