backbone

Definition backbone

backbone: backbone (spinal column, spine, vertebral column) n. a flexible bony column extending from the base of the skull to the small of the back. It encloses and protects the spinal cord, articulates with the skulln ribs, and hip girdle, and provides attachment for the muscles of the back. It is made up of individual bones (see vertebra) connected by discs of fibrocartilage (see intervertebral disc) and bound together by ligaments. The backbone of a newborn baby contains 33 vertebrae: seven cervical (neck), 12 thoracic (chest), five lumbar (lower back) and four coccygeal. In the adult the sacral and coccygeal vertebrae become fused into two single bones (sacrum and coccyx, respectively); the adult vertebral column therefore contains 26 bones (see illustration). Anatomical name: rachis.