Anatomy of the Spine and Disc

There are 3 sections of spinal vertebrae. The 7 vertebrae in the neck are called cervical vertebrae, the 12 vertebrae in the middle section are thoracics to which the 12 pairs of ribs attach, and the 5 bottom vertebrae in the lower back are lumbars. Each section is numbered from top to bottom so C1 attaches to the skull at the top and L5 attaches to the pelvis at the bottom.

A disc separates each vertebra and acts like a cushion, absorbing shock along the spine and allowing motion between each segment. The disc is a cartilage-like material made up of a jelly-like substance in the center known as the nucleus, covered with many strong and fibrous, ligament-like outer layers called the annulus. These type tissues do not have a rich blood supply like most other body tissues to nourish and replenish them; rather, disc tissue depends on a transfer of extracellular fluids to bring in the needed nutrients and oxygen. This transfer of fluid occurs between the bone (vertebral body endplate) above and below the disc and depends on the difference in pressure between the inside of the discs and the surrounding tissues. This is why normal joint motion that results in a pumping action is so essential, and explains why most disc nutrition and regeneration takes place when we lie down - because the pressure inside the disc is reduced and the fluids migrate toward the area of low pressure. This process is not very efficient, and slows down as we age, so that the disc can rather easily be exposed to wear and tear exceeding its ability to heal and regenerate - a process known as degeneration or degenerative disc disease.

Any number of factors in addition to age can cause or contribute to degenerative disc disease. Obesity which creates additional gravitational stress on each joint is another. Not enough exercise results in a gradual weakening of the supporting muscle and ligamentous structures making the disc prone to injury from ordinary everyday activities as we use our backs each day through sitting and standing, bending and lifting. Too little activity during the week followed by too much activity on the weekend can also result in injury. Naturally, falls or accidents can directly injure even a healthy spinal joint, but is made all that much worse if it is in a weakened state to start.  Repeated episodes of even minor injuries can eventually result in muscle tension and/or inflammation limiting the motion, and thusly the pumping action of the disc, which becomes stiffer and drier causing it to lose its shock absorbing properties, and making it more prone to yet another injury. This is the very definition of degeneration where each incident lowers the pain and subsequent injury threshold so that eventually the most ordinary of activities such as walking through the grocery store is too much. Poor health habits including too much soda pop/not enough water, inadequate nutrition, alcohol use, and nicotine use contribute. There may also be an as of yet unidentified genetic factor causing some individuals to be more likely to develop this condition.

Any combination of events or circumstances that result in a weakening of the outer annular fibers of the disc may eventually lead to a bulging or herniation of disc material that can pinch the adjacent nerve root or spinal cord causing additional problems.