The middle layer of the three meninges surrounding the brain and spinal cord, characterized by its web-like appearance with delicate, fibrous strands. It lies between the dura mater and pia mater, creating the subarachnoid space where cerebrospinal fluid circulates.
From Greek 'arachne' meaning 'spider' and 'eidos' meaning 'resembling.' Named for its spider web-like appearance with thin, delicate fibers spanning between the outer and inner meningeal layers.
The arachnoid layer is where most of our cerebrospinal fluid lives and flows - it's like a liquid cushion system that lets your brain 'float' and protects it from impact! Subarachnoid hemorrhages, often from ruptured aneurysms, occur in this space and are medical emergencies.
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