The backbone is comprised of a column of 24 bones called vertebrae. Together they create a bony canal that surrounds and protects the spinal cord. Small nerves enter and exit the spinal cord through spaces in the vertebrae.

The vertebrae are held together by muscles, tendons and ligaments. Between the vertebrae are intervertebral disks, which act as "shock absorbers" by preventing the vertebrae from hitting one another when you walk, run or jump. The intervertebral disks also allow the spine to twist, bend and extend.