Why does vascular resistance increase as blood vessel radius decreases, especially in arterioles?

💡 Explanation

As vessel radius diminishes, the ratio of surface area to volume increases significantly, leading to a proportionally greater frictional resistance against blood flow because a larger fraction of the blood interacts directly with the vessel walls. Therefore, vascular resistance rises, rather than other options related to cellular properties or endothelial signaling, which have secondary effects.

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