Blood Supply & Venous Drainage

Question 1

what are the main 2 sources of blood supply to the brain? where do they are from?

Answer 1

• vertebral arteries
• internal carotid arteries
• arise in the neck

Question 2

what is the anastomotic circle of vessels in the cranial vault known as?

Answer 2

Circle of Willis

Question 3

where do the internal carotid arteries originate from?

Answer 3

at the bifurcation on the left & right common carotid arteries at the level of the fourth cervical vertebrae (C4)

Question 4

where does the internal carotid artery enter the brain?

Answer 4

via the carotid canal of the temporal bone
- pass anteriorly through the cavernous sinus

Question 5

Distal to the cavernous sinus, what does each ICA give rise to?

Answer 5

• ophthalmic artery
• posterior communicating artery
• anterior chordial artery
• anterior cerebral

Question 6

where do the vertebral arteries arise from?

Answer 6

from the subclavian arteries (medial to anterior scalene muscle)

Question 7

what do the vertebral arteries travel through in order to ascent through the neck?

Answer 7

foramen transversarium (found in the transverse processes of the cervical vertebrae)

Question 8

where do the vertebral arteries enter the cranial cavity?

Answer 8

via the foramen magnum

Question 9

what are the branches given off from the vertebral arteries once in the cranial vault?

Answer 9

• meningeal branch
• anterior & posterior spinal arteries
• posterior inferior cerebella artery

Question 10

what do the two vertebral arteries converge to form?

Answer 10

the basilar artery

Question 11

what are the constituents of the Circle of Willis?

Answer 11

• anterior cerebral arteries
• internal carotid arteries
• posterior cerebral arteries
• anterior communicating artery
• posterior communicating artery

Question 12

what arteries located in the Circle of Willis are considered ‘connecting vessels’?

Answer 12

• anterior communicating arteries
• posterior communicating arteries

Question 13

what two arteries does the anterior communicating artery connect?

Answer 13

connects the two anterior cerebral arteries

Question 14

what two arteries does the posterior communicating artery connect?

Answer 14

connects the ICA to the posterior cerebral artery
- the posterior communicating artery is a branch of the internal carotid

Question 15

where does the posterior cerebral artery branch from?

Answer 15

branches off of the basilar artery to supply blood to posterior of brain

Question 16

where is the Circle of Willis located?

Answer 16

forms around the optic chiasm’s & pituitary stalk

Question 17

where does the Basilar artery lie?

Answer 17

lies over area of the pons

Question 18

What is the function of posterior cerebral arteries?

Answer 18

branch off to the side from the Circle of Willis to supply the posterior part of brain

Question 19

What is the function of the posterior communicating arteries?

Answer 19

communicate with the middle & arterial parts of circle of willis

Question 20

what arteries supply the internal capsule?

Answer 20

Lenticulostriate arteries (branches of middle cerebral)

Question 21

where does the middle cerebral artery travel to?

Answer 21

travels off to side into lateral fissure

Question 22

why is it clinically relevant that different arteries supply different areas of the brain?

Answer 22

• different lobes of the brain have specialised functions
• a stroke in a specific lobe of brain will present differently compared to having a stroke in another lobe

Question 23

if a patient has a stroke affecting the middle cerebral artery of the left hemisphere, what may the presentation look like?

Answer 23

Affected speech (aphasia)
- due to the middle cerebral artery going on to supply Broca’s area
- contralateral weakness affecting the face & arm

Question 24

what will a stroke affecting the anterior cerebral artery present as?

Answer 24

• weakness in the lower limbs (leg & foot)
• personality changes

Question 25

if a patient is having a stroke in the posterior cerebral artery, how may this present?

Answer 25

• visual agnosia
• memory impairment

Question 26

what are the dural venous sinuses?

Answer 26

spaces between the periosteal & meningeal layers of the dura

Question 27

why do the dural venous sinuses appear soon on the inside?

Answer 27

lined with epithelium

Question 28

what is the function of dural venous sinuses?

Answer 28

• venous drainage of brain
• CSF resorption via the arachnoid granulations (these extend into the dural venous sinuses)

Question 29

what are the main dural venous sinuses?

Answer 29

• superior sagittal sinus
• straight sinus
• sigmoid sinus
• petrosal sinuses

Question 30

where does the sigmoid sinus drain into?

Answer 30

the internal jugular vein

Question 31

where is the superior sagittal sinus?

Answer 31

runs along the Falx Cerebri

Question 32

what can be said about the blood flow in the cavernous sinus?

Answer 32

blood supply is slow here

Question 33

where does venous drainage of the upper part of the face go to?

Answer 33

the cavernous sinus

Question 34

why is the danger triangle of the face named so?

Answer 34

any infection here can travel into the cavernous sinus
- slow blood movement results in bacteria multiplication

Question 35

what type of haemorrhage may occur as a result of rupturing of the middle meningeal artery?

Answer 35

extradural/epidural haematoma

Question 36

A person has a fall and bangs their head, they appear to lose consciousness very quickly… what may have occurred?

Answer 36

extradural/epidural haematoma

Question 37

what type of haemorrhage is associated with old age? why?

Answer 37

subdural haematoma
- little veins pass through the tough dura, as age increases the tissues become less sturdy/vein walls thinner & any shock may cause rupture of vein

Question 38

where is a subdural haemorrhage located?

Answer 38

bleed in between the dura & subarachnoid

Question 39

how many cranial nerves are there?

Answer 39

12 bilateral pairs

Question 40

where do the cranial nerves arise from?

Answer 40

Mainly in the brainstem (medulla)
- exceptions are Olfactory & optic nerve which arise in the forebrain

Question 41

what do somatic motor axons innervate?

Answer 41

voluntary (striated) muscle

Question 42

what do visceral motor axons innervate?

Answer 42

involuntary (smooth) muscles or glands