The spine forms 33 vertebrae, of which the upper 24 are movable. The lower 5 vertebrae of the 24 are called the lumbar region. The lumbar vertebrae are the largest, as they must carry the vertebrae that stand on top (chest and neck vertebrae), but at the same time they must also be stable enough to keep the body without it swaying uncontrollably.
The pressure in the lower back is therefore of course many times greater than in the neck, for example, and therefore disc prolapses are also seen much more frequently here. About 95% of herniated discs occur at the lower lumbar spine, while about 4% at the cervical vertebrae , and less than 1% at the thoracic vertebral area.