What are bones made of?
Bones are made of hard minerals that are supported by tough fibres called collagen. Most of the substance of a bone is made of a stony material called calcium phosphate. It is a hard but brittle material. The collagen strands reinforce this brittle material to prevent it from breaking easily.
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.
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