The human spine can be divided into five sections although only three are shown here.
The main twenty four vertebrae are illustrated here. Each one is separated by a disc and it's these discs which allow us to bend and twist in all sorts of directions.
People say "keep your back straight" but that's impossible to do as the spine is, in fact, a double "S" shaped object. It's these bends that help us to take shocks to the spine as, along with the discs, they allow for a certain amount of deflection.
The vertebra are named as follows:
It's usually the lumbar vertebrae that cause trouble and where the pain is likely to be in a manual handling injury.
For reference the bottom vertebrae are called the sacrum and coccyx and as mentioned above, are are fused together.