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Y2 CONTROL & MOVEMENT > Blood Supply to Brain & Meninges > Flashcards

Blood Supply to Brain & Meninges Flashcards

1
Q

What are the 3 meningeal coverings?

What are they and what do they cover?

A
  1. Dura mater
  2. Arachnoid mater
  3. Pia mater

They cover the CNS (brain and spinal cord) and act as protective air bags

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2
Q

What is the composition of the dura mater like?

A

It is a tough fibrous protective layer

There are two layers of dura:

  1. Outer periosteal layer that is tightly attached to the surface of the skull
  2. Inner meningeal layer that is in direct contact with the arachnoid mater
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3
Q

What is the composition of the arachnoid mater like?

A

It is a thin, delicate layer that looks like a spider-web

It is vasular

It does not follow the grooves of the brain so you cannot see sulci and gyri through this layer

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4
Q

What is the composition of the pia mater like?

A

it is a microscopically thin layer that is closely attached to the cortex of the brain

It follows the gyri and sulci (they are visible through this layer)

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5
Q

Label the 3 meningeal layers

A
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6
Q

Label the meningeal layers of the brain

A
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7
Q

What is significant about having two layers of dura?

A

This allows for dural infoldings only at specific areas

the inner meningeal layer comes away from the outer periosteal layer to form a dural fold

various venous dural sinuses are located within the dural infoldings

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8
Q

What is found within a dural sinus?

A

Venous blood

Superficial veins drain into the sinuses

CSF enters the sinuses and is reabsorbed into the venous system via arachnoid villi

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9
Q

What are the functions of CSF?

A

It is produced in the ventricular system of the brain and resembles plasma

It bathes the structures of the CNS (brain and spinal cord) and cushions them

It provides nutrients to the brain and spinal cord

It acts as a shock-absorber

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10
Q

Where is the sub-arachnoid space and what is located within it?

A

It is between the arachnoid mater and the pia mater

It contains cerebrospinal fluid and blood vessels

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11
Q

What is shown in this image?

A
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12
Q

What is the purpose of the arachnoid villi?

A

They are protrusions of the arachnoid mater into the dural layer

Diffusion across the arachnoid granulations into the superior sagittal sinus returns CSF to the venous circulation

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13
Q

What are the 3 main dural folds?

Where are they located?

A

Falx cerebri:

  • crescent shaped fold of dura
  • located in the Sagittal plane between the right and left hemispheres

Tentorium cerebelli:

  • located between the occipital and temporal lobes and the cerebellum

Falx cerebelli:

  • located between the cerebellar hemispheres
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14
Q

What is located within the dural infoldings?

A

Venous dural sinuses

The main ones are the superior sagittal sinus and the transverse sinus

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15
Q

Label the dural folds and sinuses

A
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16
Q

Label the dural folds

A
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17
Q

What are the 2 sites of attachment of falx cerebri?

A

Anterior attachment:

  • crista gali of the ethmoid bone

Posterior attachment:

  • occipital bone
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18
Q

What is the relationship between the periosteal and meningeal layers of dura?

A

They are tightly fused together except at dural venous sinuses and various infoldings (reflections)

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19
Q

What are the 3 main reflections of the dura?

A

There are 2 large reflections of dura that extend into the cranial cavity:

  1. Between the cerebral hemispheres - falx cerebri
  2. Between the cerebrum and cerebellum - tentorium cerebelli

There is a smaller reflection of dura between the cerebellar hemispheres - falx cerebelli

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20
Q

Where is the sub-dural space located?

A

The space between the arachnoid and the dura

This is a very thin potential space

The dura is tightly attached to the arachnoid, but a space could be created if a vessel was to rupture

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21
Q

Label the meninges of the spinal cord

A
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22
Q

What is the purpose of the denticulate ligaments?

A

They are lateral extensions of the pia

They anchor the spinal cord to the arachnoid mater on either side

As the arachnoid is already tightly anchored to the dura, this prevents excessive movement of the spinal cord

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23
Q

What is the difference in the dura in the spinal cord, compared to the brain?

A

It has NO periosteal component (only meningeal)

It is separated from the bone of the vertebrae by the epidural space

This is a real space, filled with fat

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24
Q

What is located between the pia and arachnoid of the spinal cord?

A

Subarachnoid space

This is filled with cerebrospinal fluid

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25
Q

What is the difference between a ‘real’ and ‘potential’ space?

A

Potential space:

  • A space between 2 adjacent structures which are usually tightly pressed together

Real space:

  • A space which exists all the time
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26
Q

What are the real and potential cranial spaces?

A

Real spaces:

  • subarachnoid space - contains CSF

Potential spaces:

  • epidural space (between periosteal and meningeal layers of dura)
  • subdural space (between arachnoid and dura)
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27
Q

Why is the cranial epidural and subdural space called a potential space?

A

Subdural:

  • can be opened by the separation of the dura from the arachnoid

Epidural:

  • can be opened by the separation of the 2 layers of the dura

This happens due to trauma or pathological processes

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28
Q

What are the real and potential spaces in the spinal cord?

A

real spaces:

  • epidural space - contains fat
  • subarachnoid space - contains CSF

potential spaces:

  • subdural space (between arachnoid and dura)
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29
Q

What are the 2 pairs of arteries that supply the brain?

How are they connected?

A

Vertebral arteries and internal carotid arteries

They are connected by the circle of Willis at the base of the brain

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30
Q

Where to the vertebral arteries originate from?

What is their pathway into the skull like?

A

Origin:

  • they are direct branches of the subclavian arteries

Pathway:

  • they ascend in the neck through the transverse foramen of the cervical vertebrae
  • they enter the skull via the foramen magnum

Fusion:

  • the vertebral arteries fuse at the base of the brainstem to form basilar artery
31
Q

What passes through the foramen magnum with the vertebral arteries?

A

spinal cord leaves through the foramen magnum

32
Q

What is the passage of the internal carotid artery like?

A

Origin:

  • it is a branch of the common carotid arteries

Passage:

  • they enter the skull via the carotid canals
  • They emerge at the floor of the skull, on either side of the optic chiasma
33
Q

Label the bones and foramen in the inferior view of the skull

What structures pass through these foramina?

A
34
Q

What arteries are shown in the drawing?

A
35
Q

What are the 3 pairs of cerebellar arteries and where do they originate?

A

Originate from basilar artery:

  • Superior cerebellar artery (SCA)
  • Anterior inferior cerebellar artery (AICA)

Originate from vertebral artery:

  • Posterior inferior cerebellar artery (PICA)
36
Q

Label the vessels that make up the Circle of Willis

A
37
Q

Label the arteries of the brain

A
38
Q

What is the role of the Circle of Willis?

A

it interconnects the internal carotid and vertebral-basilar system

it ensures compensation of decreased blood flow if one vessel is occluded

(acts as a collateral blood supply)

39
Q

What are the constituents of the Circle of Willis?

A
  • Anterior, middle and posterior cerebral arteries
  • anterior and posterior communicating arteries
  • internal carotid arteries
  • basilar artery
40
Q

What is meant by a berry aneurysm?

Why does it occur?

A

abnormal dilations around the circle of Willis or at the points of arterial branching within the brain

it occurs due to thinning of blood vessel walls, leading to blood pressure causing the walls to balloon

41
Q

What parts of the brain are more prone to aneurysm?

A

aneurysms are most common at branching points or where 2 vessels meet

sites prone to aneurysm will have lots of branches

42
Q

What complication is associated with rupture of a berry aneurysm?

A

If the aneurysm ruptures, this causes bleeding into the arachnoid space

This is a sub-arachnoid haemorrhage

10% of vascular strokes are caused this way

43
Q

Label the angiogram of a berry aneurysm

A

This angiogram shows the vertebral-basilar artery system

44
Q

Label the angiogram

What system and significant features does it show?

A

Internal carotid system

it shows the internal carotid artery (ICA) bend as it enters the skull in the carotid canal

It shows the ACA supplying the medial aspect of the hemispheres and the MCA supplying the lateral aspect of the hemispheres

45
Q

Which cortical areas are supplied by the anterior cerebral artery (ACA)?

A
  • Superior and medial areas of frontal and parietal lobes
  • Corpus callosum

(regions in blue)

46
Q

Which cortical areas are supplied by the middle cerebral artery (MCA)?

A
  • Lateral areas of the frontal, parietal and temporal lobes

(areas in pink)

47
Q

Which cortical areas are supplied by the posterior cerebral artery (PCA)?

A
  • Occipital lobe
  • Inferior and medial surface of temporal lobe

(areas in orange)

48
Q

Where do the cerebral arteries originate from?

A

Anterior cerebral artery (ACA) = internal carotid artery

Middle cerebral artery (MCA) = internal carotid artery

Posterior cerebral artery (PCA) = terminal branch of basilar artery

49
Q

What is meant by deep (or perforating arteries) of the brain?

What are some of them called?

A

Some of these are called striate arteries

They are branches of the cerebral arteries that supply the grey matter and structures inside the hemisphere

50
Q

What structures inside the hemisphere are supplied by deep or perforating arteries?

A
  1. Deep nuclei
  2. Deep grey matter
  3. Internal capsule (major fibre bundle to and from the cerebral cortex)
51
Q

Identify which areas are supplied by which cerebral artery.

What striate artery is present?

A
52
Q

What is meant by a ‘watershed area’ of the brain?

A

It is a portion of the brain supplied by the distal tips of 2 or more vessels

53
Q

What condition are watershed regions susceptible to?

Why?

A

ischaemia (Watershed stroke)

they are susceptible to ischaemia (watershed stroke) when there is decreased systemic blood pressure

they do not receive much blood from either of the 2 vessels usually, so they receive even less when blood pressure falls

54
Q

What are the 2 different types of veins which drain the brain?

A

Superficial veins:

  • these cover the surface of the cortex

Deep veins:

  • these drain the internal surfaces of the brain
55
Q

Identify which veins are superficial and which are deep.

Label the sinuses

A
56
Q

Where does all venous blood from the brain drain into?

A

Internal jugular veins

57
Q

What are dural venous sinuses?

How do they form?

A

They are channels formed when the inner meningeal layer of the dura separates from the outer periosteal layer

They are located within the dural folds

58
Q

Which vessels drain into the dural venous sinuses?

A

Vessels from superficial veins drain DIRECTLY into the sinuses

Deep veins bring all the blood into the great cerebral vein of Galen, which then connects to the sinus system

59
Q

Which sinus connects with the internal jugular vein directly?

A

sigmoid sinus

60
Q

Label the dural venous sinuses

A
61
Q

What is meant by the ‘confluence of sinuses’?

A

It is a connecting point of:

  1. Superior sagittal sinus
  2. Straight sinus
  3. Occipital sinus

The blood then drains into the right or left transverse sinus

62
Q

Label the veins and sinuses

A
63
Q

Where do the dural sinuses drain into?

A

they receive venous blood from the brain and drain into the internal jugular vein

64
Q

Complete the diagram showing the pathway of venous drainage

Where would the inferior sagittal sinus drain into?

A

The superficial veins drain into the inferior sagittal sinus

this then drains into the straight sinus

65
Q

Label the meningeal layers and the blood vessels that pass through them

A
66
Q

In what type of injury is the middle meningeal artery vulnerable?

A

In a fracture of the pterion

This is the area where the parietal, frontal, temporal and sphenoid bones join

Rupture of the middle meningeal artery leads to epidural haemorrhage and creation of a pathological space

67
Q

What is meant by the bridging veins being briefly in the subdural space?

A

The subdural space is a potential space

The bridging veins are part of the superficial veins which pierce the arachnoid mater to enter the superior sagittal sinus

They pass through the subdural space

68
Q

What is the role of the meningeal arteries and veins within the dura?

A

They supply and drain the dura

69
Q

Label the joints and features of the lateral skull

A
70
Q

Label the vessels, meninges and spaces

A
71
Q

What are the 3 types of haemorrhage that can occur in the brain?

A
  1. Epidural
  2. Subdural
  3. Subarachnoid
72
Q

What type of haemorrhage is shown here?

How is it caused?

A

Epidural haemorrhage

this is caused by a torn middle meningeal artery

it causes separation between the skull and the dura

73
Q

What type of haemmorhage is shown here?

What causes it?

A

Subdural haemorrhage

This is caused by torn bridging veins

Blood enters the space between the dura and arachnoid

74
Q

What type of haemorrhage is shown here?

What causes it?

A

Subarachnoid haemorrhage

Caused by torn cerebral arteries (may be through rupture of berry aneurysm)

It causes blood to leak through the brain tissue and into the subarachnoid space

Y2 CONTROL & MOVEMENT (69 decks)

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