Viscosity of blood changes with the rate of blood flow and shear rate. This anomalous viscosity can significantly increase resistance to flow when the perfusion pressure is low as in shock states, contributing to the resulting blood flow deficit. Blood is a non-Newtonian, thixotropic (demonstrating memory) fluid. In a Newtonian fluid viscosity is independent of shear rate and flow velocity.
Fahraeus-Lindqvist effect: viscosity is dependent on the diameter of the vessel it is flowing through. Viscosity appears to decrease as the vessel diameter decreases.
Plasma skimming: in vessels, red cells tend to accumulate in the centre of the flowing stream (axial streaming). Branches leaving a large vessel at right angles may receive a disproportionate amount of red cell-poor blood.
Was this article helpful?