The Body

Grown-ups

Skeleton

Your skeleton is the frame of bones inside you that holds you up and keeps you safe.

A thigh bone cut open: a hard wall outside, honeycomb at the ends, and soft marrow in the middle making new blood. Tap any part!

A frame that is alive

Your skeleton is the frame inside your body. Without it, you would flop like a bowl of jelly. With it, you can stand, sit, run and hug.

Bones in a museum look dry and white. But the bones inside you are alive! They have blood vessels, which are tiny tubes for blood. They have nerves, which carry messages. And they are full of busy living cells.

Because bones are alive, they grow as you grow. They get stronger when you use them. And if one breaks, it can fix itself.

Five big jobs

Job one: hold you up. Your bones are like the poles of a tent. They give your body its shape.

Job two: protect. Your skull is a helmet for your brain. Your ribs are a cage around your heart and lungs. Your backbone is a tunnel for your spinal cord.

Job three: move. Muscles hold on to bones and pull them. The bones are levers, and the muscles do the pulling.

Job four: make blood. The soft middle of some bones, called marrow, makes new blood cells all day and all night.

Job five: store minerals. Minerals are things like calcium that your body needs. Almost all the calcium in your body is kept in your bones and teeth, like money saved in a bank.

Babies have more bony parts

A new baby has about 270 to 300 bony parts. A grown-up has 206 bones. So where do the extra ones go?

They don't get lost. As you grow, some small parts slowly join together, or fuse, into one bigger bone. Parts of your skull, your hips and the bottom of your backbone all do this.

A baby's skeleton also has lots of cartilage. That is the bendy stuff in the tip of your nose. Bit by bit, much of it turns into hard bone. That's one reason babies are so bendy.

Hands and feet win

Here is a surprise: more than half of your bones are in your hands and feet! Each hand has 27 bones, and each foot has 26. That makes 106 bones, out of 206.

Why so many? Lots of small bones means lots of joints, the places where bones meet. That lets your fingers do tiny jobs like tying a shoelace. It lets your feet bend over bumpy ground.

Try it: wiggle each finger, one at a time. Then curl your toes. Every bend you see is bones moving at a joint.

What bones are made of

Bones are made of two main things. One is a tough, stretchy material called collagen. It is a bit like the threads in a rope. The other is hard minerals, mostly calcium.

The threads keep bones from snapping. The minerals make them hard. Together they make bone very strong for how light it is.

A science trick to try with a grown-up: put a clean chicken bone in a jar of vinegar for about a week. The vinegar pulls out the calcium, and the bone turns rubbery! That shows how much calcium helps keep bones hard.

Always being rebuilt

Inside your bones, two teams of cells work all the time. Builder cells add new bone. Cleaner cells clear away old bone.

Bit by bit, they rebuild your whole skeleton about every 10 years. So your bones today are not the same bits of bone you had as a baby.

When you run, jump and play, your bones feel the push. The builder cells answer by making your bones thicker and stronger.

🤩 Wow facts

  • The biggest bone in your body is your thigh bone. The smallest is the stirrup, deep inside your ear.
  • Myth: Bones are dead and dry. Truth: Your bones are alive, with blood, nerves and cells that grow and heal.
  • Almost all the calcium in your body, about 99 out of every 100 bits, is stored in your bones and teeth.
  • A giraffe's long neck has 7 neck bones. That's the same number as yours!
  • Kids and teens build most of the bone they will have as grown-ups. Playing and eating well now helps your bones for life.
  • Not everyone has exactly 206 bones. Some people have a few tiny extra ones, and that is perfectly normal.

💚 Look after it

  • Eat calcium foods like milk, yogurt, cheese, beans and leafy greens.
  • Get vitamin D, which helps your body use calcium. Eggs, fish and milk with added vitamin D help, and so does playing outside.
  • Run, jump, dance and climb. Bones get stronger when they carry your weight.
  • Wear a helmet on bikes and scooters, and buckle up in the car every time.
  • Get plenty of sleep. Your body does lots of growing while you sleep.

🩹 When something goes wrong

When a bone breaks. A broken bone hurts and may puff up. Tell a grown-up right away. A doctor takes an X-ray, a special picture that shows your bones, and may put on a cast to hold the bone still. Then your bone heals itself, usually in a few weeks.

🙋 Questions kids ask

Do bones feel pain?

Yes. A thin skin on the outside of each bone has nerves, so a hurt bone feels sore. That soreness tells you to rest it and tell a grown-up.

Why are museum skeletons white?

Those bones are not alive anymore. The blood and living parts are gone, so only the hard minerals are left. Your living bones are full of blood and busy cells.

Why do bones break?

Bones are strong, but a very hard fall or bump can push on a bone more than it can take. Then it cracks. The good news is that bones can heal.

Do bones ever stop growing?

Bones stop getting longer around the end of the teen years. But they keep rebuilding themselves your whole life.

🧠 Quick quiz

Question 1 of 3About how many bones does a grown-up have?

🔗 It works with

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