Suboccipital triangle musculature.  The suboccipital region has been dissected bilaterally to demonstrate the muscles that form the suboccipital triangle: obliquus capitis inferior, obliquus capitis superior, and rectus capitis posterior major.  A fourth muscle, rectus capitis posterior minor, is located medial to the triangle on each side.  The vertebral artery is located deep within the suboccipital triangle as it courses along a groove on the posterior arch of the atlas (C1). The greater occipital nerve (dorsal ramus of C2) emerges from beneath the obliquus capitis inferior muscle and supplies sensory innervation to the posterior aspect of the scalp. The occipital artery arises laterally from the external carotid artery and crosses the suboccipital region to supply the posterior scalp. (Image courtesy of PA Rubino)