Anterior view of atlantoaxial articulation. The first and second cervical vertebrae have unique names as well. The C1 vertebra is the atlas and the C2 vertebra is the axis. The atlas superior articular processes articulate with the occipital condyles and form the atlantooccipital joint. This joint provides anterior-posterior (flexion, extension) movement of the head. The axis articulates with the atlas to form the atlantoaxial joint, which provides about 60 degrees of axial rotation of the head on the cervical spine. In this dissection view, the dens of the axis projects superiorly from its body and passes upward into the vertebral foramen of the atlas. The anterior arch of the atlas to which the dens articulates has been drilled away. The strong transverse ligament (not labeled) of the atlas crosses posterior to the dens and holds it firmly in place against the anterior arch. The ligament attaches to small tubercles on the medial edges of the lateral masses of the atlas. The rounded cord-like alar ligaments attach the sides of the dens to tubercles on the medial surfaces of the occipital condyles, thus connecting the skull to the dens. These serve as check ligaments to limit axial rotation and contralateral flexion of the head. The tectorial membrane is a strong flat band that covers the ligaments of the dens. It is a continuation of the posterior longitudinal ligament of the vertebral canal and attaches superiorly to the basilar part of the occipital bone in front of the foramen magnum. (Image courtesy of PA Rubino)