Intervertebral Discs
Between two vertebrae lies a gel-like cushion called an intervertebral disc. When you
walk, or run, the discs act as shock absorbers and prevent the vertebrae from bumping
against one another. They help the spine move, twist, and bend. Intervertebral discs are
flat and round, and about a half inch thick. They are made up of two components – a
tough outer ring, and a dense jelly-like center.
Components of intervertebral discThe outer part of the disc is a stronger, more fibrous, capsule-like material called the
annulus fibrosus. The annulus fibrosus surrounds and supports the inner jelly material.
The annulus is also in contact with nerve fibers or pain receptors, called nociceptors.
The inner jelly-like portion of the disc is called the nucleus pulposus. The discs have no
blood supply of their own. They rely on nearby blood vessels to keep them nourished.
Disc material is primarily composed of water (80%) and other proteins. As a normal
part of aging, the water content gradually diminishes which can cause the disc to flatten
out and even develop tears or cracks throughout the annulus fibrosus. These discs are
often referred to as degenerative discs.
At times, the nucleus pulposus can bulge out and press up against the annulus fibrosus.
When this happens, it stimulates the pain receptors in the annulus fibrosus causing back