Exam One - Meninges, CSF, and Neurovasculature of Brain Flashcards
Which meninges develop from the neural crest?
pia and arachnoid
Which meninges develop from the mesoderm
dural
how many layers are the embryonic meninges?
single layered
when do the 3 layer meninges develop by?
end of the first trimester
What are the 3 roles of the meninges?
protection
supportive framework
enclose a fluid filled cavity
Name the layers from outer most to inner most
periosteal dura
meningeal dura
dural border cell
arachnoid barrier cells
basement membrane
arachnoid trabeculae
pia mater
basement membrane
What constitutes leptomeninges?
arachnoid and pia
meningeal dura separates from periosteal dura at specific locations called ___________
falx cerebri
tentorium cerebelli
falx cerebri
longitudinal fissue between cerebral hemispheres
tentorium cerebelli
horizontal between cerebral hemispheres and cerebellum
name the cranial venous sinuses
superior sagittal
inferior sagittal
straight
confluence of sinuses
transverse
sigmoid
sup and inf petrosal sinuses
supratentorial cavity
superior to tentorium cerebelli with right and left halves, contains the hemispheres
infratentorial cavity
inferior to tentorium cerebelli, contains the brainstem and the cerebellum
herniation syndromes
occur when brain tissue, blood, or csf shift from their normal position inside the skull across structures such as flax cerebri, tentorium cerebelli, and foramen magnum
herniation type 1
subfalcine (cingulate) herniation:
- one cerebral hemisphere herniates under the flax cerebri (most common)
herniation type 2a
central (downward transtentorial) herniation: diencephalon and part of temporal lobes are squeezed through a notch into tentorium cerebelli
herniation type 3
uncal (transtentorial) herniation: the medial temporal lobe (uncus) herniates over the edge of tentorium cerebelli
herniation 2b
central (upward transtentorial) herniation: an infratentorial mass (tumor, cerebellar hemorrhage) compresses the brainstem, twisting it and causing patchy brainstem ischemia *more serious than 2a
herniation 4
cerebellar-tonsillar herniation: the cerebellum undergoes downward herniation through the foramen magnum
What causes herniation syndromes?
develops as a complication of a disorder that causes increased intracranial pressure
increased intracranial pressure may be caused by…
- space occupying lesions
- generalized swelling or edema of the brain
- increased venous pressure
- obstruction of csf flow
meninges of the spinal cord
spinal dura - single layer corresponding to meningeal dural
- epidural space (not in brain)
- spinal arachnoid
-subarachnoid space
- spinal pia (denticulate lig, filum terminale)
spinal cord ends at
conus medullaris (L1-2)
spinal dura ends at
S2
epidural space
between dura and vertebral periosteum
- contains fatty tissue, loose connective tissue, and epidural venus plexus
- extends from the base of the skull to S2 vertebrae
tethered cord syndrome is a defect of what?
secondary neurulation
- conus medullaris and filum terminale are abnormally fixed to the vertebral column
clinical signs of tethered cord syndrome
- lower extremety weakness
- sensory loss
- asymmetrical growth of legs and feet
- bowel and bladder disfunction
What allows suspension of the csn?
- periosteal dura serves as periosteum of the cranium
- adhesion between dura and arachnoid
- adhesion of pia to arachnoid by trabeculae
- pia adhesion to brain
- denticulate ligamnets
- buoyancy in csf
meningitis
inflammation of the pia-arachnoid and fluid built up in the resulting enclosed space
is viral or bacterial meningitis more severe?
bacterial
- viral is more frequent and less severe
what are clinical signs of meningitis
fever, headache, stiff and painful neck, acutely ill, may have depressed consciousness
- increased csf may compress CNS structures leading to impaired mental status, seizures, hemiparesis, and cranial nerve palsy
CSF produced?
produced by the choroid plexuses within the ventricles of the brain
composition is like plasma except it has few cells and very little protein/cholesterol
What is the major way to clear CSF from the cranium
- arachnoid projections
arachnoid granulations (villi)
protusions into the superior sagittal sinus, transport csf from the subarachnoid space into the venous system
in which direction does csf flow?
down the pressure gradient
extradural (epidural) hemorrhage
bleeding inside the skull but outside the dura
-fast
subdural hemorrhage
blood collects at dura-arachnoid junction, but still outside the brain
-slow, really dangerous
what is the main cause of meningeal hemorrhages?
TBI
Main role of brain ventricles
production and circulation of csf
ependymal cells
- line ventricles
- layer of cuboidal epithelial cells
-luminal surface ciliated with microvilli - base is connected with the subependymal layer of astrocytic processes
tanycytes
extend processes through astrocytic layer to blood vessels from nutrient transport
choroid plexus represents the…
blood-csf barrier
cause of hydrocephalus
blockage of the csf movement or failure of the absorption mechanism that results in csf accumulation in ventricles
obstructive hydrocephalus
- due to blockage of flow of csf
- occurs where there is no choroid plexus
communicating hydrocephalus
- overproduction or decreased absorption of csf
What are the 2 major arterial systems serving the brain?
-vertebral-basilar artery
- internal carotid artery
VBA and ICA unite to form
circle of willis
ICA supplies
most of the telencephalon and diencephalon
VBA supplies
brainstem, cerebellum, and parts of the occipital and temporal lobes and diencephalon
circle of willis suppllies
deep cerebral structures
branches off ICA
- middle cerebral
-anterior cerebral - posterior communicating
-anterior communicating
branches off VA
anterior spinal
posterior spinal
post. inferior cerebellar a. (PICA)
branches off BA
- anterior inferior a (AICA)
- superior cerebellar
posterior cerebral
circle of willis encircles…
optic chiasm, infundibulum of pituitary gland, mammillary bodies (hypothalamus)
MCA supplies…
lateral surface of frontal, parietal, occipital, and temporal lobes
What are segements off MCA
- lenticulostriate arteries (LCA)
- M1
M1 supplies…
medial temporal lobe and lenticulostriate a
Where do aneurysms on the MCA frequently arise?
bifurcation of M1 trunks
ACA supplies…
medial portion of the cerebral hemispheres
30-50% of intracranial aneurisms are found at ACA - proximity to optic chiasm results in visual deficits
PCA supplies
midbrain, thalamus, and ventral and medial surfaces of temporal and occipital lobes
watershed infarcts
lateral surfaces where ACA, MCA, and PCA overlap
- inadequate perfusion of the border zones may result in watershed infarcts caused by hypotension, vasculities, or blot cloth obstruction
cause of most neurological deficits in CNS is…
cerebrovascular accidents
ischemia
reduced blood supply - more dangerous
hemorrhagic stroke
bleeding into cns
risk factors for CVAs
hypertension, anticoagulation and or inherited coagulation deficit
3 causes for CVAs
- aneurysm
-embolism
-arteriovenous malformation
aneurysm
dilation of a vessel wall - usually an artery
embolism
occlusion of a cerebral vessel by clot, tumor or bacteria
arteriovenous malformation
communication between major arteries and veins do not develop normally
