The vertebral, or spinal, column is composed of 26 bone segments, called vertebrae, that are arranged in 5 divisions from the base of the skull to the tailbone. The bones are seperated by pads of cartilage called intervertebral disks (discs).
The first set of 7 bones of the vertebral column are the cervical vertebrae (c1 to c7).
The second set of 12 bones are the thoracic vertebrae which articulates with the ribs (T1 to T12).
The third set of 5 bones are the lumbar vertebrae (L1 to L5) they are the strongest and largest of the backbones. Like the cervical vertebrae, these bones do not articulate with the ribs.
The sacral vertebrae are 5 seperate bones that fuse together when you are a yound child. In adults, the sacrum is a slightly curved, triangularly shaped bone.
The coccyx is the tailbone, and it, too, is a fused bone, having been formed from four small coccygeal bones.