Organ Specificity and Functional Relevance of the Arterial Structure: A Comparative Study in the Kidney and the Skeletal Muscle with Electron Microscopy

Abstract

The differences in circulation among various organs are well known, but the structural differences have only been poorly investigated. In the present study the wall structure of arteries was observed with electron microscopy in rat kidney and skeletal muscle. The wall thickness was almost equal in both organs at about 40 μm in luminal diameter, while it was relatively thin in the larger arteries and thick in the smaller arteries in the kidney compared with that in the skeletal muscle. The smooth muscle cells were regularly arranged in parallel in circular or slightly spiral orientation in the kidney, whereas those in the skeletal muscle were irregularly arranged in heterogeneous orientations. Extracellular matrices were more abundant in the arterial media in the skeletal muscle than in the kidney. The inner elastic lamina was continuous in the kidney, and arranged in longitudinal bundles in the skeletal muscle. The adventitial collagen fibers were abundant and dense in the skeletal muscle, and were scattered in small bundles in the fluid-filled spaces in the kidney. While the arteries in the skeletal muscle are under severe mechanical stress during muscle contraction and dilate dramatically during exercise, those in the kidney regulate glomerular pressure almost constantly.