Formation of the cardiac vascular system and ventricular compact wall

The corrosion cast method for scanning electron microscopy, transmission electron microscopy and auto-injection of tracers for light microscopy were used to examine the cardiac coronary development and the forming of the ventricular compact wall to the embryonal sponge-work wall. Our observations suggest that the coronary artery first extends over outer layer, and later over middle and inner layers. As intertrabecular spaces are closed by fusion to each endocardium in the inner layer position, the veins are formed by the remaining expanded sinusoidal intertrabecular spaces. The capillaries of the coronary vessels are then connected to the veins to finally complete the cardiac vascular system.