Arachnoid mater

Brain: Arachnoid mater
Coronal view of the brain showing the Arachnoid mater and neighboring anatomical structures.
Gray's	subject #193 876
Part of	Meninges
NeuroNames	ancil-561
MeSH	Arachnoid

The arachnoid mater, is one of the three meninges, the protective membranes that cover the brain and spinal cord. It is named after the Greek words "Arachne" and suffix "-oid" -"in the image of", and "mater" the Latin word for mother, because of the fine spider web-like appearance of the delicate fibres of the arachnoid which extend down through the subarachnoid space and attach to the pia mater.

It is interposed between the two other meninges, the more superficial dura mater and the deeper pia mater, from which it is separated by the subarachnoid space. The delicate arachnoid layer is attached to the inside of the dura and surrounds the brain and spinal cord. It does not line the brain down into its sulci (folds), as does the pia mater, with the exception of the longitudinal fissure, which divides the left and right cerebral hemispheres. Cerebrospinal fluid flows under this membrane in the subarachnoid space.

The pia mater covering the brain is referred to as the "arachnoidea encephal", and the portion covering the spinal cord as the "arachnoidea spinalis". The arachnoid and pia mater are sometimes considered as a single structure, the leptomeninx, or the plural version, leptomeninges. ("Lepto"- from the Greek root meaning "thin"). Similarly, the dura in this situation is called the pachymeninx.

Additional images

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  Meninges of the CNS

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  Diagrammatic section of scalp.

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  The medulla spinalis and its membranes.

References

• Orlando Regional Healthcare, Education and Development. 2004. "Overview of Adult Traumatic Brain Injuries." Retrieved on 2008-01-16.

External links

• SUNY Figs 02:05-09
• Slide

See also

• Arachnoid cyst
• Leptomeningeal collateral circulation