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Brain - Wikipedia, the free encyclopedia |
 | | This three-layered covering is made of, from the outside in, dura mater, arachnoid mater, and pia mater. |
| | The arachnoid and pia are physically connected and thus often considered as a single layer, the pia-arachnoid. |
| | Below the arachnoid is the subarachnoid space which contains cerebrospinal fluid, a substance that protects the nervous system. |
| en.wikipedia.org /wiki/Brain (3678 words) |
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