Your skin

Skin is the largest organ in your body and weighs about 12% of your total body weight!  It is always active, making sure your main barrier to invaders is secure, and replaces itself about once every two weeks.  Skin has very important jobs, the most important of all is to make sure it holds all your inside bits, inside!  Your skin is very tough and acts as protection against microbes and other things that could damage your internal organs.  It is also waterproof, which is why you don’t swell up and slosh around when it rains or if you go swimming!  One of the greatest things your skin does is to sense the world you can touch.  Your skin tells you about the temperature, shape and weight of the world around you, as well as telling you if things are painful, sharp, hard, soft or cuddly!

Your skin is make up of three thick layers.  The outside layer is called the epidermis and this is the layer you see every day.  This layer is touch and acts as protection for your body.  It is thicker in some places that in others, usually in places where there is lots of activity – like the soles of your feet and the palms of your hands.  These skin cells of your epidermis are dead and lie flat to form the tough, protective outer layer of your skin.  They are easy to rub off but skin cells are constantly replaced without you even noticing, so you don’t have any gaps!

Your epidermis also contains a pigment (like a dye) called melanin.  Melanin gets darker when you are out in the sun to give the lower layers of your skin some protection.  People with fair skin have less melanin and do get sunburnt more quickly than people with dark skin who have more melanin.  Having lots of melanin won’t stop you from getting sunburnt though, no matter how dark your skin is.  You need to wear sunscreen, cover your head with a hat, put on sunglasses and a long-sleeved T-shirt to protect yourself from the sun.  Remember the Australian saying: Slip on a T-Shirt, Slop on the sunscreen, Slap on a hat and wrap around those sunglasses - Slip, slop, Slap & Wrap!

The middle layer of your skin is called the dermis.  Your dermis is made up of a protein called collagen that makes it stretchy.  It has nerve endings that send signals to your brain to help it to decide if the things you touch are hot or cold, hard or soft, flat or pointy.  Your hair follicles (the tunnel where each of your hairs grow) are in the dermis, as are the blood vessels that carry your blood to all of your cells.  Your dermis also has glands that produce sweat to help you keep cool and different glands that produce oils to keep your skin waterproof and your hair shiny.  It also has other glands that are not so good – these are the glands that make you smell!

The final layer of your skin is called the subcutaneous layer and it is where fat is stored.  Some fat is very useful as it protects your body when you bump into things or fall over.  Your body fat keeps you warm when it is cold outside and can also be used as fuel if you have to wait a very long time between meals.  Too much fat is bad for you, but we all need some!

Your sense of touch is very important.  It allows you to sense your environment and to sense if something is safe or dangerous.  Your sense of touch is found all over your body as it comes from the dermal layer (the dermis) of your skin.  There are tiny hairs that stimulate your nerve endings and send the information through your spinal cord to your brain.  There are about 20 different types of nerve endings in your skin, each type sending your brain a different message.  Of these, they are four types of nerve endings that are more common than the rest.  These tell you about pressure, pain, heat and cold and are extremely important because they tell you if you are in danger or if your body has been damaged.

You don’t need every area of your skin to be really sensitive to pressure, pain, heat or cold!  Some areas have more nerve endings and some, where they aren’t really needed, have less.  You have more nerve endings in places that are in contact with the world most often, like your fingertips, your lips and your tongue and less in places like the back of your knee!

The other types of sensors, things that tell you about the world around you, are the hairs on your body.  Your hair comes from your hair follicle, a tunnel where each of your hairs grows, in your dermis.  If you pull out a single hair from anywhere on your body, you will see that it has a tiny bulb at the end, like a really tiny onion!  Your hair grows from this bulb, even if you get it cut really short.  Hair can grow quite slowly but eventually it will return to its original length.