Blood brings them food and oxygen and takes away waste. If bones weren't made of living cells, things like broken toes or arms would never mend. But don't worry, they do. When you break your toe, blood clots form to close up the space between the broken segments. Then your body mobilizes bone cells to deposit more of the hard stuff to bridge the break.
Many bones are hollow.
Their hollowness makes bones strong and light. It's in the center of many bones that bone marrow makes new red and white blood cells. Red blood cells ensure that oxygen is distributed to all parts of your body and white blood cells ensure you are able to fight germs and disease. You have over 230 moveable and semi-moveable joints in your body.