Cranial and Spinal Meninges

The meninges consist of three layers protecting the central nervous system. The dura mater is the thick, outermost layer adhering to the skull. The arachnoid mater is the delicate middle layer containing arachnoid granulations that absorb cerebrospinal fluid. The pia mater is the innermost layer firmly adhering to the brain and spinal cord, providing additional protection and contributing to the blood-brain barrier.

The dura mater extends inward to form three dural septa: the falx cerebri, falx cerebelli, and tentorium cerebelli. These structures act as internal partitions that restrict excessive movement of the brain within the cranium, providing structural support and stability during head motion and impact.

The subarachnoid space, located between the arachnoid mater and pia mater, contains cerebrospinal fluid that helps absorb external shocks and impacts to the central nervous system. This fluid-filled compartment provides cushioning protection for both the brain and spinal cord against mechanical trauma.

Cranial meninges have a dura mater with two layers: the periosteal layer adhering to the skull and the meningeal layer. Spinal meninges have only the meningeal layer of dura mater. Additionally, the epidural space surrounding the spinal dura contains fat and blood vessels that provide extra cushioning, unlike the cranial epidural region.

Arachnoid granulations are projections of the arachnoid mater extending into the superior sagittal sinus. These specialized structures are essential for absorbing cerebrospinal fluid from the subarachnoid space, maintaining proper CSF balance and pressure within the cranial cavity and protecting neural tissue.

The pia mater is a thin, highly vascularized membrane that firmly adheres to the surface of the brain and spinal cord. It provides additional mechanical protection and contributes to forming the blood-brain barrier. In the spinal cord, the pia mater extends as the filum terminale, anchoring the spinal cord to the coccyx for structural stability.

The epidural space lies between the spinal dura mater and the vertebral column, containing a network of veins and fatty tissue. This space provides additional cushioning and shock absorption for the spinal cord, protecting it from mechanical trauma and vertebral contact during movement and impact.