January 21, 2012 9:10
The heat from dog paws not go through a special organization of blood vessels: the venous vessels intercept heat from the arteries, preventing it evaporate into space.
Why do dogs run on snow or ice, do not freeze feet? Everyone knows that the hair on the pads of dogs not — and then there is no insulation from the cold. True, there is animal fat layer that freezes much more slowly, but due to the fact that the surface of pads a lot more of its volume, the heat should dissipate quite rapidly. And how do we protect ourselves from such heat? The walls of the vessels of the extremities are reduced, due to this they reduced blood flow, and blood is supercooled. On the one hand, the body does not freeze because of hypothermia in the hands and feet of blood, and the other — the arms and legs at the same time it is possible to freeze.
Researchers from the University of Yamasaki Gakuen (Japan) carefully examined the location of blood vessels in the legs several adult dogs, to publish the results in the journal Veterinary Dermatology. It was found that the arteries that bring blood to the dog paws, equipped with counter-network of small veins. That is, each artery that carries blood to pads, accompanied by several venules through which it flows in the opposite direction. Heat exchange between the vessels: the heat from the arterial blood enters the venous vessels, without having to dissipate into outer space.
Blood does not have time to cool, and does not cool the body, but the legs and are not without blood supply, and therefore do not freeze.
A similar system teplosohraneniya there are a few species that has to face the cold. In the wings and feet of Antarctic penguins and dolphins fins arranged around blood vessels as well as in the paws of dogs. According to scientists, this confirms that the ancestors of domestic dogs lived in a cold climate before they were domesticated by man. However, over time, the "home" of life, some species have begun to lose this adaptation, allowing the fingers do not freeze in winter. So now, in the winter vygulivaya their pets better protect their tender pads from hypothermia, writes compulenta.ru.