The primary functions of the spine include:
- Protect the spinal cord, nerve roots, and internal organs.
- Provide flexibility of motion.
- Provide structural support and balance for upright posture. The spine bears the load of the head, shoulders and arms, and upper body. The spine attempts to keep the body’s weight balanced evenly over the pelvis. This reduces the amount of work required by the spinal muscles and can eliminate muscle fatigue and back pain.
The normal adult spine is balanced over the pelvis, requiring minimal workload on the muscles to maintain and upright posture.
Regions of the Spine
There are 33 vertebrae (bones) in the spine. Anatomically, the spine is divided into four regions:
- The top seven vertebrae that form the neck are called the cervical spine and are labeled C1-C7.
- The upper back, or thoracic spine, has 12 vertebrae, labeled T1-T12.
- The lower back, or lumbar spine has five vertebrae, labeled L1-L5.
- The sacrum and coccyx (tailbone) are made up of nine vertebrae that are fused together to form a solid bone. The sacrum is labeled S1.
Curves of the Spine
When viewed from the front or back, the normal spine is in a straight line, with each vertebra sitting directly on top of the other. A side-to-side curve in the spine is called a scoliosis.
When viewed from the side, the normal spine has three gradual curves:
- The neck has a lordosis; it curves toward the back.
- The thoracic spine has a kyphosis; it curves toward the front.
- The lumbar spine also has a lordosis.
These curves help the spine to support the load of the head and upper body, and maintain balance in the upright position.