[Cushion-like structure in coronary arteries of rats].

The vascular architecture in the rat heart was investigated with SEM using a corrosion cast and light microscopy of paraffin sections stained with Hematoxylin-Eosin and Elastica-Domagk methods. In corrosion cast models of the left and right descending coronary arteries, Y- and T-type branching patterns were distinguished. The Y-type bifurcations were found at branching sites of the larger vessels and precapillary arterioles in the myocardium, whereas the T-type bifurcations were found at branching sites of the smaller vessels. On the surface of the corrosion cast of the T-type bifurcation symmetrical shallow depressions were observed at an orifice of a daughter vessel. The depression was confirmed to be produced by protrusions consisting of smooth muscles and elastic fibers of the vascular wall. The structure is presumed to be an arterial cushion which plays some role in avoiding plasm skimming and regulating blood flow.