Spinal Cord Dura and Pia Layer Vertebrae Review

Meninges of the brain and spinal cord

Writer: Jana Vasković Medico • Reviewer: Roberto Grujičić MD
Last reviewed: March 22, 2022
Reading fourth dimension: 18 minutes

The meninges are the three membranes that envelop the brain and spinal cord and carve up them from the walls of their bony cases (skull and vertebral column). Based on their location, meninges are referred to equally the cranial meninges which envelop the brain, and spinal meninges which envelop the spinal cord. Still, the cranial and spinal meninges are continuous with each other and consist of the same iii meningeal layers. From superficial to deep the meninges are the:

Dura mater, too known every bit the pachymeninx
Arachnoid mater
Pia mater

These layers bound three clinically of import potential spaces: the epidural, subdural, and subarachnoid spaces. The function of the meninges is to protect the encephalon and spinal string from mechanical trauma, to support the blood vessels and to form a continuous cavity through which the cerebrospinal fluid (CSF) passes. Specifically, the CSF passes between the inner ii meningeal layers (arachnoid and pia) which are together chosen the leptomeninges.

This article will talk over the anatomy and role of the cranial and spinal meninges.

Fundamental facts about the meninges
Definition	Three membranous layers that envelop the brain and the spinal cord
Meninges and meningeal spaces	Meninges: Dura mater, arachnoid mater, pia mater Meningeal spaces: Epidural space, subdural space, subarachnoid space
Function	Mechanical protection of encephalon and spinal cord, support of cognitive and spinal claret vessels, passage of the cerebrospinal fluid (CSF)

Contents

Dura mater
Arachnoid mater
1. Arachnoid granulations
2. Subarachnoid cisterns
Pia mater
Spinal meninges
1. Spinal dura mater
2. Spinal arachnoid mater
3. Spinal pia mater
Meningeal spaces
1. Epidural space
2. Subdural space
3. Subarachnoid infinite
Clinical relations
1. Epidural bleeding
2. Subdural haemorrhage
3. Subarachnoid haemorrhage
Sources

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Dura mater

The cranial dura mater is the outermost meningeal layer, consisting of dumbo irregular connective tissue. It is composed of ii layers;

The superficial layer is the periosteal cranial dura. It overlies the inner tabular array of the cranial vault bones, interim like the periosteal layer of the cranium.
The meningeal cranial dura, which lies superficial to the arachnoid mater.

The two dural layers are firmly attached to each other, except in places where they separate to enclose the dural venous sinuses. In these places, the meningeal layer projects inward, towards the cognitive tissue, forming the fibrous septa that partially separate the cranial crenel. The fibrous septa inside the cranium are the:

Falx cerebri, which is the largest of fibrous septa. It extends across the midline on the inner surface of the calvaria, from crista galli to the internal occipital protuberance. It separates the left and right cognitive hemispheres and houses the superior sagittal and inferior sagittal sinuses. Posteriorly, the falx blends with tentorium cerebelli.
Tentorium cerebelli, which spans in a transverse plane from the inner surface of the occipital bone. It separates the cerebrum from the cerebellum and contains the transverse, straight and superior petrosal sinuses. The tentorium divides the intracranial infinite into supratentorial and infratentorial compartments that contain the forebrain and hindbrain, respectively.
Falx cerebelli, which projects from the midline of the occipital bone. It separates the hemispheres of the cerebellum and houses the occipital sinus.
Diaphragma sellae, which is a flat membrane that surrounds the pituitary stalk and forms a roof over the hypophyseal fossa. It contains the anterior and posterior intercavernous sinuses.

The meningeal dura mater overlies the trigeminal ganglion, enclosing it in a compartment known equally the trigeminal cave (Meckel's cavern).

Struggling to sympathize the dural septa? Learn the parts of the encephalon with our diagrams and quizzes!

Arachnoid mater

The cranial arachnoid mater is a spiderweb-like meningeal layer, interposed betwixt the dura and pia. The potential infinite between the arachnoid and dura is chosen the subdural infinite and according to some authors, it contains a very thin layer of fluid. The space between the arachnoid and pia is called the subarachnoid space and it is filled with the cerebrospinal fluid (CSF). Additionally, all cerebral arteries and veins are located in this space.

The outer surface of the arachnoid attaches to the dura mater forming a barrier that prevents the leakage of CSF into the subdural space. At the sites where dura forms the venous sinuses, the arachnoid shows mushroom-like protrusions called the arachnoid granulations. The inner surface of arachnoid shows sparse fibrous projections called the arachnoid trabeculae that traverse the subarachnoid infinite and adhere to the outer surface of the pia mater. Due to their embryological and cellular similarities the pia mater and arachnoid together are referred to as the leptomeninges.

Arachnoid granulations

The arachnoid granulations (Pacchionian bodies) are protrusions of the arachnoid mater that pierce the meningeal dura and protrude into the lumina of the dural venous sinuses. The core of each arachnoid granulation is continuous with the subarachnoid infinite, therefore, containing the cerebrospinal fluid.

The CSF diffuses through the lining of the arachnoid granulations into the dural venous sinuses. Therefore, the function of the arachnoid granulations is to enable the continuous drainage of the cerebrospinal fluid from the subarachnoid into the vascular arrangement. It is of import that the CSF drainage is held in remainder with the production of new CSF from the choroid plexus, warranting a constant corporeality of the CSF in the brain (usually around 150 milliliters). Since the skull is a rigid case, whatever increase in the amount of CSF in the brain increases the intracranial pressure and can cause various neurological disorders (e.g. hydrocephalus)

Subarachnoid cisterns

The arachnoid mater does not follow precisely the contours of the brain. Moreover, in sure sites, information technology completely separates from the pia mater, thus forming the expansions of the subarachnoid space, called the subarachnoid cisterns. At that place are ten major subarachnoid cisterns of the brain that are continuous with each other through the full general subarachnoid infinite. These include the:

Cisterna magna (cerebellomedullary cistern)
Pontine cistern
Chiasmatic cistern
Quadrigeminal cistern
Interpeduncular cistern
Ambience cistern
Crural and carotid cisterns
Cistern of lateral cerebral fossa (Sylvian cistern)
Cerebellopontine cistern
Cistern of lamina terminalis

Learn more about the subarachnoid cisterns with our video tutorials, quizzes, articles, and labelled diagrams.

Pia mater

The cranial pia mater is a highly vascular membrane that closely follows the contours of the brain. It doesn't prevarication on the surface of the encephalon directly but rather is separated from information technology by a thin infinite called the subpial infinite formed by the end-feet of the astrocytes (glia limitans). Many superficial blood vessels of the brain are related to the pia mater. However, given that it is a very sparse membrane, these blood vessels are partially embedded within the thickness of the pia, while partially are suspended past the arachnoid trabeculae.

The office of the pia mater is to physically separate the neural tissue from the blood vessels in the subarachnoid space, adding to the efficacy of the blood-encephalon barrier. Furthermore, it contributes to the degradation of the neurotransmitters, preventing their prolonged activeness on the nervous tissue.

Take the quiz below to exam your knowledge on the meninges and superficial vessels of the brain!

Spinal meninges

Spinal dura mater

The dura mater of the spinal string differs from that of the brain by having merely 1 layer; the meningeal layer. The periosteal layer is missing because the vertebral culvert, unlike the skull, has its own, true periosteum. The spinal dura mater attaches to the tectorial membrane and posterior longitudinal ligament superiorly. Inferiorly, it extends upward to S2 vertebral level, thus extending below the spinal cord termination (L1/L2).

The infinite between the spinal dura mater and the periosteum of the vertebral column is called the epidural space. It is filled with loose connective and adipose tissues, and traversed by the anterior and posterior internal vertebral venous plexuses.

Spinal arachnoid mater

The arachnoid mater of the spinal string is continuous with that of the brain. It lies close and below the spinal dura, with a narrow subdural infinite existing between them. Deep to the arachnoid is the spinal pia mater. Between arachnoid and pia, there is the spinal subarachnoid space. This space expands at the level of the conus medullaris of the spinal cord, forming the lumbar cistern.

The lumbar cistern extends from L1-S2 and it contains the dorsal and ventral rootlets of L2-Co spinal nerves (cauda equina). It is clinically significant as it is the site of lumbar puncture (extraction of CSF for biochemical, microbiological and cytological analyses or application of certain medicine).

Spinal pia mater

The spinal pia mater continues onto the cranial pia at the level of the foramen magnum. It closely envelops the spinal cord, containing a vascular plexus for the spinal cord tissue. From the noon of the conus medullaris, the pia mater gives off a gristly project chosen the filum terminale. The filum terminale extends around 20 centimeters downwards and attaches to the periosteum of the first coccygeal vertebra.

Starting from the level of the foramen magnum to the level of vertebra T12, the spinal pia shows 21 pairs of ligamentous lateral projections that pass through the arachnoid and adhere to the spinal dura mater. These projections are called the denticulate ligaments. Each pair of denticulate ligaments is located halfway between the successive pairs of the spinal nerves. The function of denticulate ligaments is to position and hold the spinal cord in place.

Consolidate your knowledge of the spinal meninges and meningeal spaces with the following quiz.

Meningeal spaces

The meningeal spaces are the spaces betwixt the meningeal layers. There are 3 clinically significant meningeal spaces; epidural, subdural, and subarachnoid. Nosotros take described the anatomy of each of the spaces in the text above, withal, we'd like to epitomize the nigh important facts and sum them up in the following paragraphs.

Epidural space

"Epi" is a prefix indicating that something is "above". Thus, it should come up easy to remember that the cranial epidural infinite is a potential infinite between the superficial layer of dura mater and the calvarium. On the other hand, the spinal epidural space is located between the spinal dura mater and the tissues that line the vertebral culvert.

The spinal epidural space is a site of applying the local epidural anesthesia. The procedure may be performed at any vertebral level, and the selection depends on the body region that is desired to be anesthetized for an upcoming surgical/obstetric process. The applied anesthetics (e.g. lidocaine) hypnotize the local spinal nerve rootlets resulting in analgesia (pain relief).

Subdural space

"Sub" is a prefix that tells united states that something is "beneath". And so, the subdural space is a potential space between the dura mater and the underlying arachnoid mater. The spinal subdural infinite is continuous with the cranial subdural infinite. They're both very narrow and likely contain a sparse film of fluid.

Subarachnoid space

The subarachnoid space is a space between the arachnoid and pia mater. The subarachnoid space contains cerebrospinal fluid (CSF) and major claret vessels and provides expansions known as cisterns. The subarachnoid spaces of the attic and vertebral column are continuous with each other, creating a closed route for the CSF circulation. Let's recap the route of the cerebrospinal fluid in lodge to understand the continuity of the subarachnoid infinite;

The CSF is formed by the cells of the choroid plexus within the walls of the brain ventricles. The fluid passes from the lateral to the third ventricle, so to the fourth ventricle.
From the 4th ventricle, the CSF passes into the central canal of the spinal cord and into the interpeduncular and quadrigeminal subarachnoid cisterns.
The CSF so reaches the subarachnoid space of the brain and spinal cord, circulating through them.
Finally, the CSF is reabsorbed into the dural venous sinuses by diffusing through the subarachnoid granulations in the cranial subarachnoid space.

Clinical relations

Epidural bleeding

Epidural hemorrhage is a rare status caused by the rupture of one of the meningeal vessels. Usually, the source of bleeding is the middle meningeal artery, or rarely, 1 of the dural venous sinuses. Epidural haemorrhage usually occurs due to a fracture of the parieto-temporal region of the skull which often causes a rupture of the aforementioned blood vessels. The hemorrhage separates the periosteal dura mater from the skull, forming the epidural hematoma between the calvaria and dura mater.

The epidural bleeding normally affects the younger population, since with age, the periosteal dura gets more firmly attached to the diploë. The epidural hematoma is diagnosed with CT, on which it is seen as a biconvex hyperdense germination. The biconvex form is ordinarily caused by a business firm attachment of the dura to the cranial sutures, limiting the haemorrhage. If treated surgically and on fourth dimension, the private unremarkably recovers fully within a couple of days.

Subdural bleeding

Subdural hemorrhage refers to the process of collecting the blood within the subdural infinite, between the dura and arachnoid mater. Information technology is unremarkably caused by a traumatic injury to the head and rupture of the bridging veins that connect the superficial veins of the brain with the dural venous sinuses. The subdural hematoma is usually located in the convexities of the skull. They are usually diagnosed by caput CT, in which they are seen every bit high-density crescent shaped formations. Subdural hematoma are divided into acute and chronic, depending on the timeframe of their formation.

Acute subdural hematoma is by and large caused by a strong strength that rips the bridging veins, has progressive growth and is often associated with underlying encephalon injury. If it'south compressing the brain it is surgically treated by evacuation. Modest asymptomatic cases, withal, may be managed expectantly.
Chronic subdural hematoma can result from even an insignificant or weak trauma of the head. It usually occurs in the elderly. Other take chances factors are booze abuse, seizures, CSF shunts, coagulopathies and patients at take a chance for falls (due east.k. hemiparesis from a stroke). The patients oft don't even call back any trauma that might have caused the subdural bleeding, as it usually happens during falls which they don't perceive as pregnant.The chronic subdural haemorrhage and the formation of the hematoma is quite irksome. The symptoms appear only in one case the hematoma reaches a critical size so information technology starts pressing the underlying brain tissue. The chronic subdural bleeding is diagnosed usually with a CT, on which it is seen as a crescent-shaped formation with a gristly capsule. The handling is the same as for the acute subdural hematoma, i.e. neurosurgical process.

Subarachnoid bleeding

Subarachnoid hemorrhage (SAH) is the most common post-traumatic bleeding. Note that it can also be non-traumatic, related to the rupture of an intracranial aneurysm or arterial malformation.

The fundamental symptom of this condition is a sudden onset of a headache which patients describe as the worst they've e'er had in their life. Other symptoms include deterioration of consciousness (confusion, stupor or even coma) and positive meningeal signs. It is diagnosed with Angio-CT, classical angiography, or lumbar puncture. The treatment is oriented towards iii key principles;

Back up of vital functions - breathing and eye rate.
Treating the cause of bleeding - neurosurgical closing of the ruptured claret vessel.
Avoiding vasospasm due to the degradation of the blood and reflexive vasoconstriction.

Sources

All content published on Kenhub is reviewed by medical and anatomy experts. The data we provide is grounded on academic literature and peer-reviewed enquiry. Kenhub does not provide medical communication. You can acquire more about our content creation and review standards by reading our content quality guidelines.

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