Atlas vs axis (C1 and C2): how they differ, in 3D

Frequently asked questions

How do the atlas and the axis differ in shape?

The atlas is a ring with no body and no spinous process, made of an anterior arch, a posterior arch and a lateral mass on each side. The axis has a body with a peg, the dens, rising from it and fitting inside the front arch of the atlas.

Where do nodding and turning the head happen?

Nodding happens mainly at the atlanto-occipital joint between the occipital bone and the atlas. Turning the head from side to side happens mainly at the atlanto-axial joint between the atlas and the axis.

Where do the names atlas and axis come from?

The atlas is named after the Titan of Greek myth who held up the sky, because it holds up the skull. The axis is named for the pivot it forms, around which the atlas and the head turn.