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n. The innermost layers of the meninges; the pia mater and the arachnoid

In anatomy, the pia mater and arachnoid.

n. the two innermost layers of the meninges; cerebrospinal fluid circulates between these innermost layers

"Cerebral amyloid angiopathy (CAA) refers to the deposition of b - amyloid in the media and adventitia of small - and mid-sized arteries (and less frequently, veins) of the cerebral cortex and the leptomeninges."

meninges    meninx   

leptomeningeal