Skeletal Muscle Capillaries in Nondiabetics

To evaluate the variations of capillary calibers and those of basal lamina (BL), pericytes, endothelium, and lumen within a sample of skeletal muscle and among samples from different anatomic sites, areas occupied by total capillary cross sections, by the lumen, endothelium, pericytes, and BL were measured on electron micrographs. Twenty capillary cross sections from each of the 41 specimens of skeletal muscle from 23 nondiabetic males were used. For all parameters, a marked variation was noted within each specimen, between specimens from identical sites of different individuals, and between different anatomic sites of the same individuals. In general, the capillaries are largest in the lower leg and foot muscles; the lumen is smallest at the levels of mid-thigh and lower leg; the capillaries of the lower extremity have a greater investment of BL, endothelium, and pericytes than the capillaries of the trunk and hand muscles. The areas occupied by endothelial cytoplasm, pericyte cytoplasm, and by BL are larger in bigger capillaries apparently owing to greater circumference. In addition, the capillaries of the leg, particularly those of the lower leg, have an absolutely greater investment of BL than capillaries from proximal sites. Reasons for these regional differences in the overall size of capillaries and in the investment of BL are not known.