How does blood viscosity influence vascular resistance and blood flow?

How does blood viscosity influence vascular resistance and blood flow?

• A. Higher viscosity decreases vascular resistance.
• B. Lower viscosity increases resistance.
• C. Viscosity does not affect flow.
• D. Higher viscosity increases vascular resistance and reduces blood flow.

Answer: (D)

Blood viscosity is the internal friction of the moving blood. When it’s higher, the layers of blood rub against each other more, increasing resistance to flow in the vessels. Since flow is determined by the pressure difference divided by resistance, a rise in resistance from thicker blood means less blood flow for the same pressure gradient. So thicker (more viscous) blood increases vascular resistance and reduces blood flow. Conversely, thinner blood lowers resistance and enhances flow. This is why conditions that raise hematocrit or plasma proteins can slow flow, while dilution or anemia can ease it. The overall idea is that viscosity directly boosts friction inside vessels, raising resistance and lowering flow.

Blood viscosity is the internal friction of the moving blood. When it’s higher, the layers of blood rub against each other more, increasing resistance to flow in the vessels. Since flow is determined by the pressure difference divided by resistance, a rise in resistance from thicker blood means less blood flow for the same pressure gradient. So thicker (more viscous) blood increases vascular resistance and reduces blood flow. Conversely, thinner blood lowers resistance and enhances flow. This is why conditions that raise hematocrit or plasma proteins can slow flow, while dilution or anemia can ease it. The overall idea is that viscosity directly boosts friction inside vessels, raising resistance and lowering flow.