Skull Base

Related pages

• Cranial Foramina

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)