Why dont Antarctic penguines feet freeze in the winter
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Two mechanisms help address the problems. First, the penguins body can actually control the rate of blood flow to the feet by varying the diameter of vessels supplying the blood. In cold conditions, that flow is reduced; when its warm, the flow increases. Humans do this too: Our hands and feet become white when were cold, pink when were warm.
Second, penguins have countercurrent heat exchangers at the top of their legs. Arteries supplying warm blood to the feet break up into many small vessels, as do the veins, bringing cold blood back from the feet. Because these capillary beds are so close to each other, they modulate the temperature of the blood in both directions ...more