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|Diagrammatic representation of a section across the top of the skull, showing the membranes of the brain, etc. ("Subarachnoid cavity" visible at left.)|
|Latin||Spatium subarachnoideum, |
|Gray's||subject #193 876|
|Diagrammatic transverse section of the medulla spinalis and its membranes. (Subarachnoid cavity colored blue.)|
It is occupied by spongy tissue consisting of trabeculae (delicate connective tissue filaments that extend from the arachnoid mater and blend into the pia mater) and intercommunicating channels in which the cerebrospinal fluid is contained.
This cavity is small on the surface of the hemispheres of the brain. On the summit of each gyrus the pia mater and the arachnoid are in close contact, but in the sulci between the gyri, triangular spaces are left, in which the subarachnoid trabecular tissue is found. Whilst the pia mater closely follows the surface of the brain and dips into the sulci, the arachnoid bridges across them from gyrus to gyrus.
At certain parts of the base of the brain, the arachnoid is separated from the pia mater by wide intervals, which communicate freely with each other and are named subarachnoid cisternæ; in these the subarachnoid tissue is less abundant. The subarachnoid space is the location of the interface between the vascular tissue and the cerebrospinal fluid and is active in the blood brain barrier.
The arachnoid mater continues down the spinal cord too, and the subarachnoid layer with it. It serves a similar function in the spinal cord as it does in the brain.
This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.
|Meninges of the brain and medulla spinalis|
Dura mater - Falx cerebri - Tentorium cerebelli - Falx cerebelli - Arachnoid mater - Subarachnoid space - Cistern - Cisterna magna - Median aperture - Cerebrospinal fluid - Arachnoid granulation - Pia mater