3. Meninges And Dural Folds Flashcards
What are the meninges?
The three membranous layers that surround and protect the brain
What are the 3 meningeal layers and where do the spaces come between them? What is the structure of each like?
Dura - tough fibrous membrane.
Subdural space.
Arachnoid - soft translucent membrane.
Subarachnoid space - contains CSF and cerebral blood vessels.
Pia - microscopically thin, delicate closely adherent to surface of brain.
What meningeal layer consists of the periosteal (endosteum lining inner bones of skull) and meningeal (layer adjacent to arachnoid) layer?
Dura
What does separation of the two layers of the dura in places form?
Dural folds and dural venous sinuses
The dura forms two folds, one in the coronal plane and one in the sagittal plane. What is each called?
Sagittal - falx cerebri.
Coronal - tentorium cerebelli.
What are the 2 main functions of the dural folds?
Stabilise the brain and act as rigid dividers.
A rise in pressure inside the skull (eg secondary to a bleed) can lead to compression and displacement of the brain against rigid dural folds and/or through the foramen magnum. What is this called?
Herniation
What are dural venous sinuses?
Venous blood filled spaces created by separation of meningeal from endosteal layer of dura.
Where does the blood from dural venous sinuses eventually drain into?
Internal jugular vein
What veins from the venous sinuses transverse the subdural space?
Bridging veins
What are the 3 types of intracranial haemorrhages that can occur between the meningeal layers?
Extradural.
Subdural.
Subarachnoid.
What is the name for a bleed that occurs within the brain tissue itself?
Intracerebral haemorrhage
What is an extradural haemorrhage?
An arterial bleed eg from the middle meningeal artery in the dura.
What is a subdural haemorrhage?
A venous bleed eg from a bridging vein (veins that transverse the subdural space from venous sinuses). Can only spread down one side of the skull as the flax cerebri stops it passing from one side to the other.
What is a subarachnoid haemorrhage? Where does it normally occur?
An arterial bleed secondary to trauma or spontaneous rupture of blood vessel eg aneurysm. Is usually a branch of circle of Willis. Blood leaks into the subarachnoid space, mixing with CSF which is sudden and often fatal.
