What is counter current heat exchange and what kinds of animal have it?
It's a mechanism often used in mammals living in cold climates I believe, I've seen it used as an example in polar bears, so heat isn't lost from their paws which are in contact with the ice, they use this mechanism to move heat from blood going to the paws to the blood returning to the body and heart.
Counter Current Heat Exchange
Countercurrent Heat Exchange
A lot of animals (like us) have it. It basically is a mechanism to conserve heat. For example, picture a blood vessel making a U loop. As it goes from the heart to let's say, down the left side of the U, heat from the center of the body is transferred to the exterior. The blood vessel will then bring blood back to the heart on the right side of the U, as well as heat left over. But, while the blood is going down the left side, some heat reaches the right side of the U because of the temperature difference, so excess heat is not lost. That is the crucial part of counter current heat exchange. Fish also do stuff like that, but they can do counter current exchange with oxygenated blood.
