Structure of Spine
Our spine consists of 33 small bones – each known as a vertebra. These are held together by various strong muscles and ligaments attached to them. The spine is a very strong but flexible structure. There are seven vertebrae in the neck, 12 at the back of the chest, and 5 in the lower back. Other vertebrae are fused in tail bones. Thoracic vertebrae form part of the rib cage, which moves during breathing. Those in the neck and low back are involved in the movements in different directions and, therefore, more liable to wear and tear and resultant pain. The central body of the vertebra bears weight. Muscles are attached to 3 processes arising from the vertebra. An arch on the back of the body of the vertebra transforms it into a canal that protects the spinal cord from injury. The spinal cord, a bundle of nerve fibers, is a vital structure that transmits signals from and to the brain. There are three joints between two adjacent vertebrae. One of these is in the form of a fibrous disc intervening bodies of two vertebrae.
The intervertebral disc, which acts as a shock absorber, consists of a strong fibrous outer ring and a soft central nucleus. Discs in the neck and lower back region are thicker and allow free movement. Nerves supplying the trunk and extremities emerge from an opening behind the disc. They can get compressed if the disc is damaged. The spine starts from the skull base and ends at a joint (known as sacroiliac joint) with pelvic bones. The spine has normal curvatures – backward in the thorax and forwards in the neck and low back. It supports the head and trunk over the pelvis in an upright posture, protects many vital organs, and provides attachment for various muscles and ligaments. It also transmits body weight in an erect position, acts as a shock absorber during load-bearing, and serves as a foundation for extremities.