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 The bones in our skeleton are made of a thick outer shell called the cortex, and a strong honeycomb-like centre called the medulla.
Bone is constantly being destroyed and rebuilt.
Old, worn-out bone is destroyed by cells called osteoclasts and new bone is built by osteoblasts. Collagen, protein and minerals like calcium are the "building blocks" used to construct bone. |
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| When we are young our osteoblasts work very hard to allow the skeleton to grow. Every 2 years the skeleton completely renews itself. |
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| Although we stop growing in our late teens, our bones continue to get stronger right into our mid twenties. Then the osteoblasts work less quickly and the balance between the bone building and bone destruction is stable. In our mid thirties, as a result of natural ageing, the osteoblasts slow down even more and as the osteoclasts are still working well, bone loss becomes the main process. From then on our bones gradually lose density and strength. |
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| After women go through the menopause, bone loss accelerates, and so post-menopausal women are at particularly high risk of osteoporosis and fractures. |
