Myocardium – middle layer. Two layers are present in heart musculature: the muscular layers of the atrium and of ventricles.The superficial and deep muscular layers are present in atria: superficial layer – consists of circular fibres (encircle both atria); deep layer is made up by longitudinal fibers (are separate in each atrium). The musculature of the ventricles, three layers are present: Thin superficial layer – is composed of longitudinal fibers; the fibers of the middle layer are more or less circular. The longitudinal inner layer – upper fibers’ ends are attached to fibrous rings. Conducting system of the heart: has important role and coordination of the musculature activity of heart chambers.
1) The atrioventricular bundle – as thickening of atriaventricular node, lying in wall of right atrium near cuspis septalis. The fibres of node directly goes to septum between ventricles.
2) The sinoatrial node: located in area of right atrial wall. It’s connected with musculature of atria.
Blood supply: right, left coronary arteries; venous sinus (v.cordis magna, v.posterior ventriculi, v. oblique atrii, v. cordis media, v. cordis parva), vv.cordis anteriores.
Nerve supply: n. cardiacus superior, n. cardiacus cervicalis medius and inferior, ganglion cervicothoracicum s. ganglion satelleatum.