The middle of your chest
Press gently on the middle of your chest. That flat, hard bone is your breastbone. Its science name is sternum.
In a grown-up, it is long and flat, about as long as a hand.
Your ribs reach around from your back and join it in the front, like the hoops of a basket meeting in the middle.
Shaped like a tie, or a sword
Your breastbone has three parts. People say it looks a bit like a necktie, or like an old sword pointing down.
The top part is like the handle. It's the widest part, and your collarbones join it here. The middle part is like the long blade. The bottom tip is small and pointy.
That tip's science name, xiphoid, comes from an old Greek word for sword. In kids, the tip is still soft cartilage. It slowly turns to bone when people are grown up.
A joining place for ribs
Your top 7 pairs of ribs join the breastbone with their own strips of cartilage. Cartilage is bendy, so your chest can move as you breathe.
The next 3 pairs of ribs hook on lower down, using the cartilage of the ribs above them.
Try it: feel the top of your breastbone, just below your neck. There's a little dip there. On each side of the dip, you can feel where your collarbones begin.
A shield and a blood maker
Your breastbone sits right in front of your heart. With your ribs, it makes a strong shield.
It also has red marrow inside, so it helps make new blood cells all day long.