Scanning Electron Microscopic Observation of the Media of Blood Vessels Revealed after Removal of Connective Tissue Components

Abstract

Three-dimensional cytoarchitecture of blood vessels from aorta to vein via microvasculature were revealed by scanning electron microscopy after connective tissue components were removed. The blood vessel of the mammary gland was continuously observed from an arteriole to a venule. Spindle-shaped smooth muscle cells (SMCs) and branched- SMCs, and elongated- pericytes and spidery-pericytes were found on the endothelial tube in accord with the description of microvasculature reported by Rhodin. In the intermediate segment of the arteriovenous anastomoses, the SMCs of the outer layer were irregularly spindle-shaped and circularly arranged, while the epithelioid cells of the inner layer were polygonal in shape and irregularly oriented. In the mesenteric artery, the SMCs were sickle-like and almost circularly oriented. Those of the thoracic aorta were closely apposed to form muscle bundles, forming a lattice-like structure in the outermost lamella, and arranged parallel to form muscle sheets in the inner lamellae. The SMCs in the mesenteric vein were circumferentially flattened, and along with the SMCs in the coronary artery, were irregular in shape and arrangement. The asteroid SMCs were observed in the subarachnoidal arteriole. Even denuded vessels were observed in some transgenic mice. These results suggested the usefulness of scanning electron microscopy in vascular research.