||Ver"te*bra (?), n.; pl.
Vertebræ (#). [L. vertebra, fr.
vertere to turn, change. See Verse.]
1. (Anat.) One of the serial segments of the
spinal column.
&fist; In many fishes the vertebræ are simple cartilaginous
disks or short cylinders, but in the higher vertebrates they are composed
of many parts, and the vertebræ 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 vertebræ 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 vertebræ are specially designated: those
vertebræ 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 vertebræ, twelve dorsal, five lumbar, five sacral, and
usually four, but sometimes five and rarely three, coccygeal.
2. (Zoöl.) One of the central ossicles
in each joint of the arms of an ophiuran.
||Ver"te*bra (?), n.; pl.
Vertebræ (#). [L. vertebra, fr.
vertere to turn, change. See Verse.]
1. (Anat.) One of the serial segments of the
spinal column.
&fist; In many fishes the vertebræ are simple cartilaginous
disks or short cylinders, but in the higher vertebrates they are composed
of many parts, and the vertebræ 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 vertebræ 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 vertebræ are specially designated: those
vertebræ 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 vertebræ, twelve dorsal, five lumbar, five sacral, and
usually four, but sometimes five and rarely three, coccygeal.
2. (Zoöl.) One of the central ossicles
in each joint of the arms of an ophiuran.
