The<unk>  is a region of the neck bounded by the following three muscles of the<unk>  group of muscles: * Rectus capitis posterior major - above and medially * Obliquus capitis superior - above and laterally * Obliquus capitis inferior - below and laterally (Rectus capitis posterior minor is also in this region but does not form part of the triangle) It is covered by a layer of dense fibro-fatty tissue, situated beneath the semispinalis capitis. The floor is formed by the posterior atlantooccipital membrane, and the posterior arch of the atlas. In the deep groove on the upper surface of the posterior arch of the atlas are the vertebral artery and the first cervical or<unk>  nerve. In the past, the vertebral artery was accessed here in order to conduct angiography of the circle of Willis. Presently, formal angiography of the circle of Willis is performed via catheter angiography, with access usually being acquired at the common femoral artery. Alternatively, a computed tomographic angiogram or magnetic resonance angiogram is performed.
Suboccipital triangle
Occipital triangle
Submandibular triangle
Kernohan's notch
Collateral eminence
Pretectal area
Muscular triangle
Watershed area 