The spine is made of a column of bones called vertebrae, and extends from the base of the skull to the pelvis. The vertebrae protect the spinal cord, which runs within the vertebral column and sends out nerve roots between the vertebrae. Between the bony bodies of each vertebra is a gelatinous ring of tissue, called a disc. The discs absorb shock and cushion motion between the vertebral bones.
Occasionally, trauma or injury causes the intervertebral disc to bulge beyond the boundaries of the vertebral body. When this happens, the disc may put pressure on a nerve exiting the spine in the same area. This phenomenon is known by many names such as slipped disc, bulging or herniated disc, or pinched nerve.