Erythrocyte deformability

Erythrocyte deformability refers to the ability of erythrocytes (red blood cells, RBC) to change shape under a given level of applied stress, without hemolysing (rupturing). This is an important property because erythrocytes must change their shape extensively under the influence of mechanical forces in fluid flow or while passing through microcirculation. The extent and geometry of this shape change can be affected by the mechanical properties of the erythrocytes, the magnitude of the applied forces, and the orientation of erythrocytes with the applied forces. Deformability is an intrinsic cellular property of erythrocytes determined by geometric and material properties of the cell membrane, although as with many measurable properties the ambient conditions may also be relevant factors in any given measurement. No other cells of mammalian organisms have deformability comparable with erythrocytes; furthermore, non-mammalian erythrocytes are not deformable to an extent comparable with mammalian erythrocytes. In human RBC there are structural support that aids resilience in RBC which include the cytoskeleton- actin and spectrin that are held together by ankyrin.

Shape change of erythrocytes under applied forces (i.e., shear forces in blood flow) is reversible and the biconcave-discoid shape, which is normal for most mammals, is maintained after the removal of the deforming forces. In other words, erythrocytes behave like elastic bodies, while they also resist to shape change under deforming forces. This viscoelastic behavior of erythrocytes is determined by the following three properties: 1) Geometry of erythrocytes; the biconcave-discoid shape provides an extra surface area for the cell, enabling shape change without increasing surface area. This type of shape change requires significantly smaller forces than those required for shape change with surface area expansion. 2) Cytoplasmic viscosity; reflecting the cytoplasmic hemoglobin concentration of erythrocytes. 3) Visco-elastic properties of erythrocyte membrane, mainly determined by the special membrane skeletal network of erythrocytes.

Erythrocyte deformability is an important determinant of blood viscosity, hence blood flow resistance in the vascular system. It affects blood flow in large blood vessels, due to the increased frictional resistance between fluid laminae under laminar flow conditions. It also affects the microcirculatory blood flow significantly, where erythrocytes are forced to pass through blood vessels with diameters smaller than their size.

...
Wikipedia