SCANNING ELECTRON MICROSCOPICAL STUDY OF VASCULAR SMOOTH MUSCLE CELLS IN THE MESENTERIC VESSELS OF THE MONKEY: ARTERIAL SMOOTH MUSCLE CELLS

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Abstract
The smooth muscle cells in monkey [Macaca fuscata] mesenteric arteries ranging from 100-600 .mu.m in outer diameter were investigated with SEM [scanning electron microscopy] after removal of perivascular and intramural connective tissue components by HCl hydrolysis. The shape, arrangement and dimensions of the muscle cells were evaluated at the fine structural level. The muscle cells ran parallel to each other and were almost circularly oriented with respect to the vessel axis to form a compact and regular media. The muscle cells in the outer portion of the media were elongated, sickle-like and flattened in the axial direction of the vessel with a maximum thickness of .apprx. 3.5 .mu.m and a maximum width of .apprx. 6.5 .mu.m. They ranged from 65-85 .mu.m in length irrespective of the vascular diameter. The outermost cells had a highly rugged adventitial surface with many nodular protrusions and occasional transverse or oblique folds, whereas the deeper muscle cells had a generally smooth surface. The innermost cells characteristically possessed a series of cross ridges projecting inwards. Adjacent ridges were connected laterally to form parallel longitudinal folds. The muscle cells in the outer portion of the media were frequently connected to each other by cylindrical processes < 0.5 .mu.m in diameter.