Cranial Cavity, Venous Sinuses and Brain - LO 3

3. What are the three types of cranial meninges? What is the difference between cranial and spinal dura mater? Where are dural infoldings/partitions located?

• Pia mater ("delicate mother")

  • is a delicate investment that is closely applied to the brain and dips into fissures and sulci.

  • enmeshes blood vessels on the surface of the brain.

• Arachnoid mater ("spidery mother")

  • is a filmy, transparent, layer that is connected to the pia mater via trabeculae.

  • is separated from the pia mater by the subarachnoid space, which is filled with cerebrospinal fluid (CSF). The subarachnoid space may contain blood after hemorrhage of a cerebral artery (formation of subarachnoid hematoma).

  • projects into the superior sagittal sinus to form arachnoid villi, which serve as sites where CSF diffuses into the blood.

  • Arachnoid granulations

    • are tuft-like collections of highly folded arachnoid that project into the superior sagittal sinus and its lateral lacunae (lateral extensions of the superior sagittal sinus).

    • release CSF into the superior sagittal sinus and often produce erosion or pitting (granular foveolae) of the inner surface of the calvaria.

• Dura mater ("tough mother")

  • outermost covering

  • two layers in the cranium (one in the spinal canal)

    • periosteal dura - lines the cranial cavity

    • meningeal layer - inner layer that is sometimes separated from the periosteal layer, forming dural venous sinuses and partitions

Dural partitions are elaborations of the meningeal layer of cranial dura mater. There are four partitions: 

• falx cerebri, 

• falx cerebelli, 

• tentorium cerebelli, and 

• diaphragma sellae.