Are bones alive?
Bones consist of a solid stony material that is laid down in layers by living bone cells. New bone is constantly being reabsorbed and then replaced, to keep it healthy. The surface of a bone is covered by a skin that is full of nerves, so it hurts when you bruise or break a bone. Inside the bone are blood vessels and marrow, a soft material in which new blood cells are produced. When people get old, their bones may become very spongy and weak, and so they are more prone to breakage.
How can bones heal themselves after a break?
Bones are alive, and so the bone cells can gradually replace and repair the solid bone when it is broken. The damaged material is gradually absorbed back into the body, and the bone cells secrete more hard bone. This eventually builds up into a thickened area on the repaired bone, which is actually stronger than the original bone.
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