The spinal column, or the vertebrae, consists of 24 separate bones along with the fused bones of the sacrum and coccyx. The vertebral column is a strong, flexible rod that protects the spinal cord, supports the head and provides an attachment for the ribs.
There are four major components of the spine: the vertebrae, joints, discs and nerves.
The separate bones of the vertebra link together to form a "tunnel" that protects the nerves and spinal cord. The lumbar vertebrae are under constant pressure from the weight of the upper body. The "wear and tear" of this pressure over a period of time can contribute to the development of back pain.
Joints, or the spaces between two or more bones, are found throughout the body. Joints allow different degrees of movements that change the position of bones, since bones are too rigid to bend without damage. Joints are located at each vertebrae and provide flexibility and stability within the vertebral column.
Discs located in between the vertebrae act as "shock absorbers," preventing the vertebrae from rubbing together. Discs function as the "glue" that holds the vertebrae together and they also provide flexibility within the vertebral column. Discs often show the first signs of "wear and tear" associated with the aging process, since they are constantly "squeezed" and "stretched" under the forces of the vertebrae.
At each disc level, a pair of spinal nerves exits and passes into the arms and legs. The spinal cord (which runs through the middle of the vertebrae) and the spinal nerves act as a "telephone" to allow messages, or impulses, to travel to the brain and then to the arms and legs to control sensation and movement.
What happens to the structure of the spine as people age?
Intervertebral discs have a fiber-like ring (annulus) and a gelatin-like center (nucleus). As people age, the nucleus of the disc begins to "dry up," reducing the effectiveness of the shock-absorbing quality of the discs. As this protection is lost, daily activities can wear down the vertebrae, causing the development of jagged edges (called bony spurs) on the vertebrae. Bone spurs can cause the center canal that encases the spine and the side canals which protect the nerves to become narrowed.