Ask Dr. Universe

How are bones made? Asked by Oscar, 10.

Dear Oscar,

A couple months before you were born, your skeleton was soft and bendy. It was made out of cartilage, the same material that’s in your nose and ears now. But when certain cells in your body called osteoblasts and osteoclasts began to work together, new bone started to form.

In fact, you were born with about 300 tiny bones in your body. As you began to grow, some of the bones fused together and became single bones. Now, you carry around a skeleton of 206 bones.

Those bones are pretty strong, too. They are mostly made up of the same minerals th...