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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.
η(δ) = viscosity of blood in the wall plasma release-cell layering; r = radius of the blood vessel; δ = distance in the plasma release-cell layer; Blood resistance varies depending on blood viscosity and its plugged flow (or sheath flow since they are complementary across the vessel section) size as well, and on the size of the vessels.
Consequently, if a liquid has dynamic viscosity of n centiPoise, and its density is not too different from that of water, then its kinematic viscosity is around n centiStokes. For gas, the dynamic viscosity is usually in the range of 10 to 20 microPascal-seconds, or 0.01 to 0.02 centiPoise. The density is usually on the order of 0.5 to 5 kg/m^3.
Hematocrit levels that are too high or too low can indicate a blood disorder, dehydration, or other medical conditions. [4] An abnormally low hematocrit may suggest anemia, a decrease in the total amount of red blood cells, while an abnormally high hematocrit is called polycythemia. [5] Both are potentially life-threatening disorders.
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.
As the blood moves into the aortic arch, the area with the highest velocity tends to be on the inner wall. Helical flow within the ascending aorta and aortic arch help to reduce flow stagnation and increase oxygen transport. [4] As the blood moves into the descending aorta, rotations in the flow are less present.
To perform the test, anticoagulated blood is traditionally placed in an upright tube, known as a Westergren tube, and the distance which the red blood cells fall is measured and reported in millimetres at the end of one hour. [3] Since the introduction of automated analyzers into the clinical laboratory, the ESR test has been automatically ...
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 blood changes with the diameter of the vessel it travels through. In particular there is a decrease in viscosity as the vessel diameter decreases, but only at small diameters of 10–300 micrometers (mainly ...