Spinal discs are located between each of the 33 vertebrae, which are the interlocking bones of the spine that are stacked on top of one another. These discs act as shock absorbers for the spine and allow it to flex, bend, and twist.

The outer portion of a spinal disc, called the capsule (annulus fibrosus), is made of tough, elastic cartilage. The capsule surrounds a mass of jellylike material called the nucleus (nucleus pulposus).

Aging, injury, and illness can cause the spinal discs to crack or rupture. The jellylike nucleus can leak out, which can irritate or put pressure on the spinal nerves. Pain, numbness, and weakness may result, and sometimes surgery is needed.

Spinal discs are also called intervertebral discs.