the ___________ is comprised of fused vertebrae and forms the back of the pelvis.
The vertebral column is composed of a series of 31 separate bones known as vertebrae. There are seven cervical or neck vertebrae, 12 thoracic vertebrae, and five lumbar vertebrae. The sacrum is composed of five fused vertebrae, and there are two coccygeal vertebrae which are sometimes fused (fig. 1). In the normal adult there are four curvatures in the vertebral column in an anteroposterior plane. These serve to align the head with a vertical line through the pelvis (fig. 2).