Have you ever wondered why a dog can play and roll around in the snow, skid across an icy pond and plunge their paws into frosty places without getting frostbite?  If humans go barehanded and barefooted in the snow and ice, our skin may freeze and we could get frostbite.  Not dogs…and scientists in Japan have figured out why.

The scientists have determined that dog paws don’t freeze because the arrangement of blood vessels beneath their skin keeps the temperature just right according to Science News for Kids.  This helps their body hold on to heat, which might otherwise be easily lost through their hairless paws.

The Japanese scientists studied the arteries and veins in dogs.  Just a little science lesson here–arteries carry warm blood from the heart to the rest of the body; veins bring blood back to the heart.  They discovered that veins surround the arteries that deliver warm blood to dog paws.  The two kinds of blood vessels are so close together that they exchange heat.  Because of this, the warm arteries heat up the cooler veins and thus the temperature in the dog paw stays balanced. Dogs don’t get frostbite in their paws because the warm blood reaches the pad’s surface which prevents frostbite.  This also helps to keep the dog from loosing too much body heat.

This kind of system found in dogs is called a counter-current heat exchanger.  It is found in other animals as well.  Penguins, whales and seals use this system in their feet, fins and flippers to keep their body heat balanced.

The scientists also found that the blood vessels in a dog’s paw open and close as the temperature changes around them.  This allows more or less blood to flow, depending on where it is needed in the animal’s body.

The scientists are going to study cats next to see if they have the counter-current heat exchange mechanism in their paws like the dog.


Filed under: All About Dogs

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