The spinal cord is highly sensitive and passes through the middle of the vertebral column. It contains nerve cells and bundles of nerve fibres that connect all parts of the body to the spine.
A slipped disc occurs when the outer case of the disc splits, resulting in the gel inside bulging out of the disc.
The damaged disc can put pressure on the whole spinal cord or on a single nerve root (where a nerve leaves the spinal cord).
This means a slipped disc can cause pain both in the area of the protruding disc and in the area of the body controlled by the nerve that the disc is pressing on.
It is not always clear what causes a disc to break down, although age is a common factor in many cases. As you get older, your spinal discs start to lose their water content, making them less flexible and more likely to rupture. Smoking also plays a role as it causes the discs to lose their natural flexibility.
In the older population where the discs loose their flexibility they mimic wear and tear of the joints and as their height shrinks the joints close in upon each other leaving a person with what is also know as disc degenerative disease which can also lead to pain and lack of movement.