Question

If we consider blood as a suspension of RBCs in a Newtonian fluid, the shear forces experienced by the RBCs during blood flow would

• A. Randomize the orientation of blood cells
• B. Align RBCs along their long axes with streamlines
• C. Align RBCs along their short axes with streamlines
• D. Create an equal distribution of RBCs aligned in their long and short axes

Hint:

In blood flow, red blood cells align along their long axis in the direction of flow, reducing shear resistance in the vessels.

Answer 1

The Correct Option is B

In a fluid flow, particles (such as red blood cells, or RBCs) experience shear forces that cause them to align in the direction of flow. RBCs, which are biconcave in shape, align with their long axes parallel to the flow streamlines, minimizing resistance to fluid flow. This alignment is due to the shear forces acting on the cells in a Newtonian fluid.
- Option (A) is incorrect because RBCs do not randomize in normal flow conditions; instead, they align with the flow direction.
- Option (B) is correct because the RBCs align with their long axes, reducing friction and allowing for easier movement through the blood vessels.
- Option (C) is incorrect because the short axis of the RBCs does not align with the flow, as this would increase resistance.
- Option (D) is incorrect because RBCs do not randomly orient; they align with their long axes to minimize resistance.
Thus, the correct answer is (B) Align RBCs along their long axes with streamlines.
Final Answer: (B)