Bones: How they grow and support the body

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Learn what bones are made of, how they grow and why it is important to keep them healthy.

Key points

  • Your child's bones contain collagen to help keep them flexible and calcium to keep them strong.
  • Bones contain living tissue that turns over (renews itself) regularly. Bone turnover slows down as we get older.
  • You can help your child develop strong bones for life by offering foods rich in calcium and vitamin D and encouraging them to do weight-bearing exercise.

Healthy bones contain collagen and calcium. Collagen is a protein that provides a soft, spongy framework to help bones stay flexible under stress. Calcium phosphate is a mineral that provides a hard outer surface to make bones strong.

How do bones change and grow?

Just like other organs in the body, bones contain living tissue that turns over (renews itself) regularly. Bone turnover happens in two steps: cells called osteoblasts build new bone and other cells, called osteoclasts, remove old bone and return the calcium to the blood stream.

Bone turnover Illustration of osteoclast and osteoblast in a bone
Within our bones are special cells that constantly break down bone and build new bone. Osteoclasts break down bone, and osteoblasts make new bone.

Bone turnover happens right through a person's life, but it slows down as we get older. From childhood through the teen years, the body adds new bone more quickly than it can remove old bone. This helps to build bone mass, or bone density. From about age 20, however, our bodies add new bone more slowly. Eventually, we lose bone mass, as the body removes old bone more quickly than it can replace it.

Why is it important to keep my child's bones healthy?

Early childhood through the teen years is the main bone-building phase of your child's life. This is when your child's body adds the most calcium to their bones to help them become denser and stronger.

As a parent, you need to make sure that your child's bones have the best chance to stay strong right through their lives. Feeding your child a diet rich in calcium and vitamin D will help them add enough calcium to their bones. You can also help your child's bones get stronger by encouraging your child to do weight-bearing exercise.

Last updated: December 19th 2013