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I. Ocular Physiology > Corneal Hydration (M1) > Flashcards

Corneal Hydration (M1) Flashcards

1
Q

What is the relationship between hydration and corneal thickness?

A

linear positive relationship

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2
Q

When the pump rate exceeds the leak rate what is the result in the cornea?

A

Corneal Deturgescence

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3
Q

When the leak rate exceeds the pump rate what is the result in the cornea?

A

Corneal Swelling

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4
Q

What are the five factors that determine corneal hydration?

A
  1. Stromal swelling pressure (SP)
  2. Intraocular pressure (IOP)
  3. barrier function of the epithelium and endothelium/ imbibing pressure (IP) (“leak”)
  4. endothelium pump
  5. tear evaporation (minor)
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5
Q

What is equal to the force necessary to prevent stromal swelling at a given hydration? 1. What is the normal value of this? 2

A
  1. Stromal swelling pressure (SP)

2. 55 mmHg (at 78% [H2O])

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6
Q

What happens to the swelling pressure when there is an increased corneal thickness?

A

decrease because GAGs are further apart

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7
Q

What is the negative imbibition pressure caused by? 1. What does this draw in? 2. What is a normal value for this? 3

A
  1. negatively charged glycosaminoglycans (GAGs)
  2. Na+
  3. -40 mmHg
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8
Q

What is more permeable: corneal epithelium or corneal endothelium?

A

corneal epithelium

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9
Q

What is corneal epithelial permeability mediated by?

A

Claudins (tight junctions)

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10
Q

What is corneal epithelial permeability mediated by?

A

Claudins (tight junctions)

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11
Q

Where is the NKA pump located? 1. What does it move? 2

A
  1. stromal end of epithelial cell

2. 3 Na+ out, 2 K+ in

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12
Q

Where is the NBCe1 pump located? 1. What does it move? 2. What drives it? 3

A
  1. stromal end of epithelial cell
  2. 1 Na+ in, 2 HCO3- out
  3. Na+ stromal concentration
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13
Q

Where is the NHE1 pump located? 1. What does it move? 2. What drives it? 3

A
  1. stromal end of epithelial cell
  2. 1 Na+ in, 1 H+ out
  3. Na+ stromal concentration
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14
Q

What does increasing the intracellular pH favor?

A

reversible reaction of carbonic anhydrase (CAII) toward HCO3-

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15
Q

Where is the AE2 pump located? 1. What does it move? 2. What drives it? 3

A
  1. stromal end of epithelial cell
  2. 1 HCO3- out, 1 Cl- in
  3. High [HCO3-]
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16
Q

Where is the NKCC pump located? 1. What does it move? 2. What drives it? 3

A
  1. stromal end of epithelial cell
  2. 1 Na+ in, 1 K+ in, 2 Cl- in
  3. high stromal [Na+]
17
Q

Where is the NKA pump located? 1. What does it move? 2

A
  1. stromal end of epithelial cell (basolateral membrane)

2. 3 Na+ out, 2 K+ in

18
Q

Where is the NBCe1 pump located? 1. What does it move? 2. What drives it? 3

A
  1. stromal end of epithelial cell (basolateral membrane)
  2. 1 Na+ in, 2 HCO3- out
  3. Na+ stromal concentration
19
Q

Where is the NHE1 pump located? 1. What does it move? 2. What drives it? 3

A
  1. stromal end of epithelial cell (basolateral membrane)
  2. 1 Na+ in, 1 H+ out
  3. Na+ stromal concentration
20
Q

Where is the AE2 pump located? 1. What does it move? 2. What drives it? 3

A
  1. stromal end of epithelial cell (basolateral membrane)
  2. 1 HCO3- out, 1 Cl- in
  3. High [HCO3-]
21
Q

Where is the NKCC pump located? 1. What does it move? 2. What drives it? 3

A
  1. stromal end of epithelial cell (basolateral membrane)
  2. 1 Na+ in, 1 K+ in, 2 Cl- in
  3. high stromal [Na+]
22
Q

Where is the CaCC and CFTR pump located? 1. What does it move? 2. What drives it? 3

A
  1. aqueous end of epithelial cells (Apical membrane)
  2. 1 HCO3- out, 1 Cl- out
  3. High intracellular [HCO3-] and [Cl-]
23
Q

What drives Na+ paracellularly into the aqueous?

A

High negative charge

24
Q

What draws water paracellularly into the aqueous?

A

Osmotic pressure of high Na+, Cl- and HCO3-

25
Q

Secreted ATP and adenosine can stimulate receptors to increase intracellular cAMP, which causes what?

A

CFTR (efflux of Cl-)

26
Q

What does GABA stimulate?

A

HCO3- efflux

27
Q

Where is Aquaporin 1 highly expressed?

A

corneal endothelium

28
Q

When is corneal thickness greatest?

A

during sleep (less evaporation of tears so lower osmolarity)

29
Q

What is permanent swelling of cornea due to loss of endothelial pump function?

A

Bullous Keratopathy (BK) (~-30 mmHg)

30
Q

What is permanent swelling of cornea due to loss of endothelial pump function?

A

Bullous Keratopathy (BK) (~-30 mmHg)

31
Q

How does age dependent loss of endothelial cells normally affect endothelial pump function?

A

It doesn’t

32
Q

What is corneal guttata (local thickening of descemet’s membrane) that can cause overlaying endothelial cells to thin and slow pump function?

A

Fuch’s Endothelial Dystrophy

I. Ocular Physiology (20 decks)

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