Not all animals have a skeleton of bone. Earthworms and snails have a skeleton of water. It is held inside the body and supports the organs and gives the muscles a material on which they can push. Water like bone cannot be squashed. Just fill a balloon with water and try to squashing it if you find this hard to believe. Crabs, lobsters and insects have a skeleton on the outside of the body. It acts like a suit of armour but also supports the organs inside and helps the muscles move the body. One group of animals have a skeleton of bone inside their bodies. They are called vertebrates. They get their name from the bones which make up the backbone. These bones are called vertebrae and one name for the backbone is the vertebral column. Fish, amphibians, reptiles, birds and mammals (including us) are vertebrates.

The main supporting part of the human skeleton is the backbone. As you look down a backbone you will see that the vertebrae get larger. This is due to the extra weight that the lower vertebrae have to support. The hip bone or pelvis spreads out at the base of the backbone to give extra support to the lower part of the body.

The bones of the limbs provide support for the muscles so that when they pull and get shorter they can move the limb powerfully.

The skeleton also provides protection for some organs in addition to support. The brain is enclosed and protected by twenty one bones which make up the skull. The spinal cord which links the brain to all the nerves in the body is enclosed and protected by the vertebrae in the backbone. The ribs enclose and provide protection for the heart and lungs.

We tend to think of skeletons as dead and lifeless things but in fact they are made of living cells and the bones grow to make you the size you are today. When a skeleton first forms it is made from a material called cartilage or gristle. The body soon stores calcium in this substance and changes it to bone. Not all the cartilage is changed to bone. Some remains at the ends of the bones and helps the bones move in their joints. When a person reaches about eighteen years old most of the their bones are fully grown.

In addition to growing the bones can also repair themselves if they are broken. They most probably need help to grow properly again but when the broken parts are set in place new bone material grows between them and bonds them together.