The normal spinal intervertebral disc comprises an outer annulus fibrosus, which surrounds the inner nucleus pulposus.
- The former is made up of layers of annular fibres of fibrocartilage.
- The latter contains loose fibres suspended in a mucoprotein jelly. Its function is to act as a shock absorber between the vertebrae.
As we age, the contents of the nucleus pulposus is replaced with fibrocartilage similar to that of the annular capsule (and the distinction between the two becomes hazy) and there is a decreased peptidoglycan content. The result can be annular tearing and/or disc prolapse, causing a radiculopathy, spinal stenosis and other similar conditions.