Final answer:
Blood moves slower in capillaries than arterioles due to wider total cross-sectional area, decreased blood pressure, and vasodilation and vasoconstriction mechanisms in the precapillary sphincters.
Explanation:
Blood moves slower in the capillaries compared to the arterioles due to several factors:
- Total cross-sectional area: Capillaries have a much greater total cross-sectional area compared to arterioles, allowing the blood to flow through a wider channel and at a slower rate.
- Blood pressure: Blood pressure significantly decreases as it enters the capillaries, as capillaries have tiny diameters and numerous vessels which reduce pressure.
- Vasodilation and vasoconstriction: The precapillary sphincters can close, diverting blood into capillaries and regulating the distribution of blood flow.
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