Microvascular hemodynamics: System properties1.

The hemodynamics of the microcirculation reflect system properties of the involved components. The blood itself is a complex suspension of water, small and large molecules and different cell types. Under most conditions, its rheologic properties are dominated by the different behaviour of fluid and cellular compartments. When perfused through small-bore tubes or vessels, the suspension exhibits specific emergent properties. The Fahraeus-effect and the Fahreaeus-Lindqvist-effect result from the interaction of cellular particles with each other and with the vessel wall. Additional phenomena occur in vascular networks due to the uneven distribution of blood cells and blood plasma at divergent microvascular bifurcations. In order to understand microvascular hemodynamics in vivo but also in artificial microfluidic geometries it is thus necessary to recognize the pertinent system properties on the level of the blood, the microvessels and the microvascular networks or perfused structures.