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Questions and Answers
Which cranial nerve is associated with the internal acoustic meatus?
Which cranial nerve is associated with the internal acoustic meatus?
Which of the following structures does NOT pass through the jugular foramen?
Which of the following structures does NOT pass through the jugular foramen?
What is the outermost layer of the meninges called?
What is the outermost layer of the meninges called?
What is the correct description for the hypoglossal canal?
What is the correct description for the hypoglossal canal?
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Which part of the dura mater serves as the periosteum on the inner cranial surface?
Which part of the dura mater serves as the periosteum on the inner cranial surface?
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Which dural fold is sickle-shaped and located between the cerebral hemispheres?
Which dural fold is sickle-shaped and located between the cerebral hemispheres?
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What is the primary function of the superior sagittal sinus?
What is the primary function of the superior sagittal sinus?
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Where does the straight sinus primarily drain?
Where does the straight sinus primarily drain?
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Which sinus is primarily located at the junction of the falx cerebri and tentorium cerebelli?
Which sinus is primarily located at the junction of the falx cerebri and tentorium cerebelli?
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What is one of the main nerves providing innervation to the middle cranial fossa?
What is one of the main nerves providing innervation to the middle cranial fossa?
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The sigmoid sinuses eventually drain into which major vein?
The sigmoid sinuses eventually drain into which major vein?
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Which cranial fossa is primarily supplied by branches from the vagus nerve?
Which cranial fossa is primarily supplied by branches from the vagus nerve?
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What structure does the tentorium cerebelli separate?
What structure does the tentorium cerebelli separate?
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Where are cavernous sinuses located?
Where are cavernous sinuses located?
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Which of the following sinuses is most directly associated with draining the cerebral veins?
Which of the following sinuses is most directly associated with draining the cerebral veins?
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Which cranial fossa contains the olfactory foramina?
Which cranial fossa contains the olfactory foramina?
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Which cranial nerve does not pass through the superior orbital fissure?
Which cranial nerve does not pass through the superior orbital fissure?
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Which foramina transmits the mandibular division of the trigeminal nerve?
Which foramina transmits the mandibular division of the trigeminal nerve?
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What is located at the junction of the temporal, sphenoid, and occipital bones?
What is located at the junction of the temporal, sphenoid, and occipital bones?
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Which cranial nerve is transmitted through the foramen rotundum?
Which cranial nerve is transmitted through the foramen rotundum?
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What structure separates the cerebrum from the cerebellum?
What structure separates the cerebrum from the cerebellum?
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Which of the following is NOT a function of the meninges?
Which of the following is NOT a function of the meninges?
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What does the dural partition known as the falx cerebri separate?
What does the dural partition known as the falx cerebri separate?
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Which structure is directly related to the middle meningeal artery?
Which structure is directly related to the middle meningeal artery?
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The subarachnoid space is primarily filled with what substance?
The subarachnoid space is primarily filled with what substance?
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Which cranial nerve does NOT pass through the foramen magnum?
Which cranial nerve does NOT pass through the foramen magnum?
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What is contained within the hypoglossal canal?
What is contained within the hypoglossal canal?
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Which layer of the meninges is described as the strongest and outermost?
Which layer of the meninges is described as the strongest and outermost?
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Where are the cranial meninges primarily located?
Where are the cranial meninges primarily located?
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Which structure adheres tightly to the inner meningeal layer of the dura mater?
Which structure adheres tightly to the inner meningeal layer of the dura mater?
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Which structure is found within the anterior cranial fossa?
Which structure is found within the anterior cranial fossa?
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What is the primary content that passes through the foramen spinosum?
What is the primary content that passes through the foramen spinosum?
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Which cranial nerve is associated with the foramen rotundum?
Which cranial nerve is associated with the foramen rotundum?
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In which cranial fossa is the sella turcica located?
In which cranial fossa is the sella turcica located?
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Which meningeal layer is directly in contact with the brain?
Which meningeal layer is directly in contact with the brain?
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What is the primary content of the superior orbital fissure?
What is the primary content of the superior orbital fissure?
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Which of the following structures does not contribute to the posterior cranial fossa?
Which of the following structures does not contribute to the posterior cranial fossa?
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Which passage contains the internal carotid artery?
Which passage contains the internal carotid artery?
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What is the main function of the falx cerebri?
What is the main function of the falx cerebri?
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Which sinus primarily receives drainage from the inferior sagittal sinus?
Which sinus primarily receives drainage from the inferior sagittal sinus?
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What is the primary role of the confluence of sinuses?
What is the primary role of the confluence of sinuses?
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Which cranial nerve contributes least to meninges innervation in the posterior cranial fossa?
Which cranial nerve contributes least to meninges innervation in the posterior cranial fossa?
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Which structure does the falx cerebri NOT separate?
Which structure does the falx cerebri NOT separate?
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Which dural venous sinus is located on the attached edge of the falx cerebri?
Which dural venous sinus is located on the attached edge of the falx cerebri?
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What is a distinctive feature of the cavernous sinuses?
What is a distinctive feature of the cavernous sinuses?
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Which sinus is primarily involved in draining cranial blood into the internal jugular vein?
Which sinus is primarily involved in draining cranial blood into the internal jugular vein?
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What potential complication can arise due to the proximity of cranial structures to the cavernous sinuses?
What potential complication can arise due to the proximity of cranial structures to the cavernous sinuses?
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Which dural fold primarily separates the cerebrum from the cerebellum?
Which dural fold primarily separates the cerebrum from the cerebellum?
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What contents are found in the foramen rotundum?
What contents are found in the foramen rotundum?
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Which of the following foramen transmits the abducens nerve?
Which of the following foramen transmits the abducens nerve?
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Which structure is located at the junction of the temporal, sphenoid, and occipital bones?
Which structure is located at the junction of the temporal, sphenoid, and occipital bones?
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What is the function of the arachnoid mater?
What is the function of the arachnoid mater?
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Which cranial fossa is not associated with the optic nerve?
Which cranial fossa is not associated with the optic nerve?
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Which meningeal layer is primarily responsible for the separation of the cerebral hemispheres?
Which meningeal layer is primarily responsible for the separation of the cerebral hemispheres?
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The middle meningeal artery is mainly associated with which foramen?
The middle meningeal artery is mainly associated with which foramen?
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What is the primary content that passes through the superior orbital fissure?
What is the primary content that passes through the superior orbital fissure?
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Which cranial nerve passes through the optical canal?
Which cranial nerve passes through the optical canal?
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The structure commonly referred to as the 'tent' of the cerebellum is known as which of the following?
The structure commonly referred to as the 'tent' of the cerebellum is known as which of the following?
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Which cranial nerve is transmitted through the jugular foramen along with the other two listed cranial nerves?
Which cranial nerve is transmitted through the jugular foramen along with the other two listed cranial nerves?
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Which of the following options accurately describes the content of the foramen magnum?
Which of the following options accurately describes the content of the foramen magnum?
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What anatomical feature separates the outer endosteal layer from the inner meningeal layer of the dura mater?
What anatomical feature separates the outer endosteal layer from the inner meningeal layer of the dura mater?
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Which layer of the meninges is directly in contact with the cranial structures?
Which layer of the meninges is directly in contact with the cranial structures?
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Which cranial nerve is specifically associated with the internal acoustic meatus?
Which cranial nerve is specifically associated with the internal acoustic meatus?
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What is the pathway of drainage for the superior sagittal sinus?
What is the pathway of drainage for the superior sagittal sinus?
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Which sinus connects the left and right cavernous sinuses?
Which sinus connects the left and right cavernous sinuses?
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What cranial fossa receives innervation primarily from the meningeal branches of the vagus nerve?
What cranial fossa receives innervation primarily from the meningeal branches of the vagus nerve?
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Which structure is primarily responsible for separating the cerebellar hemispheres?
Which structure is primarily responsible for separating the cerebellar hemispheres?
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Where is the straight sinus primarily located?
Where is the straight sinus primarily located?
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Which structure is NOT located within the lateral wall of the cavernous sinuses?
Which structure is NOT located within the lateral wall of the cavernous sinuses?
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What major veins drain into the sigmoid sinuses?
What major veins drain into the sigmoid sinuses?
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Which nerve primarily innervates the anterior cranial fossa?
Which nerve primarily innervates the anterior cranial fossa?
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What is a defining feature of the transverse sinuses?
What is a defining feature of the transverse sinuses?
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Which layer of the meninges extends into the grooves and fissures of the brain?
Which layer of the meninges extends into the grooves and fissures of the brain?
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Study Notes
Cranial Fossae
- The base of the skull is the floor of the cranial cavity and is divided into three fossae:
- Anterior Cranial Fossa: Frontal bone, ethmoid bone, and sphenoid bone (lesser wings and body).
- Middle Cranial Fossa: Temporal bone and sphenoid bone (greater wings and sella turcica).
- Posterior Cranial Fossa: Temporal bones, occipital bones, with small contributions from the sphenoid and parietal bones.
Cranial Nerves
- The cranial nerves are:
- CN I: Olfactory Nerve
- CN II: Optic Nerve
- CN III: Oculomotor Nerve
- CN IV: Trochlear Nerve
- CN V: Trigeminal Nerve
- CN VI: Abducens Nerve
- CN VII: Facial Nerve
- CN VIII: Vestibulocochlear Nerve
- CN IX: Glossopharyngeal Nerve
- CN X: Vagus Nerve
- CN XI: Accessory Nerve
- CN XII: Hypoglossal Nerve
Cranial Foramina
Anterior Cranial Fossa Foramina
-
Olfactory Foramina: Located on the cribriform plates of the ethmoid bone.
- Contents: CN I (Olfactory nerves)
Middle Cranial Fossa Foramina
-
Optic Canal: Located on the sphenoid bone.
- Contents: CN II (Optic nerve) and Ophthalmic artery.
-
Superior Orbital Fissure: Located between greater and lesser wings of the sphenoid bone.
- Contents: CN III (Oculomotor nerve), CN IV (Trochlear nerve), CN V1 (Ophthalmic division of the trigeminal nerve), CN VI (Abducens nerve), ophthalmic veins.
-
Foramen Rotundum: Located on the greater wings of the sphenoid bone.
- Contents: CN V2 (Maxillary division of the trigeminal nerve).
-
Foramen Ovale: Located on the greater wings of the sphenoid bone.
- Contents: CN V3 (Mandibular division of the trigeminal nerve) and Accessory meningeal artery.
-
Foramen Spinosum: Located on the greater wings of the sphenoid bone.
- Contents: Middle meningeal artery and vein.
-
Foramen Lacerum: Located at the junction of temporal, sphenoid, and occipital bones.
- Contents: Deep petrosal nerve, internal carotid artery, and greater petrosal nerve.
Posterior Cranial Fossa Foramina
-
Internal Acoustic Meatus: Located on the greater wings of the sphenoid bone.
- Contents: CN VII (Facial nerve) and CN VIII (Vestibulocochlear nerve).
-
Jugular Foramen: Located at the junction of temporal and occipital bones.
- Contents: CN IX (Glossopharyngeal nerve), CN X (Vagus nerve), and CN XI (Accessory nerve).
-
Hypoglossal Canal: Located on the occipital bones.
- Contents: CN XII (Hypoglossal nerve).
-
Foramen Magnum: Located on the occipital bones.
- Contents: CN XI (Accessory nerve), meninges, vertebral and spinal arteries, and medulla oblongata.
Meninges
-
The meninges stabilize the shape and position of the central nervous system.
- The cranial fossa and brain are covered by the meninges.
-
There are three layers of meninges (superficial to deep):
-
Dura mater: Outermost layer.
- Outer periosteal layer: Adheres to the inner meningeal layer.
- Inner meningeal layer: Separates from the periosteal layer and protrudes into the cranial cavity.
-
Arachnoid mater: Intermediate layer.
-
Pia mater: Innermost layer.
-
Dura Mater
- Also known as pachymeninx.
- Strongest layer protecting the brain and spinal cord.
- Double-layered membrane: Outer periosteal layer (endosteal layer) and inner meningeal layer.
Outer periosteal layer (endosteal layer)
- Acts as the periosteum on the cranial inner surface.
- Adheres tightly to the inner meningeal layer.
- Two spaces exist around the dura mater:
- Epidural (Extradural) space: Between the cranium and periosteal layer.
- Subdural space: Between the inner meningeal layer and arachnoid mater.
Inner meningeal layer
- Separates from the periosteal layer and protrudes into the cranial cavity.
- This separation creates double-layered dural folds (dural reflections/septa).
Dural Venous Sinuses
- Located where the dural layers separate.
- Cerebral veins drain into these spaces.
- Location of each sinus is determined by dural fold attachment.
Dural Folds
- Falx cerebri: Sickle-shaped fold between cerebral hemispheres.
- Falx cerebelli: Partially extends between cerebellar hemispheres.
- Tentorium cerebelli: Horizontal fold between the cerebrum and cerebellum.
- Diaphragma sellae: Overlies pituitary fossa and allows infundibulum of the pituitary gland through.
Dural Venous Sinuses
-
Superior sagittal sinus: Located on the attached edge of the falx cerebri.
- Runs from anterior to posterior (along the midsagittal plane).
- Drains veins draining the brain and cerebrospinal fluid.
-
Inferior sagittal sinus: Located on the free edge of the falx cerebri.
- Runs from anterior to posterior (along the midsagittal plane).
- Drains veins draining the brain and cerebrospinal fluid.
-
Straight sinus: Located at the junction of the falx cerebri and tentorium cerebelli.
- Runs from anterior to posterior (along the midsagittal plane).
- Drains the cerebral, great cerebral, superior cerebellar veins and the inferior sagittal sinus.
- Drains into the confluence of sinuses.
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Confluence of sinuses: Connecting point of Superior sagittal sinus, straight sinus, and occipital sinus.
- Located near the internal occipital protuberance.
- Drains into the left and right transverse sinuses.
-
Transverse sinuses: Extend horizontally along the attached edge of the tentorium cerebelli.
- Right transverse sinus usually drains the superior sagittal sinus.
- Left transverse sinus usually drains the straight sinus.
- Receives blood from the superior petrosal sinus.
- Become the sigmoid sinuses.
-
Sigmoid sinuses: Descends within the posterior cranial fossa towards the jugular foramen.
- Drains cerebral, cerebellar, diploic, and emissary veins.
- Drains into the internal jugular vein.
-
Cavernous sinuses: Lie against the lateral aspect of the body of the sphenoid.
- Receives blood from cerebral ophthalmic and emissary veins.
- Left and right sinuses are connected by intercavernous sinuses (anteriorly and posteriorly).
- Several structures pass through each sinus:
- Internal carotid artery and the abducens nerve
- Oculomotor, trochlear nerve, ophthalmic nerve, and maxillary nerve (lateral wall of each sinus).
Meninges: Arachnoid Mater
- Avascular membrane that lines the meningeal layer of the dura mater.
- Thin processes extend from it into the subarachnoid space.
- It is continuous with the pia mater.
- Lies over sulci and gyri, but not within the sulci.
Meninges: Pia Mater
- Thin, delicate layer that closely adheres to the brain surface.
- Enters grooves and fissures of the brain.
Innervation of Meninges
- Meningeal innervation is primarily from the meningeal branches of the trigeminal nerve and the vagus nerve.
- Upper cervical spinal nerves contribute to a lesser degree.
Anterior Cranial Fossa
- Ophthalmic division of the trigeminal nerve.
- Meningeal branches from the maxillary nerve (CN V2).
Middle Cranial Fossa
- Meningeal branches of ophthalmic, maxillary, and mandibular divisions of the trigeminal nerve.
Posterior Cranial Fossa
- Meningeal branches from the vagus nerve (CN X) and glossopharyngeal nerve (CN IX) supply the inferior surface of the tentorium and dura of the posterior fossa.
Cranial Foramina
- Cranial Foramina are openings in the skull that allow passage of nerves, blood vessels, and other structures.
- They are found within three cranial fossae at the base of the skull: the anterior, middle, and posterior cranial fossae.
- Each fossa is formed by specific bones:
- Anterior cranial fossa: Frontal bone, ethmoid bone, and sphenoid bone (lesser wings and body).
- Middle cranial fossa: Temporal bone and sphenoid bone (greater wings and sella turcica).
- Posterior cranial fossa: Temporal bones, occipital bones, with small contributions from the sphenoid and parietal bones.
- Anterior cranial fossa contains the olfactory foramina within the cribriform plates of the ethmoid bone, which allow passage for the olfactory nerves (CN I).
-
Middle cranial fossa contains the following foramina:
- Optic canal: Located on the sphenoid bone, it contains the optic nerve (CN II) and ophthalmic artery.
- Superior orbital fissure: Located between the greater and lesser wings of the sphenoid bone, it contains the oculomotor nerve (CN III), trochlear nerve (CN IV), ophthalmic division of the trigeminal nerve (CN V1), abducens nerve (CN VI), and ophthalmic veins.
- Foramen rotundum: Located on the greater wings of the sphenoid bone, it contains the maxillary division of the trigeminal nerve (CN V2).
- Foramen ovale: Located on the greater wings of the sphenoid bone, it contains the mandibular division of the trigeminal nerve (CN V3) and the accessory meningeal artery.
- Foramen spinosum: Located on the greater wings of the sphenoid bone, it contains the middle meningeal artery and vein.
- Foramen lacerum: Located at the junction of the temporal, sphenoid, and occipital bones, it contains the deep petrosal nerve, internal carotid artery, and greater petrosal nerve.
-
Posterior cranial fossa contains the following foramina:
- Internal acoustic meatus: Located on the greater wings of the sphenoid bone, it contains the Facial nerve (CN VII) and Vestibulocochlear nerve (CN VIII).
- Jugular foramen: Located at the junction of the temporal and occipital bones, it contains the Glossopharyngeal nerve (CN IX), Vagus nerve (CN X), and Accessory nerve (CN XI).
- Hypoglossal canal: Located on the occipital bones, it contains the Hypoglossal nerve (CN XII).
- Foramen magnum: Located on the occipital bones, it contains the Accessory nerve (CN XI), meninges, vertebral and spinal arteries, and medulla oblongata.
Meninges
- The meninges are a three-layered membrane that surrounds and protects the brain and spinal cord.
- They stabilize the shape and position of the central nervous system.
- The three layers are (from superficial to deep): Dura mater, Arachnoid mater, and Pia mater.
Dura Mater
- Also known as pachymeninx, the dura mater is the outermost layer of the meninges.
- It is the strongest layer and provides substantial protection for the brain and spinal cord.
- It is a double-layered membrane:
- Outer endosteal layer (Outer periosteal layer): Serves as the periosteum on the cranial inner surface. It adheres tightly to the inner meningeal layer and lacks a clear boundary except at the sinuses.
- Inner meningeal layer: Separates from the periosteal layer and protrudes into the cranial cavity, creating dural septa.
- Two spaces around the dura mater are:
- Epidural (Extradural) space: Lies between the cranium and the periosteal layer.
- Subdural space: Lies between the inner meningeal layer and the arachnoid mater.
Dural Venous Sinuses
- Occur where the dural layers separate.
- Spaces where cerebral veins drain.
- Location of each sinus is determined by the dural fold attachment.
- There are four types of dural folds:
- Falx cerebri: Sickle-shaped fold located between the cerebral hemispheres.
- Falx cerebelli: Partially extends between the cerebellar hemispheres.
- Tentorium cerebelli: Horizontal fold located between the cerebrum and cerebellum.
- Diaphragma sellae: Overlies the pituitary fossa and allows the infundibulum of the pituitary gland to pass through.
Dural Venous Sinuses - Specific Sinuses
- Superior sagittal sinus: Runs from anterior to posterior along the attached edge of the falx cerebri, drains veins draining the brain and cerebrospinal fluid.
- Inferior sagittal sinus: Runs from anterior to posterior along the free edge of the falx cerebri, drains veins draining the brain and cerebrospinal fluid.
- Straight sinus: Runs from anterior to posterior at the junction of the falx cerebri and tentorium cerebelli, drains the cerebral, great cerebral, superior cerebellar veins, and the inferior sagittal sinus.
- Confluence of sinuses: Connecting point of the Superior sagittal sinus, straight sinus, and occipital sinus, located near the internal occipital protuberance, drains into the left and right transverse sinuses.
- Transverse sinuses: Extend horizontally along the attached edge of the tentorium cerebelli, from posterior to anterior.
- Sigmoid sinuses: Descends within the posterior cranial fossa towards the jugular foramen, drains cerebral, cerebellar, diploic, and emissary veins.
- Cavernous sinuses: Lies against the lateral aspect of the body of the sphenoid, receives blood from cerebral ophthalmic and emissary veins.
Meninges: Arachnoid Mater
- Avascular membrane that lines the meningeal layer of the dura mater.
- Thin processes extend from it into the subarachnoid space.
- Continuous with the pia mater.
- Lies over sulci and gyri, but does not lie within the sulci.
Meninges: Pia Mater
- Thin, delicate layer that closely adheres to the brain surface.
- Enters grooves and fissures of the brain.
Innervation of Meninges
- Meningeal innervation is primarily from the meningeal branches of the Trigeminal nerve and Vagus nerve, with the Upper cervical spinal nerves contributing to a lesser degree.
- Anterior cranial fossa: Innervated by the ophthalmic division of the trigeminal nerve and meningeal branches from the maxillary nerve (CN V2).
- Middle cranial fossa: Innervated by meningeal branches of the ophthalmic, maxillary, and mandibular divisions of the trigeminal nerve.
- Posterior cranial fossa: Innervated by meningeal branches from the vagus nerve (CN X) and glossopharyngeal nerve (CN IX), which supply the inferior surface of the tentorium and dura of the posterior fossa.
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Test your knowledge on the structure of cranial fossae and the twelve cranial nerves. This quiz covers the bones involved in the cranial fossae and the functions of each cranial nerve. Perfect for students studying anatomy.
