howthings.work · a picture encyclopedia for small children
Skin
Inside your skin · by @virpo
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If you could cut a tiny slice of your skin and look at it from the side, this is what you'd see: layers, like a cake, each with its own job.
Outer skin
The top layer of your skin is made of tiny cells packed close together, like bricks in a wall.
- New cells grow at the bottom and slowly move up.
- The old ones on top dry out and flake off, so new ones take their place.
- This wall keeps germs out and water in.
A skin cell
Look at the big round cell in the outer skin. Your whole body is made of cells like this one.
- Each cell is far too small to see without a microscope.
- The dark dot in the middle is the nucleus, the cell's control room.
- Look inside it: tap 'Inside: The Cell' below.
Hair
Every hair grows from a little pocket deep in your skin called a follicle.
- A tiny muscle next to it can make the hair stand up when you're cold: goosebumps!
- A little oil gland keeps the hair and skin soft.
- Hair keeps growing all your life.
Sweat gland
This coiled tube makes sweat and sends it up to a tiny hole on the surface, called a pore.
- When you're hot, sweat comes out and dries on your skin, which cools you down.
- You have millions of sweat glands, most of all on your hands and feet.
- Can you see the drop of sweat at the top?
Blood vessels
Red and blue tubes run all through the skin, bringing it the food and air it needs.
- Red ones bring fresh blood from the heart, blue ones take it back.
- When you're hot they widen, which is why your cheeks go pink.
- The smallest ones are thinner than a hair.
Nerves
The thin yellow threads are nerves. They feel things and tell your brain.
- Some feel a soft touch, some feel a push, some feel hot or cold.
- If you touch something hot, they tell you to pull your hand away fast.
- Your fingertips have lots of them, so they are very good at feeling.
Fat layer
Under the skin is a layer of soft yellow fat cells.
- It keeps you warm, like a blanket.
- It's a cushion if you bump into something.
- It also stores energy for later.