darker, less makes it lighter. Sunlight causes more melanin to be manufactured in your skin cells and that gives you a tan – or sunburn. Watch out – you need your skin to protect you!
Waxes and oils that the skin produces keep it waterproof and protected against germs; they keep it softer but can also give you spots. The skin contains glands which manufacture sweat, which helps cool the body and gets rid of chemicals it doesn’t need.
Adults have nearly two square metres of skin - about the size of a blanket. You are likely to shed 18 kg (40 pounds) of skin in a lifetime. Every minute betwen 30,000 and 40,000 dead skin cells fall from your body. Every four weeks your body has made a whole new layer of skin cells!
Bladder
Hair grows all over your body except on the soles of your feet and the palms of your hands. Think how difficult it would be if you had hairy palms. Hair can stand up and trap a layer of air to help keep you warm.
Your fingernails grow twice as fast as your toenails, at 0.05 cm a week.
BODY QUIZ Solve the clues to find two organs your body can’t do without. You may have to do some research, as some of the words are not to be found on these pages.
Where waste water is stored The back of the eye, where light is focused The part of the body holding the stomach and intestines Your body contains enough of this element to make a nail They carry messages to the brain
Keeps your body warm Vibrates as sound waves reach the outer ear Blood vessel which carries blood from the heart Bones which protect the lungs and heart Strings attaching muscles to bones
The skeleton accounts for about one fifth of a person’s weight. It protects internal organs and allows movement. There are 206 bones in an adult body. When you were a baby you had more bones which have fused together as you have grown. A baby has 22 different bones which become the cranium (skull), protecting the brain. The smallest bone is the stirrup bone in the inner ear and the largest is the femur, or thigh bone, which can be about 50cm long. The only bone not attached to any other bone is a U-shaped bone at the base of the tongue, called the hyoid. Each hand has 27 separate bones and each foot has 26. As a baby you had more than 26 bones in your back, but as with the cranium, some of these have now joined together.
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