Your spine, also called the backbone, runs down the length of your back from the base of your neck to your pelvis. The spine has 25 joints connecting 33 individual bones. (The bottom four bones of the spine are fused together to form the terminal vertebrae called the coccyx, or tailbone—and the five bones above that are fused together to form the sacrum. They are caged within the bones of the pelvis.) Each bone in the spine is called a vertebra and they are grouped together to perform specific tasks.
The spine supports your head, lets you twist and bend, and holds your body upright. It also protects the spinal cord, a large bundle of nerves that sends information from your brain to the rest of your body.