Dura mater

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Dura mater

Meninges of the CNS
Gray's	subject #193 872
MeSH	Dura+Mater

The dura mater, or dura, is the outermost of the three layers of the meninges surrounding the brain and spinal cord. The other two meningeal layers are the pia mater and the arachnoid mater. The dura surrounds the brain and the spinal cord and is responsible for keeping in the cerebrospinal fluid. The name "dura mater" is derived from the Latin "hard mother"^[1], and is also referred to by the term "pachymeninx" (plural "pachymeninges").^[2] The dura has been described as "tough and inflexible" and "leather-like".^[2]

[edit] Layers and functions

Spinal needles used in lumbar puncture.

The dura mater has several functions and layers. The dura mater is a sac that envelops the arachnoid mater. It surrounds and supports the dural sinuses (also called dural venous sinuses, cerebral sinuses, or cranial sinuses) and carries blood from the brain toward the heart.

The dura mater has two layers, or lamellae: The superficial layer, which serves as the skull's inner periosteum, called the endocranium; and a deep layer, the actual dura mater.

[edit] Dural folds and reflections

Spinal reflections and folds.

The dura separates into two layers at dural reflections (also known as dural folds), places where the inner dural layer is reflected as sheet-like protrusions into the cranial cavity. There are two main dural reflections:

The tentorium cerebelli exists between and separates the cerebellum and brainstem from the occipital lobes of the cerebrum.^[3]

The falx cerebri, which separates the two hemispheres of the brain, is located in the longitudinal cerebral fissure between the hemispheres.^[4]

[edit] Drainage

The two layers of dura mater run together throughout most of the skull. Where they separate, the gap between them is called a dural venous sinus. These sinuses drain blood and cerebrospinal fluid from the brain and empty into the internal jugular vein.

They drain via the arachnoid villi, which are outgrowths of the arachnoid mater (the middle meningeal layer) that extend into the venous sinuses. These villi act as one-way valves.

Meningeal veins, which course through the dura mater, and bridging veins, which drain the underlying neural tissue and puncture the dura mater, empty into these dural sinuses.

[edit] Clinical significance

Many medical conditions involve the dura mater. A subdural hematoma occurs when there is an abnormal collection of blood between the dura and the arachnoid, usually as a result of torn bridging veins secondary to head trauma. An epidural hematoma is a collection of blood between the dura and the inner surface of the skull, and is usually due to arterial bleeding.

The American Red Cross and some other agencies accepting blood donations consider dura mater transplants, along with receipt of pituitary-derived growth hormone, a risk factor due to concerns about Creutzfeldt-Jakob disease.^[5]

Dural ectasia is the enlargement of the dura and is common in connective tissue disorders, such as Marfan Syndrome and Ehlers-Danlos Syndrome.

Spontaneous Cerebrospinal Fluid Leak is the fluid and pressure loss of spinal fluid due to holes in the duta mater.

[edit] References

^ http://www.medterms.com/script/main/art.asp?articlekey=32513
^ ^a ^b http://www.medterms.com/script/main/art.asp?articlekey=32512
^ Shepherd S. 2004. "Head Trauma." Emedicine.com.
^ Vinas FC and Pilitsis J. 2004. "Penetrating Head Trauma." Emedicine.com.
^ Red Cross: http://www.redcross.org/services/biomed/0,1082,0_553_,00.html

[edit] Additional images

Diagrammatic representation of a section across the top of the skull, showing the membranes of the brain, etc.	Diagrammatic transverse section of the medulla spinalis and its membranes.	Upper part of medulla spinalis and hind- and mid-brains; posterior aspect, exposed in situ.	Diagrammatic section of scalp.
Autopsy photo from the CDC: The white "sheet" being held by the forceps is the dura mater.	Human brain dura mater