09/11/2020
The intervertebral disc is a cartilaginous and articulating structure between the vertebral bodies of the vertebrae. Intervertebral discs have the dual role of providing the primary support for the vertebral column while possessing enough elasticity to permit the required mobility of the spine. The discs accounts for 25% to 30% of the overall height of the spine. We are tallest first thing in the morning when the discs are their most plump, and we slowly become shorter during the day as the discs subtly flatten under our body weight (Botsford et al 1994).
These discs are made up of a central, gelatinous nucleus pulposus that is surrounded by a tough but elastic annulus fibrosis. Collagen fibers continue from the annulus into the adjacent tissues, which ties this structure to each vertebral body at its rim, to the anterior and posterior longitudinal ligaments, and to the cartilaginous endplates superiorly and inferiorly. This is why the discs cannot “slip” irrespective of this really unhelpful terminology that is often used! The nucleus pulposus is a self-contained, pliable gelatinous structure that is approximately 88% water in a healthy young disc. It is essentially a hydraulic system that provides support and separates the vertebrae, absorbs shock, permits transient compression, and allows for movement (Roberts et al 2006).
At birth, the intervertebral disc has some vascular supply within both the cartilage end plates and the anulus fibrosus, but these vessels soon recede, leaving the disc with little direct blood supply in the healthy adult (Roberts et al 2006).
References:
Botsford, D., Esses, S. and Ogilvie-Harris, D. (1994) ‘In Vivo Diurnal Variation in Intervertebral Disc Volume and Morphology.’ Spine 19, 8, 935–940.
Roberts, S., Evans, H., Trivedi, J. and Menage, J. (2006) ‘History and pathology of the human intervertebral disc.’ J Bone Joint Surg Am 88, suppl 2, 10–4.