A helmet made of bones
Your skull looks like one big bone. But it is really about 22 bones fitted together! Some make a round case for your brain. The rest make your face.
The brain case is made of 8 bones. They are curved like the pieces of a bowl, and they fit snugly around your brain.
The face part is made of 14 bones. They build your cheeks, the bridge of your nose, your upper and lower jaws, and parts of the bowls around your eyes.
Try it: gently tap the top of your head. Then tap your cheek. Both are skull, but they are different bones.
Zig-zag seams
The bones of your skull meet at wiggly lines called sutures. A suture is a seam, like the stitched line on a baseball.
The zig-zag shape helps the bones lock together like puzzle pieces. In a grown-up, these seams barely move at all.
The seams are joints, the places where bones meet. They are a kind of joint that stays still.
Soft spots on a baby's head
A new baby's skull bones are not joined yet. Between them are soft spots, where the bones haven't met. Tough skin covers them, so the baby is safe.
The gaps let a baby's skull change shape a little. They also leave room for the brain, which grows very fast in the first few years.
Bit by bit, the bones grow toward each other. The big soft spot on the top of the head closes by about age 2.
Eye sockets and air pockets
Your eyes sit in two deep bowls called eye sockets. Each one is built from 7 bones. The bony rim around each eye helps keep a bump from reaching your eye.
Try it: gently trace the edge of the bone around your eye with one finger. That ring is the rim of your eye socket.
Your skull also has air pockets called sinuses, in the bones around your nose. They help make your skull lighter, so your neck has less to hold up.
At the bottom of your skull is a big round hole. That's where your brain joins your spinal cord, the long bundle of nerves in your backbone.
Strong but not too heavy
The bones of the brain case are like a sandwich. They have two hard layers with a spongy layer in between. That makes them strong but not too heavy.
Inside the skull, your brain floats in a thin layer of liquid. The liquid works like a cushion when you bump your head.
Even so, a skull can't stop every hard knock. That's why you wear a helmet when you ride a bike or a scooter.