The vertebrae are separated by discs that are in front of the spinal cord and exiting nerves. The discs serve two purposes – work as hinge and shock absorber. As a person ages, the discs begin to dehydrate, which makes them more vulnerable to injuries. This, however, doesn’t mean that well-hydrated discs cannot sustain an injury.
Each disc is made up of a jelly-like substance (the nucleus) surrounded by a tough outer tissue. A herniated disc occurs when the nucleus breaks through the outer tissue and presses against the spinal cord or nerves.