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HNNS > HNS03 Meninges And Blood Supply > Flashcards

HNS03 Meninges And Blood Supply Flashcards

1
Q

Meninges

A

Membranes covering Brain + Spinal cord (Dura + Arachnoid + Pia mater):

  1. Protection
  2. Support blood vessels supplying the brain
  3. Space for CSF flow
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2
Q

Layers of head

A 
Skin of scalp
—> Periosteum
—> Skull bone
—> ***Dura mater (Periosteal / Endosteal —> Meningeal)
—> ***Arachnoid mater
—> ***Pia mater
(記: DAP)
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3
Q

Dura mater

A

(Dense irregular CT)

  1. Endosteal / Periosteal layer (outer)
    - tough, lines inner surface of skull
    - continuous along outside of skull (包住成個頭骨, 但剩係入面嗰層叫endosteal layer)
    - tightly adhered to skull (esp. along sutures)
    - ends at ***Foramen magnum
    - ∴ ONLY in head, NOT in spine
  2. Meningeal layer (inner)
    - lines endosteal layer most of the time EXCEPT at dura folds
    - extend into spine —> ends at ***filum terminale (S2 level)
    - ∴ covers brain + spinal cord
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4
Q

Dural folds

A

Meningeal layer invaginates and separate from endosteal layer

4 Places:

  • Falx cerebri
  • Tentorium cerebelli
  • Falx cerebelli
  • Diaphragma sellae

Form compartments of brain:

  • Left / Right
  • Supratentorial / Infratentorial
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5
Q

Dura’s blood supply

A

Middle Meningeal artery (mostly)

  • located in ***epidural space (above Dura, under skull)
  • a lot of causes of intracranial haemorrhage (Epidural haemorrhage)
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6
Q

Dura’s nerve supply

A

Supratentorial: Trigeminal nerve CN5

Infratentorial: Spinal nerves C1-3

Dura / Meninges: very pain sensitive —> common source of headache (migraine / tension headache)

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7
Q

Tumour of meninges

A

Meningiomas

—> usually arise from dural folds e.g. Falx cerebri, Tentorium cerebelli

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8
Q

Arachnoid layer

A
  • Loose spider-web like layer
  • Trabeculae of collagen fibres (Arachnoid trabeculae) linking Arachnoid membrane + Pia mater
  • CSF runs in subarachnoid space (between arachnoid and pia)

Functions:

  1. Space for CSF circulation
  2. Support ***cerebral vessels (blood supply of brain)
  3. Space for cranial nerves
  4. Cushion the brain
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9
Q

Arachnoid granulations

A

Projections from Arachnoid into Venous sinuses (in between 2 layers of Dura) for CSF circulation back to venous blood (將CSF由subarachnoid space送返入venous blood)

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10
Q

Pia mater

A
  • Soft, tender, very thin, innermost membrane
  • Tightly covers brain and spinal cord surface
  • Follow all cerebral sulci and gyri
  • Invaginates into ventricles forming Choroid plexus (珊瑚體) which produces CSF
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11
Q

Clinical relevance

A

Epidural hematoma:

  • hematoma between dura (above dura) and skull
  • bleeding usually from fractured skull bone (brain not injured)
  • hematoma press on brain
  • arterial blood (from Middle meningeal artery)

Subdural hematoma:

  • deep to dura
  • bleeding usually from brain / vessels supplying brain (as a result of brain injury)
  • worse prognosis
  • venous blood

Subarachnoid haemorrhage:
- bleeding from subarachnoid space (e.g. aneurysm in artery in subarachnoid space)

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12
Q

Cerebrospinal fluid

A
  • crystal clear fluid within subarachnoid space
  • produced by Choroid plexus
  • ~150mL in adult (~50ml in brain, 100ml in spine)
  • daily production ~450mL (imbalance / obstructive: hydrocephalus)
  • Functions:
    1. Cushion the brain
    2. Nourish the brain
    3. More Na, Cl; Less Ca, K compared to serum
    4. >50% of serum glucose, trace of protein
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13
Q

Choroid plexus

A

Consists of:

  1. Ependymal cells (Glial cells forming epithelial lining of ventricles’ wall)
  2. Blood capillaries

Blood filtered into ventricle space —> CSF
(blood capillary —> Ependymal cells —> ventricle space)

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14
Q

CSF ventricular system

A

CSF secreted by choroid plexus in Right + Left Lateral ventricle
—> Interventricular foramen (Foramen of Monro)
—> Third ventricle (Choroid plexus in third ventricle adds more CSF)
—> Aqueduct
—> Fourth ventricle (Choroid plexus in fourth ventricle adds more CSF)
—> 2x Foramen of Luschka (lateral apertures), 1x Foramen of Magendie (median aperture)
—> CSF go outside of ventricle into subarachnoid space
—> fills subarachnoid space
—> bathes external surface of brain and spinal cord
—> CSF reabsorbed into venous blood of dural venous sinuses at arachnoid villi

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15
Q

Meningitis

A

Infection of meninges (Arachnoid, Pia mater)

—> Pus like CSF

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16
Q

Four major blood vessels going into brain

A
  1. Right / Left Internal Carotid artery

2. Right / Left Vertebral artery

17
Q

Network of blood vessels at base of brain

A

Anterior circulation:
Internal Carotid artery (R/L)
—> Anterior cerebral artery (joined by Anterior communicating artery) + Middle cerebral artery

Posterior circulation:
Vertebral artery (R/L)
—> Basilar artery (form Vertebrobasilar complex)
—> 2x Posterior cerebral artery

Anterior and Posterior circulation joined by:
***Posterior communicating artery (between Middle + Posterior cerebral artery)
—> form Circle of Willis

18
Q

Anterior circulation

A

From Internal carotid artery (R/L) (ICA)

Gives off:

  1. Anterior cerebral artery (ACA)
  2. Middle cerebral artery (MCA)
  3. Ophthalmic artery
  4. Perforators / Lenticulo-striate arteries (small blood vessel go to base of brain / brainstem into deep nuclei of cerebrum; great haemodynamic stress —> degeneration/blockage/rupture —> ischaemic/haemorrhagic stroke)
19
Q

Posterior circulation

A

From Vertebral artery (R/L)

Gives off (先—>後, 下—>上):

  1. Posterior inferior cerebellar artery (PICA) —> Cerebellum
  2. Anterior inferior cerebellar artery (AICA) —> Cerebellum
  3. Basilar artery
  4. Superior cerebellar artery —> Cerebellum
  5. Posterior cerebral artery (PCA)
20
Q

Major cerebral arteries

A

Anterior circulation

  1. Anterior cerebral artery:
    - travels within interhemispheric fissure
    - supplies ***front part of cerebrum
  2. Middle cerebral artery:
    - travels within lateral (Sylvian) fissure
    - supplies ***side of cerebrum

Posterior circulation

  1. Vertebral-basilar artery complex:
    - travels around
    - supplies **brainstem + **cerebellum and finally ***back of cerebrum

ALL branches at last anastomose throughout the brain

21
Q

ACA, MCA, PCA territories

A

ACA:

  • Medial side of anterior brain (frontal lobe)
  • affects cognition

MCA:

  • Lateral brain
  • affects sensori-motor cortex (contralateral body side)

PCA:

  • Medial side of posterior brain
  • affects visual cortex
22
Q

Cerebral infarction

A
  • Major arteries have communicating arteries (AComA, PComA) —> form collaterals within brain —> support blood supply in each other’s territory
  • Collaterals have limits —> interruption in one key artery can still cause ischaemia / cerebral infarction within its own territory
  • Extent of ischaemia / infarction varies between patients, depending on anatomy of the circle of Willis and “dominance” of affected artery
  • Clinical signs and symptoms depend on location and extent of ischaemia / infarction
23
Q

Circle of Willis

A
  • a circle formed by AComA, PComA
  • Only 25% people have complete circle
  • several variants may result in poor “cross over” of circulation (e.g. Hypoplastic PComA, Hypoplastic AComA)
24
Q

Cerebral venous drainage

A

Superficial cerebral veins (X rmb individual names)

  • Superior cerebral veins
  • Superficial middle cerebral vein
  • Inferior cerebral veins

Deep cerebral veins

  • Internal cerebral veins x2
  • Basal vein of Rosenthal x2
  • Great vein of Galen
  • Veins of cerebellum, colliculi etc.

ALL go to **Dural venous sinuses
—> finally drains through 2x **Internal Jugular veins

25
Q

Dural venous sinuses

A

Superficial system:
Superficial cerebral veins
—> Superior sagittal sinus

Deep system:
Deep cerebral veins + Basal vein of Rosenthal
—> Great vein of Galen
—> Inferior sagittal sinus
—> Straight sinus

Both system meet at Confluences of the sinuses
—> Transverse sinus (at edge of Tentorium cerebelli)
—> Sigmoid sinus
—> Internal jugular vein

26
Q

Cerebral sinus thrombosis

A

Can cause:

  1. Venous congestion
  2. Cerebral ischaemia
  3. Bleeding due to high pressure within affected brain region

HNNS (58 decks)

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