Weller - Complete back workbook: a practical approach to healing common back ailments

Think of your spine, or backbone, as a strong, flexible column that can rotate and bend backwards, forwards and sideways. It encloses and protects the spinal cord, which is an extension of the brain and which consists of nervous tissue. It supports the head and provides attachment for the ribs, pelvic girdle and muscles of the back.

The spine is composed of 33 bones called vertebrae (singular: vertebra). Of these, seven are cervical (neck), twelve are thoracic (chest or mid-back) and five are lumbar (in the loins or lower back). Five are fused into one bone called the sacrum (sacred bone) and the remaining four, known as the coccyx (resembling a cuckoos bill), are fused to form a single bone. The upper 24 bones are movable, whereas those composing the sacrum and coccyx are not.

When viewed from the side, the spine shows four normal curves. The cervical and lumbar curves bulge forwards and the thoracic and sacral curves cup inwards. These curves are important: they increase the strength of the spine, help us to maintain balance when we are in an upright position, absorb shock when we walk and help to protect the spine from fractures.

With some variations according to the part of the spine they occupy, vertebrae typically consist of a body, a vertebral (or neural) arch and several processes (projections).

The body , which is the weight-bearing part, forms the front of the vertebra. Its upper and lower surfaces (end plates) are roughened to accommodate the attachment of spinal (intervertebral) discs. The front and sides contain openings for blood vessels.

The vertebral arch is composed of two short, thick pedicles projecting backwards to unite with laminae (bony plates), which are flat.

The processes , seven in number, arise from the vertebral arch. They consist of one transverse process on each side and a single spinous process. These act as levers to which muscles are attached by tendons. The remaining four processes form joints, with vertebrae above and below.

Contained within the bony canal that runs the entire length of the spine are the spinal cord and nerves. Between the bones that form the spine are openings (foramina) for the passage of nerves, which connect the spinal cord to various parts of the body.

As the spinal cord approaches the tail bone (coccyx) it forms separate nerves that collectively are known as the cauda equina (Latin for horses tail). These nerves supply the hips, legs, ankles, feet and toes.

Between every two vertebrae are joints formed by smooth cartilage and strengthened by ligaments that run behind and in front of the vertebral bodies throughout the entire length of the spine. In addition, there are facet joints at the back of the vertebrae.

The facets so-called because of their smooth surface, like that of a cut gem form joints (facet joints) with those of the vertebrae above and below. Each joint is surrounded by synovial membrane, which secretes a lubricating fluid (synovial fluid). The joint surfaces are covered with a smooth cartilage that facilitates the moving of one vertebra on the other.