Intervertebral Discs

Between each vertebra is a soft tissue, elastic structure called a spinal disc, or intervertebral disc. Discs are comprised of fibrocartilage tissue. The outer layer (annulus fibrosus) is tough and fibrous, composed of multiple overlapping layers similar to a Kevlar ("bullet proof") vest. The inner core (nucleus pulposus) is soft and gelatinous. Together, the disc forms a hydraulic "shock absorber", able to cushion the stress during movement of the spine. The intervertebral discs help the spine return to and keep its normal curves following any spinal movement. A healthy disc in a young adult consists of approximately 90% water. With normal aging, discs lose some of their water content and decrease in height; this shortens the spine over time to a small but measurable degree (We all get shorter as we get older) and result in a mild diffuse bulging of the disc. If the structural integrity of the outer fibers of the disc becomes impaired due to simple wear-and-tear or injury, a piece of the disc's softer center can escape through the outer layer and put pressure on the spinal cord or cause irritation of adjacent spinal nerve roots. This condition is called herniated disc, and is also known as a "ruptured" or "slipped" disc. Mild to severe pain and/or weakness of the back or leg can result from herniated discs. [Figure 1 ]

Figure 1: Herniated disc pressing on nerve root