Posterolateral view of the suboccipital region.  The muscles of the suboccipital triangle have been removed on the left side to expose the posterior arch of C1 (atlas) and the lamina of C2 (axis).  A portion of ligamenta flava can be seen connecting the posterior components of these two vertebrae.  The atlantic part of the vertebral artery can be seen traversing the transverse foramen of C1 and then coursing along the posterior arch of C1 before entering the skull via foramen magnum.  The C2 spinal nerve can be seen emerging between the C1 and C2 vertebrae before branching into dorsal and ventral rami.  The dorsal ramus of C2, also called the greater occipital nerve, supplies sensory innervation to the posterior aspect of the scalp.  The dorsal root ganglion of C2 contains the sensory neurons associated with the greater occipital nerve. (Image courtesy of PA Rubino)