[Morphological characteristic of the interatrial septum and the conducting system of the heart].

Layer-by-layer preparations of interatrial septum, atrium walls and the histological study of its transverse serial sections in 84 human heart specimens revealed 6 kinds of interatrial muscle fascicles: posterior horizontal, posterior oblique-horizontal, superior horizontal, anterior horizontal (Bachmann's), Z-shaped superior (above the oval fossa) and inferior (below the oval fossa). In the oval fossa and its valve, a particular structure consisting of the transitional T-cells of the heart conducting system was detected, which contacted the muffs of the entries of all pulmonary veins by means of working myocardium muscle fascicles.