Red blood cells in shear flow

Orateur : Thomas FISCHER (Institut für Physiologie, Medizinische Fakultät, Rheinisch-Westfälische Technische Hochschule, Aachen, Germany)

From a rheological point of view is blood a suspension of red cells (concentration 45% v/v) in blood plasma (viscosity 1.3 mPas at 37 ∞C). To study the flow behaviour of red cells in vitro we increase the viscosity of the suspending medium and decrease the cell concentration. Subjecting this suspension to shear flow we observe two modes of motion. In the first the red cells rotate as solid bodies, a mode called tumbling. In the second mode the red cells are elongated in ellipsoid like bodies. The long axis of these ellipsoids assumes an almost steady state orientation in the shear field. The external shear flow induces an eddy like flow in the red cell cytoplasm. This flow is transmitted via the red cell membrane moving around the ellipsoidal shape, a motion called tank-treading. In our experiments we observed (a) the shear rate of the transition between mode one and two and (b) the instantaneous angle the long axis of the ellipsoidal cells includes with the undisturbed flow direction. This data will be compared to results of computer modelling.

Télécharger dans mon agenda