The epidermis is the body's environmental shield made up of tough keratinized cells glued together in stacks by fats. The epidermis is a barrier against injury, disease, and damage from ultraviolet light. Obviously, the horny layer protects the internal organs from exposure and massive fluid loss. The ability to quickly replace a damaged epidermis is critical in mending trauma, particularly in cases where burns, abrasions, or cuts leave the body vulnerable to infection and dehydration. Skin protects dogs from ultraviolet rays of the sun by providing a foundation for the haircoat and by producing melanin to color hair and skin.
Melanin is a natural sunscreen.
Humans can increase the production of melanin by repeated exposure to the sun, but dogs do not tan. The epidermis is joined to the dermis at the basement membrane, a layer of collagen and other products of the basal cells. Collagen is a tough, durable, fibrous protein that makes up 90 percent of the dermis and provides strength to the skin. Tanned collagen from cattle skin is otherwise known as leather. Collagen occurs in bundles.