Intervertebral discs are the 23 narrow spongy shock absorbers which fit between the 24 separate bones of you spine. Without the discs these bones would grate and crunch every time you moved.

Each disc has a strong fibrous outer casing - called the annulus fibrosis - and a soft, squashy, jelly-like interior called the nucleus pulposus - which is reinforced with strands of fiber.

Intervertebral discs have very little in the way of nerve supply and contain no blood. They are made up largely of water. As you get older the amount of fluid in your discs will diminish slightly - and as a result you will get shorter.