title: Biology of red cells: non-nucleated erythrocytes as fluid drop-like cell fragments.
abstract: Red blood cells as transport cells for oxygen can only be understood by appreciating their specialist functions. In addition to the specific functions of intracellular haemoglobin concentration, their flow behaviour as non-nucleated cell fragments is central to their role in taking up, transporting and releasing reversibly bound oxygen. The unique biology of mammalian red blood cells stems from the fact that they behave akin to fluid droplets. The specific details of their motion in shear fields have been demonstrated in a scientific film: 'Blood fluidity as a consequence of erythrocyte fluidity', film No. C 1494, available through the Institute for the Scientific Film, Nonnenstieg 72, 3400 Göttingen, FRG. The present review presents theoretical details of the flow and deformation of fluids, of suspensions of particles, and of emulsions of fluid droplets immersed in another immiscible fluid. Cytological causes, microrheological details of continuous red cell deformation by deformation orientation, membrane tanktreading, and cytoplasmic eddy flow are described. In addition, the consequences of the fluid drop-like behaviour of the red cells during blood flow in vivo and in vitro are given; an appendix contains an outline of the mechanics of the red cell membrane as a two dimensional elastoviscous fluid film with suspended proteins.
mesh_terms: D001809:Blood Viscosity; D004548:Elasticity; D004907:Erythrocyte Deformability; D004910:Erythrocyte Membrane / Q000502:physiology; D004912:Erythrocytes / Q000502:physiology*; D006801:Humans; D008560:Membrane Fluidity; D008833:Microcirculation / Q000502:physiology; D012039:Regional Blood Flow