Vertebrae
The backbone is made of a series of small bones called vertebrae*. Each one is separated by a layer of cartilage.

These bones must be aligned for the backbone to do its job. When one vertebrae moves out of alignment, it is called a slipped disc.

This condition can be very painfull. It interferes with your normal body functions. Sometimes doctors must operate to correct a slipped disc.

Image Credit: NASA
Space Science Group | College of Science and Technology | Northwestern State University | A Part of the University of Louisiana System