Blood Supply Flashcards
The brain is only about 2% of body weight, yet receives about 15% of total cardiac output and consumes about 20% of total
Oxygen
Peripheral arterial supply of the brain is divided into
Anterior and posterior circulations
Anterior blood supply is form the
Internal carotid Artery
Posterior blood supply is from the
Vertebral artery
Anterior and posterior circulations will anastomose to form the
Circle of Willis
The circle of Willis will divide into the following arteries to supply the brain:
Anterior cerebral a, Middle cerebral a, and Posterior cerebral a
Allows collateral blood flow if there is an occlusion
Circle of Willis
Completely balanced circle of Willis present in only about
18% of the population
We see hypoplasia of one or both posterior communicating arteries in about
20-30% of the population
The anterior circulation (internal carotid artery) will divide into
Anterior and middle cerebral artery
The posterior circulation (vertebrobasilar system) will contribute to the
Posterior cerebral artery
Supply the anteromedial cortex of the brain, from the frontal lobe to the anterior parietal lobe, where the superior parts of the primary motor and primary sensory cortex are located
Superficial branches of the ACA
Supply the anterior portion of the internal capsule and basal ganglia
Deep branches of the ACA
Supply the lateral frontal, parietal and temporal lobes, where the inferior parts of the primary motor and sensory cortex are located, as well as language and auditory areas
Superficial branches of MCA
Supply a large region of the basal ganglia and internal capsule
Deep branches of the MCA (lenticulostriate arteries)
Supply the inferior and medial temporal lobes and the occipital lobes, where the visual cortex is located
Superficial branches of PCA
The deep branches of the PCA (thalamoperforator arteries) supply the
Thalamus
A medial term referring to regions of the body that receive dual blood supply from distal branches of two large arteries
Watershed Areas (border zones)
These areas are vulnerable to ischemia during systemic hypoperfusion
Watershed areas (border zones)
Watershed infarcts (WI) account for
10% of all cerebral infarcts
Normal cerebral blood flow is about
50ml/100g/min
Cerebral blood flow (CBF) is dependent on a number of factors that can broadly be divided into those affecting:
Cerebral Perfusion Pressure (CPP) and those affecting Cerebral Blood Vessels (CBV)
What affects CPP?
Mean Arterial Pressure (MAP) and Intracranial Pressure (ICP)
What affects the radius of CBV?
Cerebral metabolsim, CO2 and O2, and Neuronal innervation
Cerebral blood flow is strongly autoregulated within a range of
CPP
At normotension, cerebral blood flow is strongly dependent on the
PaCO2 but not as much on PaO2
Cerebral veins will drain superficial brain tissue into dural venous sinuses via
Bridging Veins
Formed by the folding of periosteal and meningeal dura mater layers
Dural Venous SInuses
The blood in the dural sinuses will ultimately drain into the
Internal Jugular Vein
Will travel in the subarachnoid space and drain into dural sinuses using bridging veins
Cerebral Veins
A dural sinus on either side of the pituitary gland
The Cavernous Sinus
Contents of the cavernous sinus include the internal carotid artery and cranial nerves
III, IV, V1, V2, and VI
Venous communication from the face, sinuses, teeth or ears will allows infection to spread to the
Cavernous sinus
Infections of the cavernous sinus can lead to cavernous sinus syndrome resulting in deficits in the associated
Cranial Nerves
A highly-selective semipermeable membrane that separates the circulating blood from the brain
Blood-Brain barrier
This “barrier” results from the selectivity of the tight junctions between endothelial cells in CNS vessels, which restricts the passage of solutes
Blood-brain barrier
Areas where the blood-brain barrier has fenestrated capillaries, therefore an interrupted BBB
Circumventricular Organs
