The abdominal portion of the spine is formed by five lumbar vertebrae, referred to as L1 through L5. These vertebrae are much larger than those of the thoracic spine, which in turn are larger and stronger than the cervical vertebrae. The vertebrae increase in size from top to bottom to accommodate the increasing body weight.

 

Between vertebral bodies are small fibrocartilage cushions called discs. These act, in part, as shock absorbers. Strong ligaments bind the vertebrae together. Although the ligaments will stretch to permit limited movement, they are rigid enough to maintain alignment of the spinal canal as it passes through each vertebrae.

 

The vertebrae, discs, and ligaments are able to maintain the correct alignment and consequently protect the spinal cord against all but the most violent injury.

The L5 vertebrae rests on the sacrum, a large bone made up of several smaller vertebrae-like bones which have fused together. The sacrum forms a base for the spine and the back part of the pelvis.

Posture too plays an important role in spinal disorders.