The structure of the walls of the heart. Myocardium.

The structure of the walls of the heart. Myocardium.

The walls of the heart consist of 3 membranes: the inner endocardium, the middle myocardium, and the outer epicardium, which is the pericardium visceral leaflet, pericardium. The thickness of the walls of the heart is formed mainly by the middle sheath, myocardium, myocardium, consisting of cardiac striated muscle tissue. The outer sheath, epicardium, is a serous coat. The inner lining, endocardium, endocardium, lines the cavity of the heart.

Myocardium, myocardium, or muscular tissue of the heart, although it has a transverse striation, but differs from skeletal muscles in that it is not composed of individual multicore fibers, but is a network of mononuclear cells — cardiomyocytes. In the musculature of the heart there are two sections: the muscle layers of the atrium and the muscle layers of the ventricles. The fibers of those and others start from two fibrous rings – anulifibrosi, of which one surrounds ostium atrioventriculare dextrum, the other – ostium atrioventriculare sinistrum. Since the fibers of one section, as a rule, do not pass into the fibers of another, the result is the possibility of reducing the atria separately from the ventricles. In the atria, the superficial and deep muscular layers are distinguished: the superficial consists of circular or transversely located fibers, deep – from the longitudinal, which with their ends begin from the fibrous rings and loop around the atrium. Around the circumference of large venous trunks, flowing into the atria, there are circular fibers covering them, like sphincters. Fibers of a superficial layer cover both auricles, deep belong separately to each auricle.

The muscles of the ventricles are even more complex. Three layers can be distinguished in it: a thin surface layer is composed of longitudinal fibers that start from the right fibrous ring and go obliquely downwards, passing to the left ventricle; at the apex of the heart, they form a curl, vortex cordis, bending here loop-like in depth and forming the inner longitudinal layer, the fibers of which are attached to the fibrous rings with their upper ends. The fibers of the middle layer, located between the longitudinal outer and inner, go more or less circularly, and, unlike the surface layer, they do not pass from one ventricle to another, but are independent for each ventricle.

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