Cerebral Vasculature Flashcards
How much Cardiac Output does the brain use?
10-20%
How much O2 does the brain consume?
20%
How much liver glucose does the brain use?
66%
Why is the brain vulnerable when blood supply is impaired?
Due to it’s high metabolic demands
Which arteries supply the brain?
- Internal carotid (entry through the carotid canal)
- vertebral artery (foramen magnum)
Arteries in the brain?
The Circle of Willis
(2 x vertebral > basilar artery > posterior cerebral > posterior communicating > middle cerebral (internal carotid) > anterior cerebral > anterior communicating)
Where does atherosclerotic build-up occur most often in the cerebral arteries/circle of willis?
Where it divides.
What happens if there is an effective blockage of the cerebral arteries in the Circle of Willis?
Theoretical chance of compensatory flow from the other side.
Realistically compensation between the posterior and anterior cerebral arteries is weak as P communicating are very thin.
Venous drainage of the brain?
Drains mainly through venous sinuses in the dura mater (through the cerebral veins) > internal jugular vein
Order of venous drainage through the sinuses?
superior (+inferior) sagittal sinus + straight sinus> confluence of sinuses > sigmoid sinus (lateral/transverse drainage)
What are the different types of intracranial haemorrhage
- extradural
- subdural
- subarachnoid
- intracerebral
Where do sinuses form?
In between the meningeal (inner) and periosteal (outer) layers of the dura mater
What causes a extradural cranial haemorrhage?
- trauma
- high pressure arterial bleed
What causes a subdural cranial haemorrhage?
- trauma
- low pressure, venous bleed
What causes a subarachnoid cranial haemorrhage?
Ruptured aneurysms
(normally congenital)
- blood vessel weakness
- may burst in hypertensive patients
What causes a intracerebral cranial haemorrhage?
- spontaneous hypertensive
normal in chronic hypertensives
Where is a fragile point in the head?
Pterion
Why is the Pterion so vulnerable?
Protects the artery supplying the dura (if ruptured causes an extradural bleed)