Surface morphology of human aorta as revealed by the scanning electron microscope.

Human aorta was prepared for scanning electron microscopy using critical point drying. The aortic surface is lined by a continuous layer of squamous endothelial cells. The luminal surface of these cells contains many microvilli or microappendages and pinocytotic vesicles. In addition, at the periphery of each cell, larger marginal appendages or microfolds are present which allow the observer to see the cell boundaries clearly. The marginal folds are superficial to the cell junctions and could be observed without any staining procedures. These observations on human aorta are generally in agreement with our findings on the rabbit and guinea pig aorta and vena cava but in contrast to others who have reported the presence of ridges, intercellular bridges, and "hair-like" processes on the endothelial surfaces.