Dura mater (dura mater)
The dura mater (dura mater) is the outermost, dense fibrous tissue layer that is richly vascularized and innervated, but contains few elastic fibers.
In the cranial cavity, the cranial dura mater (dura mater encephali) is represented by two layers:
- External layer (lamina externa) — closely adheres to the cranial bones, acting as their internal periosteum. It contains a well-developed vascular network.
- Internal layer (lamina interna) — has a smooth, shiny surface lined with endothelium and faces the arachnoid mater.
At the points where these layers separate, venous sinuses (sinus durae matris) are formed — rigid, valve-less vascular channels that provide venous drainage from the brain tissues, orbit, and cranial bones.
Additionally, the dura mater extends dense folds into the cranial cavity that divide different parts of the brain. These include:
- Falx cerebri (falx cerebri)
- Falx cerebelli (falx cerebelli)
- Tentorium cerebelli (tentorium cerebelli)
- Diaphragma sellae (diaphragma sellae)
Innervation of the cranial dural structures is provided by the meningeal branches of the trigeminal nerve, branches of the vagus nerve, and the sympathetic nervous system. Blood supply comes from branches of the carotid arteries (specifically, a. meningea media).
The spinal dura mater (dura mater spinalis) has a different structure: it is an elongated cylindrical sac hanging loosely in the vertebral canal. It does not fuse with the periosteum, leaving room for the epidural space. Inferiorly, the membrane continues as the external terminal filum (filum terminale externum).
Arachnoid mater (arachnoidea)
The arachnoid mater (arachnoidea) is a thin, avascular, transparent layer covered by endothelium. Its main topographical feature is that it does not follow the contours of the brain, but bridges across its sulci, lying between the dura and pia mater.
The membrane is firmly connected to surrounding structures:
- It is connected to the pia mater by a network of fine threads — the arachnoid trabeculae.
- It contacts the dura mater at the exits of the spinal nerve roots, and in the cranial cavity forms arachnoid granulations (granulationes arachnoideales). Through these protrusions, cerebrospinal fluid is reabsorbed into the venous sinuses.
Pia mater (pia mater)
The innermost layer, the pia mater (pia mater), closely adheres directly to the spinal cord and brain tissue. It is a thin layer with a dense vascular network.
Unlike the arachnoid mater, the pia mater precisely follows all topographical irregularities, extending deep into every sulcus. Its blood vessels penetrate into the substance of the brain, allowing the membrane to perform a crucial trophic function — nourishing the nervous tissue.
Intermeningeal spaces
The spaces between the meninges have anatomical variations depending on the region of the central nervous system:
- Epidural space (cavitas epiduralis) — truly exists only around the spinal cord. It is located between the vertebral periosteum and the dura mater. It is filled with adipose tissue, loose connective tissue, and venous plexuses.
- Subdural space (spatium subdurale) — is located between the dura and arachnoid mater. It is a slit-like, so-called "potential" space.
- Subarachnoid space (cavitas subarachnoidea) — a true space between the arachnoid and pia mater, continuous for the brain and spinal cord. It is filled with cerebrospinal fluid (liquor cerebrospinalis). In certain areas of the brain, it widens to form subarachnoid cisterns (cisternae subarachnoideae).
Briefly: answers to topical questions
Which nerves innervate the cranial dura mater?
The cranial dura mater is innervated by branches of the trigeminal, vagus, hypoglossus, and upper cervical spinal nerves, as well as sympathetic fibers.
- Trigeminal nerve (n. trigeminus) — innervates the supratentorial part via meningeal branches from the ophthalmic, maxillary, and mandibular nerves.
- Vagus nerve (n. vagus) — gives off meningeal branches to the infratentorial part in the posterior cranial fossa.
- Hypoglossal nerve (n. hypoglossus) — also gives off meningeal branches in the area of the posterior cranial fossa.
- Spinal nerves — branches from the upper cervical segments innervate the membrane inferior to the tentorium cerebelli.
What subarachnoid cisterns of the brain exist?
Subarachnoid cisterns are widenings of the subarachnoid space of the brain. The following main cisterns are distinguished:
- Cerebellomedullary cistern (cisterna cerebellomedullaris) — located between the cerebellum and the medulla oblongata.
- Chiasmatic cistern (cisterna chiasmatis) — located anterior to the optic chiasm.
- Interpeduncular cistern (cisterna interpeduncularis) — located between the cerebral peduncles.
- Cistern of the lateral recess of the cerebrum (cisterna fossae lateralis cerebri) — lies in the lateral sulcus of the brain.
There are also the interhemispheric, transverse, ambient, pontine cisterns, and the cistern of the vermis.
Which arteries supply blood to the dura mater?
The blood supply to the dura mater is provided by branches of the external and internal carotid arteries, as well as the vertebral arteries.
- Middle meningeal artery (a. meningea media) — a large branch of the maxillary artery.
- Anterior meningeal artery — a branch of the anterior ethmoidal artery from the internal carotid artery system.
- Posterior meningeal artery — supplies the membrane in the posterior cranial fossa.
- Meningeal branches (rr. meningei) — branch off from the vertebral artery and the cavernous part of the internal carotid artery.
- Ascending pharyngeal artery (a. pharyngea ascendens) — also participates in the blood supply.
What dural venous sinuses exist?
The following venous sinuses are formed within the duplicatures of the dura mater:
- Superior and inferior sagittal sinuses (sinus sagittalis superior et inferior)
- Straight sinus (sinus rectus)
- Transverse sinus (sinus transversus)
- Sigmoid sinus (sinus sigmoideus)
- Occipital sinus (sinus occipitalis)
- Cavernous sinus (sinus cavernosus)
- Sphenoparietal sinus (sinus sphenoparietalis)
- Superior and inferior petrosal sinuses (sinus petrosus superior et inferior)
The junction of several sinuses forms the confluence of sinuses (confluens sinuum).
Which structures form the internal and external terminal filum of the spinal cord?
The terminal filum is formed by the fusion of the spinal meninges below the level of the spinal cord termination.
- Internal terminal filum (filum terminale internum) is formed by the fusion of the pia mater, arachnoid mater, and dura mater, and contains no nervous tissue.
- External terminal filum (filum terminale externum) is the caudal continuation and derivative exclusively of the spinal dura mater (dura mater spinalis).
The English mnemonic DAP helps remember the layers from outside to inside: Dura mater, Arachnoid mater, Pia mater.
Class and exam questions
In the brain, the outer layer of the dura mater fuses with the cranial bones (acts as the periosteum), whereas in the spinal cord, the membrane hangs freely within the canal, separated from the vertebrae by the epidural space.
In the brain, the outer layer of the dura mater fuses tightly with the cranial bones, serving as their internal periosteum. In the vertebral canal, the dura mater does not fuse with the bones, forming a loose sac and leaving room for the epidural space.
Where is cerebrospinal fluid located and where does it drain?
Cerebrospinal fluid circulates in the subarachnoid space (between the arachnoid and pia mater). Its resorption occurs via arachnoid granulations into the dural venous sinuses.
Which meningeal layer contains the most blood vessels?
The pia mater (pia mater) is the most vascular meningeal layer. It extends into all sulci and accompanies blood vessels deep into the brain tissue, performing a trophic function.
What else to study on this topic
- Topography and structure of the dural venous sinuses
- Dural folds (falx cerebri, tentorium cerebelli)
- Anatomy and location of subarachnoid cisterns
- Arachnoid granulations and the mechanism of CSF resorption
- Contents of the spinal epidural space
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