cranial vertebra

cranial vertebra

n.

A segment of the skull regarded as homologous with a spinal column segment.

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vertebra

pl. vertebrae [L.] any of the separate segments comprising the spine (vertebral column). See also spine, vertebral.

The vertebrae support the body and provide the protective bony corridor through which the spinal cord passes. The number of bones in the vertebral column varies with the animal species and even within each species. Average numbers are given in Table 10.

The compression-resisting portion of a typical vertebra is the vertebral body, the most ventral portion. This is a cylindrical structure that is separated from the vertebral bodies in front and behind by disks of cartilage and fibrous tissue. These intervertebral disks act as cushions to spread and absorb the mechanical shock during body movements. See also slipped disk.

A semicircular arch of bone protrudes from the dorsum of each vertebral body, surrounding the spinal cord. Directly in its midline a bony projection, the spinous process, grows upward from the arch. Three pairs of outgrowths project from the arch. One of these protrudes horizontally on each side and in the thorax connects with the ribs. The remaining two form joints with the vertebrae in front and behind. The joints permit the spine to bend flexibly. The vertebrae are held firmly in place by a series of strong ligaments.

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anticlinal vertebra

1. the vertebra whose spinous process is directed vertically at which point the backward slope of the cranial vertebrae changes to a forward inclination. Is usually the sixteenth thoracic vertebra in the horse.

2. (improperly) the diaphragmatic vertebra.

block vertebra

anomalous development in which two or more vertebrae are fused.

butterfly vertebra

anomalous development of a vertebra that is nearly divided in half by a longitudinal defect; caused by the persistence of the sagittal membrane remnant of the notochord. The vertebral body resembles a butterfly on ventrodorsal radiographs.

caudal vertebra

coccygeal vertebrae.

cranial vertebra

the segments of the skull and facial bones, regarded by some as modified vertebrae.

vertebra dentata

the second cervical vertebra, or axis.

diaphragmatic vertebra

the vertebra which marks the transition between those located cranially with a thoracic type of articular facet to those located caudally with a lumbar type. It is often the same vertebra as the anticlinal vertebra (above).

false vertebra

those vertebrae which normally fuse with adjoining segments such as the sacral vertebrae or the human coccygeal vertebrae.

vertebra magnum

the sacrum.

odontoid vertebra

the second cervical vertebra, or axis.

opisthocoelus vertebra

a vertebra with a concave caudal surface to the body.

vertebra plana

a condition of spondylitis in which the body of the vertebra is reduced to a sclerotic disk.

transitional vertebra

see transitional vertebra.

true vertebra

those segments of the vertebral column that normally remain unfused throughout life: the cervical, thoracic, lumbar and coccygeal vertebrae.

wedge-shaped vertebra

hemivertebra.