Shape and orientation of arterial loops in cat sartorius muscle

A method is described to quantify the shape and orientation of vascular loops (arcades). Shape is characterized by an ellipticity factor, calculated from area and perimeter values. Orientation is measured as the angle formed by the great axis of the loop with the muscle fibers. These parameters were calculated for 772 arteriolar loops of the cat sartorius muscle. The results show that, on the average, the ellipticity factor is a linear function of the number of segments. The observed values change in the opposite direction from the expected values for regular polygons. Simple calculations are presented to rectify this discrepancy. Most loops are oriented parallel to the muscle fibers.