Session 3: Meningeal Layers, Dural Folds and Dural Venous Sinuses Flashcards
State the three membranous layers that surround the brain and spinal cord.
Pia mater
Arachnoid mater
Dura mater
Briefly explain the pia mater.
A microscopically thin layer adherent to the surface of the brain. This layer follows every sulcus, gyrus and fissure.
Briefly explain the arachnoid mater.
A loose connective tissue layer that is said to make the brain ‘smoother’. It follows every fissure but it does not go into gyri.
Briefly explain the dura mater.
A dense irregular connective tissue. It consists of two layers. It does not go into any gyri or fissures.
What are the two layers of the dura mater?
Periosteal dura Meningeal dura
What are the leptomeninges?
That is what the pia mater and the arachnoid mater is collectively called.
What is the space between the dura and arachnoid called?
It is called subdural space. However it is only potential subdural.
Why is the subdural space only a potential space?
Because the arachnoid layer is usually pushed up against the dura mater and the space becomes ‘sealed’.
What is the space between the arachnoid and pia called?
The subarachnoid space.
What is found in the subarachnoid space?
CSF Cerebral vessels supplying and draining the brain.
What makes the arachnoid mater be pushed up against the dura mater?
The cerebrospinal fluid.
What is the periosteal layer of the dura?
It is dura which is the same as the ‘periosteum lining’ that lines the inner table of the skull bones.
What is the meningeal layer of the dura?
The inner part of the dura mater that is adjacent to the arachnoid.
Are the two layers of the dura separate?
For most part the two layers closely adhere so they appear as a single layer. However in some areas they separate.
What does the separation of these two layers form?
Dural folds and dural venous sinuses.
Which are the areas where the two layers of the dura separate?
By fissures usually. The great longitudinal fissure is an example of where they meningeal separate from the periosteal and form a DVS and dural fold. The DVS is the superior sagittal sinus.
What is a dural fold?
When the meningeal dura separate from the periosteal by the great longitudinal fissure it goes into the fissure where as the periosteal layer follow along the skull bone. The two layers of meningeal dura will meet in the fissure and adhere to each other.
That is a dural fold.
What is the dural fold in the great longitudinal fissure called?
Falx cerebri.
What does the falx cerebri attach to?
Anteriorly to the crista galli of the ethmoid bone.
Posteriorly it attaches to the superior part of tentorium cerebelli.
What is the function of the falx cerebri?
Separates the two cerebral hemispheres.
What is the tentorium cerebelli?
An extension of the meningeal dura that separates the cerebellum from the inferior occipital lobes.
Purpose of dural folds.
Helps to stabilise the brain and act as a rigid divider.
What are some issues with the dural folds?
A rise in pressure inside the skull can lead to compression and displacement (herniation) of parts of brain under rigid dural folds.
Parts of the brain can also herniate through the foramen magnum.
What are dural venous sinuses?
Venous blood filled spaces created by separation of meningeal from periosteal layer of dura.
They are found in various spaces throughout the skull.
They are all connected and receive blood from cerebral veins draining the brain.
