Structural peculiarities in developing coronary arteries located in the epicardial connective tissue.

A striking difference was observed in the coronary bed between the histogenesis of the main stem vessels and that of their branches. The developing main stem vessels exhibited the structural pattern of arteries submitted to intense hemodynamic stresses, whereas the developing branches showed the structural pattern of arteries protected against these stresses. This striking difference was related, histologically, to the existence of sphincteral mechanisms located in all the branching points present in both right and left coronary arteries.