Lecture 4 Flashcards
three meningeal layers of CNS
dura, arachnoid, pia
two layers of dura mater
periosteal (endosteal) layer = adheres to inner surface of skull
meningeal layer = fused with periosteal layer except sinua and dural folds, forms a sheath for the cranial nerves to exit skull
dural folds
falx cerebri = divides R/L hemispheres
tentorium cerebelli = separates cerebellum from hemispheres
falx cerebelli = divides R/L cerebellar hemispheres
dural sinuses
large venous channels that are formed within the layers of the dura
5 dural sinuses
superior sagittal sinus
inferior sagittal sinus
straight sinus
transverse sinus
sigmoid sinus
arachnoid layer
- anchored to pia layer via arachnoid trabeculae allowing a little mobility with stability
- cerebral blood flow occurs
pia layer
- cerebral arteries penetrate to supply blood in the brain tissue
- pia anchors to glial membrane layer - glial layer formed by astrocytes
meningitis
- inflammation of meningeal layers of CNS, viral or bacterial causes
- Brudzinski’s or Kernig’s test
epidural space
- potential space between the fused dura and skull
- does not exist in healthy individual -> hematoma or infection may grow or create epidural space
epidermal hematoma
hemorrhage into space due to trauma, rupture of middle meningeal artery
bridging veins
travel through subdural space (potential space between dura and arachnoid) to drain the veins of cerebral hemispheres into the venous sinuses
subdermal hematoma (hemorrhage) SDH
rupture of bridging veins as they pass from brain to venous sinus, they cross suture lines
- associated with high mortality
subarachnoid space
- space between arachnoid and pia matter
- contains CSF and CNS arteries, CSF protects (cushions) the brain
arachnoid trabeculae
in subarachnoid space “anchoring” to pia layer,
arachnoid trabeculae help anchor brain
arachnoid granulations
small sub-arachnoid “out-pockets” of subarachnoid space that interfere with the dura sinuses
- one way valves allowing CSF to flow from arachnoid granulations into dural sinuses
subarachnoid hemorrhage SAH
artery ruptures in subarachnoid space, often due to saccular (berry) aneurysms rupture
“worst headache of my life”
cisterns
widened areas of subarachnoid space
lumbar cistern
located caudal to T12/L1, site for lumbar puncture
lumbar puncture LP
CSF accessed at the lumbar cistern, obtain sample, measure CSF pressure, remove CSF to treat hydrocephalus, inject pharmaceuticals
ventricular system
cavities within the brain and spinal cord that contain circulating CSF
lateral ventricles
R/L, form C-shaped horn, most superior space
foramen of Monro R/L
interventricular foramen that connects the R/L lateral ventricles with the third ventricle
third ventricle
located in midline between the R/L thalamus
cerebral aqueduct (aqueduct of Sylvius)
connects the third ventricle with the fourth ventricle, located in midbrain between tectum and tegmentum
fourth ventricle
located posterior to the tegmentum of the pons, CSF fluid exits through foramen of Luschka and R/L lateral foramen of Magendie
central canal of spinal cord
midline of spinal cord, CSF from fourth ventricle also circulates within the spinal cord via central canal
CSF function
protects brain, remove waste products from metabolism, provide stale environment for interstitial fluid of brain tissue
total quantity of circulating CSF
150mL
CSF flow pressure gradients
hydrostatic pressure in subarachnoid space > pressure in dural sinuses
- gradient allows CSF to flow from arachnoid granulations into venous sinuses
- at least 1mmHg greater
- dural sinus pressure is 5mmHg
- rate of CSF flow into venous sinus is critical for maintaining appropriate CSF volume
hydrocephalus
blockage of CSF flow in ventricle system or imbalance of CSF production/reabsorption
lumbar puncture pressures
sidelying = 8-15mmHg
sitting = 14-22 mmHg
blood brain barrier BBB
- barrier between circulation and the CNS
- substances allowed to flow to and from CSF are tightly controlled by physical characteristics of choroid capillary wall and choroid cell
- interface between brain capillaries and brain tissue
ependymal cells
line the walls of the ventricles
choroid plexus
- specialized vascular structures located in the lateral, 3rd, and 4th ventricles
- produce CSF
- lined with choroid epithelial cells
function of BBB
- monitor nutrients and electrolyte balance
- prevent circulating transmitters (AcH, dopamine, and NE/E) from entering CNS
- prevent toxins, large molecules and water soluble molecules from entering CNS
