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Physiology

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Basic Concepts

Question
70 out of 95
 

Increased blood viscostiy and slow circulation causes



A RBC rouleux formation

B Increased plasma skimming

C Increased number of RBC in capillaries

D None

Ans. A RBC rouleux formation

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.

  1. 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.

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