Anatomy of the Spine
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The vertebral column, also called the backbone, is made up of 33 vertebrae that are separated by spongy disks and classified into 4 distinct areas. The cervical area consists of 7 bony parts in the neck; the thoracic spine consists of 12 bony parts in the back area; the lumbar spine consists of 5 bony segments in the lower back area; 5 sacral* bones; and 4 coccygeal* bones (the number of coccygeal bones can vary from 5 to 3).
(* By adulthood, the 5 sacral vertebrae fuse to form 1 bone, and the 4 coccygeal vertebrae fuse to form 1 bone.)