Dura mater

Recommended video: Meninges of the brain [11:40]

Meninges and superficial vessels of the brain.

The meninges are three layers of connective tissue that surround, support and protect the central nervous system (brain and spinal cord). From superficial to deep these layers are named the dura, arachnoid and pia. The dura mater is a thick, tough, fibrous membrane. It receives blood and nerve supply from the meningeal arteries, veins and nerves.

In the cranium, the dura consists of two layers; an outer periosteal dura and an inner meningeal dura. The periosteal dura is closely attached to the internal surface of the skull bones while the inner meningeal dura is continuous with the dura of the spinal cord. The periosteal dura and meningeal dura are tightly fused together, except in a few places where they separate to form the dural venous sinuses; spaces that collect venous blood from the large veins of the brain. The dural venous sinuses are named as follows; superior sagittal sinus, inferior sagittal sinus, straight sinus, occipital sinus, transverse sinus, sigmoid sinus, marginal sinus, superior petrosal sinus, inferior petrosal sinus, petrosquamous sinus, cavernous sinus, sphenoparietal sinus, intercavernous sinus. The straight, occipital, transverse and superior sagittal sinuses all meet at the confluence of the sinuses. Arachnoid granulations, small tufts of arachnoid, protrude through the dura mater into the dural venous sinuses. They are the site of cerebrospinal fluid absorption into dural venous sinuses. Another feature of  cranial dura are the dural folds. These are reflections of the inner meningeal dura which divide the cranium into separate compartments. The four dural folds are the falx cerebri, tentorium cerebelli, falx cerebelli, diaphragma sellae, in brief they separate the cerebral and cerebellar hemispheres into divisions.

In the spinal cord, only one layer of dura mater is found. Unlike in the cranium, the dura is not closely integrated with the overlying bones. Instead, a space exists between the dura and the vertebral bones known as the epidural space. The inferior aspect of the spinal dural sac is anchored to the coccyx by a thin connective tissue strand called the filum terminale.