Orientation of medial smooth muscle in the wall of systemic muscular arteries.

The study was undertaken to determine the pattern of alignment of muscle cells in the tunica media of muscular arteries. Brachial and femoral arteries from two small Rhesus monkeys and renal arteries from two rabbits were fixed under pressure with formalin, or glutaraldehyde followed by formalin. Sections were cut at 7 micron thickness at specific angles varying from zero to 30 degrees, and then stained with haematoxylin and eosin. The end coordinates of the medial muscle nuclei (appearing dark with the H & E stain) were recorded using a digitizer. Analysis was done as suggested by a previous modelling study by one of the authors; lengths of the individual nuclei as they appeared on the section were plotted as a function of the distance around the perimeter of the vessel. The distribution of lengths was consistent with a truly circumferential pattern of alignment for the muscle nuclei in the wall of muscular arteries. The standard deviation about the average circumferential pattern was +/- 13 degrees in the plane of the histological sections cut in cross section. The number density Nv of 4.4 x 10(5) mm-3 was higher than determined previously for human brain arteries and the nuclear length was 20% shorter (30 micron).