The Intervertebral Disc

Before the age of twenty-five, the disc has a blood supply. Two blood vessels enter the disc from the back and these vessels angle towards the centre and supply the nucleus with oxygen and nutrients. These blood vessels enter the disc from the posterolateral direction or 4:00 and 8:00 positions, if you can imagine the top of the disc like a clock with the flat portion at 6:00. Coincidentally, these positions correspond with the areas of the disc that are closest to the nerves that exit the spine.

After the age of twenty-five or so, these two blood vessels dry up. That leads to two problems: Firstly, without a blood supply, the discs only get the sustenance they need from osmosis, which is greatly aided by spinal movement. Flexing, extending and rotating a disc through exercise pumps the disc and draws in oxygen and nutrients. Therefore, I'm sure you can readily see how a sedentary lifestyle prematurely ages and breaks down the discs.

The second factor in the drying up of these blood vessels is the fact that the vessels leave a channel through the annulus to the nucleus thereby creating a weakness in the disc. In fact, almost all disc herniations and bulges follow this inherent weakness as the nucleus forces its way through the annulus to the posterolateral edge of the disc. It is at this edge, as we pointed out before, that the spinal nerves lay. In the case of the lumbar spine, the most commonly herniated discs are the lower three which also correspond to the pathways of the sciatic nerve.

At some point in the near future, I will write another article about the intervertebral disc, Part 2, if you like. Thanks for reading.

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