Blood Supply Flashcards
What is an aneurysm?
dilation of vessel of wall
- common at branch points (ex: ACA, Acomm, Basilar)
- lead to subarachnoid hemorrhage
- mass effects on other things
What is a vascular territory?
region of tissue supplied by an artery
What are the 2 major arteries that supply brain? where?
Internal carotids As: antero-superior cerebrum, ant. diencephalon
Vertebral As: posteroinferior, brainstem, cerebellum, post. diencephalon
Where does the ICAs enter brain? What are its branches?
through carotid canals - over foramen lacerum
- SIPHON @ cavernous sinus
- PComms, ACAs, anterior choroidal As, MCAs
Where does the vertebral Arteries enter the brain? What are its branches
-from Subclavin As in transverse foramena > foramen magnum > merge => Basilar A on ventral pons
> PICA
Basilar : AICA, PCA, Superior Cerebellar As
Anterior spinal artery
Name the vessels involved in Circle of Willis
2 Posterior Cerebral As 2 Posterior Communicating As 2 Anterior Cerebral As 1 Anterior Communicating A 2 Internal Carotid As
What are 2 common variations in Circle of Willis
1 large Acomm > most ACA comes from 1 ICA
or large Pcomm and small PCA > ICA supplies PCA territory instead of VAs
Terriotory of ACAs
medial surface, frontal pole
Territory of PCAs
inferior surface, occipital pole
Territory of MCAs
superior-lateral surface, temporal pole
What is a watershed area? What is the relevance?
-border zone of tissue receiving blood from 2 major vessels
-but at the end so loss of blood > perfusion deficit
-these areas are first to suffer
(30% perfussion loss > electrical activity fails
10% loss > neurons die)
What is the blood supply for spinal cord?
What are segmental medullary arteries?
-vessels connecting radicular As around cord to the ASAs and 2PSAs on cord
Aorta > intercostal A > Spinal Branches > Radicular As > ASAs and PSAs < Vertebral arteries
What are dura sinuses?
folds of dura - contain CSF and blood
Distinguish 3 types of Intracranial bleeds
-where? give ex.
- extradural: aka epidural > lens shape lesion
ex: tearing meningeal A - subdural:
ex: tearing cerebral vein as it cross bt subarachnoid space to venous sinus > opens the space bt arachnoid and dura matters - subarachnoid
ex: cerebral A
- fast onset, immediate headache because of ICP
What are arteriovenous malformations?
direct a-v connections with no cap beds
- mass effects
- rupture > hemmorhage
What is embolism?
-occlusion of vessel from anything blocking blood flow
> infarction, ischemia
Thrombus = embolism from a clot
What is CSF? fnc?
- buoyancy - prevent compression, protect brain from impact, equalize pressure
- turned over 3x/day
- remove metabolites
- clear, colourless, low in protein, cells, IgG
- continuous with interstitial fluid
- ventricles lined with ependymal cells (have NO tight junctions)
- total volume = 140ml, most in subarachnoid space
How is the blood-brain barrier maintained?
2: blood-ISF barrier and blood-CSF barrier
- continuous capillaries with tight jncs bt endothelial cells: prevent leaking
- water, gases, lipid-soluble can diffuse through
- transporters required for others
What is hydrocephalus?
-increase CSF, enlarged ventricles, increase pressure
-due to
1. Noncommunicating (Obstruction) > enlarged lateral/3rd ventricles
ex: narrowing of aqueduct
2. Communicating (impaired absorption) > all ventricle enlarged
-caused by agenesis of arachnoid granulations, blockage
(usually cause 2)
What happens with blood-brain barrier breaks down?
What are possible causes?
-leaky > vasogenic edema - increase ICP
-mass effect > midline shift
-on MRI, see gadolinium outside of blood vessel
ex cause: tumour, inflammation
Describe CSF production.
Choroid plexus in lateral, 3rd, 4th ventricles
- invagination of vessels through ependymal cells into ventricles > villi
- have FENESTRATED capillaries
- tight junctions bt ependymal cells
How is CSF reabsorbed?
- via arachnoid granulations in dura sinuses > venous space
2. into lymphatics
What is monro-kellie doctrine?
- skull is closed compartment: brain, blood, CSF
- intracranial space is fixed
- changes to contents > change intracranial pressure nd redistribute contents
What is the ICP?
intracranil pressure = 5-7mmhg/9-12 mmhg
- formed by CSF movement from ventricle to subrachnoid space
- INCREASE > dysfnc > organ failure (sleepiness, confusion, LOC, coma, death)
