Vertebrae

Vertebrae (singular: vertebra) are the individual irregular bones that make up the vertebral or spinal column. There are normally thirty three (33) vertebrae in humans, including the 5 that are fused to form the sacrum (the others are separated by intervertebral discs) and the 4 coccygeal bones which form the tailbone. The upper three regions comprise the remaining 24, and are grouped under the names cervical (7 vertebrae), thoracic (12 vertebrae) and lumbar (5 vertebrae), according to the regions they occupy.