L4 - blood supply to the brain Flashcards
what % of o2 consumption does the brain use
20
what happens with an increase in intracranial pressure
- herniations or certain structures into other places
- compression of ventricles
TIA
transient ischaemic attack
main arteries which supply the brain
- vertebral
- internal carotid
what is the vertebral artery a branch of
subclavian
how does the vertebral artery travel from neck to brain
- Ascend in the neck through transverse foramen of the cervical vertebrae
- Enter skull via foramen magnum
- fuse at base of brainstem to form basilar artery
basilar artery - how it forms
fusion of vertebral arteries at base of brainstem
what is the internal carotid artery a branch of
common carotid
where does the common carotid artery give off the internal and external carotid artery
neck
how many branches does the external artery supply to the face
8
how does the internal carotid artery enter the skull
carotid canals in temporal bone
where does the internal carotid artery emerge
other side of optic chiasm
where are the characteristic bands of the internal carotid artery
cavernous sinus
how many pairs of cerebellar arteries does the vertebral artery give off
3
what are the pairs of arteries which the vertebral artery gives off
- posterior inferior cerebellar artery (PICA)
- superior cerebellar artery (SCA)
- posterior cerebral artery (PCA)
which arteries does the vertebral artery give off
- posterior inferior cerebellar artery
- anterior spinal artery
- posterior spinal artery
- anterior inferior cerebellar artery
- basilar artery
- superior cerebellar artery
- posterior cerebral artery
how many branches of the vertebral artery are there
7
posterior inferior cerebellar artery (PICA)
supplies the posterior and inferior surface of the cerebellum
anterior spinal artery
anterior aspect of spinal cord
posterior spinal artery
- posterior aspect of spinal cord
- In some people they come from the VA and in some people, they come from the PICA
anterior inferior cerebellar artery
supplies anterior and inferior portions of the cerebellum
basilar artery
Tiny branches in the surface of the pons of the brainstem: transverse pontine branches – supply the anterior aspect of the pons
superior cerebellar artery
tucks under and supplies the superior aspect of the cerebellum
posterior cerebral artery
- terminal branch of the basilar artery
- supplies posterior aspect of the cerebrum
terminal branch of the basilar artery
posterior cerebral artery
branches of the internal carotid artery
middle cerebral artery
anterior cerebral artery
paired branches of the internal carotid artery
middle cerebral artery
middle cerebral artery
Supply the middle and lateral portions of the cerebrum
anterior cerebral artery
Tucks under the midline portion of each hemisphere to supply its anterior and medial aspect
circle of willis
Anastomotic loop interconnecting the internal carotid and vertebral / basilar system
function of circle of willis
ensures collateral circulation if decreased blood flow if one vessel is occluded
location of circle of willis
surrounds optic chiasma and hypothalamus
constituents of the circle of willis
- anterior, middle , posterior cerebral arteries
- anterior and posterior communicating arteries
- internal carotid arteries
- basilar artery
examples of variations within the circle of willis
- Absence of anterior communicating artery
- Both anterior cerebral arteries come from the same internal carotid artery (1 common trunk)
- Under-developed / not present posterior communicating artery
- Under-developed / not present posterior communicating artery x2
- Under-developed PCA x1
- Under-developed PCA x2
when does a berry aneurysm occur
weakening of the wall, especially when the arteries are highly branched
what % of strokes are caused by a berry aneurysm
10%
what does the ACA supply
superior and medial area of the frontal and parietal lobes and the corpus callosum
what does the MCA supply
lateral areas of the frontal, temporal and parietal
what does the PCA supply
occipital lobe and inferior and medial surface of the temporal lobe
striate arteries
deep / perforating arteries
functions of striate arteries
- grey matter
- thalamus
- deep white matter
- internal capsule
- supply includes descending motor pathway
internal capsule
major fibre bundle to and from cerebral cortex and aids motor functions
watershed areas
regions which receive blood supply from distal areas of adjacent cerebral arteries
what happens to watershed areas when there is a drop in pressure
neither of the distal branches reach the areas which can result in a susceptible ischaemia
where do superficial veins drain into
straight into the dural sinuses
where do deep veins drain into
great cerebral vein –> straight sinus –> confluence of sinuses
cavernous sinus
located lateral to the body of the sphenoid bone
confluence of sinuses
where the superior sagittal, straight and transverse sinuses meet
where does venous blood drain into from the confluence of sinuses
internal jugular veins
clinical relevance of cavernous sinus anatomy
Infections are likely to reach the cavernous sinus if there is injury to the ‘danger triangle’ of the face
what is the danger triangle
here, veins which have direct communication to the cavernous sinus
examples of infections which can spread into the cranial cavity from the cavernous sinus
- meningitis
- cavernous sinus thrombosis
clinical features of cavernous sinus thrombosis
- headaches
- oedema of the eyeball
- numbness of the face
- palsies of cranial nerves
location of meningeal artery
periostial dura
bridging veins
the way in which the superficial cerebral arteries empty into the superior sinus
how to the bridging veins enter the superior sagittal sinus
pierce the arachnoid before piercing the superior sagittal sinus
where are the cerebral arteries and veins
subarachnoid space
epidural / extradural haemorrhage
torn meningeal artery
subdural haemorrhage
torn bridging veins
subarachnoid haemorrhage
torn cerebral arteries
location of superior sagittal sinus
along the edge of the falx cerebri
cerebrovascular accident = CVA
a stroke
when does a CVA occur
when the blood vessel is occluded and the brain becomes infracted
communicating arteries
little blood - the blood will flow from one direction to another if there is blockage in the system using these communicating vessels
