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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.
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 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.
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]
Although the pia mater adheres to the surface of the brain, closely following the contours of its gyri and sulci, the arachnoid mater only covers its superficial surface, bridging across the gyri. This leaves wider spaces between the pia and arachnoid and the cavities are known as the subarachnoid cisterns. [citation needed]
The brain and spinal cord are covered by the meninges, the three protective membranes of the tough dura mater, the arachnoid mater and the pia mater. The cerebrospinal fluid (CSF) within the skull and spine provides further protection and also buoyancy, and is found in the subarachnoid space between the pia mater and the arachnoid mater.
Leptomeningeal collaterals lie within the leptomeninges, the two deep layers of the meninges called the pia mater and the arachnoid mater. [4] Their diameter has been measured at approximately 300 micrometers, [ 5 ] but there is variability between individuals in the size, quantity and location of these vessels, and between either hemisphere ...
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.