martin chapter 3 Flashcards
transient ischemic attack
brief reduction of blood flow
produces transient neurological signs
infarction
death of the tissue due to lack of blood supply
ischemic stroke
Ischemic stroke occurs when there is a blockage in a blood vessel that supplies blood to the brain, resulting in a reduction of oxygen and nutrients to brain tissue. This leads to neuronal damage and, if not promptly treated, tissue death (infarction).
hemorragic stroke
when an artery ruptures thereby releasing blood into the surrounding tissues.
consequences
-loss of downstream flow
-damage to the tissues surrounding the rupture due to the release of blood
anterior brain circulation is fed by?
the internal carotid artery
the anterior circulation is also called carotid circulation
posterior brain circulation is fed by?
vertebral artery
the posterior circulation is also called vertebral basilar circulation.
The vertebral arteries join and form the basilar artery at the pontomedullary junction->the junction between the medulla and the pons.
the brain stem receives blood from which of the 2 circulations?
by the posterior circulation
the hemispheres instead by both anterior and posterior
the arterial supply for the spinal cord is supplied by which circulation?
the systemic circulation
is also provided (at a lesser degree) by the vertebral arteries
the spinal cord receives blood from 2 sources
- anterior and posterior spinal arteries, branches of the vertebral arteries
- radicular arteries, which are branches of intercostal, lumbar and cervical arteries
artery of Adamkiewicz
particular important radicular artery that supplies the lower portion of the spinal cord (caudal to T8)
3 groups of arteries arise from the vertebral and basilar arteries to supply brain stem and cerebellum
paramedial branches, for regions of brain stem close to the midline
short circumferential for lateral regions of brain stem
long circumferential for dorsal regions of brain stem and cerebellum
posterior inferior cerebellar artery
its a long circumferential artery
nourishes the most dorsolateral region of the medulla
this region of the medulla does not receive any other arteries so occlusion in the PICA would result in serious consequences.
do spinal arteries supply the medulla?
yes, the most medial medulla is supplied by spinal arteries
the rest of the medulla is supplied by vertebral arteries
pons vascularization
base= supplied by paramedian and short circumferential arteries
dorsolateral surface: anterior inferior cerebellar artery
rostral to dorsolateral surface: by superior cerebellar artery
AICA and SCA are long circumferential arteries
cerebellum vascularization
supplied by long circunferential branches of the vertebral and basilar aaretries
PICA supplies the caudal portion
AICA and SCA supply more rostral regions of the cerebellum
the basilar artery at the pons-midbrain splits into
the two posterior cerebral arteries
midbrain vascularization
posterior cerebral artery vascularizes most of the midbrain. paramedial and short circumferential branches supply the base and tegmentum, while long circumferential branches supply the tectum.
the colliculi, most important part of the tectum, receive vascularization from the SCA
4 segments of the internal carotid artery
- cervical portion: from common carotid artery bifurcation till the entrance in the carotid canal
- intrapetrosal segment: the portion that passes in the petrous portion of the temporal bone
- intracavernous segment: the portion that passes inside the cavernous sinuses (that overlies the sphenoid bone)
- cerebral segment: till the bifurcation into anterior and middle cerebral artery
what makes the carotid siphon and what is it?
an important radiological landmark and is made by the cerebral and intracavernous portions of the internal carotid artery
3 main branches of the cerebral segment of the internal carotid artery (caudal to rostral)
ophtalmic artery
posterior communicating branch
anterior choroidal artery
what do the deep branches of the 3 cerebral arteries and the branches of the cerebral portion of ICA vascularize?
deep brain white and grey matter regions
the circle of Willis is formed by
the proximal portion of the cerebral arteries and the communicating arteries. Located at the ventral inferior side of the brain
the anterior communicating artery in the circle of willis allow communication between
the anterior cerebral arteries
the posterior communicating arteries in the circle of Willis allow communication between
the middle and posterior cerebral artery (on both sides)
where do the terminal ends of the cerebral arteries anastomose with each other?
in the dorsal convexity of the cerebral hemisphere.
these anastomoses occur when branches are located in the cortex, they don’t occur when the artery has penetrated the brain.
border zones
the peripheral borders of the regions supplied by major vessels. These zones are the ones with the highest ischemic risk cause supplied by the terminal branches of the main arteries, which are the ones with the lowest perfusion
internal capsule vascularization
superior half= supplied by branches of middle cerebral artery
inferior half of anterior limb and genu= supplied by the anterior cerebral artery
posterior limb= supplied by the anterior choroidal artery
basal ganglia blood supply
receive blood supply from anterior and middle cerebral arteries and anterior choroidal artery
many of the branches of anterior and middle cerebral arteries are also called?
lenticulostriate arteries
thalamus and hypothalamus blood supply
thalamus: receive blood supply from branches of the posterior communicating arteries and posterior cerebral arteries
hypothalamus: receive blood supply from branches of anterior and posterior cerebral arteries and the two communicating arteries
the posterior cerebral artery arises from the bifurcation of which artery?
the basilar artery
names of 2 important superficial cerebral veins
superior anastomotic vein lying across the parietal lobe
inferior anastomotic vein lying across the temporal lobe
difference between superficial and deep cerebral veins
superficial cerebral veins UNDERLY the white matter
deep cerebral veins drain structures deep in the white matter (such as the basal ganglia and parts of the diencephalon)
many deep cerebral veins drain into?
the great cerebral vein (of Galen)
do spinal cord and caudal medullary veins drain into the dural sinuses?
no they don’t. through a series of plexus they drain directly into the systemic circulation.
the majority of CNS veins, before going into the systemic circulation, drain into?
dural sinuses
dura mater has 2 layers
periosteal layer, attached to the bone
inner meningeal layer, that apposes the arachnoid mater
where are dura sinuses positioned in respect to the dura mater layers?
in between the periosteal and the meningeal layer
the ophthalmic and facial vein drain into?
the cavernous sinus
the inferior sagittal sinus and the great cerebral vein drain into?
straight sinus
the superior sagittal sinus and the straight sinus form?
the 2 transverse sinuses
the two transverse sinuses drain into?
the 2 sigmoid sinuses that drain into the 2 internal jugular veins
veins of the midbrain drain into?
the great cerebral vein that then drains into the straight sinus
the pons and rostral medulla veins drain into?
the superior petrosal sinus
the cerebellar veins drain into?
the great cerebral vein and the superior petrosal sinus
endothelial cells of the CNS have 2 unique characteristics
- adjacent endothelial cells are tightly joined preventing movements of compounds into the extracellular compartment
- the endothelial cells lack the required transport mechanism
->little transcellular movement of compounds from intravascular to extracellular compartment.
the 8 structures that lack the BBB are collectively called
circumventricular organs
in these areas neurons recognize blood born compounds or neurosecretory products are secreted into the blood
–>they serve to regulate the body’s internal environment
the CSF contained in the ventricles and in the subarachnoid space is approximately?
140ml
25 ml is in the ventricles, the rest in the subarachnoid space
what is approx. the intraventricular pressure?
10-15 mmHg
do ventricles have a barrier?
no, neurochemicals inside the CSF contained in the ventricular system can easily reach the brain tissues adjacent to the ventricles
blood-CSF barrier
imposed by the choroid epithelium
analogous to the BBB
inhibits component from the blood to go into the CSF
choroid plexus is made by
-choroid epithelium that secretes CSF
-blood vessels
-pia mater
the ventricles are lined by?
ependymal cells
ciliated cuboidal cells that allow the inflow of extrachoroidal CSF (secreted by brain capillaries)
the CSF produced in the 3rd ventricle is mixed with the one produced in the lateral ventricles thanks to?
the inter ventricular foramina, one for each lateral ventricle
the CSF in the third ventricle flows into the 4th ventricle through?
the cerebral aqueduct
three apertures in the roof of the 4th ventricle drain fluid into the subarachnoid space
2 foramina of luschka on the lateral margins of the 4th ventricle and the foramen of magendie in the middle
the Pia penetrates the brain together with blood vessels forming
perivascular spaces or Virchow Robin spaces through which CSF can flow from the subarachnoid space to interstitial spaces within the brain and spinal cord
the subarachnoid space is dilated in regions called cisterns where CSF accumulates. 5 major cisterns:
-lumbar cistern
-interpeduncular cistern
-quadrigeminal cistern
-pontine cistern
-cisterna magna
the lumbar cistern, where is it?
in the caudal portion of the spinal canal
we can insert a needle in the interverterbral space (between 3rd-4th or 4th-5th lumbar vertebrae) to collect CSF without risk of damage the spinal cord
the most caudal segment of the spinal cord is at the level of which vertebra?
first lumbar vertebra
cauda equina, what is it?
a bundle of spinal nerve roots that extend from the lower segment of the spinal cord
CSF fluid passes from the arachnoid space into the dural sinuses thanks to?
arachnoid villi, microscopic evaginations of the arachnoid mater
arachnoid granulations
clusters of arachnoid villi present in the dorsal (superior) convexity of the cerebral hemispheres
glymphatic system
The glymphatic system describes how CSF flows into the brain interstitium along perivascular spaces (also known as Virchow-Robin spaces). These spaces are essentially formed between the pia mater and the blood vessels as they penetrate the brain tissue.
