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Life Control > Brain Blood Supply and Venous Drainage > Flashcards

Brain Blood Supply and Venous Drainage Flashcards

1
Q

What bones does the skull consist of?

A
  • cranium
  • facial skeleton
  • mandible
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2
Q

What is the cranium?

A

bony container for the brain

made up on the skull base and vault (calvaria)

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3
Q

What is the calvaria made up of?

A

several bones which give their names to the underlying loves of cerebral hemispheres

  • parietal
  • frontal
  • occipital
  • temporal

these bones unite at relative immobile fibrous joints called sutures

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4
Q

What does the frontal bone help define the structure of?

A
  • forehead prominence
  • bridge of nose
  • roof of orbits
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5
Q

What is the majority of the side wall of the cranial vault made up of?

A

coronal suture: joining of the frontal bone with 2x parietal bones

join in the midline at the saggital suture

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6
Q

What makes up the posterior part of the cranium?

A

occipital bone

also contributes to the skull base

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7
Q

What are the different portions of the temporal bone?

A

[complex 3D shape]

  • squamous
  • petrous
  • zygomatic
  • mastoid
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8
Q

What important structures are contained within the petrous portion of the temporal bone?

A

petrous is pyramid shaped

[base faces laterally, apex directed anteromedially]

  • inner ear
  • facial nerve
  • internal carotid artery
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9
Q

Where is the sphenoid bone located?

A

at interval between the facial skeleton (anteriorly) and cranium (posteriorly)

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10
Q

What are the aspects of the sphenoid bone structure?

A

CENTRAL REGION
“body”
contains pituitary gland

TWO WINGS of sphenoid
on each side of the body

DEEP CLEFT
wings are separated by this the “superior orbital fissure”

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11
Q

What does the skull base contain?

A

3 broad recesses (fossae):

  • cranial fossae (lie at progressively lower levels)
  • anterior fossa (highest)
  • posterior fossa (lowest)

these accept the inferior surface of the brain

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12
Q

What is the anterior cranial fossa?

A

overlies orbital and nasal cavities

consists of the orbital plate of frontal bone (LATERALLY)
and
cribriform plate of themoid bone (MEDIALLY)

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13
Q

What does the cribriform plate contain?

A

multiple openings that transmit the fascicles of the olfactory nerve (CN I) from the mucosa of upper nasal cavity

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14
Q

Where does the middle cranial fossa lie?

A

between the sphenoid ridge (anteriorly) and the petrous ridge (posteriorly)

located either side of the pituitary region

contains important skyll base foraminae

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15
Q

Where does the pituitary gland lie?

A

central within the pituitary fossa in the body of the sphenoid bone

contained within the anterior and posterior clinoid structures

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16
Q

What does the posterior fossa contain?

A
  • brain stem
  • cerebellum

below the tentorium cerebelli

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17
Q

Where is the brain stem said to be continuous with the spinal cord?

A

at the level of the foramen magnum

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18
Q

What is the majority of the cerebral hemisphere supplied by?

A

internal carotid artery

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19
Q

Where does the internal carotid artery arise?

A

in the neck at ~ upper border of the thyroid cartilage

from bifurcation of the common carotid artery

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20
Q

What are the 4 portions of the internal carotid artery?

A
  • cervical
  • petrous
  • cavernous
  • supraclinoid
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21
Q

Where does the cervical portion of the internal carotid artery terminate?

A

as it enters the skull base via the carotid canal

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22
Q

Where is the carotid canal located?

A

in the pyramid-shaped petrous portion of the temporal bone

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23
Q

What is the course of the internal carotid as it enter the skull?

A

runs anteriorly and medially within the petrous bone until it reaches the foramen lacerum

internal carotid occupies the superior portion of the foramen lacerum, inferior portion is occupied by soft tissue

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24
Q

What is the appearance of the foramen lacerum in the skull?

A

jagged or torn appearance

[lacerum = tear (in latin)]

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25
Q

Where does the internal carotid go after it leaves via the foramen lacerum?

A

passes through a bony groovy to enter the cavernous sinus

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26
Q

Where does the cavernous portion of the internal carotid run?

A

runs forward with the wall of the sinus with the abducens nerve lateral to it

then the internal carotid turns upwards, medial to the anterior clinoid process to enter the subarachnoid space

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27
Q

What is the course of the supraclinoid internal carotid artery?

A

supraclinoid is the terminal portion of the internal carotid

turns posteriorly forming the “carotid siphon”

then it passes lateral to become the ‘middle cerebral artery’

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28
Q

What is the “carotid siphon”?

A

hair pin bend of supraclinoid portion of the internal carotid artery

can be seen on angiography

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29
Q

Where does the middle cerebral artery emerge?

A

from the lateral sulcus

branches to supply much of the hemisphere

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30
Q

What are the main cortical branched to the internal carotid artery?

A
  • middle cerebral artery

- anterior cerebral artery

31
Q

What are the various portions of the middle cerebral artery?

A

bifurcates into the upper and lower divisions within the lateral sulcus
[this overlays the insular complexes]

32
Q

What are the main areas that the middle cerebral artery supplies?

A

gives off branches to the frontal, parietal and temporal lobes and supplies most of the hemisphere convex surface, inc:

  • primary motor and sensory areas of face and upper extremity
  • main cortical language areas in frontal + temporal lobes
33
Q

What are the 2 main cortical language areas called?

A

BROCA AREA
located in frontal lobe
on usually LHS
involved in speech production

WERNICKE’S AREA
located surrounding the auditory cortex of the lateral sulcus
comprehension of written/spoken language

34
Q

What is the structure of the anterior cerebral artery?

A

much smaller than the middle cerebral artery

receives only 20% of the internal carotid blood flow

35
Q

Where is the middle cerebral artery located?

A

wraps around the genu and body of the corpus callosum

passes as far back as the parieto-occipital sulcus

36
Q

Where does the anterior cerebral artery give off its branches? What do they supply?

A

as it encircle the corpus callosum, it becomes the pericallosal artery

cortical branches supply
- medial surface of frontal and parietal lobes
[- inc: motor and sensory areas of the lower limbs and genitalia]

37
Q

Where does the posterior circulation (to the brain) derive from?

A

from the paired vertebral arteries (branches of subclavian)

these ascend the neck nay passing through the transverse foramina in the upper six cervical vertebrae

38
Q

What is the course of the vertebral artery as it passes the atlas (C1)?

A

winds around the lateral mass of the atlas

then pierces the atlanto-occipital membrane

then passes through the foramen magnum to enter the subarachnoid space

39
Q

Where do the 2 vertebral arteries unite?

A

in front of the brain stem
at the junction of the pons and medulla

=> form the (unpaired) basilar artery

40
Q

What does the basilar artery occupy?

A

basilar groove of the pons

lies between the brain stem and the sloping clivus of the skull base

41
Q

What is the course of the basilar artery?

A

runs superiorly to the upper border of the pons

then divides into the 2 posterior cerebral arteries (terminal branches)

these vessels wind around the midbrain and then pass posteriorly (above the tentorium cerebelli)

to supply:

  • occipital lobe
  • ventral surface of temporal lobe
42
Q

What is the circle of Willis?

A

circulus arteriosus formed by combo of three communicating vessels

formed at the base of the brain

example of a “collateral circulation” - helps to maintain circulation in the event of a vascular obstruction

43
Q

In what proportion of people, is there an incomplete circle of Willis?

A

<50%

therefore the collateral circulation will be ineffective

44
Q

What is the structure of the circle of Willis?

A

anterior communicating artery (only 2-3mm) connects the left and right anterior cerebral arteries

posterior communicating arteries: extend from the internal carotid anteriorly to the posterior cerebral artery posteriorly

45
Q

In what proportion of people is the anterior cerebral artery absence or very narrow?

A

<10%

in these cases, the medial parts of the frontal and parietal lobes are supplied by a single anterior cerebral artery

and an abnormally large anterior communicating artery

46
Q

What do the deep cerebral veins drain?

A

the hemispheric grey and white matter

47
Q

Where do the superficial and deep cerebral veins drain?

A

into the dural venous sinuses

48
Q

What are the dural sinuses?

A

large, endothelium-lined vascular channels

similar to veins, but lack valves

found at the free and attached margins of the dural partitions

return venous blood to the superior vena cava and right atrium

49
Q

What do the dural venous sinuses include?

A

SUPERIOR SAGGITAL SINUS
runs along attached margins the falx cerebri

INFERIOR SAGGITAL SINUS
runs along g the free edge of falx cerebri

STRAIGHT SINUS
found at junction of the falx cerebri and tentorium cerebelli

TRANSVERSE SINUSES
located along the attached margin of the tentorium

SIGMOID SINUS
drains from the transverse sinus into the internal jugular vein

CAVERNOUS SINUS
lateral to body of the sphenoid bone

50
Q

What is the confluence of the sinuses?

A

where the superior, straight and transverse sinuses meet

51
Q

Where does the superficial drainage system converge?

A

on the superior saggital sinus, which usually drains into the right transverse sinus

52
Q

Where does the deep drainage system drain?

A

into the straight sinus and left transverse sinus

53
Q

Where does the cavernous sinus sit?

A

on either side of the body of the sphenoid bone

54
Q

Why is the cavernous sinus of clinical importance?

A

contains the

  • internal carotid artery
  • abducens nerve (in its medial wall)
  • cranial nerves III, IV, V1, V2 (in its lateral wall)
55
Q

What is a “cavernous sinus syndrome”?

A

involves all or some of the structures contained with the cavernous sinus

pathologies: thrombosis aneurysm, tumour infiltration etc

56
Q

Where does the middle meningeal artery enter?

A

enters skull via the foramen spinousum (adjacent to foramen ovale)

branches over inner surface of the cranial vault

supplies the skull and dura mater

57
Q

Why is the middle meningeal artery described as extradural?

A

it lies in a plane between the dura mater and the skull bone

58
Q

What is the clinical significance of part of the middle meningeal artery running beneath the pterion in the temporal region?

A

one of the thinnest parts of the skull

therefore, a modest impact here can fracture the skull bone
And damage the underlying artery
(= EXTRADURAL HAEMORRHAGE)

blood escapes under arterial pressure, which can strip the dura from the bone, expanding the haematoma and eventually causes brain compression

59
Q

What is the typical clinical presentation of an extradural haemorrhage?

A

follows a lateral impact to the head

  • brief LoC
  • period of confusion
  • nausea and memory disturbance (= concussion)
  • then ‘lucid interval’
  • rapid deterioration which may rapidly end in death
  • raise ICP and brain shift/internal herniation
    “talk and die syndrome”
60
Q

What supplies the deep structures of the brain (eg/ basal ganglia, thalamus and subcortical white matter)?

A

central perforating arteries

arise from the circle of Willis

arranged into anterior and posterior groups

61
Q

Were does the anterior group of central perforating arteries enter the brain?

A

via the anterior perforated area
just lateral to the optic chiasm (on each side)

can be further divided into the medial and lateral subgroups:

  • medial
  • lateral lenticulostriate arteries
62
Q

Why are the lateral lenticulostriate arteries referred as the “arteries of brain haemorrhage”?

A

60% of spontaneous intracerebral haemorrhages occur in deep structures supplied by these vessels

esp. the putamen (basal ganglia)

63
Q

How are the posterior group of the central perforating vessels arranged?

A

into medial and lateral groups

MEDIAL
entry brain via the posterior perforated area

64
Q

Where is the posterior perforated area located?

A

lies between the cerebral peduncles of the midbrain

supplies the anteromedial thalamus

65
Q

What is the posterior and lateral thalamus supplied by?

A

the posterolateral group of the central perforating vessels

66
Q

What is the grouping system for the vessels that supply the brain stem and cerebellum?

A
  • paramedian
  • short circumferential
  • long circumferential
67
Q

Where do the paramedian vessels arise?

A

close to the midline
e.g. posterior aspect of the basilar artery

then they pass directly backwards through the full thickness of the brain stem to reach the ventricular floor

supply a rectangular-shaped block of tissue on either side of the midline

68
Q

What is the course of the short and long circumferential vessels?

A

pass laterally around the circumference of the brain stem
e.g. arising from the lateral aspect of the basilar artery

supply a wedge-shaped area of the midbrain, pons or medulla

69
Q

What are the 3 long circumferential vessels that supply the postero-lateral parts of the brain stem and various parts of the cerebellum?

A

SUPERIOR CEREBELLAR ARTERY
arises from basilar artery
supplies the superior cerebellum

ANTERIOR INFERIOR CEREBELLAR ARTERY
usually arises from the lowermost part of the basilar artery
supplies the anterior inferior cerebellum

POSTERIOR INFERIOR CEREBELLAR ARTERY
usually a branch of the vertebral artery
supplies the lateral part of medulla and posterior inferior cerebellum

70
Q

What other branches do the vertebral arteries give rise to?

A
  • single anterior spinal artery

- two posterior spinal arteries

71
Q

What is the course of the anterior spinal artery?

A

runs along the ventral median fissure of the medulla and spinal cord

supplies the anterior 2/3 of cord
(including the anterior horns and antero-lateral columns)

72
Q

What do the anterior and lateral columns of the spinal cord contain?

A
  • spinothalamic

- corticospinal tracts

73
Q

Where do the posterior spinal arteries sit?

A

they occupy the postero-lateral portions of the spinal cord

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