Skin care- Dieseases and prevention

The cell layers of the epidermis grow down around the papillae. On the fingertips, the papillae form the lines and whorls called finger- prints. The dermis carries the skin's blood supply. Through microscopically thin walls of tiny capillary vessels in this layer of skin, the blood supply of the body can be brought close to the surface. 

When the body becomes overly warm, these blood vessels dilate. When dilated, the capillaries have more surface area, permitting an increase in the rate of evaporation and cooling. When the body becomes cool, the capillaries constrict, reducing heat loss through the skin. Along with blood vessels, bundles of nerve fibers enter the skin and branch out in profusion. The supply of nerve endings makes the dermis highly responsive, especially in such areas as the fingertips, where the nerve endings are in particularly heavy supply.

There are involuntary muscles in the skin which dilate and contract the capillaries. There is also an erector muscle connected to the side of each follicle, or hair pocket. When erector muscles contract, hairs stand upright. It is this that makes furred animals appears larger when they are in danger; it also provides an insulating air layer between the hairs as protection against cold. Some investigators believe that the action of erector muscles in man, which produces "goose pimples," stems from the days when our ancestors had hairy bodies. 

The subcutaneous layer under the skin is attached loosely to inner body structures such as bones and muscles. Along with blood vessels and nerves, the subcutaneous layer contains fat globules which serve both to insulate the body against heat and cold and to cushion inner organs against bumps and jolts. If fatty tissues become too thick, graceful movement of muscles may be hindered. As people grow older, the fatty tissue in the subcutaneous layer may be absorbed, causing the outer skin layers to form uneven folds, or wrinkles.