関: arachnoid、arachnoidal

WordNet

a thin pliable sheet of material
a pliable sheet of tissue that covers or lines or connects the organs or cells of animals or plants (同)tissue layer
relating to or resembling a member of the class Arachnida (同)arachnidian, spidery, spiderlike, spiderly
the middle of the 3 meninges (同)arachnoid_membrane

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(生物の)膜,皮膜

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/05/25 18:30:41」(JST)

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The arachnoid mater is one of the three meninges, the protective membranes that cover the brain and spinal cord.

Structure

It is interposed between the two other meninges, the more superficial and much thicker 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 (CSF) flows under the arachnoid in the subarachnoid space. The arachnoid mater makes arachnoid villi, small protrusions through the dura mater into the venous sinuses of the brain, which allow CSF to exit the subarachnoid space and enter the blood stream.

The arachnoid mater and dura mater are very close together throughout the cranium all the way to S2, where the two layers fuse into one layer and terminate. Sandwiched between the dura and arachnoid maters lie some veins that connect the brain's venous system with the venous system in the dura mater.^[1]

The arachnoid mater covering the brain is referred to as the "arachnoidea encephali," 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.

There are two subdivisions of arachnoid mater surrounding the subarachnoid space, the dorsal layer and the ventral layer. The dorsal layer covers internal cerebral veins and fixes them to the surrounding tela choroidea. The ventral layer of arachnoid membrane, on the other hand, is a direct anterior extension of this arachnoid envelope that the dorsal layer forms over the pineal region.^[2]

Function

CSF circulates in the subarachnoid space (between arachnoid and pia mater). Cerebrospinal fluid is produced by the choroid plexus (inside the ventricles of the brain, which are in direct communication with the subarachnoid space so the CSF can flow freely through the nervous system). Cerebrospinal fluid is a transparent, colourless fluid and it is produced at about 500 ml/day. Its electrolyte levels, glucose levels, and pH are very similar to those in plasma, but the presence of blood in cerebrospinal fluid is always abnormal.^[3]

History

The arachnoid mater is named after the Greek words "Arachne" ("spider") 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.

Additional images

Meninges
Diagrammatic section of scalp.
The arachnoid mater lies under the dura mater, and arteries and veins run on top of it.
Spinal dura mater opened, arachnoid mater visible.
The medulla spinalis and its membranes.
Spinal cord. Spinal membranes and nerve roots.Deep dissection. Posterior view.
Meninges and superficial cerebral veins.Deep dissection.Superior view.
Meninges and superficial cerebral veins.Deep dissection.Superior view.

References

^ ¨Microscopic Morphology and Histology of the Human Meninges¨. Mar2005. p22-34.
^ "Overview of Adult Traumatic Brain Injuries." Retrieved on 2008-01-16. The Distribution of arachnoid membrane within the velum interpositum". Acta neurochirurgica Sept2012Vol 154 Issue 9, page 1711-1715. Authors: Zhang, Xi-an; Qi, Songtao; Fan, Jun; Huang, Guanglong; Peng, Junxiang; Xu, Jiaming.
^ "The intracranial arachnoid mater". Child's Nervous system; Jan2013, Vol29, Issue 1, p17-33, 17p. Authors: Adeeb, Nimer; Deep, Aman; Griessernauer, Christoph; Mortazavi, Martin; Watanabe, Koichi; Loukas, Marios; Tubbs, R.; Cohen, Aaron.

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

External links

Anatomy figure: 02:05-09 at Human Anatomy Online, SUNY Downstate Medical Center
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English Journal

Meningeal-like organization of neural tissues in calanoid copepods (Crustacea).

Mercier F, Weatherby TM, Hartline DK.SourceBékésy Laboratory of Neurobiology, Biological Electron Microscope Facility, Pacific Biosciences Research Center, University of Hawai'i at Manoa, Honolulu, Hawai'i 96822. fmercier@pbrc.hawaii.edu.
The Journal of comparative neurology.J Comp Neurol.2013 Mar 1;521(4):760-90. doi: 10.1002/cne.23173.
Meninges, the connective tissue of the vertebrate central nervous system (CNS), have not been recognized in invertebrates. We describe the ultrastructure of the adult brain, antennules, and cord in five marine copepods: Calanus finmarchicus, Gaussia princeps, Bestiolina similis, Labidocera madurae,
PMID 22740424

Novel therapeutic use of polysaccharide nanosheets for arachnoid plasty and enhancement of venous tensile strength in rat microneurosurgery.

Otani N, Kinoshita M, Fujie T, Saito A, Takeoka S, Saitoh D, Hagisawa K, Nawashiro H, Shima K.SourceDepartment of Neurosurgery, National Defense Medical College, Tokorozawa, Saitama, Japan.
Journal of clinical neuroscience : official journal of the Neurosurgical Society of Australasia.J Clin Neurosci.2013 Feb;20(2):301-5. doi: 10.1016/j.jocn.2012.05.028. Epub 2012 Dec 7.
Subdural effusion sometimes occurs during neurosurgery after opening the Sylvian fissure, due to cerebrospinal fluid (CSF) leakage from the torn arachnoid membrane. Unexpected bleeding from the fragile bridging veins may also result from brain retraction. Neurosurgeons must always watch carefully fo
PMID 23219826

Drug Transporters on Arachnoid Barrier Cells Contribute to the Blood-cerebrospinal Fluid Barrier.

Yasuda K, Cline CB, Vogel P, Onciu M, Fatima S, Sorrentino BP, Thirumaran RK, Ekins S, Urade Y, Fujimori K, Schuetz EG.Source1 St Jude Children's Research Hospital;
Drug metabolism and disposition: the biological fate of chemicals.Drug Metab Dispos.2013 Jan 8. [Epub ahead of print]
The subarachnoid space, where CSF flows over the brain and spinal cord, is lined on one side by arachnoid barrier (AB) cells that form part of the blood-cerebrospinal fluid (CSF) barrier. However, despite the fact that drugs are administered into the CSF, and CSF drug concentrations are used as a s
PMID 23298861

Japanese Journal

Modified Three-Dimensional Brain Model for Study of the Trans-sylvian Approach

HARADA Naoyuki,KONDO Kosuke,MIYAZAKI Chikao,NOMOTO Jun,KITAJIMA Satoru,NEMOTO Masaaki,UEKUSA Hiroyuki,HARADA Masashi,SUGO Nobuo
Neurologia medico-chirurgica = 神経外科 51(8), 567-571, 2011-08-15
NAID 10029338220

Subacute Subdural Hygroma and Presyrinx Formation After Foramen Magnum Decompression With Duraplasty for Chiari Type 1 Malformation : Case Report

SUZUKI Fumio,KITAGAWA Tadashi,TAKAGI Kenji,NOZAKI Kazuhiko
Neurologia medico-chirurgica = 神経外科 51(5), 389-393, 2011-05-15
… Reoperation with wide opening of the arachnoid membrane lead to a rapid resolution of the hydrocephalus and the presyrinx. … The present case shows that wide opening of the arachnoid membrane is an effective therapeutic option. …
NAID 10029138056

Related Pictures

★リンクテーブル★

リンク元	「くも膜」「arachnoidal」
関連記事	「membrane」

「くも膜」

Arachnoid mater
	Coronal view of the brain showing the Arachnoid mater and neighboring anatomical structures.
Details
Part of	Meninges
Identifiers
Gray's	p.876
MeSH	A08.186.566.166
NeuroNames	ancil-561
Dorlands; /Elsevier	a_56/12149123
TA	A14.1.01.201
FMA	9591
	Anatomical terms of neuroanatomy