The protective membranes from outermost to innermost are which of the following sequences?

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Multiple Choice

The protective membranes from outermost to innermost are which of the following sequences?

The concept being tested is the order of the protective brain membranes. The outermost layer is the dura mater, a tough protective sheath. Beneath it lies the arachnoid mater, a lighter, web-like layer. The innermost layer is the pia mater, a delicate membrane closely adherent to the brain and spinal cord surfaces. This arrangement creates the subdural space between the dura and arachnoid, and the subarachnoid space between the arachnoid and pia, which houses cerebrospinal fluid and vessels. Other sequences place the pia mater outside or swap the middle layer, which contradicts how the membranes envelop the CNS (pia adheres to the brain, arachnoid sits between dura and pia). So the correct order from outermost to innermost is dura mater, arachnoid mater, then pia mater.

The concept being tested is the order of the protective brain membranes. The outermost layer is the dura mater, a tough protective sheath. Beneath it lies the arachnoid mater, a lighter, web-like layer. The innermost layer is the pia mater, a delicate membrane closely adherent to the brain and spinal cord surfaces. This arrangement creates the subdural space between the dura and arachnoid, and the subarachnoid space between the arachnoid and pia, which houses cerebrospinal fluid and vessels.

Other sequences place the pia mater outside or swap the middle layer, which contradicts how the membranes envelop the CNS (pia adheres to the brain, arachnoid sits between dura and pia). So the correct order from outermost to innermost is dura mater, arachnoid mater, then pia mater.

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