Review Question - QID 1181

As a person ages through adulthood, neovascularization of the intervertebral disc originates from the outer annulus.

The intervertebral disc is composed of an outer structure called the annulus fibrosis and an inner structure called the nucleus pulposus. The annulus fibrosis is composed of type 1 collagen, water, and proteoglycans. The inner nucleus pulposus is composed of type 2 collagen, water, and proteoglycans. Intervertebral discs are avascular with capillaries terminating at the end plates. The nucleus pulposus receives nutrition primarily through diffusion through blood vessels within the endplate.

Roberts et al. review the histology and pathology of the intervertebral disc. They note that at birth, the cartilagenous end plates have large vascular channels through them as well as vascular channels through the annulus. Soon after birth, these vascular channels close with none remaining at the end of the first decade of life. However, with age, more blood vessels grow into the disc from the outer annulus fibrosis in response to degenerative changes.

Illustration A is a diagram of the vascular supply in an adult intervertebral disc.

Incorrect Answers:
Answer 1: Blood vessels cannot reach the inner nucleus pulposus.
Answer 3: The vascular channels through the end plates close soon after birth.
Answers 4 and 5: There is an increase in vascularization with age.