BONES AND SKELETONS

Flexible framework body
Bones support your body, make up about one-fifth of your total weight. Without them, you would not be able to move, to eat, or even to breathe. Bones change as you grow up, and they also get thicker and stronger if they have to do a lot of extra work or carry extra weight. Together, they make a flexible framework for your body. Some bones have a Latin name as well as an English name.

What are bones made of?
The human skeleton is made up of bones of many shapes and sizes. About one-tenth of all the bones in your body form your skull, while more than half are crammed into your hand and feet. Some bone, such as the shoulder blades, are thin and flat, but most of the bigger bones are long and hollow.Nearly two-thirds of a bone's weight is made up by crystal of a mineral called calcium phosphate. The other third is made up by fibres of a substance called collagen. The crystals and fibres are produced by bone cells, which are scattered throughout the bone. Tiny channels running through the bone allow blood to reach the bone cells.

Inside a bone
This a part of a section through a bone, magnified around 100 times. The rings are made of mineral crystal. Fibre and bone cells live in the small gaps between the rings. The mineral crystals give a bone its strength, while the fibres help it to bend without breaking.