Dear Gwynneth:

Bones are like the walls of your house. They support your body much like the outside walls of your house keep your house from falling down. If you live in a brick house, you may have noticed that the walls contain bricks as well as the stuff between the bricks called mortar. Bones are made in a similar way. Bones are composed of both a living portion and a non-living portion called the matrix. The living portion contains bone-making cells which are somewhat like the individual bricks in your house. These cells produce the non-living portion or matrix which is more like the mortar or the stuff between the bricks. In the outside wall of your house there are far more bricks than mortar. However, in bone there is far more matrix than bone-making cells.

This matrix is what makes bones strong enough to support you but flexible enough so that they are not easily broken as you twist and turn and run and jump. In order to make the matrix, the bone-making cells need lots of calcium. That is why it is so important that someone like you who is growing so fast needs to eat foods that contain calcium. Dairy products such as milk and cheese contain lots of calcium.

If you wanted to make the walls of your house taller, you would have to add more bricks and mortar. In a similar way, bone-making cells found in special regions near both ends of a bone produce more matrix. This makes bone get longer. This process continues until you are a teenager. At that time these special regions at the ends of the bone becomes inactive and growth stops. That is why you are getting taller all the time while adults stay the same height. Perhaps some day you will even be taller than your parents!

Thanks for your question,
Aubie and Dr. Wit