Orientation and deformation of erythrocytes in flowing blood.

The effects of flow on the changes of electrical resistivity and light-scattering characteristics of blood are experimentally and theoretically discussed. Studies indicate that most erythrocytes deform and orient themselves in the flow direction when blood flows in a conduit. Such oriented blood shows anisotropic properties. Anisotropic electrical resistivity of flowing blood is measured in three rectangular directions with a measurement cell of coaxial cylindrical type. From these experimental results, the orientation and deformation of erythrocytes are discussed. The orientation ratio and the deformation are calculated using a simplified spheroidal model of an erythrocyte. Calculated results show that the fractions of erythrocytes with their short axis parallel to each direction and the equivalent axis ratio for a simplified spheroidal model change with the shear rate of flow.