Dura Mater and Dural Folds PDF

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Dura Mater and Dural Folds...

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Dura Mater and Dural Folds The dura mater consists of outer and inner fibrous layers. The outer layer is fused to the periosteum of the cranial bones. As a result, there is no epidural space superficial to the dura mater, as occurs along the spinal cord. The outer periosteal cranial dura and inner meningeal cranial dura are typically fused together In several locations, the meningeal cranial dura extends into the cranial cavity, forming a sheet that dips inward and then returns. These inward projections, known as dural folds, provide additional stabilization and support to the brain. Dural venous sinuses are large collecting veins located within the dural folds. The veins of the brain open into these sinuses, which deliver the venous blood to the veins of the neck. The three largest dural folds are called the falx cerebri, the tentorium cerebelli, and the falx cerebelli (Figure 14–3b): ■ The falx cerebri (FALKS SER-e-brı . ; falx, sickle shaped) is a fold of dura mater that projects between the cerebral hemispheres in the longitudinal cerebral fissure. Its inferior portions attach anteriorly to the crista galli of the ethmoid and posteriorly to the internal occipital crest, a ridge along the inner surface of the occipital bone. The superior sagittal sinus and the inferior sagittal sinus, two large dural venous sinuses, lie within this dural fold. The posterior margin of the falx cerebri intersects the tentorium cerebelli. ■ The tentorium cerebelli (ten-TO . -re . -um ser-e-BEL-e . ; tentorium, tent) protects the cerebellum and separates the cerebral hemispheres from the cerebellum. It extends across the cranium at right angles to the falx cerebri. The transverse sinus is a paired dural venous sinus that runs along the occipital bone. It allows blood to drain from the back of the head. ■ The falx cerebelli divides the two cerebellar hemispheres along the midsagittal line inferior to the tentorium cerebelli. The dura mater may be separated from the next layer of membrane, the arachnoid mater, by a narrow gap called the subdural space Arachnoid Mater The arachnoid mater is a membrane that resembles a spider web. In life, its arachnoid barrier cell layer is attached to the dural border cell layer of the dura mater, and no natural space occurs at this interface. (However, a subdural space may form as a result of trauma, disease, or lack of cerebrospinal fluid, as in a cadaver.) The cranial arachnoid mater covers the brain, providing a smooth surface that does not follow the brain’s underlying folds. The subarachnoid space, containing cells and fibers of the arachnoid trabeculae, lies between the arachnoid mater and the pia mater. Pia Mater

The pia mater sticks closely to the surface of the brain, anchored by the processes of astrocytes. It also accompanies the branches of cerebral blood vessels as they penetrate the surface of the brain to reach internal structures....