Lecture 4 - Blood Supply Flashcards
Unconsciousness occurs in - seconds if blood flow to brain is completely interrupted.
5-10
Blood flow to CNS delivers ___, ____, and ___.
Blood flow to CNS removes ____, ____, and ____.
delivers: O2, glucose, nutrients
removes CO2, lactic acid, metabolites
The ____ supplies the anterior circulation. The _____ supplies the posterior circulation.
paired internal carotid arteries, paired vertebral arteries
What do the paired internal carotid artery pass through to enter the cranium?
carotid canal
How do the paired vertebral arteries pass through to enter the cranium?
foramina transverseria to the foramen magnum
Trace the path of the anterior supply from the heart to just as it enters the cranium.
Right (aorta -> brachiocephalic artery -> right common carotid artery -> internal carotid artery -> carotid canal)
Left (aorta -> left common carotid artery -> internal carotid artery ->carotid canal)
what are the 2 divisions of the common carotid artery?
internal & external
External carotid artery supplies what 3 structures?
face, scalp and meninges
Which branch of the external carotid artery runs in epidural space between the cranium and the periosteal layer of the dura?
middle meningeal artery
The middle meningeal artery enters the skull through what?
foramen spinosum
What does the middle meningeal artery supply? Rupture of the middle meningeal artery would give rise to hemorrhage where?
dura mater; epidural space
What are the 5 branches of the internal carotid artery?
Opthalmic Posterior Communicating Anterior Choroidal Anterior Cerebral Middle Cerebral
What other structure runs alongside the opthalmic artery through the optic foramen?
optic nerve
The Opthalmic artery supplies what structure?
retina
The Posterior Communicating Artery runs in which direction and joins what 2 arteries?
posterior;
posterior cerebral artery and internal carotid artery
The Posterior Communicating Artery forms part of what structure?
Circle of Willis
The Anterior Choroidal Artery supplies _____ structures, namely _____, ______, and _____.
deep;
basal ganglia
thalamus
internal capsule
What is the internal capsule?
Bunch of tightly packed axons descending from the cerebrum (part of the frontal lobe), running anterior ->posterior.
The Anterior Cerebral Artery travels in what structure of the brain?
sagittal fissure
The Anterior Communicating Artery joins what?
the Anterior Cerebral Arteries from each side
T/F: The Anterior Cerebral Artery runs over the thalamus.
False (runs over corpus callosum)
The Anterior Cerebral Artery travels in the _______ space and sends penetrating branches to cortex and ____ matter
sub-archnoid; white
The cortical (surface) branches of the Anterior Cerebral Artery supply which section of the cerebrum?
anterior-medial
T/F: The cortical branches of the Anterior Cerebral artery supply the primary somatosensory region. Does it supply all sections of the primary somatosensory regions?
True; mostly medial section
The Anterior Cerebral Artery supplies the motor and sensory cortical areas for the ____ limbs.
lower
How are deep structures of the brain supplied?
supplied by small penetrating branches from initial segments of main cerebral arteries
Deep branch of the Anterior Cerebral Artery supplies ____ and ____.
basal ganglia and internal capsule.
Which three arteries both supply the basal ganglia and the internal capsule?
Anterior Choroidal Artery
Anterior Cerebral Artery
Middle Cerebral Artery
What is the significance of the Recurrent
artery of Heubner?
Common area checked for plaque deposits impeding circulation.
What is the largest branch of the Internal Carotid Artery?
Middle Cerebral Artery
The Middle Cerebral Artery runs ____ in the ____ fissure.
laterally; Sylvian
The cortical (surface) branches of the Middle Cerebral Artery supply mostly the ____ surface of the cerebral hemispheres.
lateral
Infarct of the Middle Cerebral Artery, supplying the lateral part of the primary motor and sensory cortex, will show deficits mainly in which 2 parts of the body?
upper extremities and face
Deep penetrating branches of the Middle Cerebral Artery supply which 2 structures?
basal ganglia & internal capsule
What are lenticulostriate arteries and where are they located?
They’re the deep penetrating branches of the Middle Cerebral Artery and are located deep.
What is a Cerebrovascular Accident (CVA)? What are the 2 main types of CVAs? Of the two which is most common?
A sudden death of brain tissue by a lack of oxygen and glucose delivery due to interrupted blood supply.
2 types: ischemic (most common) & hemorrhagic
Which is more common: anterior circulation stroke or posterior circulation stroke?
anterior circulation stroke
What are the 3 causes of ischemic stroke?
- Atherosclerotic plaque/thrombosis
- Thrombo-embolus
- Embolus
Define: Thrombosis, Thrombo-embolus, and Embolus.
Thrombosis: blood clot (usually plaque)
Thrombo-embolus: blood clot that has traveled from artery to artery within the brain
Embolus: blood clot that traveled to the brain from a different location
What is a hemorrhagic stroke? What are the 4 causes?
A rupture of weak vessel wall causing blood to leak into brain tissue around it.
- longstanding hypertension
- rupture of aneurysm
- arteriovenous malformation
- trauma to head
What are the 2 categories of intracranial hemorrhage?
intracerebral hemorrhage
subarachnoid hemorrhage
T/F: The Middle Cerebral Artery is a common site for hemorrhagic stroke.
False (ischemic)
What kind of deficits would be typical of Middle Cerebral Artery large vessel infarcts (on surface of cerebrum)?
motor and sensory loss, especially affecting the face and upper limb; speech/language
Why are lenticulostriate arteries prone to infarcts (2 reasons)?
- b/c prone to narrowing with hypertension
2. b/c prone to rupturing
Trace the path of the posterior circulation from heart to just as it enters the cranium.
aorta -> subclavian artery -> vertebral artery
Branches from the _____ artery supplies the spinal chord.
vertebral
Describe the blood supply to the spinal chord.
There are paired posterior spinal arteries and one anterior spinal artery.
Posterior Inferior Cerebellar Artery is a branch of what main artery?
Vertebral Artery
The Posterior Inferior Cerebellar Artery supplies what 2 structures?
- Inferior surface of cerebellum
2. Medulla oblongata
What is the lowest part of the brain?
medulla oblongata
Which arteries join to form the Basilar Artery? Where on the brain does this occur?
vertebral arteries; lower border of the pons
What are the 5 branches of the Basilar Artery?
(Hint: LAPPS)
- Lasbyrinthine artery
- Anterior inferior cerebellar artery
- Pontine arteries
- Posterior CEREBRAL artery
- superior cerebellar artery
Are the Anterior Inferior Cerebellar arteries and the Posterior Inferior Cerebellar arteries supplied by the same main artery?
No
Anterior Inferior Cerebellar arteries (Basilar Artery)
Posterior Inferior Cerebellar arteries (Vertebral artery)
Posterior Cerebral Arteries: the cortical branches supply which 2 lobes of the brain?
occipital and temporal
The damage of which 2 arteries could lead to vision damage?
Opthalmic arteries and Posterior Cerebral arteries
The deep branches of the Posterior Cerebral Arteries supply which 3 structures?
thalamus, midbrain, posterior part of internal capsule
Define the Circle of Willis.
A “circle‟ of anastomoses of anterior and posterior circulations
Since all major cerebral vessels communicate via the Circle of Willis it serves as what?
a back up for cerebral circulation b/c of collateral circulation
List the 7 arteries included in the Circle of Willis.
Anterior cerebral arteries Anterior communicating artery Middle cerebral artery Internal carotid artery Posterior communicating artery Posterior cerebral artery Basilar artery
What are Watershed zones an why are they clinically important?
They are regions between cerebral arteries that are highly susceptible to ischemia and infarctions.
Do Watershed zones get the most amount of circulation?
No: they are on the borders of the 2 arteries so they usually receive the least amount of blood flow
What would the Watershed zone between the Anterior Cerebral Artery and the Middle Cerebral Artery be called?
ACA - MCA watershed
Nearly all venous drainage of brain is via _____ _____ vein.
Internal Jugular
How does the internal jugular vein exit the skull?
Jugular foramen
Superficial veins of the cerebral hemisphere drain mainly into which 2 sinuses?
- superior sagittal sinus
2. cavernous sinus
Deep veins of the cerebral hemisphere drain into what?
great vein of Galen
Trace the venous drainage pathway from the superior sagittal sinus.
Superior Sagittal sinus -> Transverse Sinus -> Sigmoid Sinus -> Internal Jugular Vein
Trace the venous drainage pathway from the cavernous sinus.
a) Cavernous sinus ->superior petrosal sinus ->Transverse sinus -> Sigmoid sinus -> Internal jugular vein
b) Cavernous sinus -> Inferior Petrosal Sinus -> Internal Jugular vein
Trace the venous drainage pathway from the great vein of Galen.
great vein of Galen -> inferior sagittal sinus ->straight sinus -> transverse sinus -> internal jugular vein
Define the Blood Brain Barrier (BBB).
The blood–brain barrier (BBB) is a separation of circulating blood from the brain extracellular fluid in the central nervous system (CNS).
List the 4 ways in which the BBB maintains an optimum environment for CNS function.
- maintains brain electrolyte levels
- modulates entry of various substrates into the CNS (e.g. glucose levels)
- removes waste products
- excludes toxins
What are the 2 main features of a brain capillary (as opposed to a systemic capillary) which forms the BBB?
tight junctions between endothelial cells; astrocytes
Where is the choroid plexus located? Describe how the barrier forms between the blood and the CSF in the choroid plexus.
ventricles;
capillaries in the choroid plexus are permeable but there’s a layer of choroid epithelial cells that separate the capillaries from the ventricles. These epithelial cells have tight junctions which prevent the blood from mixing with the CSF.
Separate the following into those that would cross and wouldn’t cross the BBB:
- O2
- alcohol
- potassium
- lipid insoluble molecules
- lipid soluble molecules
- lipid soluble drugs
- large molecules
Would cross BBB: o2, CO2, lipid soluble drugs, alcohol
Would not cross BBB: potassium, lipid insoluble molecules, large molecules
The Blood Brain Barrier could break down due to what 4 things? If the BBB does break down, it could cause what 2 disorders?
infection, brain tumour, trauma, stroke;
encephalitis, excessive fluid (edema) in interstitial space
