Increased blood viscostiy and slow circulation causes
|A||RBC rouleux formation|
|B||Increased plasma skimming|
|C||Increased number of RBC in capillaries|
a. Rouleaux → RBC pile one over another like a pile of coin
b. Visocity of the blood is increased by high hematocrit value (↑RBC counts, polycythemia) and very low velocity and vice versa
c. At slower velocities in blood vessels axial flow of the RBC is absent ~ RBC are now scattered and cause resistance to the movement of the fluid ~ further, at very low velocities (tviscosity) -J Rouleaux formation of RBC may occurs, further obstructing the flow
d. Newtonian fluid ~
i. Where the viscosity does not change with change of the shearing force (velocity) and
ii. when moves through a tube, shows a laminar (stream line) flow.
- Blood is a non-Newtonian fluid. Q
f. Fahraeus-LindQvist Effect ~ Blood flow in minute tubes exhibits for less viscous effect than it does in large vessels.
g. Plasma skimming:
i. In the vessels, red cells tends to accumulate in the centre (axial flow) of flowing stream
ii. Consequently, the blood along the side of the vessels has a low hematocrit, and branches leaving a large vessels at right angles may receive a disproportionate amount of Red-cellpoor blood. This is known Plasma skimming that is why hemotocrit of capillary blood is 25% lower than the 'whole blood hematocrit. Q
iii. Low viscocity, high velocity ~ Axial flow of RBC ~ dec. Hematocrit ~ plasma skimming.
iv. High viscosity, low velocity ~ absent axial flow of RBC ~ inc. Hematocrit ~ plasma skimming.