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ANATOMY1: Osteology > Meninges and dural venous sinuses > Flashcards

Meninges and dural venous sinuses Flashcards

1
Q

What are the three layers of meninges?

A
  1. Dura mater (pachymeninx)
  2. Arachnoid mater (leptomeninx)
  3. Pia mater (also part of the leptomeninges)
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2
Q

Where is the subarachnoid space?

A

between the arachnoid and pia

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3
Q

What is the subarachnoid space filled with?

A

cerebrospinal fluid

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4
Q

What two things is the dura mater theoretically ‘divided’ into? Why is this only theoretical?

A
  1. endosteal layer (periosteum on inner surface of skull)
  2. meningeal layer

only theoretical because one the whole they’re fused except for where they separate to form dural venous sinuses and dural folds

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5
Q

What are the only places where the endosteal layer and meningeal layer of the dura mater separate?

A

dural venous sinuses and dural folds

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6
Q

What are dural folds?

A

connective tissue septae that extend into the cranial cavity and serve to subdivide it into compartments

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7
Q

What function is served by the dural folds?

A

in association with CSF, they aid in providing physical support and protection for the brain

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8
Q

What are the dural venous sinuses?

A

valveless, highly specialised firm-walled veins within the cranial cavity that drain venous blood from the brain and cranial bones

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9
Q

What are 2 key features of the walls of the dural venous sinuses?

A
  1. sinuses are lined by vascular endothelial cells (like other veins)
  2. walls contain no smooth muscle cells (unlike other veins)
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10
Q

Label the following dural venous sinuses:

  1. superior sagittal sinus
  2. inferior sagittal sinus
  3. transverse sinus
  4. sigmoid sinus
  5. straight sinus
  6. superior petrosal sinus
  7. cavernous sinus
A
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11
Q

Where are the cavernous sinuses located?

A

lie either side of the body of the sphenoid. sinus extends from the superior orbital fissure in front to the apex of the petrous temporal bone behind

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12
Q

What is the importance of the cavernous sinuses?

A

position, relations and extensive communications

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13
Q

How big are the cavernous sinuses and what do they consist of?

A

each is 2-3 cm long in the sagittal plane

consist of a series of incompletely fused venous channels or single venous channel partially subdivided by trabeculae

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14
Q

What is the wall of the cavernous sinuses?

A

dura mater (like other venous sinsues)

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15
Q

What are 5 structures that pass through the cavernous sinuses?

A
  1. oculomotor nerve III
  2. trochlear nerve IV
  3. Ophthalmic nerve V1
  4. Abducent nerve VI (most medial, in sinus)
  5. Maxillary nerve (V2)
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16
Q

How does the cavernous sinuses communicate with each other?

A

via anterior and posterior intercavernous sinuses

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17
Q

What are 4 tributaries which drain into the cavernous sinuses?

A
  • anteriorly: superior ophthalmic veins and inferior ophthalmic veins
  • sphenoparietal sinuses - anteriorly
  • superficial middle cerebral vein - drains from brain into the sinus from above
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18
Q

What do the superior and inferior ophthalmic veins drain blood from?

A

eye and orbit, skin around periorbital region of face and nose

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19
Q

Where may blood drain from the cavernous sinuses? 2 options

A
  • via superior and inferior petrosal sinuses directly into internal jugular veins (inferior petrosal) OR
  • via superior and inferior petrosal sinuses to the transverse sinuses and thus to the internal jugular veins

other exits include venous plexi around the internal carotid artery or veins traversing the foramen ovale or sphenoidal emissary foramen to communicate with the pterygoid plexus and other veins in the region of the skull base

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20
Q

What can cause the path that blood drains out of the cavernous sinuses to vary?

A

depends on relative pressures

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21
Q

How can communications between the cavernous sinuses and the vertebral venous plexus in the epidural space exist?

A

via basilar venous plexus on the clivus

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22
Q

What are 2 conditions that demonstrate hte importance of the cloes relationship of the internal carotid within the cavernous sinuses?

A
  1. cavernous sinus thrombosis
  2. arteriovenous fistulas
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23
Q

What are the 4 major dural folds? Label them

A
  1. falx cerebri
  2. tentorium cerebelli
  3. cavum trigeminale
  4. diaphragma sella
24
Q

Where are the meningeal arteries located?

A

within the inner (or periosteal) layer of dura with their accompanying veins

25
Q

What can damage of the meningeal arteries in the inner layer of dura lead to?

A

can result in extradural and subdural haematomas

26
Q

In addition to arteries what else is located within the dura?

A

lymphatics

also richly endowed with tissue resident immune cells (incl macrophages, dendritic cells and mast cells)

27
Q

Where do lymphatics within the dura travel?

A

alongside the superior sagittal sinus, are especially numerous in the dura that lines th efloor of the cranial cavity

28
Q

What is the largest and most important meningeal artery?

A

middle meningeal artery

29
Q

Where does the middle meningeal artery enter the skull?

A

through the foramen spinosum

30
Q

What is supplied by the meningeal arteries?

A

the meninges and diploë (bone marrow of cranial bones) - do NOT supply the brain

31
Q

What is the arachnoid?

A

delicate fibrocellular layer beneath the dura (separated by potential subdural space) that is connected to the pia mater covering the brain by numberous fibrocellular bands that cross the cerebrospinal fluid-filled subarachnoid space

32
Q

What does the arachnoid bridge over, and what does this create?

A

over the sulci, gyri and other irregularities on the brain surface

creates the subarachnoid cisterns, or enlargements in the subarachnoid space

33
Q

What are 2 types of specialised regions of arachnoid?

A
  1. arachnoid villi
  2. granulations (fibrous aggregations of villi)
34
Q

What is the function of arachnoid villi / granulations?

A

project into several of the dural venous sinuses and act as one-way pressure-sensitive valves allowing cerebrospinal fluid to drain from the subarachnoid space into the dural venous sinuses and possibly also the lymphatics

35
Q

What is located in the subarachnoid space?

A
  • structures passing to and from the brain to the skull or its foramina e.g. cranial nerves
  • all cerebral arteries and veins
36
Q

Where does the CSF containing subarachnoid space extend and why?

A

for a short istance around all cranial nerves - because the arachnoid fuses with the perineurium of cranial nerves

37
Q

How does the arachnoid relate to the optic nerve?

A

it surrounds it in a cuff-like manner as far as the posterior surface of the eye

38
Q

What is the pia mater formed of?

A

vascular fibro-cellular membrane

39
Q

How does the thickness of the pia mater compare to the arachniod?

A

pia mater is thicker than the arachnoid

40
Q

Where is the pia mater located?

A

closely follows the contours of the brain and veins entering or leaving the brain parenchyma carry a pial sheath

41
Q

What type of cell is the pia mater rich with, and where are they located?

A

astrocytes - extend along the vessel walls and form an important component of the blood-brain barrier

42
Q

What is another name given to the perivascular spaces around the vessels within the pia mater?

A

Virchow-Robin spaces

43
Q

What may the Virchow-Robin spaces in the pia mater be in communication with? What is the clinical relevance of this?

A

CSF of the arachnoid space

may be dilated in pathological states

44
Q

What are 3 symptoms of arteriovenous fistulas in the cavernous sinus and why do they occur?

A
  1. Pulsating protrusion of the globe
  2. Congestion of the vessels of the lids and conjunctiva
  3. Hearing noises resembling rushing water

due to raised venous pressure

45
Q

What is likely the cause of hearing rushing water sounds in ateriovenous fistulas in the cavernous sinus?

A

increased flow rates in labyrinthine plexus, whcih is in communication with the cavernous sinus via the superior petrosal sinus

46
Q

What are 6 initial sites of infection which can spread to the cavernous sinus causing cavernous sinus thrombosis?

A
  1. nose
  2. lides
  3. behind the ear
  4. bony labyrinth
  5. pharynx
  6. temporomandiblar joint
47
Q

What do the symptoms of cavernous sinus thrombosis depend on?

A

structures affected in and around the sinus

48
Q

What are 3 possible nerves that may be affected in cavernous sinus thrombus and the resultant symptoms?

A
  1. ophthalmic nerve V1: facial pain
  2. abducent nerve VI: lateral rectus paralysis
  3. oculomotor nerve III
49
Q

Why is involvement of the other cavernous sinus nerves (other than CNVI and V1) less common in cavernous sinus thrombosis?

A

because they’re protected in the lateral wall of the sinus

50
Q

Why is cavernous sinus thrombosis usually bilateral?

A

due to communications via the intercavernous sinuses

51
Q

Why can cavernous sinus thrombosis cause papilloedema?

A

obstruction of central retinal venous return

52
Q

What can cause damage to the middle meningeal vessels, especially frontal branch of the middle meningeal artery and vein?

A

blows to the head, especially in the temporal region (pterion) where the bones are thinnest and most likely to fracture

53
Q

What will bleeding from meningeal vessels result in?

A

slow bleeding from veins or more rapid arterial bleeding will cause extradural (epidural) haematoma

54
Q

What is the result of bleeding causing an extradural haematoma?

A

raised intracranial pressure

55
Q

Why must an extradural haematoma be rapidly drained?

A

coma and death will occur if not drained as soon as possible after symptoms or raised ICP such as papilloedema

56
Q

What can cause a subdural haematoma from trauma?

A

if the trauma results in brain laceration or tearing of intradural veins

ANATOMY1: Osteology (4 decks)

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