Meningeal Layers, Dural Folds and Dural Venous Sinuses Flashcards
What are the three membranous layers that surround and protect the brainstem and spinal cord?
Pia - This is a microscopically thin, delicate and adherent to the surface of the brain. It follows every fold.
Between arachnoid and pia is subarachnoid space which contains CSF and cerebral vessels. Arachnoid - This is a soft, translucent membrane.
There is a potential space between arachnoid and dura where haematomas
Dura - This is a tough fibrous membrane
What blood vessels run in the dura?
Middle meningeal arteries
What are the two layers of the dura?
Periosteal dura (periosteum) - part against the inner table of bone Meningeal dura - part adjacent to arachnoid
When the two dural layers separate, what do they form?
Dural folds
Dural venous sinuses (spaces which are filled with venous blood = venous channels)
What is tentorium cerebelli?
an extension of the dura mater that separates the cerebellum from the inferior portion of the occipital lobes (runs horizontal).
What is the falx cerebri?
It is a large fold of meningeal layer of dura mater that descends vertically in the longitudinal fissure between the cerebral hemispheres of the human brain.
What are the roles of dural folds?
To help stabilise the brain and act as rigid dividers.
What are the dural venous sinuses?
Venous blood filled spaces created by separation of meningeal from periosteal layer of dura.
These are found throughout the skull, surrounding the brain within the areas where dura has separated.
Dural venous sinuses connected to each other, and receive blood from cerebral veins.
Where do the dural venous sinuses drain into?
Internal Jugular Vein
What are bridging veins?
The connection between dural sinuses and cerebral veins
What are emissary veins?
Veins that travel through the skull and connect with dural venous sinuses.
Why do intercranial haemorrhages damage the brain?
The addition of ‘volume’ to an already fixed space (the skull) leads to rise in pressure and damage to brain tissue, brainstem and other important structures e.g. cranial nerves.
In an extradural, haemorrhage, what artery bleeds?
Middle meningeal artery.
In a subdural haemorrhage, what artery bleeds?
Venous bleeds usually from bridging veins.
This is more common in older people.
How does a subarachnoid haemorrhage occur?
Secondary to trauma or spontaneous rapture of blood vessels e.g. aneurysm.
The blood leaks into the subarachnoid space, mixing with CSF. It is sudden and often fatal.
