About the spine
The spinal column refers to the bones that bear the weight of the body. The spinal cord is the nerve system that runs along the spinal column. The brain transmits electric signals along the spinal cord in order to control our bodies. This page contains physiological information on the spine.
The spinal column
There are three main functions of the spinal column:
- To house and protect the spinal cord and its associated nerves.
- To support the frame of the body in an upright position.
- To provide motion throughout the body.
Consisting of thirty-three bones called vertebrae, the spine runs from the base of the skull down to the pelvis. Apart from the top two vertebrae, the anatomy of each individual bone is essentially the same, differing only in size and shape.
The vertebrae are held together by a combination of ligaments and muscles that allow flexibility and are separated by cartilage discs that act as shock absorbers. Two joints at the back of each bone allow for maximum movement, and pairs of spinal nerves exit holes at each level of the spine, sending the brain’s electric information to and from the various parts of the body.
A healthy spine is straight when viewed from the front. When viewed side-on, a fully-grown spine has three obvious curves that form an “S” shape. The neck and lower back curve slightly inwards (concave) and the upper back curves out (convex).
Regions of the spine
The thirty-three vertebrae are divided into five separate regions, each with different specific functions. The regions are:
- Cervical (neck) – Seven vertebrae, which in descending order are named C1 to C7.
- Thoracic (upper to mid back) – Twelve vertebrae, T1 to T12.
- Lumbar (lower back) – Five vertebrae, L1 to L5.
- Sacrum (pelvis area) – Five fused vertebrae, S1 to S5.
- Coccyx (tailbone) – The four fused vertebrae of the tailbone.
Only the top twenty-four vertebrae can move, with the fused bones of the bottom two regions providing structural support.