atlas
Last reviewed 01/2018
The atlas is the most superior cervical vertebra. It supports the skull and is named after a character in Greek mythology who supported the earth on his shoulders. It exhibits little resemblance to other vertebrae:
- ring-shaped
- vertebral body is lost in development to the immediately inferior vertebra, the axis, where it forms the odontoid peg or dens
- vertebral foramen:
- more oval than the rest of cervical vertebrae
- consists of anterior and posterior arches joined by lateral masses on each side
- anterior arch:
- shorter and straighter than posterior arch
- connects lateral mass on each side to median anterior tubercle on its anterior surface
- posterior to anterior tubercle on the surface of atlas facing vertebral canal is a facet for articulation with the dens of the axis
- posterior arch represents pedicles and laminae of typical cervical vertebra:
- connects lateral mass on each side to median posterior spinous tubercle; spinous process does not develop
- close to lateral mass on superior surface is groove for vertebral artery as it passes to foramen magnum
- lateral mass: junction of anterior and posterior arches
- medial small tubercle for attachment to atlas ligament
- has superior & inferior articular facets
- superior articular facets:
- articulate with condylar process of occipital bone
- kidney-shaped and concave
- inferior articular facets:
- round and less concave than superior facets
- articulate with axis
- transverse process: broad, strong, occasionally bifid
- represents posterior tubercle of other vertebrae
- foramen transversarium: within the transverse process, it transmits vertebral vessels and sympathetic nerves