The Fine Structure of the Mesenteric Arteries of the Rat

Abstract

Electron microscopic studies were made of collapsed and of noncollapsed mesenteric arteries from 150 g rats. Material was fixed in buffered osmic acid or in glutaraldehyde. Three cellular layers were analyzed, intima, media and adventia, separated by 2 elastic laminae. The intima comprised endothial cells separated from the internal elastic lamina, both in collapsed and non-collapsed vessels, by collagen fibers and grout-1 substance. Medial muscle cells occasionally communicated bj liscontinuous sarcoplasmic processes but were generally separatee* by collagen fibers, elastic laminae and basement membranes. Muscle cells extended processes prove occasional fenestrae in the external elastic laminae to come in contact with parts of advential autonomic nerve cells. The evidence obtained shows that the lumens of the arteries may communicate directly with medial muscle cell plasma membranes, that medial muscle cells may adjoin directly and that peri-arterial nerve fibers may come in occasional direct contact with medial muscle cells.