A cage that guards
Your ribs are long, curved bones. In the back, each one joins your backbone. In the front, most of them join your breastbone with strips of bendy cartilage.
Together they make your rib cage. It's like a strong, bendy basket around your heart and lungs.
Try it: put your hands on the sides of your chest. Feel the bumps? Those are your ribs. Gently count as many as you can feel.
Twelve pairs
You have 12 ribs on each side, so 24 in all. They come in pairs: one on the left and one on the right.
Each pair joins one of the 12 bones in your upper back.
A few people have one small extra rib, or one fewer. That isn't common, and it's usually just fine.
True, false and floating
Scientists sort ribs into three groups. The top 7 pairs are called true ribs. Each one joins the breastbone with its own strip of cartilage.
The next 3 pairs are called false ribs. They don't reach the breastbone on their own. Instead, they hook on to the cartilage of the rib above.
The last 2 pairs are floating ribs. They join your backbone but nothing in the front. Their tips are tucked into the muscles of your sides.
Ribs that breathe
Your rib cage isn't stiff. Small muscles between your ribs lift them up and out when you breathe in. Your chest gets bigger, and air rushes into your lungs.
At the same time, a big dome of muscle under your lungs, called the diaphragm, pulls down to make even more room.
Your ribs swing up like the handle of a bucket being lifted. The bendy cartilage in front lets them move and spring back.
Try it: put your hands on your ribs and take a big, slow breath. Feel them rise and spread? Now breathe out and feel them sink.
Ribs make blood too
Ribs aren't just a cage. Inside them is red marrow, the soft part of a bone that makes new blood cells.
Grown-ups make lots of their blood in flat bones like the ribs, the breastbone, the hips and the backbone.