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The arachnoid mater (or simply arachnoid) is one of the three meninges, the protective membranes that cover the brain and spinal cord. It is so named because of its resemblance to a spider web . The arachnoid mater is a derivative of the neural crest mesoectoderm in the embryo.
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 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 dura covers the arachnoid mater and the pia mater the other two meninges in protecting the central nervous system. At major boundaries of brain regions such as the longitudinal fissure between the hemispheres , and the tentorium cerebelli between the posterior brain and the cerebellum the dura separates, folds and invaginates to make the ...
The membrane in this area is much thicker than the cranial pia mater, due to the two-layer composition of the pia membrane. The outer layer, which is made up of mostly connective tissue, is responsible for this thickness. Between the two layers are spaces which exchange information with the subarachnoid cavity as well as blood vessels.
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 ]
In the skull, the periosteal layer of the dura mater adheres to the inner surface of the skull bones while the meningeal layer lays over the arachnoid mater. Between them is the epidural space . The two layers of the dura mater separate at several places, with the meningeal layer projecting deeper into the brain parenchyma forming fibrous septa ...
The bases of denticulate ligaments arise in the pia mater and are firmly attached to the arachnoid mater and dura mater at the apex. [2] The denticulate ligaments extend across the subarachnoid space between anterior nerve roots and posterior nerve roots, piercing the intervening spinal arachnoid mater to reach the dura.