The adult human spine is a column comprised of 24 bones, referred to as vertebrae. With the addition of the sacrum and coccyx the spine contains 26 bones. The vertebrae of the spinal column can be divided into three primary groups. 

The first group is referred to as cervical spine comprised of 7 vertebrae.  The second group is referred to as the thoracic spine comprised of 12 vertebrae, the third group is referred to as the lumbar spine and is comprised of 5 vertebrae.

The sacrum, the base of the spine, consists of 5 fused spinal segments.  The sacrum attaches to the iliac bones on the right as well as the left joining together to form the pelvis.  Below the level of the sacrum, there are 3-5 fused or partially mobile segments, which form the coccyx (“tailboneâ€?).