vertebras

Vertebrae, sometimes listed as vertebras, are the bones that stack to form the vertebral column, or spine, in most vertebrates. In humans, the typical adult spine comprises 24 presacral vertebrae organized into cervical (7), thoracic (12), and lumbar (5) regions, with the sacrum and coccyx formed by fused rudiments. The vertebral column protects the spinal cord, supports body weight, and provides a flexible axis for movement.

Each vertebra has a vertebral body anteriorly and a vertebral arch posteriorly, which together enclose the vertebral foramen and form the spinal canal. The vertebral arch bears several processes: a spinous process posteriorly, transverse processes laterally, and superior and inferior articular processes that create facet joints (zygapophyses) with adjacent vertebrae. An intervertebral disc sits between consecutive vertebral bodies, consisting of a tough annulus fibrosus and a gel-like nucleus pulposus, acting as a cushion and spacer to permit motion and absorb load.

Regional differences are notable. Cervical vertebrae typically have smaller bodies, a triangular vertebral foramen, and transverse foramina; thoracic vertebrae bear facets for rib articulation and tend to have longer spinous processes; lumbar vertebrae have large bodies and robust, short processes. The sacrum is formed by five fused vertebrae that anchor the spine to the pelvis, while the coccyx comprises small, variably fused elements.

Developmentally, vertebrae arise from embryonic somites, and segmentation influences alignment and variation. Clinically, vertebral injuries and degenerative changes—such as fractures, vertebral compression, disc herniation, spondylolisthesis, and scoliosis—affect structure and function and are common targets of medical assessment.