The spine (columna vertebralis) forms the central supporting structure of the trunk and, in adults, consists of 24 free vertebrae plus the fused sacrum and coccyx – around 33 to 34 vertebral bodies in total.
It is divided into five sections: cervical spine, thoracic spine, lumbar spine, sacrum and coccyx. Viewed from the side, it shows typical curvatures (lordosis and kyphosis) that cushion loads in a double-S shape. The spinal cord runs in the spinal canal, giving off nerve roots to the periphery in each segment.