Meninges Flashcards
describe the layers of the brain
Dura mater (tough fibrous bridges attached to skull) bridges over fissures and sulci
Arachnoid (delicate sealed bag for CSF)
–arachnoid trabeculae (ropes)
Pia mater (delicate, dips into crevices)
CEREBRAL ARTERY BRANCH
what is found embedded within the pia mater
cerebral artery branch
what helps position the brain in one place
arachnoid trabeculae
what arteries are found within the dura mater
branches of the middle meningeal artery
which courses close to pterion
what happens if the middle meningeal artery is damaged
extradural haemorrhage
what are the different cisterns found in the brain
what are cisterns
2 AT FRONT:
interpeduncular cistern
-central part of midbrain
-in between peduncles
cisterna pontis
-junction of pons and medulla
2 AT BACK:
superior cistern
-behind midbrain
-behind superior and inferior colliculus
cisterna magna
-junction between cerebellum and brainstem
SPACES FILLED WITH CSF
what is the clinical significance of the cisterna magna
accessible by a neurosurgeon (v delicate)
vital centres in brainstem- so dangerous
rare times to sample csf under radiographic control
where does the arterial circle of Willis lie
what is the clinical significance of this
in subarachnoid space
can cause a subarachnoid haemorrhage
it can swell (BERRY ANEURYSM) and burst– thunderclap headache– unconsciousness
90% occur in anterior circulation
a frequent site is where posterior communicating artery arises from the ICA
if there was a venous bleed around brain- subdural haem evolves over days
what are pia denticulate ligaments
position mechanism supporting spinal cord in meningeal system
NOT ARACHNOID TRABECULAE
tooth like
where is a good place to sample csf
cauda equina collection of roots good place to sample csf
why are the roots long at the cord end
early- S1 root origin close to S1 vertebra
vertebral column grows faster than spinal cord during development
S1 roots exits well below the origin in the cord
spinal cord tapers off to form conus medullaris
what is special about the veins in the brain
they have thin walls and NO VALVES
they emerge from the brain and lie in the subarachnoid space
drain into cranial venous sinuses
grouped into EXTERNAL (variable) and INTERANAL cerebral veins
what is the point of the dural folds
what are the dural folds
dura compartmentalises the brain
good protection mechanism
decreases the energy (if trauma) minimises these effects
dural folds
FALC CEREBRI with a free edge
divides posteriorly to form TENTORIUM CEREBELLUM
cerebral veins join into superior sagittal sinus
drains posteriorly and joins straight sinus
what is in the floor of the lateral ventricle
top thalamus (is floor of LV)- next to third ventricle
caudate nucleus (pair of LV)
what does the great vein of galen do
drains deep structures via internal cerebral vein and basal vein
what do the deep veins above the thalamus do
great cerebral vein (vein of galen) drains deep structures via internal cerebral vein and basal vein
internal cerebral vein has thalamostriate vein- drains caudate nucleus and putamen
choroidal vein drain choroid plexus of lateral ventricle
what sits in the tentorium notch
what is clinical significance
midbrain/ brainstem
midbrain = 2 big bulges and an aqueduct
so if there is a space occupying lesion from eg. herniating temporal lobe pushes into this space is dangerous
forces bit of brain into this “space”
CONING
-vital centres are particularly sensitive
what is csf
how much produced
clear colourless fluid which fills the ventricles of the brain surrounds the brain and spinal cord
150ml produced at 0.5ml/min
turns over 4 times a day
production about 500ml
75ml in cisterns
50ml in subarach space
25ml in ventricles
how is csf formed
formed in the choroid plexus
specialised ependymal cell on surface
adapted to make csf in all ventricles
core of vascular tissue in pia
also made from blood vessels around ventricles
how does csf flow
csf flows out of ventricle system in subarachnoid space via apertures in fourth ventricle
choroid plexus is in lateral ventricle, roof of 3rd and 4th ventricles
continually produced and nudged along due to pulsation of arteries and access subarachnoid space through 3 apertures
3 apertures in 4th ventricle to allow subarachnoid space
SINGLE MEDIAN
- Magendie
PAIRED LATERAL APERTURES
-Luschka
what happens to csf after ventricles
flows to cistern/ subarachnoid space and exits to arachnoid granulations
interfacing with venous system
therefore csf to venous blood
uptake of csf from subarachnoid space in arachnoid granulations and then superior sagittal sinus
what is a singular arachnoid granulation and how does it bridge through dura
arachnoid villus
bridging in superior sagittal sinus
therefore movement of csf into venous system
what is hydrocephalus
due to blocked transport (non-communicative)/ overproduction/ blocked absorption (communicative) of CSF
blocked exits eg. meningitis, congenital
if fused sutures
get brain compression
brain box extension if sutures not fused
catheter (shunt) in ventricular system -CSF into peritoneal to decompress system
