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Other Terms: Backbone, Spinal column, Spine, Columna vertebralis, Épine, Colonne vertébrale, Columna vertebral
These 33 segments form the 26 bones of the vertebral column. The bones are divisible into seven cervical vertebrae, twelve thoracic vertebrae, five lumbar vertebrae, and the fused sacrum and coccyx. The column supports the trunk and skull, protects the spinal cord, and provides attachment for muscles that move this flexible column.
The word vertebral arises from the Latin verb vertere meaning to turn. In 30 A.D., Celsus originally used the word to describe a joint as well as a bone of the spine. It was during the Renaissance revival of anatomy that the term attained its present meaning as a reference to the back bones. Column comes from the Latin columna meaning a projecting object.
With the exception of the skull, the vertebral column is the most highly jointed region of the skeletal system. The joints are both cartilaginous and synovial. The cartilaginous joints occur between the vertebral bodies. They are the symphyses formed by the intervertebral discs. These discs comprise a fourth of the vertebral column's total length above the sacrum. More numerous than the cartilaginous joints are the synovial joints formed between adjacent zygapophyses and with neighboring ribs. These are plane joints showing limited ranges of motion.
The vertebral column ossifies endochondrally from serially homologous segments. Each vertebral bone forms from a body center, a costal center, and a neural arch center. In the thoracic region the costal center remains separate from the other two centers as the rib. However, in the cervical, lumbar, and sacral regions the costal center fuses to the other centers contributing to the so-called transverse process.