Axis (C2)

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The axis is the second cervical vertebra (C2).
The axis articulates with:
- the atlas (C1) above, forming the atlanto-axial joint.
- C3 below, forming the C2-C3 joint complex via the paired facet joints and the disc joint.

NOTES:

What would have been the body of the atlas (C1 above) fused onto the axis instead, creating the odontoid process, aka the dens.
The dens creates a vertical axis of motion that the ring-shaped atlas can rotate around (left and right rotation in the transverse plane). The atlanto-axial joint between the atlas and axis is responsible for 45% of all cervicocranial rotation.
The axis has the largest spinous process in the cervical spine.

Posterior view of the axis (C2).

Anterior view of the axis (C2).

Right lateral view of the axis (C2).

Superior view of the axis (C2).

Inferior view of the axis (C2).