「Vertebrae are the 33 individual, interlocking bones that form the spinal column. Each vertebra has three main functional components: the vertebral body for load-bearing, the vertebral arch to protect the spinal cord, and transverse processes for ligament attachment. The spinal column consists of seven cervical, twelve thoracic, and five lumbar vertebrae in addition to five fused vertebrae of the sacral region and four fused vertebrae forming the coccyx. The vertebrae in each region have unique features that help them perform their main functions. Vertebrae are interconnected by facet joints that allow mobility in the spine. Intervertebral discs separate the individual bones providing additional weight-bearing support.」
」には以下のような解説が見られる。
癒合する前の仙椎および尾椎は椎骨の一つであることは理解できるのだが、癒合した後の仙骨および尾骨も椎骨の一種とみるのであろうか？恐らく癒合後の仙骨および尾骨は椎骨と呼ばないと思われるのだが、そのあたりに言及している資料は見当たらない。
