Meninges & Cisterns Flashcards
Function of meninges
- The layers surrounding the brain, inside the skull that provide attachments and fluid filled spaces for protection of the brain and spinal cord
- Lie immediately deep to the cranium
- Protect and enclose the brain and spinal cord in a fluid filled cavity
- Provide a framework for vessels: arteries, veins and venous sinuses
Dura mater
Thick external fibrous layer
Tough
Arachnoid mater
Thin intermediate layer
Pia mater
Delicate internal vascular layer
What does the PERIOSTEAL (periosteum) layer of the dura mater cover
Covers and adheres to the internal cranium surface
What does the MENINGEAL layer of the dura mater cover
A strong fibrous membrane that is continuous at the foramen magnum with the dura covering the spinal cord (1 layer of dura)
What doe the periosteal and meningeal layers of the dura mater result in
Incomplete dividers between brain regions and spaces such as the venous sinuses
3 branches of meningeal arteries and veins
Anterior
Middle
Posterior
Innervation of the dura mater
Trigeminal nerve (CN V)
What is the leptomeninx
Arachnoid and pia mater and continuous with one another
Difference between the arachnoid and pia mater
Arachnoid = AVASCULAR
Pia = highly vascularised
What’s contained in the subarachnoid space between the arachnoid and pia mater
What structures traverse the space
CSF
Arachnoid (web-like) trabeculae traverse the space
What are arachnoid granulations
- Collections of arachnoid villi
- Protrude through the meningeal layer of the dura
- Pass CSF into the venous blood system
Describe pia
A thin membrane that adheres to the surface of the brain
Epidural/extradural space
Not a natural space between the cranium and the periosteal layer of the dura
Tightly adhered to the cranium
No space should be present
Subdural space
Between the meningeal layer of the dura and the arachnoid mater - not a natural space
No attachments - CSF pressure usually keeps arachnoid mater against the dura
potential space
Subarachnoid (SA) space
- A real space between the arachnoid and pia mater
- Contains CSF, trabecular cells, cerebral arteries, bridging veins
- Cisterns are expanding areas of SA space (quadrigeminal, cisterna magna)
Overview of cisterns
Where do the periosteal folds of dura attach to
Attached firmly to the skull
What do the meningeal folds of dura form
They fold on themselves to form dividers
- 1 lies between the 2 hemispheres of the brain - sagittal in orientation
- The other divides the space containing the cerebrum from that containing the cerebellum - more horizontal in orientation
Falx cerebri (fold of dura)
Largest
Separates the hemispheres of the cerebrum
Tentorium cerebelli (fold of dura)
- Separates the cerebrum from the cerebellum
- Tentorial notch, brainstem passes through this space
- Supratentorial and infratentorial e.g. tumours
- Most childhood tumours are infratentorial, while most adult tumours are supratentorial
Falx cerebelli
Separates right and left cerebellar hemispheres
Diaphragm sellae
Smallest, covers clinoid processes and folds around the pituitary gland
2 innermost layer of the meninges
Deflated balloon with no hole - stretch it around an organ
Within the balloon is fluid that allows the layers to move relative to one another
Outer layer provides framework for vessels
What do the arachnoid and pia mater represent
Our “deflated balloon”
Structures unique to sub-arachnoid space
Arachnoid trabeculae
apex of gyrus - dimensions of pia mater
deep into sulcus
Thin layer
Pockets of CSF in sulci
What structures are formed when the pial and arachnoid mater deviate more substantially in their paths relative to one another => cisterns
What is the fold of dura technically made from
Meningeal layer
Where is the falx cerebri located
In the longitudinal fissure
Spaces related to the tentorium cerebelli
Infratentorial space (a mass here would dispace tissue towards the foramen magnum - CHILDREN)
Supratentorial space (ADULTS)
Falx cerebelli orientation
Sagittal in orientation (like falx cerebri)
Diaphragm sellae
partition in sphenoid bone
Separates the space the pituitary occupies from the rest of the cranial cavity
