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Countercurrent Heat Exchange - Basics


Countercurrent Heat Exchange is a common mechanism in organisms that utilizes parallel pipes of flowing fluid in opposite directions in order to save energy.

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A whale's tongue uses this system. As blood flows to the tip of the tongue, it heats up blood returning to the body.


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Parallel pipes that flow in the same direction are called concurrent, and are not as efficient as countercurrent flow in retaining energy.
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Countercurrent Heat Exchange - Further Reading


Gray whales take in many galloons on cold seawater into their mouths at a time, and one could imagine this would be a large heat sink, given the specific heat of water. If the gray whale were to lose a significant amount of heat to the water, it wouldn't be able to eat enough food to produce the energy required to hear its body. It was therefore essential for its survival to have a system to conserve energy in the form of heat. Through natural selection, a countercurrent heat exchange system was established in the gray whale's tongue. As warm blood flows to the tongue through an artery, it gives off heat to the blood returning to the whale through its veins. This is a significant way to save heat, as the heat would otherwise be lost to the water the whale swallows.

Similarly, the flippers of whales and dolphins use countercurrent heat exchange systems, as well as the legs of mammals and birds in cold environments.[8]