Meninges:

Meninges are membranous coverings of the brain and spinal cord. There are three meningeal layers:

1. Dura mater (the outermost layer)
2. Arachnoid mater
3. Pia mater

Dura mater:

The dura mater is a tough outer membrane of the meninges that is made up of two layers:

1. The fibrous layer (AKA endosteal layer) that is attached to the inner surface of the skull - this layer is only found in the skull NOT the spinal cord.

2. The meningeal layer which lies underneath the fibrous layer and is continuous with the spinal cord dura mater.

   There are spaces at certain points between the endosteal and meningeal layers known as Dural venous sinuses. These sinuses drain venous blood from the brain and cerebrospinal fluid (CSF) via the arachnoid granulations.

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Examples of the Dural venous sinuses are the superior sagittal sinus, the transverse sinus etc.

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The meningeal layer of the dura mater folds inwards at certain places to form partitions between parts of the brain. These reflections help stabilize the brain within the skull and include:

• Falx cerebri - lies in the longitudinal fissure between the two cerebral hemispheres. (separates the hemispheres)
• Falx cerebelli - between the two cerebellar hemispheres (below the tentorium)
• Tentorium cerebelli - separates the cerebrum (occipital lobes) above from the cerebellum below.
• Diaphragma sellae - covers the pituitary gland

Blood supply: