Blood supply of the brain

Question 1

Which 2 arteries are the main supply of the brain?

Answer 1

Vertebral artery and Internal carotid artery

Question 2

Briefly describe the course of the vertebral artery

Answer 2

The vertebral artery arises from the 1st division of the subclavian artery, ascends up the neck, passing through transverse foramina of the first 6 cervical vertebrae.
It enters the cranial cavity via the foramen magnum and joins with contralateral artery over the medulla, forming the basilar artery

Question 3

The external carotid supplies the majority of the face and scalp, which structures of the brain does it also supply?

Answer 3

the meninges

Question 4

The internal carotid artery has no branches in the neck.
Through which foramen does it enter the cranial cavity?

Answer 4

The carotid canal

Question 5

Where is the circle of Willis located and describe its branches

Answer 5

The circle of Willis surrounds the pituitary stalk.
The basilar artery splits, giving the bilateral posterior cerebral arteries.
Posterior communicating arteries join posterior cerebral arteries to the internal carotid arteries.
Branching from the internal carotid is the anterior cerebral arteries which are joined together by the anterior communicating artery - forming a circle.
The internal carotid artery also branches laterally to give off the middle cerebral arteries.

Question 6

Which artery supplies the internal capsule?

Answer 6

The lenticulostriate artery (branch of middle cerebral artery)

Question 7

Which artery supplies the corpus callosum?

Answer 7

The anterior cerebral artery

Question 8

What is the function of the circle of Willis?

Answer 8

To provide blood flow between anterior and posterior cerebral circulations and to serve as collateral routes in case of obstruction.

Question 9

What does the anterior cerebral artery supply?

Answer 9

midline regions of the frontal, parietal and cingulate cortices
corpus callosum

Question 10

What does the middle cerebral artery supply?

Answer 10

lateral side of frontal, temporal and parietal lobes

Question 11

What does the posterior cerebral artery supply?

Answer 11

occipital lobe

Question 12

Which arteries supply the lateral ventricles?

Answer 12

The vertebral, basilar and posterior cerebral arteries

Question 13

Describe symptoms typical of an obstruction in the anterior cerebral artery

Answer 13

Loss of motor innervation of lower limbs
Inability to identify objects properly
Personality changes
(frontal and parietal lobe affected)

Question 14

Describe the symptoms typical of an obstruction in the middle cerebral artery

Answer 14

Loss of motor innervation of upper limbs (pre and post central gyrus)
Asphasia (if left hemisphere is obstructed- Brocas and Wernickes area)

Question 15

Describe the symptoms typical of an obstruction in the posterior cerebral artery

Answer 15

Impairment of memory and vision (visual cortex in occipital lobe)

Question 16

The veins in the brain are valveless and pierce the arachnoid mater and meningeal layer of dura mater.
Describe the drainage of these veins

Answer 16

The veins drain into dural venous sinuses which drain into the sigmoid sinus.
Sigmoid sinus becomes continuous with the internal jugular vein.

Question 17

There are 7 paired and 5 unpaired sinuses - name these.

Answer 17

paired:
- transverse
- cavernous
- greater and lesser petrosal
- sphenoparietal
- sigmoid
- basilar

unpaired:
- superior and inferior sagittal
- straight
- occipital
- intercavernous

Question 18

what is the function of the dural septum?

Answer 18

anchors the brain in the cranial cavity

Question 19

Between which layers of dura do the dural sinuses run?

Answer 19

Dural sinuses run between periosteal and meningeal layers of dura - these layers are not separable in other areas of the brain.

Question 20

What are the 2 functions of the dural sinuses?

Answer 20

The main function is venous drainage.
The sinuses also resorb CSF (produced in ventricles) via arachnoid villi/ granulations

Question 21

What is the ‘danger triangle’ ?

Answer 21

The area between the angles of the mouth to the bridge of the nose, infection here can travel via venous drainage to the cavernous sinus.

The cavernous sinus is made up of lots of small channels therefore blood flow is slow, this allows multiplication of bacteria.

This can cause cavernous sinus thrombosis or infection spreading intercranially to meninges.

Question 22

What are the 3 different types of intercranial haemorrhage?

Answer 22

epidural
subdural
subarachnoid

Question 23

briefly describe an epidural hematoma

Answer 23

there is no epidural space in the brain (between dura and calvaria) and no space between arachnoid and dura (due to pressure in subarachnoid space) so space here is pathological.

caused by skull fracture at middle meningeal artery

loss of consciousness is quick

Question 24

Briefly describe a subdural hematoma

Answer 24

associated with old age as tissues become weaker - shock to the brain (eg fall) may cause rupture of vein and bleeding in between dura and arachnoid

slow bleeding as venous

Question 25

Briefly describe a subarachnoid haemorrhage

Answer 25

referred to as an aneurysm
arterial wall is weaker at junction of arteries, causing aneurysm to burst into subarachnoid space