Conductive system of the heart

The heart as an organ working in a system of constant automatism includes a conductive heart system, systema conducens cordis, which coordinates, corrects and assures its automatism, taking into account the reduction in the musculature of individual chambers.

The conductive heart system consists of nodes and conductive paths (bundles). These bundles and nodes, accompanied by nerves and their branches, serve to transfer impulses from one part of the heart to others, providing a sequence of contractions of the myocardium of individual chambers of the heart.

At the site of the upper vena cava in the right atrium, between the vein and the right ear, there is a sinus-atrial node, nodus sinuatrialis. Fibers from this node go along the border crest, ie, along the border separating the right ear and the sine of the hollow veins, and surround the arterial stalk passing here, heading for the myocardium of the atria and to the atrioventricular node.

The musculature of the atria is mostly isolated from the muscles of the ventricles. An exception is a fiber bundle, starting at the interatrial septum in the region of the coronary sinus of the heart. This bundle consists of fibers with a large amount of sarcoplasm and a small number of myofibrils. The structure of the bundle includes nerve fibers, they are directed to the interventricular septum, penetrating into its thickness.

In the bundle, a thickened initial part is distinguished - the atrioventricular node, nodus atrioventricularis, passing into a thinner atrioventricular fasciculus, fasciculus atrioventricularis. The initial part of the bundle is the trunk, truncus, is directed to the interventricular septum, passes between both fibrous rings and divides into the upper and posterior part of the muscular part of the septum into the right and left legs.

The right leg, crux dextrum, short and thinner, follows the septum from the right ventricular cavity to the base of the anterior papillary muscle and in the form of a network of thin fibers spreads in the muscle layer of the ventricle.

The left leg, crus sinistrum, wider and longer than the right one, is located on the left side of the interventricular septum; in its initial sections it lies more superficially, closer to the endocardium. Going to the base of the papillary muscles, it splits into a thin network of fibers that form the anterior and posterior branches that extend in the myocardium of the left ventricle.

The inner shell of the heart, or endocardium. Endocardium, endocardium, is formed from elastic fibers, among which are connective tissue and smooth muscle cells. From the side of the heart cavity the endocardium is covered with endothelium.

Endocardium lining all the chambers of the heart, tightly fused with the underlying muscle layer, follows all its irregularities, formed by fleshy trabeculae, comb and papillary muscles, as well as their tendon outgrowths.

On the inner shell of the vessels leaving from the heart and the vessels flowing into it - hollow and pulmonary veins, aorta and pulmonary trunk - the endocardium passes without sharp boundaries. In the atria, the endocardium is thicker than in the ventricles, especially in the left atrium, and thinner, where it covers the papillary muscles with tendon chords and fleshy trabeculae.

In the most thin sections of the walls of the atria, where gaps are formed in their muscle layer, the endocardium closely adjoins and even fuses with the epicardium. In the area of ​​fibrous rings of the atrioventricular apertures, as well as aortic and pulmonary trunk apertures, the endocardium by doubling its leaf - the endocardial duplication - forms the valves of the atrioventricular valves and the semilunular valves of the pulmonary trunk and aortic. The fibrous connective tissue between both leaves of each of the valves and semilunar flaps is connected to the fibrous rings and thus fixes the valves to them.