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Your amazing bodyThe skinOf all the body's wonderfully designed organs, the skin is supreme in versatility. It is the only organ directly and constantly open to the environment. It wards off harmful agents, heat and cold, the elements and bacteria. It is waterproof. It repairs itself. It is self-lubricating. It even eliminates some body wastes. Like its close relations, hair and nails, it reflects both physical and mental health. Skin can warn of inner illness by going waxen, ashen, blotchy, spotty, ruddy, pallid, yellow, purple, grey or blue. It gives you the sense of touch. It can be tough or delicate, smooth or wrinkled as your needs or age dictate. It can bristle, blister, tingle, itch, hurt, sweat, stretch, shrink, weep, creep, bleed and blush. The skin makes vitamin D - vital for healthy joints and bones. It controls body temperature. It can signal emotion, provide sexual and social attraction and denote racial origin. What the skin isSome of skin's vital statistics are amazing. Each hand has 17,000 tactile receptors and 1,300 nerve endings per square inch (200 per square centimetre). An adult's skin typically covers 20 square feet (1.86 square metres), and weighs six pounds (2.7 kg.). We shed some 40 pounds (19 kg.) of dead skin cells in the course of our lifetime. The skin has a complex structure consisting of two distinct layers, the epidermis and, beneath it, the dermis. The epidermis varies in thickness, from 1/20th of an inch (1 millimetre) on the palms and soles of our feet, where protection from pressure matters most, to 1/200th of an inch (1/10th of a millimetre) on the face, eyelids and lips, where fine and rapid movements are required. The epidermis contains no blood cells but produces melanin, which makes skin darker to protect against the sun. The pinkish colour of 'white' people is influenced by the redness of the blood cells and by carotene, which filters sunlight. In the deepest part of the epidermis, young skin cells, which are oval, soft and tender, constantly divide and rise to the surface over 28 days or so. They change as they rise through a germinative zone, filling with keratin (a fibrous substance also found in hair and nails) and become flat and tightly packed to form the two outer protective sections of the epidermis, the shiny inner membrane and the surface with its millions of hairs and sweat glands. Subject to constant wear and tear, the surface skin cells flake off but are continuously replaced. New cells provide water essential for maintaining the skin's suppleness and flexibility. Beneath the epidermis is the dermis, a fibrous layer, thicker in men than women, coarser on the back and ranging in thickness from 1/50th to 1/8th of an inch (half a millimetre to 3 millimetres). It is full of collagen, which with elastic fibres gives skin strength and elasticity. The dermis nourishes keratin production, removes waste products and regulates body temperature. Many thousands of nerve endings play a key role in the sensations of touch, cold, warmth, pressure and pain. There are also pockets of hair follicles, where the sebacious glands secret sebum, an oily substance which makes skin pliable and hair shine. The nails are simply compressed keratin. Like skin, the nail bed has a germinative zone and an underlying dermis, supplying blood and giving the nail its largely pink colour. Near its root, the nail is denser and the blood supply reduced - hence the white lunule, or half moon. The cuticle forms a watertight seal. Hair is like the uppermost layer of the epidermis and has several protective roles. Head hair insulates, eyelashes and nose and ear hairs keep out foreign objects, eyebrows help keep sweat out of the eyes.  Why skin colour vairesThe quantity and distribution of dark pigment - melanin - determines skin colour, which varies to reflect people's adaptation to different environments. Black skin, for instance, helps protect against sunburn. Scandinavians are pale to prevent vitamin D deficiency in an environment where daylight is reduced. Albinos lack the gene to produce melanin. An iron-rich pigment gives red hair its distinctive colour. Although the skin has remarkable capacity to sustain and care for itself, to withstand sun, wind, water and many forms of mistreatment from tattooing to over-zealous washing, it is prey to many disorders, infections and diseases. One square inch (six square centimetres) can harbour as many as six million bacteria. Emotional problems can cause skin problems too. Skin problemsPeople with skin problems make up to about a tenth of all patients that family doctors see. These conditions are seldom thought 'serious', and usually they are not. But they can cause pain and even disability, as well as social and emotional problems. Skin diseases often run in families but inheriting one does not mean it is incurable or that it cannot be effectively treated. The most common skin problems are:
Look after your skinThe skin is so wonderfully self-sufficient that we perhaps tend to take it for granted, or even abuse it unthinkingly. But it deserves and needs proper care and attention, especially in later life. The skin should be kept clean, but too much washing with soap will dry it out, stripping it of its protective lubricant, sebum. Also, soap can sometimes cause allergic reactions - if this happens, choose a product labelled 'hypoallergenic'. Moisturers help to relubricate the skin with a light coating of an oil and water emulsion. They are not absorbed beyond the outermost layer. The greatest risk to skin is strong sunlight. Excessive exposure not only causes dryness or sunburn but also long-term changes, which can lead to premature ageing or even skin cancer. A broad-spectrum sunscreen with a Sun Protection Factor (SPF) of at least 15, and 30 for children, blocks most of the potentially harmful ultraviolet radiation. Apply sunscreen on exposed skin before going into the sun and reapply every two hours while outdoors. Use it liberally - most people do not use enough. Even waterproof sunscreen can come off when you towel off sweat or water. June 2001 Back to the 'Your amazing body' index. |
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