To understand what a “slipped disc” is we first of all have to have an idea of the anatomy of the spine.
Understanding the back
The spine is made up of many bones called vertebrae. Between each vertebra is a ‘disc’. The discs are made of strong ‘rubber-like’ tissue which allows the spine to be fairly flexible and allows for shock absorption. A disc has a stronger fibrous outer part, and a softer jelly-like middle part called the nucleus pulposus.
The spinal cord, which contains the nerves that come from the brain, is protected by the spine. Nerves from the spinal cord come out from between the vertebrae to take and receive messages to various parts of the body.
Strong ligaments attach to the vertebrae. These give extra support and strength to the spine. Various muscles also surround, and are attached to, various parts of the spine. (The muscles and ligaments are not shown in the diagram below for clarity.)
What is a prolapsed disc?
When you have a prolapsed disc (‘slipped disc’), a disc does not actually ‘slip’. What happens is that part of the inner softer part of the disc (the nucleus pulposus) bulges out (herniates) through a weakness in the outer part of the disc. You could view this at a tear in the disc. A prolapsed disc is sometimes called a herniated disc. The bulging disc may press on nearby structures such as a nerve coming from the spinal cord. Some inflammation also develops around the prolapsed part of the disc. If the disc compresses a nerve you will experience pain, pins and needles and sometimes weakness in the area of the body the nerve travels too.
Any disc in the spine can prolapse. However, most prolapsed discs occur in the lumbar part of the spine (lower back). The size of the prolapse can vary and does not have to compress a spinal nerve.
