Dural Exposure of Posterior Cerebellum and Atlantic Part of the Vertebral Artery. An oval piece of occipital bone has been cut out to provide exposure of dura covering the cerebellum. The atlantic part of the vertebral artery is shown emerging from the transverse foramen of C2, coursing upward through the transverse foramen of C1, and around the lateral mass to occupy a groove on the superior surface of the posterior arch of the atlas. Just inferior to the foramen magnum it gives rise to a posterior meningeal branch that penetrates dura to enter the posterior cranial fossa where it provides blood to the medial portions of the dura here as well as to the falx cerebelli. Inferior to occipital bone and its condyles is the posterior arch and transverse processes of the atlas. Inferior to this arch is the spinous process and laminae of the axis. The elastic ligamenta flava bridge the gap between these bony parts contributing to the roof of the vertebral canal. Emerging between the C1 and C2 vertebrae are the C2 spinal nerves. These are formed by union of ventral and dorsal roots. The distal part of the latter shows a swelling, the dorsal root or spinal ganglion, containing the cell bodies of sensory neurons associated with this nerve. The definitive spinal nerve is short and exits the intervertebral foramen where it subsequently divides into ventral and dorsal primary rami.  (Image courtesy of PA Rubino)