Cervical vertebra – atlas (C1)

Anatomy

Highest vertebra of column of 33. Forms spine/skull joint, along with C2 (axis). C1 has no vertebral body, as it is fused with that of C2 to contribute to formation of odontoid process (or dens). C1 has no spinous process; its absence affords greater range of movement of skull on C1.

Superior facets (atlanto-occipital) shaped to allow nodding (“yes”) of skull, inferior (atlanto-axial) to allow rotation (“no”) of skull-C1 combination on rest of spine.

Clinical

Articulates up with occipital and down with axis.

Vignette

Atlas, in Greek mythology, carried the world on his shoulders; C1 carries the head. At level of C1, vertebral canal much bigger than needed for spinal cord (medulla spinalis) and so displacement/dislocation will not ordinarily cause its compression.

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