The spine is the structure that supports and stabilizes the body and enables motion. It gives humans the ability to perform activities such as walking, bending and sitting. It also provides protection for the spinal cord and nerve roots.
The spine is composed of bones called vertebrae that are stacked on top of each other and separated by softer, pliable intervertebral discs. The discs are composed of two parts: the annulus fibrosus and the nucleus pulposus. The annulus is a tough, flexible outer ring that encompasses a jelly-like nucleus. Together, the annulus and nucleus work as a "shock absorber" to distribute loads.
Regions of the Spine
The spine is divided into four regions. The cervical region contains the seven upper-most vertebrae in the neck. The thoracic region contains 12 vertebrae in the mid-back. The lumbar region contains five vertebrae in the lower back. At the base of the spine is the sacrum and coccyx bone, commonly known as the tail bone.