3. Cerebrospinal fluid Flashcards

1
Q

3 roles of the CSF

A
  • PROTECTION (buoyancy, protects against impact, surface tension between dura and arachnoid)
  • NUTRITION
  • COMPLIANCE (Monroe-Kellie doctrine)
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2
Q

2 main sources of CSF production

A

CAPILLARIES between pia and arachnoid

CHOROID PLEXI in each ventricle

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3
Q

Constituents of a choroid plexus

A
  • Capillary loop (fenestrated endothelium)
  • Pia-arachnoid
  • Ependymal cells
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4
Q

2 mechanisms of CSF production

A
  1. Passive (mainly)
  2. Active (minimally)
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5
Q

What is the rate of CSF production in dogs vs cats

A

Dogs: 0.047 ml/ml
Cats: 0.017 ml/min

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6
Q

What mainly influences the rate of CSF PRODUCTION?

A

Plasma osmotic pressure (e.g. hyperosmolar therapy)

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7
Q

What mainly influences CSF ABSOPRTION?

A

ICP (primary homeostatic mechanism)

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8
Q

2 main routes of CSF absorption?

A
  1. Arachnoid villi
  2. Veinules in the subarachnoid space
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9
Q

Other alternate routes of CSF absorption?

A

Lymphatic pathways surrouding:
* Spinal nerves at intervertebral foramina
* Cranial nerves I, II, VIII as they exit the skull

Glymphatic system, draining into the retropharyngeal lymph nodes

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10
Q

Where are arachnoid villi mostly concentrated?

A

Dorsal sagittal sinus

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11
Q

Describe the structure of an arachnoid villi

A

Prolongation of arachnoid membrane + subarachnoid space into the lumen of venous sinuses

1-way valve (opens when CSF pressure > venous pressure)

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12
Q

What are the two driving forces of CSF circulation?

A
  1. Blood pulses in the choroid plexuses
  2. Motile cilia on ependymal cells
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13
Q

Main direction of CSF circulation

A

Random, but dominantly CAUDAL

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14
Q

What kind of hydrocephalus will cause an obstruction to …
1. CSF absorption?
2. CSF circulation?

A
  1. EXTERNAL hydrocephalus (accumulates in subarachnoid space)
  2. INTERNAL hydrocephalus (accumulates in ventricular system, rostral to the obstruction) +/- hydromyelia
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15
Q

Describe CSF circulation pathways

A
  1. Lateral ventricules
  2. Interventricular foramina (foramen of monro)
  3. 3rd ventricle
  4. Mesencephalic aqueduct
  5. Fourth ventricle
  6. Lateral apertures +/- median aperture
  7. Central canal
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16
Q

CSF collection sites in
1. Dogs
2. Cats
3. Ox
4. Horses

A
  1. AO, L4-5, L5-6
  2. AO, L6-7
  3. AO, L7-S1
  4. AO, AA, L7-S1