Crossword Dictionary

What's The Definition Of Vertebra?

\Ver"te*bra\, n.; pl. {Vertebr[ae]}. [L. vertebra, fr. vertere to turn, change. See {Verse}.] 1. (Anat.) One of the serial segments of the spinal column. Note: In many fishes the vertebr[ae] are simple cartilaginous disks or short cylinders, but in the higher vertebrates they are composed of many parts, and the vertebr[ae] in different portions of the same column vary very greatly. A well-developed vertebra usually consists of a more or less cylindrical and solid body, or centrum, which is surmounted dorsally by an arch, leaving an opening which forms a part of the canal containing the spinal cord. From this dorsal, or neural, arch spring various processes, or apophyses, which have received special names: a dorsal, or neural, spine, spinous process, or neurapophysis, on the middle of the arch; two anterior and two posterior articular processes, or zygapophyses; and one or two transverse processes on each side. In those vertebr[ae] which bear well-developed ribs, a tubercle near the end of the rib articulates at a tubercular facet on the transverse process (diapophysis), while the end, or head, of the rib articulates at a more ventral capitular facet which is sometimes developed into a second, or ventral, transverse process (parapophysis). In vertebrates with well-developed hind limbs, the spinal column is divided into five regions in each of which the vertebr[ae] are specially designated: those vertebr[ae] in front of, or anterior to, the first vertebra which bears ribs connected with the sternum are cervical; all those which bear ribs and are back of the cervicals are dorsal; the one or more directly supporting the pelvis are sacral and form the sacrum; those between the sacral and dorsal are lumbar; and all those back of the sacral are caudal, or coccygeal. In man there are seven cervical vertebr[ae], twelve dorsal, five lumbar, five sacral, and usually four, but sometimes five and rarely three, coccygeal. 2. (Zo["o]l.) One of the central ossicles in each joint of the arms of an ophiuran.