vertebral column

A complex and functionally significant segment of the body consisting of a curved stack of 33 vertebrae divided into five regions; the cervical (seven vertebrae), thoracic (12 vertebrae); lumbar (five vertebrae), sacral (five fused vertebrae), and coccygeal (four small fused vertebrae) regions. The vertebral column mechanically links the upper and lower extremities, enabling motion in all three planes.