Arctic Heat Exchanger

Imagine living in a land where the best temperatures you can hope for never reach 40°F. At worse, you looking at over a 100°F below zero. In fact, most of the year, the water is warmer than the land and as such can be seen as a refuge from the cold, windy land. But 33°F water is no joke, as it is more than cold enough to kill most warm-blooded animals in short order.  To many of us, we call it Antartica.  To many penguins, it is simply home.

Penguins are finely tuned by evolutionary processes to their environments. Creatures of the sea, their form is build for the job. They have sleek, streamlined forms with thin, powerful flippers that enable speeds of over 10 mph. Their feathers are a combination of waterproof exteriors and soft, insulating interior plumage. Their black and white coloring camouflages them against both the bright sky and the dark ocean.

Heat maintenance has been dealt with in an equally impressive evolutionary manner. While not all penguins live in the wicked cold lands of Antartica, water does not need to be drastically cold to be deadly. Water drains body heat around 30 times faster than the air does. The flippers that give penguins such speed and grace in water actually become a liability in the cold. The extremely high surface area combined with the small mass of the flippers are a great heat sink, potentially draining all the flipper’s heat into the ocean.

Evolution’s solution to this problem in ingenius:

Penguins have a trick to keep this from happening.   Blood vessels of the wing in penguins form a “rete mirabile”, a plexus of arteries and veins.  This term means wonderful net in Latin, and it is indeed a wondrous evolutionary novelty.  Arteries carry oxygenated blood from the heart of the penguin to the extremities, and veins return the de-oxygenated blood back again.  In cold water, the blood from the arteries is hot, but the blood returning from the tips of the flippers and toes can be quite cold.  As the normal arteries of the penguin blood vessel system run onto the flipper, they split into multiple parallel branches called a plexus.  Each branch is closely aligned with at least two veins.  The heat from the blood in the arteries warms the returning blood in the veins, raising the blood temperature before it returns to the heart.  At the same time, the blood heading towards the flipper in the arteries is cooled, resulting in the flipper temperature dropping.

Basically, the penguin has a natural heat exchanger built right into its shoulder. Much like mechanical heat exchangers we build into our systems, the penguin’s system is very effective. It can lead to an impressive difference of up to 86°F between the core temperature and wingtip temperature. This keeps the core body warm and toasty. This enables penguins to live in waters all over the world, even in the frigid waters of Antartica.  While most penguin specializations are easily visible, this is one of the cool characteristics that make penguins work that lie hidden beneath the surface.

-That is all.


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