The skin is the body’s largest organ, a complex combination of two layers made up of variety of cells. It encloses and protects the rest of the body, and helps to keep it at an even temperature.
The outer layer, the epidermis, varies in thickness and is composed mainly of keratin, a protein made by some of its cells. Keratin is the major component of hair and nails, which are really extensions of the skin.
Beneath that outer layer is the dermis, which contains connective tissues and such structures a hair follicles, sebaceous glands, blood and lymph vessels, and nerves. The main constituent of the dermis is collagen, a substance making up about a third of body’s protein. Collagen gives the skin much of its elasticity, allowing it to stretch, twist, shake and shiver – and return smartly to its place.
As we get older, collagen loses some of its water. This process, known as polmymerisation, stretches the collagen molecules into longer chains. It behaves then like elastic that has been to long in the Sun: it loses its snap and flexibility.
Below the dermis, cushioning the skin from bones or internal organs, is a layer of subcutaneous tissue, which holds a high proportion of a fat. In time, the tissue loses fat and doesn’t replace it. The cushion becomes thinner, and the skin sags. With some of its elasticity gone, the skin folds into a crease or wrinkle, increasing in depth as more fat vanishes from the subcutaneous layer.
Not all skin wrinkles come form age or sunlight. We all get wrinkles during a long swim or a while taking a bath. Normally, the keratin in the epidermis waterproofs it and the body. If it didn’t, we would soak up water like a sponge. During prolonged immersion, the outer layer of skin takes in some water, causing it to swell. Fortunately, the wrinkling is temporary. As we dry off with a towel, all those wrinkly creases soon vanish.