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What is a Spinal Disc?

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Updated February 12, 2011

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Question: What is a Spinal Disc?
Answer:

A spinal disc (also known as an intervertebral disc) is like a little cushion that sits between each pair of vertebrae. Its job is to absorb the shock that movement, wear and tear, impact, and your body weight have on your spine. Essentially, the disc is a spine protector.

The construction of a spinal disc can be compared to a jelly donut. In the center is the nucleus, a soft, malleable substance quite similar to the grape jelly in the center of a donut. The outside of the disc is called the annulus fibrosus; it's made of tough fibers that encase the jelly material. The annulus, as it is often called for short, encloses and protects the nucleus.

Just as the jelly in the center of the donut gets squished around when you handle or bite into the breaded portion, so does the nucleus adapt to the various types of pressures put on your discs by the movements of your spine.

Annular Tears and Herniated Discs

It's possible to get tears and weakness in the annulus, which may lead to an injury known as a herniation. Annular tears or weaknesses may also lead to degenerating discs, which is a long-term process that results in significant changes in the spine. While traumatic incidents, such as car accidents, may certainly cause these fissures, often wear and tear from daily activities over time create enough damage to weaken or break fibers of the annulus. Aging and genetics also play a role in the integrity of the spinal discs.

Sources:

Stokes, IAF, Ph.D, Iatridis, JC. Mechanical Conditions That Accelerate Intervertebral Disc Degeneration: Overload VERSUS Immobiliation. Spine. Vol 29 Num 23. 2004.

Hadjipavlou, AG, Tzerminadianos, MN, Bogduk, N, Zindrick, MR. The pathophysiology of disc degeneration: A Critical Review. Journal of Bone and Joint Jurgery. Vol 90-B No 10 Oct 2008.

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