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The arachnoid mater makes arachnoid villi, small protrusions through the dura mater into the venous sinuses of the brain, which allow CSF to exit the subarachnoid space and enter the blood stream. Unlike the dura mater, which receives a rich vascular supply from numerous arteries, the arachnoid mater is avascular (lacking blood vessels).
The middle element of the meninges is the arachnoid mater, or arachnoid membrane, so named because of its resemblance to a spider web. It cushions the central nervous system. This thin, transparent membrane is composed of fibrous tissue and, like the pia mater, has an outer layer of tightly packed flat cells, forming the arachnoid barrier. [8]
Arachnoid (astrogeology), a geological structure found only on the planet Venus; Arachnoid (botany), referring to organs with a cobwebby exterior appearance; Arachnoid granulation, small protrusions of the arachnoid mater; Arachnoid mater, a layer of the meninges, membranes that contain the central nervous system
Arachnoiditis is an inflammatory condition of the arachnoid mater or 'arachnoid', one of the membranes known as meninges that surround and protect the central nervous system. The outermost layer of the meninges is the dura mater (Latin for hard) and adheres to inner surface of the skull and vertebrae. [ 1 ]
The outermost membrane, the dura mater, is a thick durable membrane, which is attached to both the arachnoid membrane and the skull. In bacterial meningitis, bacteria reach the meninges by one of two main routes: through the bloodstream (hematogenous spread) or through direct contact between the meninges and either the nasal cavity or the skin.
The arachnoid membrane and the dura mater exist in flush contact with one another in the living person's spine due to fluid pressure from CSF in the subarachnoid space pushing the arachnoid membrane out towards the dura. Therefore, once the needle has pierced the dura mater it has also traversed the thinner arachnoid membrane.
Arachnoid granulations (also arachnoid villi, and pacchionian granulations or bodies) are small outpouchings of the arachnoid mater and subarachnoid space into the dural venous sinuses of the brain. The granulations are thought to mediate the draining of cerebrospinal fluid (CSF) from the subarachnoid space into the venous system .
The walls of the dural venous sinuses are composed of dura mater lined with endothelium, a specialized layer of flattened cells found in blood and lymph vessels.They differ from other blood vessels in that they lack a full set of vessel layers (e.g. tunica media) characteristic of arteries and veins.