This study unit will help you to:
- Define the cranial meninges and explain their function.
- Describe the morphology of three cranial meninges and the spaces between them.
Separating the brain and spinal cord from their surrounding bony enclosures are three membranes known as the meninges. The outermost layer is the dura mater (also known as pachymeninx) which consists of a double layer of thick, dense irregular connective tissue. The middle layer is the arachnoid mater, so-called for its spider web-like appearance, while the innermost layer is the thin and delicate pia mater. The arachnoid and pia mater can also be collectively referred to the leptomeninges due to their common embryological and cellular structure.
These layers delimitate three clinically important spaces: the epidural (or extradural), subdural, and subarachnoid spaces. The epidural space is located between the bones of the cranium and outer (periosteal) layer of the dura mater, while the subdural space lies between the inner (meningeal) layer of the dura mater and arachnoid mater. Both of these are potential spaces, meaning that under normal circumstances they are closed. The subarachnoid space, located between the arachnoid and pia mater, is a fluid-filled space that contains CSF, as well as cerebral arteries and veins. Finally, separating the pia mater from the surface of the brain is a thin space known as the subpial space.
Do you want to deepen your knowledge of the cranial meninges? Take a look at our videos below!
Take a quiz
Solidify your knowledge of the cranial meninges by taking the following quiz.
Challenge yourself even further by taking our custom quiz below which also covers the ventricles and blood vessels of the brain.
Review all the structures you learned today with the image galleries below.
|Definition||Three membranous layers that envelop the brain|
|Meningeal spaces||Epidural space
|Function||Mechanical protection of brain
Support of cerebral blood vessels
Accommodation and circulation of CSF (subarachnoid space)
|Related structures||Dural venous sinuses (venous drainage of the brain)
Arachnoid granulations (return of CSF to venous circulation)