Between each of the vertebrae (bones) in the spine is a disc. These soft, gelatinous shock-absorbing pads keep the vertebrae from rubbing together. Endplates line the ends of each vertebra and help hold individual discs in place. Each disc contains a tire-like outer band (the annulus fibrosus) that encases a gel-like substance (the nucleus pulposus). Nerve roots exit the spinal canal through small passageways between the vertebrae and discs. In a young individual, the disc is soft and elastic. But, over time, the disc gradually looses its elasticity and is more vulnerable to injury.