Atlas, Posterior View

Description

Posterior occiput and upper cervical spine are presented in anatomical position, with the lambdoid suture spanning between the parietal bones and occipital squama above the craniovertebral junction. Inferior to the external occipital region, the atlas (C1) is highlighted, its posterior arch forming a broad ring that lies superior to the axis (C2) and posterior to the odontoid process (not visible from this angle). The posterior tubercle of C1 sits in the midline where a typical cervical spinous process would be expected, while the lateral masses extend laterally toward the transverse processes and the atlanto-occipital joints. C2 and the subaxial cervical vertebrae align inferiorly, their spinous processes projecting posteriorly along the midline. Posterior emphasis on the atlas matters because the C1 posterior arch is a frequent site of injury and an important surgical landmark at the craniovertebral junction. A Jefferson burst fracture classically involves the anterior and posterior arches after axial loading, while isolated posterior arch fractures can occur after hyperextension injuries and may mimic congenital posterior arch clefts on imaging. This is the corridor used in a C1 laminectomy for decompression at the cervicomedullary junction, where attention to the vertebral artery as it courses in the sulcus arteriae vertebralis on the superior surface of the posterior arch is nonnegotiable. Small bone. Big consequences. Use this asset for teaching upper cervical osteology in gross anatomy or neuroanatomy, for illustrating atlanto-occipital and atlanto-axial biomechanics in a spine module, or for clinician-facing materials discussing C1 fractures, posterior arch variants, and posterior decompression approaches in orthopedic spine or neurosurgery contexts. Anatomical accuracy verified by SciePro's Medical Advisory Board.