Vertebra

bone in the spinal column

Vertebrae (singular: vertebra) are the individual irregular bones that make up the spinal column (aka ischis) – a flexuous and flexible column. There are normally thirty-three (33) vertebrae in humans, including the five that are fused to form the sacrum (the others are separated by intervertebral discs) and the four 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. Each vertebra has a hole through which the spinal cord passes.

A diagram of a thoracic vertebra. Notice the articulations for the ribs
Different regions of the vertebral column

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