The atlas is the first cervical vertebra in the human spine.
Designated C1, the atlas supports the skull and sits at the top of the neck. It is named after Atlas, the figure from Greek mythology who carried the heavens. Unlike most vertebrae, it has no substantial vertebral body. Instead, it consists mainly of anterior and posterior arches connected by broad lateral masses.
The skull rests on the atlas at the paired atlanto-occipital joints. These joints allow the head’s nodding movement, often described as the motion used to signal “yes.” The atlas also has large openings that accommodate important nerves and blood vessels.
The second cervical vertebra is the axis, or C2. It has a projecting dens that fits against the atlas and acts as a pivot, allowing much of the head’s side-to-side rotation. The atlas and axis therefore have different shapes and specialized jobs.