Intervertebral discs

An intervertebral disc sits between each pair of vertebrae. The intervertebral disc is made of connective tissue. Connective tissue is the material that holds the living cells of the body together. Most connective tissue is made of fibres of a material called collagen. These fibres help the disc withstand tension and pressure.

The disc normally works like a shock absorber. It protects the spine against the daily pull of gravity. It also protects the spine during strenuous activities that put strong force on the spine, such as jumping, running, and lifting.

An intervertebral disc is made of two parts. The centre, called the nucleus, is spongy. It provides most of the disc's ability to absorb shock. The nucleus is held in place by the annulus, a series of strong ligament rings surrounding it.

A healthy intervertebral disc has a great deal of water in the nucleus pulposus (the centre portion of the disc). The water content gives the nucleus a spongy quality and allows it to absorb spinal stress. Loss of water content causes the discs to lose some of their ability to act as cushions. This can lead to even more stress on the annulus and still more tears as the cycle repeats itself. As the nucleus loses its water content, it collapses. Without the cushion effect of the discs, the vertebrae in your spine would not be able to absorb stresses or provide the movement needed to bend and twist.

When the disc collapses, it allows the two vertebrae above and below to move closer to one another. This results in a narrowing of the disc space between the two vertebrae. As this shift occurs, the facet joints (located at the back of the spine) are forced to shift. Shifting changes the way the facet joints work together and can cause problems as well.

Bone spurs, sometimes called osteophytes, may begin to form around the disc space. These can also form around the facet joints. This is thought to be due to the body's response to try to stop the excess motion at the spinal segment. The bone spurs can become a problem if they start to grow into the spinal canal and press into the spinal cord and spinal nerves. This condition is called spinal stenosis.




Back to Glossary of Terms