Science
What does skin do?
Quick answer
Skin is your body's largest organ. It covers and protects you, keeps water in and germs out, helps control your temperature and lets you feel touch.
In one sentence
Skin is the flexible covering of your body that protects you, keeps you at the right temperature and lets you feel the world.
Explained
Your skin covers you from head to toe. It is your body's biggest organ. It is made of several layers.
hand
soap
sun
- Epidermis: the thin outer layer. It is waterproof and made of tough cells. The top cells are dead and flake off, and new ones keep pushing up from below, so your skin renews itself about every month.
- Dermis: the thicker layer below. It contains nerve endings, blood vessels, sweat glands and the roots of hairs.
- Fatty layer: underneath, it cushions and keeps you warm.
Skin has important jobs:
- Protection. It keeps germs and water out and stops your body from drying out.
- Feeling. Nerve endings tell your brain about touch, heat, cold, pressure and pain. See senses.
- Temperature control. When you are hot, your sweat glands release sweat, and as it evaporates it cools you. When you are cold, tiny muscles lift your hairs and give you goose bumps, which trap a layer of warm air.
- Vitamin D. Sunlight on skin helps your body make vitamin D for strong bones.
Skin colour comes from a pigment called melanin. People with more melanin have darker skin, which gives more natural protection from the Sun's harmful UV rays. But everyone can be sunburnt, so use sun cream, shade and a hat in strong sun. Fingerprints are patterns of ridges on the skin of your fingertips, and each person's are unique.
When you cut yourself, blood clots and the skin heals; see blood. Skin links to all the parts of the human body.
Examples
| Layer | Contains | Job |
|---|---|---|
| Epidermis | skin cells | waterproof barrier |
| Dermis | nerves, sweat glands | feeling, cooling |
| Fatty layer | fat | cushion and warmth |
Common mistakes
- "Only dark skin needs protection from the Sun." Everyone needs it.
- "Skin is dead." The top layer is dead cells, but the layers below are alive.
- "Sweat smells." Fresh sweat is almost odourless; bacteria cause the smell.
Quick quiz
Skin
Check what you know with 4 quick questions.
Question 1 of 4
What is the largest organ of the human body?
Practise it
Try it
Human body practice
Practise it step by step in a full course: Grade 4 Science
For grown-ups
Related topics
The senses
The five main senses are sight, hearing, smell, taste and touch. Sense organs such as the eyes, ears, nose, tongue and skin collect information and send it to your brain.
The human body
The human body is made of trillions of cells that form organs, such as the heart, lungs and brain. Organs work together in systems that keep you moving, breathing, eating and thinking.
Materials
Materials are what objects are made from, such as wood, metal, plastic and glass. Each has properties, like being hard, bendy, waterproof or see-through, that suit it to some jobs.
Blood
Blood is the red liquid pumped around your body by your heart. It carries oxygen and food to every cell, takes away waste and helps fight germs and heal wounds.
The brain
The brain is the control centre of your body. It sends and receives messages through your nerves so you can think, feel, move, remember and breathe.
Digestive system
The digestive system is the long tube and organs that break food down into tiny pieces your body can absorb for energy and growth, then get rid of what is left as waste.