IC1 Anat - Blood supply Flashcards
[Arterial supply of the brain]
Nerve cells in the brain take up ___% of oxygen in the body
20% of cardiac output (despite brain being only 2% of TBW)
[Arterial supply of the brain]
What are the two main arterial systems that supply blood to the brain?
- Carotid arterial system
- Left and right internal carotid arteries
- Vertebrobasilar arterial system
- Left and right vertebral arteries
[Arterial supply of the brain]
Vertebrobasilar arterial system:
- Where does the vertebral artery originate from?
- How does it enter the skull to the brain?
Vertebral artery originates from the subclavian artery in the neck, enters the skull through the foramen magnum
[Arterial supply of the brain]
Vertebral artery gives off branches to supply:
- Spinal cord (anterior and posterior spinal artery)
- Medulla oblongata
- Bottom part of Cerebellum (posterior inferior cerebellar artery)
*Basically spinal cord + hindbrain (except pons)
[Arterial supply of the brain]
The left and right vertebral arteries join to form a single artery in the midline known as the _________
Basilar artery
[Arterial supply of the brain]
Basilar artery gives off branches to supply:
- Pons (pontine branches)
- Top part of Cerebellum (anterior inferior cerebellar artery, superior cerebellar artery)
- Inner ear (labyrinthine artery)
[Arterial supply of the brain]
The basilar artery ends by dividing into ________
Two posterior cerebral arteries
[Arterial supply of the brain]
Posterior cerebral artery supplies:
- Midbrain
- Medial aspect of the occipital lobe
- Base of the temporal and occipital lobes
[Arterial supply of the brain]
Carotid arterial system:
- Where does the internal carotid artery originate from?
- How does it enter the skull to the brain?
Common carotid artery in the neck
Enters the skull through carotid canals and is situated within the cavernous sinus
Carotid artery goes through the cavernous sinus
[Arterial supply of the brain]
The internal carotid artery ends by dividing into _______
Anterior cerebral artery and middle cerebral artery
[Arterial supply of the brain]
Anterior cerebral artery supplies:
Anterior cerebral artery passes forward into the medial longitudinal fissure and then sweeps back to the parieto-occipital sulcus
- Supplies most of the medial surface of the hemisphere (except medial aspect of occipital lobe - posterior cerebral artery)
- Supplies frontal lobe
- Supplies parieto-occipital sulcus, parietal lobe, part of occipital lobe
[Arterial supply of the brain]
Middle cerebral artery supplies:
Middle cerebral artery pass laterally between the temporal and frontal lobes
Emerges at the lateral fissure/sulcus
- Supplies most lateral surface of the hemisphere: all lobes
[Arterial supply of the brain]
Describe the circle of wilis
Anastomosis between left and right arteries of the vertebral and carotid systems supplying the brain
Anterior communicating artery connects the anterior cerebral arteries of both side
Posterior communicating artery connects the middle cerebral artery with the posterior cerebral artery
[Arterial supply of the brain]
Where is the circle of wilis located?
CIrcle of wilis is located at the base of the brain
[Arterial supply of the brain]
Function of circle of wilis
Help to supply blood to the opposite side in cases of slow occlusion of an artery on one side => collateral circulation
The communicating arteries have time to enlarge, to accommodate the increased blood flow
If fast/sudden occlusion, communicating arteries may not swell up in time, leading to death of tissue => circle of wilis not effective
[Stroke etiology]
- Ischemic stroke
- Hemorrhagic stroke
Ischemic stroke: thrombus/embolus in the artery
Hemorrhagic stroke: blood vessel rupture
[Stroke etiology]
How is the circle of wilis related to stroke
Hemorrhagic stroke can occur as circle of wilis is a frequent site for aneurysms
- E.g., anterior communicating artery aneurysm, middle cerebral artery aneurysm, posterior communicating artery aneurysm, basilar tip aneurysm
[Venous drainage of the brain]
Blood from the brain drains into ________ which eventually empties into _______
Blood from the brain drains into venous sinuses which eventually empties into internal jugular vein
Venous pressure in the brain is very low as sinuses in the brain are very big
[Venous drainage of the brain]
Blood from the superficial part of the superior aspect of the brain drains into the _____________
Superior sagittal sinus
[Venous drainage of the brain]
Blood from the inferior part of the brain drains into the _____________
- Transverse sinus
and
- Superficial middle cerebral vein
[Venous drainage of the brain]
Superficial middle cerebral vein drains into _______
Cavernous sinus
recall: where carotid artery goes through - carotid canels within carvenous sinus
[Venous drainage of the brain]
Carvenous sinus is closely related to cranial nerves
III, IV, V, VI
[Venous drainage of the brain]
Blood from the centre of the brain drains into _________, which then drains into ___________
Deep cerebral veins
Deep cerebral veins drain into a straight sinus
[Venous drainage of the brain]
How do the sinuses eventually drain into internal jugular veins?
Blood from superficial and deep parts of the brain drain into venous sinuses, and then into internal jugular veins
Superior sagittal and straight sinuses => transverse sinus => sigmoid sinus => internal jugular veins
How might subdural hematoma occur?
Rupture of a superior cerebral vein as it drains into the superior sagittal sinus, can result in bleeding into the subdural space
Because venous pressure is low, seepage is slow; hematoma slowly expands and eventually presses on the brain causing symptoms such as: dizziness, headaches, apathy, falling, confusion, drowsiness
[Capillaries of the brain]
How do capillaries in the brain form the blood brain barrier?
Capillaries of the brain have tight junctions between endothelial cells, forming the BBB, that prevents random entry of water soluble substances into the brain parenchyma
