L03 - Meninges and Blood Supply Flashcards
3 functions of the meninges?
Protection
Supports the blood vessels supplying the brain
Space for CSF flow
List the layers of tissue from skin of scalp to Pia Mater.
Skin of scalp
Periosteum
Bone of skull
Dura mater (Periosteal)
Dura mater (Meningeal)
Arachnoid mater
Pia mater
Difference in the coverage of 2 Dura Mater layers?
Periosteal layer: Tightly adhered to skull inner surface, only in head, not in spine
Meningeal layer: Lines endosteal layer in head except at dura folds (invagination that separates from endosteal layer),
covers brain + spinal cord
Difference in the ‘ends’ of the dura mater layers?
Periosteal: End at Foramen Magnum
Meningeal: Filum terminale (S2)
List the meningeal dura mater invaginations.
Falx Cerebri
Tentorium cerebelli
Falx cerebelli
Diaphargma sellae
Which meningeal dura mater invaginations form sinuses?
Falx cerebri = forms superior and inferior sagittal sinus
Tentorium cerebelli = forms sigmoid sinus
What are the quadrants formed by meningeal dura mater invaginations?
Form compartments
Left / Right
Supratentorial/ Infratentorial
Blood supply of meninges?
mostly middle meningeal artery
responsible for most intra-cranial haemorrhages after trauma
Nerve supply of meninges?
Supratentorial = Trigeminal nerve (mostly Opthalmic division V1, inferior aspect supplied by V2 and V3)
Infratentorial = Cervical spinal nerves C1-3
Explain how migraine occurs?
Meningitis > Inflammatory reaction causes vasodilation > Increased pressure on meninges
Describe the structure of Arachnoid mater.
Loose spider-web like
Linked to pia mater via trabeculae of collagen fibers
Separated from pia mater by CSF in subarachnoid space
Function of the Arachnoid mater?
- Arachnoid granulations (villi): for cerebrospinal fluid (CSF) circulation into venous sinus (back to venous blood)
- Support cerebral blood vessels (arteries, veins)
- Space for cranial nerves (impaired if subarachnoid space is inflamed)
- ‘Cushion’s the brain
Describe the structure of pia mater?
- Soft innermost membrane
- Tightly covers brain and spinal cord surface
- Follow all cerebral sulci and gyri
Function of pia mater?
Cover all sulci and gyri
Invaginates into ventricles
forms choroid plexus (together with ependymal cells; gives CSF)
Compare the state of the dura and vessls involved in Epidural and Subdural hematoma?
Epidural:
Dura = peeled off skull
Vessel = Middle meningeal artery
CT scan = Biconvex shape
Subdural:
Dura = attached to skull
Vessel = bridging veins
CT scan = Inner surface follows curvature of brain = crescent shape
Cause of subarachnoid hemorrhage?
Aneurysms in cerebral artery
> > bleeding within subarachnoid space (between arachnoid membrane, pia mater)
> > CSF space filled with blood
CSF typical volume, daily production and functions?
Volume = 150ml in adult (~50ml in brain, 100ml in spine)
Daily production = 450ml
Functions = Cushion, Nourish by nutrient and waste exchange, Pressure regulation
Compare CSF composition with serum.
- More sodium, chloride; less calcium and potassium than serum
- > 50% of serum glucose, trace of protein
Origin of CSF production?
Choroid plexus in each right / left lateral ventricles secretes CSF
> > flows through interventricular foramina / Foramen Monro into third ventricle
List the sequence of CSF flow in the brain.
Choroid plexus in each lateral ventricle
» Interventricular foramina/ Foramen Monro
» 3rd ventricle
» Cerebral aqueduct
» 4th ventricle
» 3 openings into subarachnoid space (2 lateral Foramen Lushka + 1 median Foramen Magendie)
» Reabsorbed into venous blood of dural venous sinuses at arachnoid villi
Which major large vessels form the cerebral arterial supply?
4 arteries
Left + Right Internal Carotid Artery
Left + Right Vertebral Artery
What delineates Anterior and posterior cerebral circulation
Horizontal cut through the posterior communicating artery/ middle of Circle of Willis
Arteries that form the anterior cerebral circulation?
From 2 x Internal Carotid Arteries (through Cavernous sinus):
–Ophthalmic artery
–Anterior cerebral artery (linked with anterior communicating artery)
–Middle cerebral artery
–Perforators
Arteries that form the posterior cerebral circulation?
From 2 x Vertebral Arteries
- Posterior Inferior Cerebellar artery
- Anterior Inferior Cerebellar artery
- Basilar artery + Pontine arteries branches
- Superior Cerebellar artery
- Posterior Cerebral artery
Connect with anterior cerebral circulation with posterior communicating arteries
Branches of the Anterior cerebral artery? Supplies which part of the brain?
Orbitofrontal artery Frontopolar artery Callosomarginal artery Pericallosal artery Posterior inferior frontal artery Superior, inferior parietal arteries
- Travels within interhemispheric fissures, supplies front part of cerebrum between 2 hemispheres
Which cerebral artery is Implicated in subarachnoid hemorrhage? Why?Where is it located?
Middle cerebral artery
Perforators branch off MCA suffer from high haemodynamic stress due to acute angle and sudden narrowing of lumen, thus prone to fissure or blockage
Between frontal and temporal lobe
Compare the vascular territory of the ACA and MCA?
ACA = anterio- medial aspects, deep branches supply caudate head, internal capsule
MCA = antero- lateral aspects, deep branches supply putamen + globus pallidus, inferior division supplies lateral occipital lobe, internal capsule
MCA deep branches block can cause what pathologies?
MCA deep branches/ perforators supply putamen, globus pallidus
Block = affect speech, basal ganglia, Sensori-motor cortex
Origin and supply of the Anterior choroidal artery?
Origin = posterior wall of the internal carotid artery (ICA) between the origin of the posterior communicating artery
Supply = anterior temporal horns of lateral ventricles + deep brain structures (i.e. optic tract, internal capsule, thalamus)
List the main cerebral vessels that lie over the medulla.
PICA
Intracranial vertebral artery
AICA
(inferior aspects of the brain stem)
List the main cerebral vessels that lie over the pons.
Pontine arteries
Basillar artery
Superior cerebellar artery
Posterior cerebral artery
List the main cerebral vessels that lie over the midbrain.
Posterior communicating artery
Middle cerebral artery
Internal carotid artery
Anterior cerebral artery
Branches of the Posterior cerebral artery? Vascular territory?
Parieto-occipital
Calcarine artery
Inferior temporal
Posterior aspect
Deep branches: thalamus, Occipital, temporal, parietal lobes (medial)
Blood supply of cerebellum?
Superior cerebellar artery
AICA
PICA
Anterior and posterior communicating arteries are collaterals that ensure no ischaemia and cerebral infarction if blocked. True or false.
False
Collaterals provide limited support blood supply in each other’s territory, cannot prevent ischaemia/ infarction
What are the variants of Circle of WIllis?
25% complete circle, 75% incomplete
Hypopalstic PComA ~ 30%
Hypoplastic AComA ~ 10%
Describe the gross venous drainage of the brain?
Superficial and Deep cerebral veins drain into dural venous sinuses
List all superficial cerebral veins.
- Superior cerebral veins
- Superficial middle cerebral vein
- Inferior cerebral veins
List all deep cerebral veins.
- Internal cerebral veins x2
- Basal vein of Rosenthal x2
- Veins of cerebellum, colliculi etc
- Great vein of Galen
Trace the major superficial and deep venous drainage of the brain from superior sagittal sinus to internal jugular vein.
Superior sagittal sinus (CSF granulations)
joined by deep drainage: Great cerebral vein + Basal vein of Rosenthal + inferior sagittal sinus»_space; straight sinus
>> Confluence of sinuses >> Transverse sinus >> Sigmoid sinus (tentorium cerebelli) >> Jugular foramen >> Internal jugular vein
List some smaller sinuses for brain vein drainage.
Occipital sinus
Cavernous sinus
Anterior and Posterior intercavernous sinuses
What passes through the cavernous sinus?
Internal carotid artery
Abducent nerve
What is in the wall of the cavernous sinus?
Cranial nerves: 3,4,5
Oculomotor
Trochlear
Opthalmic V1
Maxillary V2