Between each vertebra is a soft, gel-like cushion, called an intervertebral disc. These flat, round “cushions” act like shock absorbers by helping absorb pressure and keep the bones from rubbing against each other.
Each disc has a strong outer ring of fibers called the annulus, and a soft, jelly-like center called the nucleus pulposus. The annulus is the strongest area of the disc. It helps keep the disc’s center intact. The annulus is actually a strong ligament that connects each vertebra together.
The mushy nucleus of the disc serves as the main shock absorber. The nucleus is made up of tissue that is very moist because it has high water content. The water content is what helps the disc act like a shock absorber-somewhat like a waterbed mattress.