Figure 3.

Biofluid mechanics of the microvasculature. (a) As blood transitions from the arteries to the arterioles, capillaries, and venules, there is a significant drop in the applied pressure and blood velocity due to a significant increase in the cross-sectional area of the vessels. Panel a adapted from Reference 1. (b) Endothelial cells strongly respond to shear stress, changing morphologically and with altered signaling pathways related to growth factors, coagulation, inflammation, extracellular matrix degradation, cell division, differentiation, migration, apoptosis, and permeability. Panel b adapted from Reference 118. (c) A low hematocrity (0.15) simulation illustrates the Fåhræus-Lindqvist effect and unique noncontinuum flow physics governing the microvasculature. Panel c adapted from Reference 119. (d) Mathematical models corrected with experimental data provide an estimate of the expected relative viscosity as a function of bulk hematocrit (H_D). Notably, there can be up to a fourfold increase in smaller vessels in vivo, informed by rat mesentery microvascular measurements, as compared to in vitro, informed by glass capillary experiments. Empirically derived equations for both are available from Reference 32.