The integumentary system is the technical term for the skin. The basic function of the skin is to protect the body. It is the largest of the body’s systems consisting of several layers and includes hair follicles, hair, fur, feathers or scales. It also has nerve endings and pigmentation.
The outer most layer of the skin is called the epidural layer. It comes in a multitude of shapes and sizes accommodating the individual species. Toads have warts, snakes have scales, bird skin adapted for feathers, dogs and cats have fur that is sensitive to its environment, some lizards and cephalopods have complex pigmentation.
The covering of the skin in many mammals helps to regulate temperature. Animals living in the colder regions of the world have a thick undercoat of hair to trap in their body heat and the longer outer coat keeps out the cold. Birds have s soft down under their feathers, which they fluff out to cool their bodies. The skin also protects the body from diseases and bacteria
The skin, as all systems, is interactive. The nerve endings react to pressure so when the fur moves the nerve corresponds to the particular movement. Though the skin is tough the nerves can feel a fly.
The skin also protects the body from injury. The skin is either very thick as in an elephant or more pliable as in humans and hippopotami. Rhinoceros skin is very hard to penetrate protecting them from breeding skirmishes and predatory attacks.
The skin also protects some animals by changing colors. The pigmentation of the skin is caused by melanin. The most complex camouflage skin is that of the cuttlefish. These animals have about 200 cells called chromatophores, which help them to take on the colors of their environment.