Atlas

Description

Beginning at the craniovertebral junction, the atlas (C1) appears as a ring-shaped vertebra positioned superior to C2 and inferior to the occipital bone, with broad lateral masses linked by short anterior and posterior arches. An anterior view logically emphasizes the anterior tubercle and the anterior arch, including the articular facet for the dens of the axis on the posterior surface of that arch. Laterally, the superior articular facets face superomedially toward the occipital condyles, while the transverse processes project laterally and frame the transverse foramina that transmit the vertebral arteries. Because C1 lacks a vertebral body and spinous process, this is the cleanest level for teaching how head rotation and flexion extension are distributed between the atlanto-occipital and atlanto-axial joints. The anterior atlas matters in trauma imaging: Jefferson burst fractures classically involve the anterior and posterior arches after an axial load, and widening of the lateral masses on open-mouth odontoid or CT correlates with disruption of the transverse ligament. Surgeons also reference the anterior arch and lateral mass geometry when planning C1 lateral mass screws or assessing congenital variants such as a partial posterior arch cleft that can mimic fracture. Use this asset in gross anatomy and neuroanatomy curricula when introducing the upper cervical spine, in radiology teaching files that pair 3D anatomy with CT reconstructions, or in spine surgery publications discussing atlanto-axial instability, dens-related pathology, and fixation trajectories. Anatomical accuracy verified by SciePro's Medical Advisory Board.