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Module 8 > Blood Supply to the CNS & CSF > Flashcards

Blood Supply to the CNS & CSF Flashcards

1
Q

what are the 5 main pairs of arteries that supply the brain

A

1. rostral cerebral arteries

2. middle cerebral arteries

3. caudal cerebral arteries

4. rostral cerebellar arteries

= cerebral arterial circle (= circulus arteriosus)

  1. caudal cerebellar arteries

= basilar artery

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2
Q

what are the arteries shown

A

cerebrum

cerebellum

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3
Q

what are the arteries labelled

A
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4
Q

what is the function of the the cerebral arterial circle

A

anastromic system (junction between vessels) to preserve the brain from dramatic ischemia in case of occlusion of one of the contributing arteries to the circle

passive pressure dissipating system (maintain a constant blood pressure in the end arteries)

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5
Q

what is the cerebral arterial circle

A

elongated vascular ring at the base of the brain (below the hypothalamus surrounding the infundibular stalk of the pituitary gland)

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6
Q

what structures are shown

A
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7
Q

what are other sources for arterial blood

A
  1. internal carotid arteries
  2. single basilar artery
  3. anastomosing ramus from the maxillary arteries to the internal carotid arteries
  4. connection of the vertebral arteries to the internal carotid arteries
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8
Q

what is the rete mirabile

A

vascular network of small blood vessels

can be arterial or venous

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9
Q

what is the function of the rete mirabile

A

thermoregulation

heat exchange between warm blood from the body (rete blood) and the cooler venous drainage from the nasal mucosa (cavernous sinus)

blood is cooled before it reaches the brain

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10
Q

what is the blood supply to the brain in dogs and horses

A

internal carotid artery

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11
Q

what is the blood supply to the brain in other species

A

maxillary artery

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12
Q

what do the rostral cerebral arteries supply

A

medial aspect of cerebral hemispheres

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13
Q

what do the middle cerebral arteries supply

A

lateral ventrolateral aspects of cerebral hemispheres

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14
Q

what do the caudal cerebral arteries supply

A

occipital lobes

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15
Q

what do the rostral cerebellar arteries supply

A

rostral aspects of cerebellum

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16
Q

what do the caudal cerebellar arteries supply

A

caudal and lateral aspects of cerebellum

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17
Q

what blood reaches the brain in dogs, man and most mammals

A

carotid and vertebral blood reaches cerebellum and cerebrum

internal carotid arteries –> rostral & middle cerebral artery

basilar artery –> caudal cerebral & cerebellar artery

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18
Q

what is the flow direction in the basilar artery in dog, man

A

rostral

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19
Q

what blood reaches the sheep and cat brain

A

little or no vertebral blood reaches the brain

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20
Q

what is the flow direction in the basilar artery in the sheep and cat

A

caudal

anastomotic branches of the maxiallry artery to the internal carotid artery –> obliterated parts of the internal carotid artery (post-natally)

maxiallary artery = sole input to the brain

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21
Q

what blood reaches the bovine brain

A

vertebral and maxiallary blood reaches all parts of brain

anastomosing ramus from maxillary artery to internal carotid artery

connection of vertebral artery to internal carotid artery

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22
Q

what is the direction of flow in the basilar artery

A

caudal

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23
Q

what are the cranial system of the venous sinus divisions

A
  1. dorsal system of sinuses
  2. ventral system of sinuses
  3. connecting system of sinuses
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24
Q

what does the dorsal system of sinuses drain

A

drain the dorsal areas of the forebrain (dorsal cerebral veins)

deep dorsal parts of the forebrain (greater cerebral vein)

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25
Q

what does the ventral system of sinuses drain

A

drain the ventral areas of forebrain (ventral cerebral veins)

drains face, nasal cavity, orbit, upper teeth

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26
Q

what does the connecting system of sinuses drain

A

(paired) connecting sinus (or signoid sinus)

recieves the dorsal system (via transverse sinus) and the ventral system (via petrosal sinuses) and connects directly with the spinal sinus system

drains mainly via connecting sinus (sigmoid sinus) into maxiallary vein into the system circulation

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27
Q

what are the components of the dorsal system draining the dorsal regions of the brain

A

1. dorsal sagittal sinus (falx cerebri) drain dorsal regions (dorsal cerebral veins)

2. straight sinus (caudal part of falx cerebri) drain deeper dorsal parts (great cerebral vein)

3. transverse sinus (located in the osseous part of the tentorium cerebelli) dorsal sagittal sinus and straight sinus drain into the transverse sinus

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28
Q

what are the components of the ventral system draining the ventral regions of the brain

A
  1. cavernous sinus
  2. ventral petrosal sinuses (connects cavernous sinus to sigmoid sinus)
  3. dorsal petrosal sinuses (drains ventral region of the brain)
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29
Q

what regions do the ventral sinus sytem recieve blood from

A

face, nasal cavity, orbit and upper teeth

30
Q

what is the connecting system of venous drainage from the brain

A

sigmoid sinus

S-shaped continuation of the transverse sinus

31
Q

what blood does the connecting system recieve and where does it drain

A

dorsal system (transverse sinus) and ventral system (petrosal sinuses) and connects directly with spinal system (vertebral plexus)

drains into the maxillary vein into the systemic circulation

32
Q

what are the structures shown

A
33
Q

what is the arterial blood supply to the spinal cord

A

lumbar arteries of aorta, intercostal arteries and vertebral arteries supply,

paired spinal arteries supply,

dorsal & ventral root artery per spinal cord segments supply,

superficial and anastomosing arteries of the spinal cord supply,

deep arteries in the spinal cord leading to 3 vascular zones

34
Q

what are the structures shown

A
35
Q

what are the segmental arteries per spinal cord segment

A

lumbar artiers of aorta

intercostal arteries

vertebral arteries (supply paired spinal arteries which divide into –> dorsal and ventral root artery per each side)

36
Q

what are the 3 longitudinal trunks in the spinal cord blood supply

A

dorsolateral arteries & ventral spinal artery

anastomosing arteries (sparse & irregular network) connects the dorsolateral and ventral spinal arteries (run through the whole length)

37
Q

what do the vertical arteries of the spinal cord arise from and where do they run

A

ventral spinal artery and pass in ventral fissure towards centre of spinal cord

38
Q

where do the radial arteries arise from

A

from all other arteries on the surface of the cord

39
Q

what structures are shown

A
40
Q

what structures are shown

A

inner vascular zone (vertical arteries only)

middle vascular zone (both vertical and radial artery)

outer vascular zone (radial arteries only)

41
Q

how does venous drainage of the spinal cord occur

A

ventral spinal vein (drains into the spinal cord)

drains into

vertebral venous sinus –> segmental spinal veins –> vertebral veins (nec, C1-T4), azygos vein (thorax, T4-L3) & cadual vena cava (abdomen, L4-L7) –> systemic venous circulation

42
Q

what does the ventral spinal vein drain

A

spinal cord and vertebral bodies

escorts ventral spinal artery along in ventral fissure of spinal cord

43
Q

what structures are shown

A
44
Q

what does the vertebral venous sinus drain

A

ventral spinal vein

valvless

in epidural space longitudinal on the floor of vertebral canal

linked to the sinus system of the brain

45
Q

what is a fibrocartilage embolism

A

secondary embolism

–Acute onset of paresis / plegia

–Non-progressive

–Non-painful (most of the time)

–Most patients will be better rapidly depending on the severity of the lesion

–Secondary to embolism of fibrocartilage within the spinal cord artery (source of fibrocartilage assumed to be the intervertebral disc)

–Infarction

– ischaemia of the area of the spinal cord supplied by occluded artery

46
Q

what is the blood brain barrier

A

barrier between the plasma (blood) and the intersitital spaces (brain)

highly selective barrier which prevents substances (toxins, drugs) from passing between 2 compartments

47
Q

how is the BBB formed

A

non-fenestrated brain capillaries with tight junctions between endothelial cells of the capillary wall

surrounded by thick basement membrane and by a layer of foor processes from astrocytes

48
Q

what structures are shown

A
49
Q

what does transport between blood and brain depend on

A

physiological mechanisms within the endothelial cells

  1. diffusion
  2. carrier-mediated transport (glucose, fatty acids)
50
Q

how are drugs transported between blood and brain

A
  1. simple diffusion if drug is small, unbound and lipophilic
  2. concentration gradient for less lipophilic drugs
  3. less likely carrier-mediated transport
51
Q

where is the BBB present except a small number of discrete regions situated at margins of ventricles and the hypothalamus (circumventricular organs)

neurons in these regions need access to molecules circulating in the blood such as hormones or some potentially noxious molecules

A

throughout CNS except a small number

52
Q

what are circumventricular organs

A
53
Q

what is CSF

A

cerebrospinal fluid

clear, colourless fluid that surrounds entire CNS (located in subarachnoid space)

54
Q

where does CSF originate from

A

capillaries throughout CNS

55
Q

how is CSF produced

A

by selective ultrafiltrate of blood plasma (+active transport mechanisms)

major production site choroid plexus of lateral, third, and fourth ventricles

56
Q

what is the function of CSF

A
  1. physical support (buoyancy)
  2. protection against trauma
  3. modulates pressure changes within the skull
  4. nutrition (transport metabolites, nutrients and neurotransmitters)
  5. chemical buffer (maintains ionic balance)
57
Q

what structures are shown

A
58
Q

how does the CSF flow

A

caused by blood pulsatations and motile cilia of the surface of ependymal cells

59
Q

where does CSF flow

A

passes from lateral ventricles through the interventricular foramina into the 3rd ventricle

flow through the mesencephalic aqueduct into the 4th ventricle

flow into central canal of spinal cord or through the lateral apertures to the subarachnoid space

with each arterial pulsation CSF pressure rises and surges towards the lateral apertures

60
Q

how is the CSF absorbed

A

by arachnoid villi in venous sinuses

venules in sub-arachnoid space

or by lymphatic vessels of cranial and spinal nerve roots

61
Q

what structures are shown

A
62
Q

what are the structures shown

A
63
Q

how does communication occur in the ventricular system

A

lateral apertures

64
Q

what structure is indicated

A

lateral apertures

65
Q

what can altered CSF flow patterns lead to

A

syrinx formation (syringomyelia)

subarachnoid diverticula

hydrocephalus

66
Q

what is the central canal

A

continuous with 4th ventricle

surrounded by grey matter

lined with ependymal cells

67
Q

what is the subarachnoid space

A

contains CSF

contiguous with ventricular system circulation of CSF

a real space with clinical significance

68
Q

what is the dubdural space

A

between dura and arachnoid

a virtual space in the normal live animal but that can be created by introduction of materials such as –> hemorrhage or injection of image contrast material

69
Q

where can CSF be collected

A

cervical

flexion of neck required

enter in mid-line between skull and C1

stop advancing needle as enter CSF space

70
Q

where is lumbar CSF collected in dogs, cats, horses, cow

A

dog: L5-L6
cat: L6-L7
horse: L7-S1
cow: L7-S1

71
Q

what are the structurse shown

A

Module 8 (43 decks)

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