The vertebral column, also called the backbone, is made up of 33 vertebrae that are separated by spongy disks and classified into four distinct areas. The cervical area consists of seven bony parts in the neck; the thoracic spine consists of 12 bony parts in the back area; the lumbar spine consists of five bony segments in the lower back area; five sacral bones (fused into one bone, the sacrum); and four coccygeal bones (fused into one bone, the coccyx).

The intervertebral discs are flat, round "cushions" that act as shock absorbers between each vertebra in your spine. There is one disc between each vertebra. Each disc has a strong outer ring of fibers called the annulus fibrosus, and a soft, jelly-like center called the nucleus pulposus.

The annulus fibrosus is the disc's outer layer and the strongest area of the disc. It also helps keep the disc's center intact. The annulus fibosus is actually a strong ligament that connects each vertebra together.

The mushy nucleus pulposus 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 helps the disc act like a shock absorber - somewhat like a waterbed mattress.