• Within the ethmoid bone, lie the foramina of the cribriform plate.
    -They contain CN 1, the olfactory nerve bundles.
  • Next, medial to the anterior clinoid process, lies the optic canal and lateral to it, lies the superior orbital fissure.-CN 2 traverses the optic canal.-CNs 3, 4, and 6, and the first division of CN 5 pass through the superior orbital fissure.
  • Posterior to the superior orbital fissure, within the greater wing of the sphenoid bone, lies foramen rotundum, and posterior to it, lies foramen ovale.-CN 5 (2) traverses foramen rotundum (think of R2D2 from “Star Wars”).-CN 5 (3) traverses foramen ovale.
  • Along the petrous apex of the temporal bone, lies the internal acoustic meatus.
    -Both CNs 7 and 8 pass through it.
  • Posterior to the internal acoustic meatus, lies the jugular foramen.
    -CNs 9, 10, and 11 pass through it.
  • Medial to the internal acoustic meatus, lies the hypoglossal canal.
    -CN 12 passes through it.
  • The ophthalmic artery traverses the optic canal.
  • The superior ophthalmic vein passes through the superior orbital fissure.
  • The internal auditory artery (aka labyrinthine artery) passes through the internal acoustic meatus.
  • The internal jugular vein passes through the jugular foramen.
  • The hypoglossal canal contains a venous plexus.
  • Posterior to foramen ovale, lies foramen spinosum.
    -The meningeal branch of CN 5(3) passes through foramen spinosum and the middle meningeal artery passes through it, as well.
  • The carotid canal lies along the petrous ridge.
    -The internal carotid artery runs within it.
  • Foramen magnum lies in midline.
    -CN 11 passes up through foramen magnum (before it passes out of the cranium through the jugular foramen) and the vertebral arteries and spinal vessels traverse foramen magnum, as well.
  • Lies anterior to the posterior aspect of the lesser wing of the sphenoid bone.
  • The basal portions of the frontal lobes lie within this fossa.
  • Lies between the anterior cranial fossa and the petrous ridge of the temporal bone.
  • The basal portions of the temporal lobes lie within this fossa.
  • Lies posterior to the petrous ridge.
  • The cerebellum and brainstem lie within this fossa.
  • The anterior one-third is the frontal bone.
  • The ethmoid bone, which comprises the steeply peaked crista galli and the surrounding cribriform plate, lies in midline.
  • Posterior to the frontal bone, lies the sphenoid bone.
  • The midline portion of the sphenoid bone is the sphenoid body.-It subdivides into the jugum sphenoidale, anteriorly, and the sella turcica, posteriorly.-The lesser wing of the sphenoid bone lies anteriorly, and the greater wing lies posteriorly.-Topographically, the lesser sphenoid wing angles up over the greater sphenoid wing, which rolls downward.-The protuberance lies along the posteromedial ridge of the lesser wing as the anterior clinoid process.
  • The temporal bone lies posterior to the greater wing of the sphenoid bone.
  • We see the petrous ridge and the squamous part of the temporal bone lies laterally.
    -The squamous part makes up the bulk of the external surface of the temporal bone, whereas the petrous part makes up the bulk of the internal surface.
  • Posteromedial to the temporal bone, lies the occipital bone; it extends back to the occiput.
  • In the anterior one-third of the occipital bone, lies the foramen magnum, which is the entry zone of the brainstem.
    -The combined anterior occipital bone and posterior sphenoid bone form the clivus, which is steeply sloped, and is a clinically important anatomical region.
  • Along the lateral edge of the skull base, lies the parietal bone.
    -The parietal bones make up much of the lateral and superior surfaces of the skull.