Cranium and Cranial Nerves Learning Objectives

Question 1

Summarize the meningeal coverings and spaces of the CNS using a drawing.

Answer 1

Dura mater: dura = “tough”
Periosteal layer
—-> superior sagittal (dural) sinus between these two layers
Meningeal layer (creates 3 dural infoldings)
- falx cerebri (separates hemispheres of cerebrum)
- falx cerebelli (separates two hemispheres of cerebellum)
- tentorium cerebelli (separates cerebrum from cerebellum)

Arachnoid mater
- arachnoid villi

Pia mater (layer closest to brain)
- filum terminale (fibrous projection to coccyx)

Spaces:

• epidural (b/t cranial bones and dura; arterial; meningeal aa.)
• subdural (b/t dura and arachnoid; venous; slower progression)
• subarachnoid (b/t arachnoid and pia, contains cerebrospinal fluid; arterial; most immediately harmful)

Question 2

Explain the in-folding of dura mater and structures they separate.

Answer 2

The meningeal layer of the dura mater infolds to create the falx cerebri.

Falx cerebri:

• Separates right and left cerebral hemispheres
• Contains superior sagittal sinus, inferior sagittal sinus
• Blends with tentorium cerebelli

Falx cerebelli:

• Separates hemispheres of cerebellum
• Contains occipital sinus

Tentorium cerebelli:

• Transverse plane separating cerebellum and cerebrum
• Contains transverse petrosal sinus, straight petrosal sinus, superior petrosal sinus

Question 3

Explain the boundaries and contents of the three cranial fossae.

Answer 3

Anterior cranial fossa:

• crista galli
• cribriform plate
• olfactory nerves and bulbs
• sphenoidal crest

Middle cranial fossa:

• optics nerves
• internal carotid artery
• middle meningeal a.
• infundibulum of pituitary gl.
• oculomotor nerves
• trochlear n.
• trigeminal nn.
• trigeminal ganglion
• – V1, V2, V3
• cavernous sinus
• abducens n.
• petrous ridge of temporal bone

Posterior cranial fossa:

• facial and vestibulocochlear nn.
• glossopharyngeal and vagus nn.
• accessory n.
• hypoglossal n.
• f. magnum
• vertebral aa.
• spinal cord