Anterior cranial fossaAnterior cranial fossaBonesBones:: Orbital plate of frontal bone, Orbital plate of frontal bone, cribriform plate of ethmoid and cribriform plate of ethmoid and lesser wing of sphenoid bone.lesser wing of sphenoid bone.FeaturesFeatures:: Frontal crest, foramen Frontal crest, foramen cecum, crista galli, anterior and cecum, crista galli, anterior and posterior ethmoidal foramina and posterior ethmoidal foramina and anterior clinoid process.anterior clinoid process.ForaminaForamina:: foramen cecum, foramina foramen cecum, foramina for olfactory nerves, foramina for for olfactory nerves, foramina for anterior and posterior ethmoidal anterior and posterior ethmoidal nerves and vessels.nerves and vessels.

BonesBones:: Orbital plate of frontal bone, Orbital plate of frontal bone, cribriform plate of ethmoid and cribriform plate of ethmoid and lesser wing of sphenoid bone.lesser wing of sphenoid bone.FeaturesFeatures:: Frontal crest, foramen Frontal crest, foramen cecum, crista galli, anterior and cecum, crista galli, anterior and posterior ethmoidal foramina and posterior ethmoidal foramina and anterior clinoid process.anterior clinoid process.ForaminaForamina:: foramen cecum, foramina foramen cecum, foramina for olfactory nerves, foramina for for olfactory nerves, foramina for anterior and posterior ethmoidal anterior and posterior ethmoidal nerves and vessels.nerves and vessels.

Middle cranial fossaMiddle cranial fossaBonesBones:: Sphenoid bone (body and greater Sphenoid bone (body and greater wing), Temporal bone (squamous part, wing), Temporal bone (squamous part, petrous part) and parietal bone.petrous part) and parietal bone.FeaturesFeatures:: Middle and posterior clinoid Middle and posterior clinoid processes, sulcus chiasmaticus, tuberculum processes, sulcus chiasmaticus, tuberculum sellae, hypophyseal fossa, dorsum sellae, sellae, hypophyseal fossa, dorsum sellae, sella turcica, arcuate eminenca, tegmen sella turcica, arcuate eminenca, tegmen tympani.tympani.ForaminaForamina:: optic canal, superior orbital optic canal, superior orbital fissure, foramen rotundum, foramen ovale, fissure, foramen rotundum, foramen ovale, foramen spinosum, foramen lacerum, foramen spinosum, foramen lacerum, hiatus for greater petrosal nerve and hiatus hiatus for greater petrosal nerve and hiatus for lesser petrosal nerve.for lesser petrosal nerve.

BonesBones:: Sphenoid bone (body and greater Sphenoid bone (body and greater wing), Temporal bone (squamous part, wing), Temporal bone (squamous part, petrous part) and parietal bone.petrous part) and parietal bone.FeaturesFeatures:: Middle and posterior clinoid Middle and posterior clinoid processes, sulcus chiasmaticus, tuberculum processes, sulcus chiasmaticus, tuberculum sellae, hypophyseal fossa, dorsum sellae, sellae, hypophyseal fossa, dorsum sellae, sella turcica, arcuate eminenca, tegmen sella turcica, arcuate eminenca, tegmen tympani.tympani.ForaminaForamina:: optic canal, superior orbital optic canal, superior orbital fissure, foramen rotundum, foramen ovale, fissure, foramen rotundum, foramen ovale, foramen spinosum, foramen lacerum, foramen spinosum, foramen lacerum, hiatus for greater petrosal nerve and hiatus hiatus for greater petrosal nerve and hiatus for lesser petrosal nerve.for lesser petrosal nerve.

Posterior cranial fossaPosterior cranial fossaBonesBones:: basilar part of sphenoid and basilar part of sphenoid and basilar part of occipital (clivus), basilar part of occipital (clivus), lateral part of occipital, squamous lateral part of occipital, squamous part of occipital and petrous part of part of occipital and petrous part of temporal bones.temporal bones.FeaturesFeatures:: internal occipital crest, internal occipital crest, internal occipital protuberance, .internal occipital protuberance, .ForaminaForamina:: Foramen magnum, jugular Foramen magnum, jugular foramen, internal acoustic meatus, foramen, internal acoustic meatus, hypoglossal canal, .hypoglossal canal, .

BonesBones:: basilar part of sphenoid and basilar part of sphenoid and basilar part of occipital (clivus), basilar part of occipital (clivus), lateral part of occipital, squamous lateral part of occipital, squamous part of occipital and petrous part of part of occipital and petrous part of temporal bones.temporal bones.FeaturesFeatures:: internal occipital crest, internal occipital crest, internal occipital protuberance, .internal occipital protuberance, .ForaminaForamina:: Foramen magnum, jugular Foramen magnum, jugular foramen, internal acoustic meatus, foramen, internal acoustic meatus, hypoglossal canal, .hypoglossal canal, .

The meningesThe meningesThe brain and spinal cord are The brain and spinal cord are surrounded by three layers of surrounded by three layers of meninges which aremeninges which are::

1.1. Dura mater.Dura mater.

2.2. Arachnoid mater.Arachnoid mater.

3.3. Pia mater.Pia mater.

The brain and spinal cord are The brain and spinal cord are surrounded by three layers of surrounded by three layers of meninges which aremeninges which are::

1.1. Dura mater.Dura mater.

2.2. Arachnoid mater.Arachnoid mater.

3.3. Pia mater.Pia mater.

Dura materDura mater LayersLayers::A.A. Endosteal layerEndosteal layer: periosteum of the inner surface : periosteum of the inner surface

of the skull bones. Strongly adherent to the bone.of the skull bones. Strongly adherent to the bone.B.B. Meningeal layerMeningeal layer: dense strong fibrous : dense strong fibrous

membrane, continues through the foramen membrane, continues through the foramen magnum with dura covering the spinal cord. It magnum with dura covering the spinal cord. It send inward four septa that divide the cranial send inward four septa that divide the cranial cavity into communicating spaces and act to cavity into communicating spaces and act to restrict the rotatory displacement of the brain restrict the rotatory displacement of the brain during movement. They are:during movement. They are:1.1. Falx cerebra.Falx cerebra.2.2. Tentorium cerebelli.Tentorium cerebelli.3.3. Falx cerebelli.Falx cerebelli.4.4. Diaphragma sellae.Diaphragma sellae.

LayersLayers::A.A. Endosteal layerEndosteal layer: periosteum of the inner surface : periosteum of the inner surface

of the skull bones. Strongly adherent to the bone.of the skull bones. Strongly adherent to the bone.B.B. Meningeal layerMeningeal layer: dense strong fibrous : dense strong fibrous

membrane, continues through the foramen membrane, continues through the foramen magnum with dura covering the spinal cord. It magnum with dura covering the spinal cord. It send inward four septa that divide the cranial send inward four septa that divide the cranial cavity into communicating spaces and act to cavity into communicating spaces and act to restrict the rotatory displacement of the brain restrict the rotatory displacement of the brain during movement. They are:during movement. They are:1.1. Falx cerebra.Falx cerebra.2.2. Tentorium cerebelli.Tentorium cerebelli.3.3. Falx cerebelli.Falx cerebelli.4.4. Diaphragma sellae.Diaphragma sellae.

1. Falx Cerebri1. Falx Cerebri A sickle-shaped dural fold, lies in the midline A sickle-shaped dural fold, lies in the midline

between the two cerebral hemispheres.between the two cerebral hemispheres. AttachmentAttachment::

1.1. Anteriorly: its narrow anterior end is Anteriorly: its narrow anterior end is attached to the crista galli and frontal attached to the crista galli and frontal crest.crest.

2.2. Superiorly: it is attached to borders of the Superiorly: it is attached to borders of the groove for superior sagittal sinus.groove for superior sagittal sinus.

3.3. Posteriorly: it blends with the upper surface Posteriorly: it blends with the upper surface of the tentorium cerebelli.of the tentorium cerebelli.

Related venous sinusesRelated venous sinuses:: Superior and inferior Superior and inferior sagittal sinuses and straight sinus.sagittal sinuses and straight sinus.

A sickle-shaped dural fold, lies in the midline A sickle-shaped dural fold, lies in the midline between the two cerebral hemispheres.between the two cerebral hemispheres.

AttachmentAttachment::1.1. Anteriorly: its narrow anterior end is Anteriorly: its narrow anterior end is

attached to the crista galli and frontal attached to the crista galli and frontal crest.crest.

2.2. Superiorly: it is attached to borders of the Superiorly: it is attached to borders of the groove for superior sagittal sinus.groove for superior sagittal sinus.

3.3. Posteriorly: it blends with the upper surface Posteriorly: it blends with the upper surface of the tentorium cerebelli.of the tentorium cerebelli.

Related venous sinusesRelated venous sinuses:: Superior and inferior Superior and inferior sagittal sinuses and straight sinus.sagittal sinuses and straight sinus.

2. Tentorium Cerebelli2. Tentorium Cerebelli A crescent tent-shaped dural fold that roofs the A crescent tent-shaped dural fold that roofs the

posterior cranial fossa. It covers the upper posterior cranial fossa. It covers the upper surface of the cerebellum and supports the surface of the cerebellum and supports the occipital lobes of the cerebral hemispheres. It occipital lobes of the cerebral hemispheres. It has tentorial notch for the passage of the has tentorial notch for the passage of the midbrain.midbrain.

AttachmentAttachment::1.1. Free border: to the anterior clinoid process.Free border: to the anterior clinoid process.2.2. Attached border: to posterior clinoid process, Attached border: to posterior clinoid process,

superior border of petrous part of temporal superior border of petrous part of temporal bone and margin of the groove for the bone and margin of the groove for the transverse sinus.transverse sinus.

Related venous sinusesRelated venous sinuses:: Straight sinus, superior Straight sinus, superior petrosal sinus, transverse sinus.petrosal sinus, transverse sinus.

A crescent tent-shaped dural fold that roofs the A crescent tent-shaped dural fold that roofs the posterior cranial fossa. It covers the upper posterior cranial fossa. It covers the upper surface of the cerebellum and supports the surface of the cerebellum and supports the occipital lobes of the cerebral hemispheres. It occipital lobes of the cerebral hemispheres. It has tentorial notch for the passage of the has tentorial notch for the passage of the midbrain.midbrain.

AttachmentAttachment::1.1. Free border: to the anterior clinoid process.Free border: to the anterior clinoid process.2.2. Attached border: to posterior clinoid process, Attached border: to posterior clinoid process,

superior border of petrous part of temporal superior border of petrous part of temporal bone and margin of the groove for the bone and margin of the groove for the transverse sinus.transverse sinus.

Related venous sinusesRelated venous sinuses:: Straight sinus, superior Straight sinus, superior petrosal sinus, transverse sinus.petrosal sinus, transverse sinus.

3. Falx Cerebelli3. Falx Cerebelli A small sickle-shaped dural fold, attached A small sickle-shaped dural fold, attached

to internal occipital crest and project to internal occipital crest and project between the two cerebellar hemispheres.between the two cerebellar hemispheres.

Related venous sinusesRelated venous sinuses:: occipital sinus. occipital sinus.

A small sickle-shaped dural fold, attached A small sickle-shaped dural fold, attached to internal occipital crest and project to internal occipital crest and project between the two cerebellar hemispheres.between the two cerebellar hemispheres.

Related venous sinusesRelated venous sinuses:: occipital sinus. occipital sinus.

4. Diaphragma sellae4. Diaphragma sellae A small circular dural fold which form A small circular dural fold which form

the roof of the sella turcica. It has a the roof of the sella turcica. It has a small opening that allow the passage of small opening that allow the passage of the stalk of the hypophysis cerebri the stalk of the hypophysis cerebri (infundibulum of the pituitary gland).(infundibulum of the pituitary gland).

A small circular dural fold which form A small circular dural fold which form the roof of the sella turcica. It has a the roof of the sella turcica. It has a small opening that allow the passage of small opening that allow the passage of the stalk of the hypophysis cerebri the stalk of the hypophysis cerebri (infundibulum of the pituitary gland).(infundibulum of the pituitary gland).

Nerve supply of the dura Nerve supply of the dura matermater Dura is sensitive to stretch which Dura is sensitive to stretch which

produces the sensation of headache produces the sensation of headache or referred pain in the back of the or referred pain in the back of the neck and scalp.neck and scalp.

Nerves are branches of:Nerves are branches of:1.1. Trigeminal nerve.Trigeminal nerve.2.2. Vagus nerve.Vagus nerve.3.3. Hypoglossal nerve.Hypoglossal nerve.4.4. Upper three cervical nerves.Upper three cervical nerves.5.5. Sympathetic nerves.Sympathetic nerves.

Dura is sensitive to stretch which Dura is sensitive to stretch which produces the sensation of headache produces the sensation of headache or referred pain in the back of the or referred pain in the back of the neck and scalp.neck and scalp.

Nerves are branches of:Nerves are branches of:1.1. Trigeminal nerve.Trigeminal nerve.2.2. Vagus nerve.Vagus nerve.3.3. Hypoglossal nerve.Hypoglossal nerve.4.4. Upper three cervical nerves.Upper three cervical nerves.5.5. Sympathetic nerves.Sympathetic nerves.

Blood supply of the dura Blood supply of the dura matermater Arterial supply come from branches of:Arterial supply come from branches of:

1.1. Internal carotid artery.Internal carotid artery.2.2. Maxillary artery.Maxillary artery.3.3. Ascending pharyngeal artery.Ascending pharyngeal artery.4.4. Occipital artery.Occipital artery.5.5. Vertebral arteryVertebral artery

– Middle meningeal arteryMiddle meningeal artery is the clinically is the clinically most important artery. It a branch of the most important artery. It a branch of the first part of maxillary artery. It enters first part of maxillary artery. It enters through the foramen spinosum and grooves through the foramen spinosum and grooves the inner aspect of the squamous temporal the inner aspect of the squamous temporal bone. In cases of fracture of the pterion bone. In cases of fracture of the pterion area, this artery is injured causing bleeding area, this artery is injured causing bleeding and hematoma formation.and hematoma formation.

Arterial supply come from branches of:Arterial supply come from branches of:1.1. Internal carotid artery.Internal carotid artery.2.2. Maxillary artery.Maxillary artery.3.3. Ascending pharyngeal artery.Ascending pharyngeal artery.4.4. Occipital artery.Occipital artery.5.5. Vertebral arteryVertebral artery

– Middle meningeal arteryMiddle meningeal artery is the clinically is the clinically most important artery. It a branch of the most important artery. It a branch of the first part of maxillary artery. It enters first part of maxillary artery. It enters through the foramen spinosum and grooves through the foramen spinosum and grooves the inner aspect of the squamous temporal the inner aspect of the squamous temporal bone. In cases of fracture of the pterion bone. In cases of fracture of the pterion area, this artery is injured causing bleeding area, this artery is injured causing bleeding and hematoma formation.and hematoma formation.

Intracranial venous sinusesIntracranial venous sinuses They are blood-filled spaces between the They are blood-filled spaces between the

layers of the dura mater. They are lined layers of the dura mater. They are lined with endothelium. They posseses no with endothelium. They posseses no valves and drain brain, diploe, orbit and valves and drain brain, diploe, orbit and internal ear and communicate with the internal ear and communicate with the extracranial veins through emissary veins. extracranial veins through emissary veins. They are:They are:

Single sinusesSingle sinuses:: Superior sagittal, inferior Superior sagittal, inferior sagittal, straight, intercavernous and sagittal, straight, intercavernous and basilar plexus of veins.basilar plexus of veins.

Paired sinusesPaired sinuses:: Sphenoparietal, cavernous, Sphenoparietal, cavernous, superior petrosal, inferior petrosal, superior petrosal, inferior petrosal, transverse, sigmoid and occipital sinusestransverse, sigmoid and occipital sinuses

They are blood-filled spaces between the They are blood-filled spaces between the layers of the dura mater. They are lined layers of the dura mater. They are lined with endothelium. They posseses no with endothelium. They posseses no valves and drain brain, diploe, orbit and valves and drain brain, diploe, orbit and internal ear and communicate with the internal ear and communicate with the extracranial veins through emissary veins. extracranial veins through emissary veins. They are:They are:

Single sinusesSingle sinuses:: Superior sagittal, inferior Superior sagittal, inferior sagittal, straight, intercavernous and sagittal, straight, intercavernous and basilar plexus of veins.basilar plexus of veins.

Paired sinusesPaired sinuses:: Sphenoparietal, cavernous, Sphenoparietal, cavernous, superior petrosal, inferior petrosal, superior petrosal, inferior petrosal, transverse, sigmoid and occipital sinusestransverse, sigmoid and occipital sinuses

Cavernous sinusCavernous sinus PositionPosition:: in middle cranial fossa, on each side in middle cranial fossa, on each side

of the body of sphenoid bone.of the body of sphenoid bone. ExtentExtent:: from the superior orbital fissure to the from the superior orbital fissure to the

apex of the petrous part of temporal bone.apex of the petrous part of temporal bone. Contents Contents ::

A.A. Inside the sinus: Inside the sinus: 1.1. internal carotid artery internal carotid artery surrounded by sympathetic plexus and surrounded by sympathetic plexus and 2.2. abducent nerve. These structures are abducent nerve. These structures are separated from the sinus by endothelial separated from the sinus by endothelial layer.layer.

B.B. On its lateral wall: On its lateral wall: 1.1. oculomotor nerve, oculomotor nerve, 2.2. trochlear nerve, trochlear nerve, 3.3. ophthalmic nerve and ophthalmic nerve and 4.4. maxillary nerve (between the endothelial maxillary nerve (between the endothelial lining and the dura mater.lining and the dura mater.

PositionPosition:: in middle cranial fossa, on each side in middle cranial fossa, on each side of the body of sphenoid bone.of the body of sphenoid bone.

ExtentExtent:: from the superior orbital fissure to the from the superior orbital fissure to the apex of the petrous part of temporal bone.apex of the petrous part of temporal bone.

Contents Contents ::A.A. Inside the sinus: Inside the sinus: 1.1. internal carotid artery internal carotid artery

surrounded by sympathetic plexus and surrounded by sympathetic plexus and 2.2. abducent nerve. These structures are abducent nerve. These structures are separated from the sinus by endothelial separated from the sinus by endothelial layer.layer.

B.B. On its lateral wall: On its lateral wall: 1.1. oculomotor nerve, oculomotor nerve, 2.2. trochlear nerve, trochlear nerve, 3.3. ophthalmic nerve and ophthalmic nerve and 4.4. maxillary nerve (between the endothelial maxillary nerve (between the endothelial lining and the dura mater.lining and the dura mater.

Cavernous sinusCavernous sinus TributariesTributaries:: from from 1.1. Superior and inferior Superior and inferior

ophthalmic veins, ophthalmic veins, 2.2. cerebral veins, cerebral veins, 3.3. sphenoparietal sinus and sphenoparietal sinus and 4.4. central vein of central vein of the retina.the retina.

DrainageDrainage:: to to 1.1. superior and superior and 2.2. inferior inferior petrosal sinuses.petrosal sinuses.

Communications Communications ::1.1. With each other through intercavernous With each other through intercavernous

sinuses (anterior, middle and posterior).sinuses (anterior, middle and posterior).2.2. With pharyngeal plexus of veins by With pharyngeal plexus of veins by

emissary veins running through foramen emissary veins running through foramen ovale.ovale.

3.3. With the facial veins through deep facial With the facial veins through deep facial vein and superior ophthalmic vein.vein and superior ophthalmic vein.

TributariesTributaries:: from from 1.1. Superior and inferior Superior and inferior ophthalmic veins, ophthalmic veins, 2.2. cerebral veins, cerebral veins, 3.3. sphenoparietal sinus and sphenoparietal sinus and 4.4. central vein of central vein of the retina.the retina.

DrainageDrainage:: to to 1.1. superior and superior and 2.2. inferior inferior petrosal sinuses.petrosal sinuses.

Communications Communications ::1.1. With each other through intercavernous With each other through intercavernous

sinuses (anterior, middle and posterior).sinuses (anterior, middle and posterior).2.2. With pharyngeal plexus of veins by With pharyngeal plexus of veins by

emissary veins running through foramen emissary veins running through foramen ovale.ovale.

3.3. With the facial veins through deep facial With the facial veins through deep facial vein and superior ophthalmic vein.vein and superior ophthalmic vein.

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