CRANIAL MENINGES• Dura: – an inner (meningeal) layer and outer (periosteal) layer – Most of the dura’s venous sinuses lie between the dural layers – Dural layers are generally fused, except where they separate to provide space for the venous sinuses and where the inner layer forms septa between the brain portions – Outer layer firmly attached to inner surface of cranial bones; inner layer continuous with spinal dura
Meninges: Dura Mater• Reflections: Falx cerebri: Midline fold of dura mater extending between two cerebral hemispheres. Tentorium cerebelli: Dural fold located between cerebellum and occipital lobes of cerebral hemispheres.
Meninges: Dura Mater• Reflections: Falx cerebelli: Dural fold between two cerebellar hemispheres. Diaphragma sellae Dural fold over hypophyseal fossa.
CRANIAL MENINGES CRANIAL MENINGES• Arachnoid: – Delicate avascular membrane covers the subarachnoid space – Between the arachnoid and dura mater lies the subdural space – Arachnoid granulations project into the superior sagittal sinus
• Arachnoid granulations－ project into sinuses of dura mater, serve as sites where cerebrospinal fluid diffuses into bloodstream
Circulation of cerebrospinal fluidCSF drains from lateral ventricle interventricular foramina third ventricle mesencephalic aqueduct median and two lateral apertures fourth ventriclesubarachnoid space arachnoid granulations superior sagittal sinus vein
CRANIAL MENINGES• Pia: – Thin connective tissue membrane that covers the brain surface and extends into sulci and fissures and around blood vessels throughout the brain – Beyond the end of the spinal cord continues as the filum terminale
Dural Nerve Supply• Branches of trigeminal,vagus and 1st 3 cervical nerves• Sensitive to streching which produces the sensation of headache
Intra cranial hemorrhage1.Extra dural (middle meningeal artery)2.Subdural (sup.cerebral vein)3.Subarachnoid (the circle of willis) Blood stained csf4.Cerebral (lenticulostriate artery)
VENOUS DRAINAGE • Venous drainage of the brain and coverings includes veins of the brain itself, dural venous sinuses, dura’s meningeal veins, and diploic veins • Eventual cerebral venous drainage is the internal jugular vein • Cerebral veins contain no valves
Dural venous sinuses• : Superior sagittal sinus: Lies along superior margin of falx cerebri. receives in its course the sup.cerebral vein Inferior sagittal sinus: Lies along inferior margin of falx cerebri. joins great cerebral vein
Meninges: Dura Mater• Dural venous sinuses: Straight sinus: Lies at intersection of falx cerebri and tentorium cerebelli. Confluence of sinuses: Common confluence of superior sagittal sinus and straight sinus.
Meninges: Dura Mater• Dural venous sinuses: Transverse: Begins at confluence of sinuses. Extends along edges of tentorium cerebelli. Right receives blood from superior sagittal sinus. Left receives blood from straight sinus. receives sup.petrosal sinus,inf.cerebral n cerebellar veins n diploic veins
The flowing of the blood in dural sinus Sup. sagittal sinus Inf. sagittal sinus Straight sinus Confluence of sinus Transverse sinus Sup. petrosal sinus Sigmoid sinusCavernous sinus Inf. petrosal sinus Internal jugular vein
Cavernous sinus• Middle cranial fossa• Extends from Sup.orbital fissure to petrous part of temporal bone• Tributaries• Sup.n inf.ophthalmic veins,cerebral veins,the sphenoparietal sinus n the central vein of retina• Drains Posteriorly into sup n inf petrosal sinuses and inferiorly into pterygoid venous plexus
Cavernous sinus• Position: lies on each side of sella turcica• Relations of cavernous sinus: – Internal carotid artery and abducent nerve run through the sinus – Oculomotor and trochlear nerves and ophthalmic and maxillary divisions of trigeminal nerve lie in the lateral wall of the sinus
Veins of brainSuperficial cerebral veins• Drain blood from cortex and subcortical medullary substance and empty into adjacent sinuses of dura mater
Veins of brain• Deep cerebral veins: drain deeper parts of hemispheres, basal nuclei, internal capsule, diencephalon and choroid plexus, ultimately form great cerebral vein which enter straight sinus