View of left posterolateral neck with exposure of the suboccipital triangle. The sternocleidomastoid, trapezius, longissimus capitis, splenius capitis, and most of the semispinalis capitis muscles have been removed to expose the suboccipital triangle. The muscles that form this triangle include the obliquus capitis inferior, the obliquus capitis superior, and the rectus capitis posterior major. The obliquus capitis inferior and rectus capitis posterior major both arise from the spinous process of the axis (C2 vertebra). The former inserts into the transverse process of the atlas, from which arises the obliquus capitis superior. Both the obliquus capitis superior and the rectus capitis posterior major converge to attach to the base of the occipital bone. Within this triangular space is the vertebral artery and the suboccipital nerve. The latter is a dorsal ramus of the C1 spinal nerve and provides motor innervation to these muscles. The rectus capitis posterior minor, however, is more medial arising from the posterior arch of the atlas to attach to the base of the occipital bone. This area is supplied by the occipital artery and drained by the occipital and deep cervical veins. Emerging around the lower border of the obliquus capitis inferior muscle is the greater occipital nerve, the dorsal ramus of the C2 spinal nerve. This nerve supplies general sensation to the posterior scalp.   
Descending obliquely on the upper external surface of the internal jugular vein is the spinal accessory nerve. Posterior to the vein is the levator scapulae muscle. The splenius cervicis muscle is located between the levator scapulae and splenius capitis and has similar superior attachments with the levator, namely, the transverse processes of the upper four cervical vertebrae. (Image courtesy of AL Rhoton, Jr.)