Arachnoid mater :
- It is a thin, avascular membrane that lines but not adherent to the inner surface of the dura mater.
- From its inner surface thin processes or trabecular extend downward. Cross the subarachnoid space, and become continuous with the pia mater.
* Unlike the pia, the arachnoid dose not enter the grooves or fissures of the brain, except for the longitudinal fissure between the two cerebral hemispheres.
Cerebrospinal fluid circulation.
↳ then the CSF becomes part of the blood flow.
Pia matter :
- Is a thin, delicate, and highly vascularized membrane, that closely invests the surface of the brain.
- It follows the contours of the brain, entering the grooves or fissures on its surface.
- Provide a protective and nourishing covering for the brain
Spaces :
- 1. Extradural space : - Potential space (empty.) between dura mater and bone.
- ↳ In certain situations, such as trauma or bleeding, blood may accumulate in the space, causing epidural hematoma.
- 2. Subdural space
- 3. Subarachnoid space : -
- Between the arachnoid and the pia mater.
- It contains cerebrospinal fluid (CSF)
- Whithin it there are specialized structures called arachnoid villi or granulations project into the venous sinuses of the brain.
- ↳ Play a role in the releasing of CSF into the sinuses.