Intervertebral Discs

About the Intervertebral Discs

Intervertebral discs are the fibrocartilage cushions between the bodies of adjacent vertebrae, from the second cervical vertebra down to the sacrum. Each disc has two parts: a tough outer ring, the annulus fibrosus, made of concentric layers of collagen fibers running at alternating angles, and a soft, gel like center, the nucleus pulposus, rich in water and proteoglycans. Together they distribute compressive loads, absorb shocks, and allow bending and twisting of the spine, and they make up a significant part of the length of the spinal column. The discs have very little blood supply in adults and receive nutrients mainly by diffusion, which limits their ability to repair. With age, the nucleus loses water and the discs become thinner and less resilient, a process called disc degeneration, which is very common and often painless. When the nucleus pushes through a weakened annulus, the result is a disc herniation, which can compress nearby nerve roots and cause sciatica or arm pain, most commonly in the lower lumbar and lower cervical spine.