IC1 Anat - Blood supply

Question 1

[Arterial supply of the brain]

Nerve cells in the brain take up ___% of oxygen in the body

Answer 1

20% of cardiac output (despite brain being only 2% of TBW)

Question 2

[Arterial supply of the brain]

What are the two main arterial systems that supply blood to the brain?

Answer 2

1. Carotid arterial system

• Left and right internal carotid arteries

2. Vertebrobasilar arterial system

• Left and right vertebral arteries

Question 3

[Arterial supply of the brain]

Vertebrobasilar arterial system:

• Where does the vertebral artery originate from?
• How does it enter the skull to the brain?

Answer 3

Vertebral artery originates from the subclavian artery in the neck, enters the skull through the foramen magnum

Question 4

[Arterial supply of the brain]

Vertebral artery gives off branches to supply:

Answer 4

• Spinal cord (anterior and posterior spinal artery)
• Medulla oblongata
• Bottom part of Cerebellum (posterior inferior cerebellar artery)

*Basically spinal cord + hindbrain (except pons)

Question 5

[Arterial supply of the brain]

The left and right vertebral arteries join to form a single artery in the midline known as the _________

Answer 5

Basilar artery

Question 6

[Arterial supply of the brain]

Basilar artery gives off branches to supply:

Answer 6

• Pons (pontine branches)
• Top part of Cerebellum (anterior inferior cerebellar artery, superior cerebellar artery)
• Inner ear (labyrinthine artery)

Question 7

[Arterial supply of the brain]

The basilar artery ends by dividing into ________

Answer 7

Two posterior cerebral arteries

Question 8

[Arterial supply of the brain]

Posterior cerebral artery supplies:

Answer 8

• Midbrain
• Medial aspect of the occipital lobe
• Base of the temporal and occipital lobes

Question 9

[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?

Answer 9

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

Question 10

[Arterial supply of the brain]

The internal carotid artery ends by dividing into _______

Answer 10

Anterior cerebral artery and middle cerebral artery

Question 11

[Arterial supply of the brain]

Anterior cerebral artery supplies:

Answer 11

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

Question 12

[Arterial supply of the brain]

Middle cerebral artery supplies:

Answer 12

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

Question 13

[Arterial supply of the brain]

Describe the circle of wilis

Answer 13

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

Question 14

[Arterial supply of the brain]

Where is the circle of wilis located?

Answer 14

CIrcle of wilis is located at the base of the brain

Question 15

[Arterial supply of the brain]

Function of circle of wilis

Answer 15

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

Question 16

[Stroke etiology]

• Ischemic stroke
• Hemorrhagic stroke

Answer 16

Ischemic stroke: thrombus/embolus in the artery

Hemorrhagic stroke: blood vessel rupture

Question 17

[Stroke etiology]

How is the circle of wilis related to stroke

Answer 17

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

Question 18

[Venous drainage of the brain]

Blood from the brain drains into ________ which eventually empties into _______

Answer 18

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

Question 19

[Venous drainage of the brain]

Blood from the superficial part of the superior aspect of the brain drains into the _____________

Answer 19

Superior sagittal sinus

Question 20

[Venous drainage of the brain]

Blood from the inferior part of the brain drains into the _____________

Answer 20

• Transverse sinus

and

• Superficial middle cerebral vein

Question 21

[Venous drainage of the brain]

Superficial middle cerebral vein drains into _______

Answer 21

Cavernous sinus

recall: where carotid artery goes through - carotid canels within carvenous sinus

Question 22

[Venous drainage of the brain]

Carvenous sinus is closely related to cranial nerves

Answer 22

III, IV, V, VI

Question 23

[Venous drainage of the brain]

Blood from the centre of the brain drains into _________, which then drains into ___________

Answer 23

Deep cerebral veins

Deep cerebral veins drain into a straight sinus

Question 24

[Venous drainage of the brain]

How do the sinuses eventually drain into internal jugular veins?

Answer 24

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

Question 25

How might subdural hematoma occur?

Answer 25

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

Question 26

[Capillaries of the brain]

How do capillaries in the brain form the blood brain barrier?

Answer 26

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