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{{BioPsy}}
  
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{{Infobox Anatomy |
  
{{Infobox Anatomy |
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Name = Meninges |
 
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Caption = Meninges of the CNS |
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Caption = The meninges: dura mater, arachnoid and pia mater |
 
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The '''meninges''' (singular '''meninx''') is the system of [[Mesothelium|membrane]]s which envelops the [[central nervous system]]. The meninges consist of three layers: the [[dura mater]], the [[arachnoid mater]], and the [[pia mater]]. The primary function of the meninges and of the [[cerebrospinal fluid]] is to protect the [[central nervous system]].
 +
The '''meninges''' is the system of [[Mesothelium|membrane]]s which envelops the [[central nervous system]]. In mammals, the meninges consist of three layers: the [[dura mater]], the [[arachnoid mater]], and the [[pia mater]]. The primary function of the meninges and of the [[cerebrospinal fluid]] is to protect the [[central nervous system]].
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  +
'''Meninges''' ({{IPAc-en|m|ə|ˈ|n|ɪ|n|dʒ|iː|z}}<ref>''[[OED]]'' 2nd edition, 1989.</ref><ref>[http://www.merriam-webster.com/dictionary/meninges Entry "meninges"] in ''[http://www.merriam-webster.com/ Merriam-Webster Online Dictionary]'', retrieved 2012-07-28.</ref>) is the plural of '''meninx''' ({{IPAc-en|ˈ|m|iː|n|ɪ|ŋ|k|s}} or {{IPAc-en|ˈ|m|ɛ|n|ɪ|ŋ|k|s}}<ref>[http://www.merriam-webster.com/dictionary/meninx Entry "meninx"] in ''[http://www.merriam-webster.com/ Merriam-Webster Online Dictionary]'', retrieved 2012-07-28.</ref>), from {{lang-grc|μῆνιγξ|mēninx|membrane}}.<ref>[http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dmh%3Dnigc μήνιγξ], Henry George Liddell, Robert Scott, ''A Greek-English Lexicon'', on Perseus.</ref> The adjective form is '''meningeal''' ({{IPAc-en|m|ɪ|ˈ|n|ɪ|n|dʒ|əl}}).
   
 
==Anatomy==
  
==Anatomy==
   
−
===Pia mater===
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===Dura mater===
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The pia or '''[[pia mater]]''' is a very delicate membrane. It is attached to (nearest) the [[brain]] or the [[spinal cord]]. As such it follows all the minor contours of the [[brain]] ([[gyrus|gyri]] and [[sulcus (anatomy)|sulci]]). The pia mater is the meningeal envelope which firmly adheres to the surface of the brain and spinal cord. It is a very thin membrane composed of fibrous tissue covered on its outer surface by a sheet of flat cells thought to be impermeable to fluid. The pia mater is pierced by blood vessels which travel to the brain and spinal cord, and its [[capillaries]] are responsible for nourishing the brain.
 +
The '''[[dura mater]]''' [Latin: 'tough mother'] (also rarely called ''meninx fibrosa'' or ''pachymeninx'') is a thick, durable membrane, closest to the [[Human skull|skull]]. It consists of two layers, the periosteal layer which lies closest to the [[Calvaria (skull)|calvaria]] (skull), and the inner meningeal layer which lies closer to the [[brain]]. It contains larger blood vessels which split into the capillaries in the [[pia mater]]. It is composed of dense fibrous tissue, and its inner surface is covered by flattened cells like those present on the surfaces of the pia mater and arachnoid. The dura mater is a sac which envelops the arachnoid and has been modified to serve several functions. The dura mater surrounds and supports the large venous channels (dural sinuses) carrying blood from the brain toward the heart.
   
  +
The dura has four areas of infolding which include :
⚫
===Arachnoid mater===
  
  +
* '''Falx cerebri''', the largest, sickle-shaped; separates the [[cerebral hemisphere]]s. Starts from the frontal crest of [[frontal bone]] and the [[crista galli]] running to the [[internal occipital protuberance]].
⚫
The middle element of the meninges is the '''[[arachnoid mater]]''', so named because of its [[spider web]]-like appearance. It provides a cushioning effect for the [[central nervous system]]. The [[arachnoid mater]] exists as a thin, transparent membrane. It is composed of fibrous tissue and, like the pia mater, is covered by flat cells also thought to be impermeable to fluid. The arachnoid does not follow the convolutions of the surface of the brain and so looks like a loosely fitting sac. In the region of the brain, particularly, a large number of fine filaments called arachnoid trabeculae pass from the arachnoid through the subarachnoid space to blend with the tissue of the pia mater.
  
  +
* '''Tentorium cerebelli''', the second largest, crescent-shaped; separates the [[occipital lobe]]s from [[cerebellum]]. The falx cerebri attaches to it giving a tentlike appearance.
  +
* '''Falx cerebelli''', vertical infolding; lies inferior to the tentorium cerebelli, separating the [[cerebellar hemisphere]]s.
  +
* '''Diaphragma sellae''', smallest infolding; covers the [[pituitary gland]] and [[sella turcica]].
   
  ⚫
===Arachnoid mater===
  ⚫
The middle element of the meninges is the '''[[arachnoid mater]]''', so named because of its [[spider web]]-like appearance. It provides a cushioning effect for the [[central nervous system]]. The [[arachnoid mater]] is a thin, transparent membrane. It is composed of fibrous tissue and, like the pia mater, is covered by flat cells also thought to be impermeable to fluid. The arachnoid does not follow the convolutions of the surface of the brain and so looks like a loosely fitting sac. In the region of the brain, particularly, a large number of fine filaments called arachnoid trabeculae pass from the arachnoid through the subarachnoid space to blend with the tissue of the pia mater.
  +
 
The [[arachnoid (brain)|arachnoid]] and [[pia mater]] are sometimes together called the ''leptomeninges''.
  
The [[arachnoid (brain)|arachnoid]] and [[pia mater]] are sometimes together called the ''leptomeninges''.
   
−
===Dura mater===
 +
===Pia mater===
−
The '''[[dura mater]]''' (also rarely called meninx fibrosa, or pachymeninx) is a thick, durable membrane, closest to the [[skull]]. It consists of two layers, the periosteal layer, closest to the calvaria and the inner meningeal layer. It contains larger blood vessels which split into the capilliaries in the pia mater. It is composed of dense fibrous tissue, and its inner surface is covered by flattened cells like those present on the surfaces of the pia mater and arachnoid. The dura mater is a sac which envelops the arachnoid and has been modified to serve several functions. The dura mater surrounds and supports the large venous channels (dural sinuses) carrying blood from the brain toward the heart.
 +
The '''[[pia mater]]''' [Latin: 'soft mother'] is a very delicate membrane. It is the meningeal envelope which firmly adheres to the surface of the [[brain]] and [[spinal cord]], following the brain's minor contours ([[gyrus|gyri]] and [[sulcus (neuroanatomy)|sulci]]). It is a very thin membrane composed of fibrous tissue covered on its outer surface by a sheet of flat cells thought to be impermeable to fluid. The pia mater is pierced by blood vessels which travel to the brain and spinal cord, and its [[capillaries]] are responsible for nourishing the brain.
   
 
===Spaces===
  
===Spaces===
 
The [[subarachnoid space]] is the space which normally exists between the [[arachnoid (brain)|arachnoid]] and the [[pia mater]], which is filled with [[cerebrospinal fluid]].
  
The [[subarachnoid space]] is the space which normally exists between the [[arachnoid (brain)|arachnoid]] and the [[pia mater]], which is filled with [[cerebrospinal fluid]].
   
−
Normally, the [[dura mater]] is attached to the [[skull]], or to the bones of the vertebral canal in the [[spinal cord]]. The [[arachnoid (brain)|arachnoid]] is attached to the [[dura mater]], and the [[pia mater]] is attached to the central nervous system tissue. When the [[dura mater]] and the [[arachnoid (brain)|arachnoid]] separate through injury or illness, the space between them is the [[subdural space]].
+
Normally, the [[dura mater]] is attached to the [[Human skull|skull]], or to the bones of the vertebral canal in the [[spinal cord]]. The [[arachnoid (brain)|arachnoid]] is attached to the [[dura mater]], while the [[pia mater]] is attached to the central nervous system tissue. When the [[dura mater]] and the [[arachnoid (brain)|arachnoid]] separate through injury or illness, the space between them is the [[subdural space]].
   
 
==Pathology==
  
==Pathology==
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There are three types of [[hemorrhage]] involving the meninges:<ref>Orlando Regional Healthcare, Education and Development. 2004. [http://www.orlandoregional.org/pdf%20folder/overview%20adult%20brain%20injury.pdf "Overview of Adult Traumatic Brain Injuries."] Retrieved on [[January 16]], [[2008]].</ref>
 +
There are three types of [[hemorrhage]] involving the meninges:<ref>Orlando Regional Healthcare, Education and Development. 2004. [http://www.orlandoregional.org/pdf%20folder/overview%20adult%20brain%20injury.pdf "Overview of Adult Traumatic Brain Injuries."] Retrieved on January 16, 2008.</ref>
 
* A [[subarachnoid hemorrhage]] is acute bleeding under the arachnoid; it may occur spontaneously or as a result of trauma.
  
* A [[subarachnoid hemorrhage]] is acute bleeding under the arachnoid; it may occur spontaneously or as a result of trauma.
 
* A [[subdural hematoma]] is a [[hematoma]] (collection of blood) located in a separation of the [[arachnoid (brain)|arachnoid]] from the [[dura mater]]. The small veins which connect the [[dura mater]] and the [[arachnoid (brain)|arachnoid]] are torn, usually during an accident, and blood can leak into this area.
  
* A [[subdural hematoma]] is a [[hematoma]] (collection of blood) located in a separation of the [[arachnoid (brain)|arachnoid]] from the [[dura mater]]. The small veins which connect the [[dura mater]] and the [[arachnoid (brain)|arachnoid]] are torn, usually during an accident, and blood can leak into this area.
 
* An [[epidural hematoma]] similarly may arise after an accident or spontaneously.
  
* An [[epidural hematoma]] similarly may arise after an accident or spontaneously.
   
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Other medical conditions which affect the meninges include [[meningitis]] (usually from [[fungal]], [[bacterial]], or [[virus|viral]] [[infection]]) and [[meningioma]]s arising from the meninges or from [[tumor]]s formed elsewhere in the body which [[metastasis|metastasize]] to the meninges.
 +
Other medical conditions which affect the meninges include [[meningitis]] (usually from [[fungal]], [[bacterial]], or [[virus|viral]] [[infection]]) and [[meningioma]]s arising from the meninges or from [[Meningeal carcinomatosis|meningeal carcinomatoses]] ([[tumor]]s) formed elsewhere in the body which [[metastasis|metastasize]] to the meninges.
  +
  +
==In other animals==
  +
  +
In [[fishes]], the meninges is a single membrane (the primitive meninx). In [[amphibians]], [[reptiles]] and [[birds]], the meninges include a thick outer [[dura mater]] and a thick inner [[secondary meninx]]. [[Mammals]] retain the dura mater, and the secondary meninx divides into the [[arachnoid mater|arachnoid]] and [[pia mater]].<ref>Kardong, Kenneth V. (1995). Vertebrates: Comparative Anatomy, Function, Evolution. Dubuque, Iowa: Wm. C. Brown Publishers. pp. 539. ISBN 0069219917</ref>
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==See also==
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*[[Membranes]]
   
 
==Additional images==
  
==Additional images==
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Image:Gray1196.png|Diagrammatic section of scalp.
  
Image:Gray1196.png|Diagrammatic section of scalp.
 
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<references/>
  
<references/>
   
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{{Commons category|Meninges}}
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{{Nervous system}}
 
{{Meninges}}
  
{{Meninges}}
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[[Category:Back anatomy]]
  
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[[category:Head and neck]]
  
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[[category:Central nervous system]]
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[[Category:Central nervous system]]
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[[Category:Human head and neck]]
 
[[Category:Membranes]]
  
[[Category:Membranes]]
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[[Category:Meninges| ]]
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[[io:Meningo]]
 
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[[th:เยื่อหุ้มสมอง]]
  
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{{enWP|Meninges}}

Latest revision as of 10:52, 16 October 2012

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Meninges
File:Meninges-en.svg
The meninges: dura mater, arachnoid and pia mater
Latin '
Gray's subject #193 872
System
MeSH A08.186.566
[[Image:|190px|center|]]

The meninges is the system of membranes which envelops the central nervous system. In mammals, the meninges consist of three layers: the dura mater, the arachnoid mater, and the pia mater. The primary function of the meninges and of the cerebrospinal fluid is to protect the central nervous system.

Meninges (/məˈnɪndʒiːz/[1][2]) is the plural of meninx (/ˈmiːnɪŋks/ or /ˈmɛnɪŋks/[3]), from Ancient Greek: μῆνιγξ .[4] The adjective form is meningeal (/mɪˈnɪndʒəl/).

Anatomy

Dura mater

The dura mater [Latin: 'tough mother'] (also rarely called meninx fibrosa or pachymeninx) is a thick, durable membrane, closest to the skull. It consists of two layers, the periosteal layer which lies closest to the calvaria (skull), and the inner meningeal layer which lies closer to the brain. It contains larger blood vessels which split into the capillaries in the pia mater. It is composed of dense fibrous tissue, and its inner surface is covered by flattened cells like those present on the surfaces of the pia mater and arachnoid. The dura mater is a sac which envelops the arachnoid and has been modified to serve several functions. The dura mater surrounds and supports the large venous channels (dural sinuses) carrying blood from the brain toward the heart.

The dura has four areas of infolding which include :

  • Falx cerebri, the largest, sickle-shaped; separates the cerebral hemispheres. Starts from the frontal crest of frontal bone and the crista galli running to the internal occipital protuberance.
  • Tentorium cerebelli, the second largest, crescent-shaped; separates the occipital lobes from cerebellum. The falx cerebri attaches to it giving a tentlike appearance.
  • Falx cerebelli, vertical infolding; lies inferior to the tentorium cerebelli, separating the cerebellar hemispheres.
  • Diaphragma sellae, smallest infolding; covers the pituitary gland and sella turcica.

Arachnoid mater

The middle element of the meninges is the arachnoid mater, so named because of its spider web-like appearance. It provides a cushioning effect for the central nervous system. The arachnoid mater is a thin, transparent membrane. It is composed of fibrous tissue and, like the pia mater, is covered by flat cells also thought to be impermeable to fluid. The arachnoid does not follow the convolutions of the surface of the brain and so looks like a loosely fitting sac. In the region of the brain, particularly, a large number of fine filaments called arachnoid trabeculae pass from the arachnoid through the subarachnoid space to blend with the tissue of the pia mater.

The arachnoid and pia mater are sometimes together called the leptomeninges.

Pia mater

The pia mater [Latin: 'soft mother'] is a very delicate membrane. It is the meningeal envelope which firmly adheres to the surface of the brain and spinal cord, following the brain's minor contours (gyri and sulci). It is a very thin membrane composed of fibrous tissue covered on its outer surface by a sheet of flat cells thought to be impermeable to fluid. The pia mater is pierced by blood vessels which travel to the brain and spinal cord, and its capillaries are responsible for nourishing the brain.

Spaces

The subarachnoid space is the space which normally exists between the arachnoid and the pia mater, which is filled with cerebrospinal fluid.

Normally, the dura mater is attached to the skull, or to the bones of the vertebral canal in the spinal cord. The arachnoid is attached to the dura mater, while the pia mater is attached to the central nervous system tissue. When the dura mater and the arachnoid separate through injury or illness, the space between them is the subdural space.

Pathology

There are three types of hemorrhage involving the meninges:[5]

Other medical conditions which affect the meninges include meningitis (usually from fungal, bacterial, or viral infection) and meningiomas arising from the meninges or from meningeal carcinomatoses (tumors) formed elsewhere in the body which metastasize to the meninges.

In other animals

In fishes, the meninges is a single membrane (the primitive meninx). In amphibians, reptiles and birds, the meninges include a thick outer dura mater and a thick inner secondary meninx. Mammals retain the dura mater, and the secondary meninx divides into the arachnoid and pia mater.[6]

See also

Additional images

References

  1. ↑ OED 2nd edition, 1989.
  2. ↑ Entry "meninges" in Merriam-Webster Online Dictionary, retrieved 2012-07-28.
  3. ↑ Entry "meninx" in Merriam-Webster Online Dictionary, retrieved 2012-07-28.
  4. ↑ μήνιγξ, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus.
  5. ↑ Orlando Regional Healthcare, Education and Development. 2004. "Overview of Adult Traumatic Brain Injuries." Retrieved on January 16, 2008.
  6. ↑ Kardong, Kenneth V. (1995). Vertebrates: Comparative Anatomy, Function, Evolution. Dubuque, Iowa: Wm. C. Brown Publishers. pp. 539. ISBN 0069219917
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[[Commons: Category:Meninges

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Nervous system

Brain - Spinal cord - Central nervous system - Peripheral nervous system - Somatic nervous system - Autonomic nervous system - Sympathetic nervous system - Parasympathetic nervous system


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


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