Anatomy of the Spine
The vertebral column is also called the backbone. It 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.
The spinal cord is a bundle of nerves. It passes through the center of the vertebral column. The spine protects the spinal cord and allows nerves for your arms, legs, and organs to exit and enter at each level.