Monday, December 30, 2013

Do Dog Paws Suggest They Originated in a Cold Environment?

Scientists studied the mystery of how dogs can stand on frigid snow and ice without apparent discomfort.
Dog Paw Have Counter-Current Heat Exchange
Tokyo's Yamazaki Gakuen University studied dogs to gain understanding why dogs do not seem to feel the cold even with a high surface area-to-volume ratio, suggesting paws should loose heat easily.

Dr. Hiroyoshi Ninomiya and his research team used a scanning electron microscope to study four dogs and their paws.  They discovered that arteries supplying blood to the pads had numerous networks of small veins that acted as a counter-current heat exchange.  Essentially, the blood warms up before it returns to the body. Human extremities react differently.  When exposed to frigid temperatures, blood vessels vasoconstrict reducing blood flow.  A dog's system prevents the blood from cooling while keeping paw temperatures reasonable.  When blood arrives in the paws via arteries, heat is transferred to the veins warming the blood before it is returned.  This prevents cold blood from returning to the body and keeps paw temperature at a reasonable.

The findings suggest that dogs may have originated in a cold environment, since their paws are adapted for it. Although frostbite in dog paws is rare, it can happen.

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