The mechanism responsible for the formation of cardiac connective tissue and vascular components in early ontogenesis from various embryonal layings and the subsequent coexistance and interaction of two myocardial blood supply system in the formed heart at all stages of postnatal life form the basis for morphological and functional characteristics of organ specificity. The findings are of direct interest to practical cardiologists and cardiosurgeons who analyze some conditions which are likely to involve compensatory mechanisms in inadequate coronary blood supply of the heart.