Meninges

Source: Wikipedia, the free encyclopedia.
"Meninx" redirects here. For the Tunisian island formerly known as "Meninx", see Djerba.
Meninges
nervus spinosus
Identifiers
Latinmeninges
MeSHD008578
TA98A14.1.01.001
TA25369
FMA231572
Anatomical terminology]

In

Ancient Greek μῆνιγξ (mēninx) 'membrane'[4]) are the three membranes that envelop the brain and spinal cord. In mammals, the meninges are the dura mater, the arachnoid mater, and the pia mater. Cerebrospinal fluid is located in the subarachnoid space between the arachnoid mater and the pia mater. The primary function of the meninges is to protect the central nervous system.[5]

Structure

Dura mater

Main article: Dura mater

The dura mater (

dural sinuses
carrying blood from the brain toward the heart.

The dura has four areas of infolding:

Diagram of brain layers

Arachnoid mater

Main article: Arachnoid mater
Diagram of section of top of brain showing the meninges and subarachnoid space

The middle element of the meninges is the arachnoid mater, or arachnoid membrane, so named because of its resemblance to a spider web. It cushions the central nervous system. This thin, transparent membrane is composed of fibrous tissue and, like the pia mater, has an outer layer of tightly packed flat cells, forming the arachnoid barrier.[8]

The shape of the arachnoid does not follow the convolutions of the surface of the brain and so looks like a loosely fitting sac. In particular, in the region of the brain 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 barrier has no extracellular collagen and is considered to represent an effective morphological and physiological meningeal barrier between the cerebrospinal fluid in the subarachnoid space and the blood circulation in the dura.

The arachnoid barrier layer is characterized by a distinct continuous basal lamina on its inner surface toward the innermost collagenous portion of the arachnoid reticular layer.

Pia mater

Main article: Pia mater

The pia mater (Latin: tender mother)

capillaries
nourish the brain.

Subarachnoidal lymphatic-like membrane

This section is an excerpt from Subarachnoidal lymphatic-like membrane.[edit]

The subarachnoid lymphatic-like membrane (SLYM) is a recently described anatomical structure in the human brain that was proposed in 2023 as a possible fourth layer of the meninges.[10]

The SLYM is located in the
subarachnoid space, the space between the middle reticular meninges and the innermost tender meninges that lie close to the brain.[10] It divides the subarachnoid space into an outer, superficial compartment and an inner, deeper area surrounding the brain.[10]

Leptomeninges

The

meningococcal meningitis can lead to an exudate within the leptomeninges along the surface of the brain.[12] Because the arachnoid is connected to the pia by cob-web like strands, it is structurally continuous with the pia, hence the name pia-arachnoid or leptomeninges. They are responsible for the production of beta-trace protein (prostaglandin D2 synthase), a major cerebrospinal fluid protein.[13]

Subarachnoid space

Diagram of section of spinal cord showing the meninges and spaces. Subarachnoid space coloured blue

The subarachnoid space is the space that normally exists between the

arachnoid and the pia mater. It is filled with cerebrospinal fluid and continues down the spinal cord
. Spaces are formed from openings at different points along the subarachnoid space; these are the subarachnoid cisterns, which are filled with cerebrospinal fluid.

The dura mater is attached to the

skull, whereas in the spinal cord, the dura mater is separated from the vertebrae by a space called the epidural space, which contains fat and blood vessels. 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. There is a subpial space underneath the pia mater that separates it from the glia limitans
.

Clinical significance

Injuries involving the meninges, can result in a

hemorrhage and two types of hematoma.[14]

  • A subarachnoid hemorrhage is acute bleeding under the arachnoid; it may occur spontaneously or as a result of trauma.[15]
  • A
    arachnoid
    are torn, usually during an accident, and blood leaks into this area.
  • An epidural hematoma, bleeding between the dura mater and the skull, may arise after an accident or spontaneously.

Other medical conditions that affect the meninges include

tumors) that form elsewhere in the body and metastasize
to the meninges.

Other animals

In

ontogenetic stages, the latter divides into an internal leaflet: the secondary meninx, and into an external one: the dura mater. Finally, in higher vertebrates, even the secondary meninx divides into the arachnoid and the pia. In the same animals, Sterzi demonstrated that, while in the spinal medulla the dura keeps its identity, in the skull it fuses with the periosteum. He also demonstrated the continuity of all meninges with the envelopes of nerves and with the filum terminale
.

Mammals (as higher vertebrates) retain the dura mater, and the secondary meninx divides into the arachnoid and pia mater.[17]

Additional images

  • Illustration of the work by Antonio Pacchioni Disquisitio anatomicae de durae meningis ... published in Acta Eruditorum, 1703
    Illustration of the work by Antonio Pacchioni Disquisitio anatomicae de durae meningis ... published in Acta Eruditorum, 1703

See also

Notes

  1. ^ Also rarely called meninx fibrosa or pachymeninx

References

  1. ^ "meninges". Oxford Learner's Dictionaries.
  2. ^ "Definition of meninges". Merriam-Webster Online Dictionary. Retrieved 28 July 2012.
  3. ^ "Definition of meninx". Merriam-Webster Online Dictionary. Retrieved 28 July 2012.
  4. Perseus Project
  5. ^ Castillero Mimenza, Oscar (January 2017). "Meninges: anatomía, partes y funciones en el cerebro".
  6. ^ "Definition of dura mater". Merriam-Webster Online Dictionary. Retrieved 22 June 2022.
  7. ^ "Scalp Anatomy: Structure, Nerve Supply, Arterial Supply". 20 June 2017.
  8. S2CID 14753395
    .
  9. ^ "Definition of pia mater". Merriam-Webster Online Dictionary. Retrieved 27 November 2015.
  10. ^
    S2CID 255440992
    .
  11. ^ "leptomeninges". Oxford Dictionaries | English. Archived from the original on November 4, 2016.
  12. OCLC 892583347
    . In acute meningitis, an exudate is evident within the leptomeninges over the surface of the brain (Fig. 28-21).
  13. S2CID 15404074
    .
  14. ^ "Overview of Adult Traumatic Brain Injuries" (PDF). Orlando Regional Healthcare, Education and Development. 2004. Archived from the original (PDF) on February 27, 2008.
  15. S2CID 29126514
    .
  16. ^
    ISBN 9780125296502
    .
  17. ISBN 0-697-21991-7
    .

External links

  • Media related to Meninges at Wikimedia Commons
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