As you think about all of the organs in your body and how important they are, don’t forget the largest body organ. It’s also the one that is most visible—your skin.
Have you ever considered how incredible your skin is? The hands of a laborer may be rough like sandpaper, but his abdominal skin could be smooth and soft. The calves of your legs have skin bonded tightly to a muscle layer. The skin on your elbow can be lifted loosely in rolls. If you used a microscope to examine the skin of our scalp, lip, heel, and finger, you might think you were studying sample from different species.
Your skin is the largest body organ, and there is no other organ like it. It flexes, folds, stretches, and bends around joints. It’s sensitive to touch. The skin of your finger pads is sensitive enough to detect a grain of dust on a smooth surface or read Braille letters in a book. When you blush (something that only humans do), the blood vessels of your skin suddenly rush many times more blood than usual. Your skin even regenerates itself when it’s damaged.
Your skin shows emotions, cools and insulates your body, protects you from germs, serves as a receptor for all kinds of stimuli, and gives you that unique appearance. We often cut off the hair growing out of our skin or add some substance to soften and beautify our skin. We seldom take a moment to realize what a fantastic organ it is.
Fingerprints are often associated with identification because the police use them in criminal investigations. Nobody else has your fingerprints, so finger touch-pads are sometimes used instead of passwords to access computers or to allow entrance to secure sites. Fingerprints are used for those purposes, but have you ever wondered why we have fingerprints?
Long before anyone thought of those identification uses, fingerprints served a primary purpose in our sense of touch. The raised ridges are actually friction ridges that increase the sensitivity of our fingers to touch. Each fingertip has thousands of touch receptors, and with the aid of the friction ridges, we can feel a particle many times smaller than a human hair.
Run your fingertip lightly over a surface and notice how those fingerprint ridges detect even the smallest surface imperfection, right down to a speck of dust. Look closely, and you will see that those ridges are also present on the entire surface of the palm-side of your hand, and they are on your feet as well.
What about the case of identical twins? Do they have the same fingerprints? The answer is “No.” They are similar, but not the same. Your fingerprints are the product of genetics plus environment within the womb. Fingerprints form between six and thirteen weeks after conception. Factors that influence the formation of the prints may be blood pressure, nutrition, or the position of the hand in the womb. A finger pressing against the amniotic sac, another part of the body, or the body of a twin can cause the print to form with subtle differences. If only genetics determined the fingerprint pattern, the fingers on your left and right hands would be identical. They are not, and that’s why the police will take all ten of your fingerprints.