The atlas is the first cervical vertebra and its major distinguishing feature is that it does not have a vertebral body.

The atlas articulates with the skull and with the adjacent vertebra - the axis.

The atlas is ring shaped when viewed from above and has two lateral masses interconnected by an anterior arch and a posterior arch.

Each lateral mass articulates with an occipital condyle above (atlanto-occipital joint) and with a superior articular process of the axis below (atlanto-axial joints).

The posterior surface of the anterior arch has an impression for the dens (also known as the fovea of dens). The dens is a projection from the vertebral body of the axis.

The transverse processes of the atlas are large and project further laterally than those of other cervical vertebrae and they act as levers for muscle action.

The groove for the vertebral artery is located behind the superior articular process.

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Atlas (C1)