Microcirculation

Microcirculation is blood flow through arterioles, capillaries, and venules, where vessel dimensions are comparable with cellular length scales.

Murray's law balances viscous pumping power against the metabolic cost of maintaining blood volume. For cylindrical vessels it gives $Q\propto R^3$ and hence $R_0^3=R_1^3+R_2^3$ at an ideal bifurcation.

The Fahraeus--Lindqvist effect is the reduction of blood's apparent viscosity as a small vessel narrows over much of the microvascular range. Red blood cells migrate toward the centre and leave a relatively low-viscosity cell-free plasma layer near the wall.

A cell-free layer is a near-wall region of plasma depleted of suspended blood cells. Because plasma is less viscous than the cell-rich core, the layer can substantially reduce hydraulic resistance.

The Zweifach--Fung effect, or plasma skimming, is the disproportionate entry of red blood cells into the higher-flow daughter at an asymmetric microvascular bifurcation.