Anatomy of the Back
The spine (or backbone) is made up of small bones called vertebrae. The vertebrae are stacked on top of each other to form a column. Between each vertebra is a cushion known as a disk. Each disk has a soft, gelatinous core and a tough, fibrous capsule (outer shell). The vertebrae are held together by ligaments, and muscles are attached to the vertebrae by bands of tissue called tendons. Openings in each vertebra line up to form a long, hollow canal. The spinal cord runs from the base of the brain down through this canal. Nerves from the spinal cord branch out and leave the spine through the spaces between the vertebrae.
The lower part of the back holds most of the weight of the body. Even a minor problem with the bones, muscles, ligaments, or tendons in this area can cause pain when a person stands, bends, or moves around. Less often, a problem with a disk can pinch or irritate a nerve from the spinal cord, causing pain that runs down the leg, to below the knee. This type of pain is called sciatica.
