Your bones have a team on standby. Osteoprogenitor cells wait on the bone's surface, ready to turn into bone builders whenever new bone is needed.
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Bones are covered with a thin skin called the periosteum (say: pair-ee-OSS-tee-um). They're lined inside, too.
Osteoprogenitor cells live in these linings, right against the bone. They are flat and thin, and they don't look like much. But they're ready for action.
"Osteo" means bone, and "progenitor" means one that comes first. So these are the cells that come before bone builders!
When your body needs new bone, osteoprogenitor cells divide and change into osteoblasts, the busy bone builders.
This happens while you grow, and it's very important when a bone breaks. Lots of these cells wake up near the break and help make new bone to fix it.
Scroll up to the 3D model and press Become a builder.