Chapter 14 - Meninges and Blood Circulation of the Brain

Meninges. List them.

Meninges - three layers of protective, covering membranes that surround brain and spinal cord

• Dura mater - outermost meningeal layer

• Arachnoid mater - middle meningeal layer

• Pia mater - innermost meningeal layer

Pia mater

–Very thin, innermost meningeal layer

–Tightly adherent to outer surface of brain & spinal cord

• Follows all gyri and sulci of brain

Arachnoid mater

–Middle meningeal layer

–Separated from pia mater by subarachnoid space

• Subarachnoid space is filled with cerebrospinal fluid - fluid serves as cushioning layer between brain and bony skull

• Arachnoid trabeculae - thin, “spider-web” strands passing through subarachnoid space between arachnoid mater and pia mater

Dura mater

–Outermost meningeal layer

–Tough, fibrous layer - tightly adherent to inner skull

–At selected sites, dura splits into 2 layers:

• Outer (periosteal) layer remains attached to bone of skull

• Inner (visceral) layer separates and forms deep in-folding of dura mater that passes between parts of the brain

• Separation of dural layers also forms dural sinus - pathway for flow of venous blood

Dura Mater Infoldings

Falx cerebri

–Sickle-shaped in-folding of dura mater that passes between right & left cerebral hemispheres

• Extends downward within longitudinal cerebral fissure

• Inferior limit is just above corpus callosum

–Attached anteriorly to crista galli of ethmoid bone

–Joins posteriorly with tentorium cerebelli

Tentorium cerebelli

–“C”-shaped in-folding of dura mater that passes b/w occipital lobes (above) and cerebellum (below)

• Forms “tent” over cerebellum

• Central opening allows for passage of brain stem

–Attached to petrous ridges and inner wall of occipital bone

–Joins at mid-line with falx cerebri