Glossary of Spine-Related Terms

Atlas and Axis

Vertebrae is term used to describe more than one spinal segment or level (vertebra is one segment). The atlas, axis, cervical spine, thoracic spine, lumbar spine, sacrum, and coccyx make up all the vertebrae (bony elements) of the spinal column.

The upper cervical spine consists of two specialized vertebrae called the atlas, the first bone, and the axis, the second bone. These bones do not have discs between them like all the other vertebrae and are shaped very differently from the rest of the spinal bones. The atlas and axis house the lower portion of the brainstem, the medulla oblongata. Any shifting or trauma to this area causes pain and discomfort, as well as other symptoms to the medulla. Any disruption or trauma needs a consultation.

Coccyx and Sacrum

The sacrum is at the bottom of the spine and lies between the fifth lumbar segment and the coccyx (tailbone). The sacrum is a triangular-shaped bone and consists of five segments (S1 to S5) that are fused together and connect to the pelvis (ilium) and form joints called the sacroiliac joints.