Blood flow in contracting arterioles.

Blood flow in contracting arterioles with non-circular cross-sections due to endothelial protrusions is investigated. The flow field was determined for a viscous Newtonian fluid with a numerical computation from electron micrographs of arteriolar crossections in skeletal muscle at different stages of contraction. The results indicate that the flow field in such vessels deviates from Poiseuille flow for circular tubes of equal cross-sectional area in several respects: the resistance is elevated, the ratio of maximum and mean velocity is increased above the value of 2 for Poiseuille flow, and the wall shear stress is nonuniform with a maximum at the tip of local endothelial projections and near zero at endothelial cell junctions. The average wall shear stress is less than in circular vessels with equal lumen crossection and pressure gradient.