Skull Base

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Internal Features of Base of Skull:

Divided into anterior, middle, and posterior cranial fossae

Anterior cranial fossa

  • Contains frontal lobe of brain
  • Formed by frontal bone anteriorly, ethmoid bone medially, and lesser wing of sphenoid bone posteriorly

Features

  • Frontal crest—midline bony extension of frontal bone
  • Foramen cecum—foramen at base of frontal crest
  • Crista galli—midline ridge of bone from ethmoid posterior to foramen cecum
  • Cribriform plate—thin, sievelike plate of bone on either side of crista galli, which transmits olfactory

Middle cranial fossa

  • Contains temporal lobe, hypothalamus, and pituitary gland
  • Formed by greater wing and body of sphenoidal bone, petrous temporal bone, lesser wing of sphenoidal bone

Features

  • Sella turcica—central depression in the body of the sphenoid bone for pituitary gland
  • Tuberculum sellae—swelling anterior to sella turcica
  • Dorsum sellae—crest on the body of the sphenoid bone posterior to sella turcica
  • Anterior clinoid processes—medial projections of lesser wings of sphenoidal bones
  • Posterior clinoid processes—swelling at either end of dorsum sellae
  • Foramen lacerum (one on each side)—jagged opening closed by plate of cartilage in life, transmits nothing

Contains four foramina in a crescent on either side in the body of the sphenoidal bone

  • Superior orbital fissure
  • Foramen rotundum
  • Foramen ovale
  • Foramen spinosum

Posterior cranial fossa

  • Contains cerebellum, pons, and medulla oblongata
  • Composed largely of occipital bone, body of sphenoidal bone, petrous, and mastoid parts of temporal bone

Features

  • Foramen magnum—transmits spinal cord
  • Internal occipital crest—divides posterior fossa into two lateral cerebellar fossae
  • Grooves for transverse and sigmoid dural venous sinuses
  • Jugular foramen—transmits sigmoid sinus (internal jugular vein) and several cranial nerves
  • Internal acoustic meatus—anterior and superior to jugular foramen, transmits facial and vestibulocochlear nerves (CN VII and CN VIII)
  • Hypoglossal canal—anterolateral and superior to foramen magnum, transmits the hypoglossal nerve (CN XII)



3D models