cervical vertebra (C), one of the first seven segments of the vertebral column. They differ from the thoracic and lumbar vertebrae through the presence of a vertical costotransverse foramen in each transverse process. The first cervical vertebra (atlas) has no body, supports the head, and contains a smooth, oval facet for articulation with the dens of the second cervical vertebra. The dens extends from the cranial portion of the body of the second cervical vertebra (axis), which has a very large, strong spinous process with a bifid extremity. The seventh cervical vertebra has a very long, prominent spinous process that is nearly horizontal and is often used as a palpable reference for locating the other cervical vertebrae. The bodies of the four remaining cervical vertebrae are small, oval, and broader than the other three in transverse diameter and contain large, triangular foramina within their transverse processes. Their spinous processes are short and bifid. Compare coccygeal vertebra, lumbar vertebra, sacral vertebra, thoracic vertebra. See also vertebra.
