CRANIAL MENINGES

The cranial meninges are membranous coverings of the brain that lie immediately internal to the cranium (Fig). The cranial meninges

FIGURE .Meninges and their relationship to calvaria, brain, and spinal cord. A. The dura mater and subarachnoid space (purple) surround the brain and are continuous with that around the spinal cord. B. The two layers of dura separate to form dural venous sinuses, such as the superior sagittal sinus.

Arachnoid granulations protrude through the meningeal layer of the dura into the dural venous sinuses and effect transfer of cerebrospinal fluid (CSF) to the venous system. C. The normal fat- and vein-filled spinal epidural (extradural) space is not continuous with the potential or pathological cranial epidural space. Cranial dura mater has two layers, whereas spinal dura mater consists of a single layer. D. The calvaria has been removed to reveal the external (periosteal layer) of the dura mater. In the median plane, a part of the thick roof of the superior sagittal sinus has been incised and retracted; laterally, parts of the thin roof of two lateral lacunae (L) are reflected to demonstrate the abundant arachnoid granulations, which are responsible for absorption of CSF. On the right, an angular flap of dura has been turned anteriorly; the convolutions of the cerebral cortex are visible through the arachnoid mater. E. The internal aspect of the calvaria reveals pits (dotted lines, granular foveolae) in the frontal and parietal bones, which are produced by enlarged arachnoid granulations or clusters of smaller ones (as in D). Multiple small emissary veins pass between the superior sagittal sinus and the veins in the diploë and scalp through small emissary foramina (arrows) located on each side of the sagittal suture. The sinuous vascular groove (M) on the lateral wall is formed by the frontal branch of the middle meningeal artery. The falx cerebri attaches anteriorly to the frontal crest (FC).

- protect the brain.

- form the supporting framework for arteries, veins, and venous sinuses.

- enclose a fluid-filled cavity, the subarachnoid space, which is vital to the

normal function of the brain.

Source :  Clinically Oriented Anatomy by Keith L. Moore, Arthur F. Dalley, Anne M. R. Agur