vertebra

(ver'te-brah), pl. vertebra [LJ]. 1. Any one of the thirty-three bones of the spinal column. The vertebra comprise seven cervical, twelve dorsal, five lumbar, five sacral, and four coccygeal. Each vertebra is composed of-—(u) a body, or centrum, forming the main part of the spine; (6) four articulating proce es (sygapophyses), by which it is joined to the next vertebra. These are sometimes called obligue proce es—the upper ones the ascending oblique, the lower, the descending oblique, proce es. (c) A spinous proce which projects directly backward, those of the different vertebrae forming, with their points, the ridge of the back. (d) Two transverse proce es, which stand out at right angles, or laterally, from the body of the vertebra. and in the thoracic region articulate with the ribs. 2. By extension, any onc of the segments of which the cranium and facial bones have been a umed to be made up. basilar v., the lowest or last of the lumbar vertebra. cervical v., the seven vertebra of the neck. cranial v., the segments of the skull and facial bones, by some regarded as modified vertebric. v. dent a’ta, the axis. dorsal v., the eleven vertebra which connect the ribs and form part of the posterior wall of the thorax. false v., the segments of the sacrum and the coccyx. lumbar v., the five vertebre between the dorsal vertebra and the sacrum. Vv. ‘num, the sacrum. odontoid v., the axis. v. prom‘inens, the seventh cervical vertebra. sternalv. Same as sternebra. thoracic v., the dorsal vertebra. tricuspid v., the sixth cervical vertebra of quadrupeds. true v., the vertebre which remain unfused through life.