Neck and Spine
The spine is made up of small bones, called vertebrae, which are stacked on top of one another to create the natural curves of the back. These bones connect to create a canal that protects the spinal cord. The spinal cord extends from the skull to the lower back and travels through the middle of the stacked vertebrae. Nerves branch out from the spinal cord through openings in the vertebrae and carry messages between the brain and muscles.
Discs sit in between the vertebrae and work as shock absorbers for the spine. Discs have a jelly-like center (nucleus) and an outer ring (annulus). Between the back of the vertebrae are small facet joints that help the spine move. They have a cartilage surface, like a hip or knee joint.