In addition to giving the spine strength the vertebrae also provide essential protection for the spinal cord - the body's biggest nerve. The spinal cord carries impulses from the brain to the arms, legs and body, and then carries messages back from those areas to keep the brain informed. Hundreds of individual nerves connect the spinal cord to the various parts of the human body. If the spinal cord is damaged then paralysis will result - the precise nature of the paralysis depending on the place where the spinal cord is damaged.

Your spine is made up of 26 separate bones or vertebrae though two of these consist of several small vertebral bones fixed together. All these bones fit one on top of the other like a pile of children's building bricks. The bones at the top of the spine - where the skull fits on top - are smallest, while the bones at the bottom - where they fit into the bones of the pelvis - are largest.

Right at the bottom of spine is the sacrum (which is made up of the sacral vertebrae) and then the coccyx (which is also made of bones which are normally joined together).

Although we have said that these bones in your back are balanced one on top of the other like a pile of building bricks there is one very important difference, your spine is not straight. Indeed, it has no less than four separate curves which are there to make your spine more capable of coping with stresses and strains:
 

Each of the vertebrae in your spine connects to the one above it and below it. Consider the fourth thoracic vertebra, for example. Above, the 'superior articular process' fits onto the 'inferior articular process' of the third thoracic vertebra, and below, the 'inferior articular process' fits onto the 'superior articular process' of the fifth thoracic vertebra. Because they vary in size your vertebrae are all different but there are some important similarities between them. It is this series of joints which gives your spine its majority of them.

The more complicated part of the vertebral bone is at the back and is called the 'neural arch'. At the front of each one there is a solid block of bone called the 'body' of the vertebra. This has a hole in the middle of it through which the spinal cord runs.

Right at the top the first cervical vertebra is joined onto the bottom of your skull.

The 12 ribs which give your chest strength and which protect your lungs and heart are attached to your thoracic vertebrae. Without them you would collapse on the floor if you were bumped just as easily as a pile of building bricks falls over if nudged.

And at the bottom of your spine the sacral bones are joined onto your hip bones, these are not, however, the only joints holding your spine together, there are, altogether, nearly 150 joints in your spine.