What does vasodilation do to the radius of a blood vessel?

What does vasodilation do to the radius of a blood vessel?

• A. Increases Radius
• B. Decreases Radius
• C. No Change
• D. Causes Vessel Rupture

Answer: (A)

Vasodilation increases the radius of a blood vessel because the smooth muscle around the vessel relaxes and the lumen widens. This widening lowers vascular resistance, and due to the radius-to-the-fourth power relationship in flow through vessels, even a small increase in radius greatly boosts blood flow for a given pressure difference. This mechanism helps deliver more blood to tissues when metabolic demand is higher. The other options don’t fit physiology: decreasing the radius would be vasoconstriction, not dilation; no change would leave flow unchanged; rupture is not a normal result of dilation (it would require extreme wall stress or disease). In practice, signals like nitric oxide promote this dilation to improve perfusion.

Vasodilation increases the radius of a blood vessel because the smooth muscle around the vessel relaxes and the lumen widens. This widening lowers vascular resistance, and due to the radius-to-the-fourth power relationship in flow through vessels, even a small increase in radius greatly boosts blood flow for a given pressure difference. This mechanism helps deliver more blood to tissues when metabolic demand is higher. The other options don’t fit physiology: decreasing the radius would be vasoconstriction, not dilation; no change would leave flow unchanged; rupture is not a normal result of dilation (it would require extreme wall stress or disease). In practice, signals like nitric oxide promote this dilation to improve perfusion.