An alternative view on blood plasma in the vasculature
Résumé
Blood plasma is not only a suspending medium for blood cells but exerts important further tasks in the vasculature. It couples RBC flow with its own flow, lubricates blood flow, and contributes to the endothelial and erythrocyte (RBC) surface layers. It was long believed exhibiting a pure Newtonian behaviour, but recent developments highlight an elastic nature that is reinforced at small scale. This surprising finding is attributed to careful dynamic mechanical tests optimizing the interfacial interactions between blood plasma and surfaces of the rheometry setup. In this frame, to approach the boundary conditions of blood biophysics in flow, we coated the surfaces with a hydrogel composed of extracellular matrix proteins to mimic a dissected aortic wall. We evidence for native whole blood a shear elastic plateau at about 30 mPa for frequencies within 0.3 and 0.6 rad s-1 and gap of 0.7 mm. Such behaviour indicates that the blood oscillates in the gap as a whole. We conclude that the slow flow of blood plasma observed close to the vessel wall can generate a stationary plasma layer that contributes to the functional width of surface layers in vessels. In endothelial cells, this layer uptakes the shear stress of flow first. The shear stress term calculated out of wall shear rate and blood viscosity becomes imprecise if it does not include this utmost important intermediate layer.
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