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Blood viscosity is a measure of the resistance of blood to flow. It can also be described as the thickness and stickiness of blood. This biophysical property makes it a critical determinant of friction against the vessel walls, the rate of venous return, the work required for the heart to pump blood, and how much oxygen is transported to tissues and organs.
The Fåhræus–Lindqvist effect (/ f ɑː ˈ r eɪ. ə s ˈ l ɪ n d k v ɪ s t /) or sigma effect [1] describes how the viscosity of a fluid, in this case blood, changes with the diameter of the tube it travels through. In particular there is a 'decrease in viscosity as the tube's diameter decreases' (although only with a tube diameter of ...
Instead, there is the plugged flow which is hyperviscous because holding high concentration of RBCs. Thurston assembled this layer to the flow resistance to describe blood flow by means of a viscosity η(δ) and thickness δ from the wall layer. The blood resistance law appears as R adapted to blood flow profile :
The viscosity of blood is in the range of 3 to 6 cP, or 0.003 to 0.006 Ns/m2. [4] Blood is a non-Newtonian fluid, which means that the viscosity of blood is not a constant with respect to the rate of shearing strain. In addition to the rate of shearing strain, the viscosity of blood is also dependent on temperature and on the volume percentage ...
The Fåhræus effect (/ f ɑː ˈ r eɪ. ə s /) is the decrease in average concentration of red blood cells in human blood as the diameter of the glass tube in which it is flowing decreases. In other words, in blood vessels with diameters less than 500 micrometers , the hematocrit decreases with decreasing capillary diameter.
Erythrocyte aggregation is the main determinant of blood viscosity at low shear rate. Rouleaux formation also determines Erythrocyte sedimentation rate which is a non-specific indicator of the presence of disease. [6] Influence of erythrocyte aggregation on in vivo blood flow is still a controversial issue. [7]
There are two current major hypotheses to explain blood flow predictions and shear thinning responses. The two models also attempt to demonstrate the drive for reversible red blood cell aggregation, although the mechanism is still being debated. There is a direct effect of red blood cell aggregation on blood viscosity and circulation. [16]
Erythrocyte deformability is an important determinant of blood viscosity, hence blood flow resistance in the vascular system. [3] It affects blood flow in large blood vessels, due to the increased frictional resistance between fluid laminae under laminar flow conditions.