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Ocular Physiology > 9- Corneal Metabolism And UV Absorption > Flashcards

9- Corneal Metabolism And UV Absorption Flashcards

1
Q

What are some considerations with glucose metabolism in the cornea

A

Source of glucose

O2 availability

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2
Q

What are the active pathways in the glucose metabolism in the cornea

A 
Glycolysis
Krebs
HMP shunt
ETC
Glycogen storage
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3
Q

What causes metabolic distress in the cornea

A

Low O2

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4
Q

What does most of the glucose come from?

A

Aqueous humor

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5
Q

What is the minor source of glucose?

A

Tears

Limbaugh capillaries

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6
Q

Where can glucose be derived from?

A

Glycogen in the EPITHELIUM

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7
Q

How many ATP are made in the Krebs and ETC

A

36 ATP from 1 glucose

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8
Q

Where does the epithelium get its oxygen from

A

Limbus

Pre-corneal tear film (atmosphere)

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9
Q

Where does the endothelium gets its O2 from?

A

Aqueous humor

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10
Q

What is aerobic condition

A

Normal O2 levels

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11
Q

What is anaerobic condition

A

Reduced O2, restricts metabolism

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12
Q

What pathway is very important in the cornea

A

HMP shunt

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13
Q

What is the HMP shunt needed for

A

Regeneration of new corneal epithelial cells that are constantly being produced

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14
Q

What does the HMP shunt produce

A

Intermediates for nucleotide production

And amino acid formation

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15
Q

What affect does hypoxia cause?

A

Pyruvate is converted to lactic acid

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16
Q

What affect does lactic acid have?

A

Diffuses to stroma, causes stress, stromal swelling

17
Q

What affect does stromal swelling have

A

Halos and rainbows
Increased glare sensitivity
Decreased CS

18
Q

What can cause corneal hypoxia

A

Contact lenses

Sleeping

19
Q

What is photokeratitis?

A

Eye damage from UV radiation exposure

20
Q

What affect does low level UV exposure have in the cornea

A

Inhibit mitosis

21
Q

What effect does medium level UV exposure have in the cornea

A

Swollen nuclei and cell death

22
Q

What affect does extreme level UV exposure have on the cornea

A

Sloughing of epithelium

23
Q

At the higher levels of UV damage this molecule contributes to the damage

A

O2

24
Q

UV damage causes these to form

A

Thymine dimers

25
Q

How are thymine dimers repaired?

A
  1. Exinuclease cuts on wither side of damage
  2. Removal of damaged area
  3. Gap filled in by Pol1
  4. DNA lipase seals the nick
26
Q

What are DNA repair molecules in eukaryotes

A

Pol beta and epsilon

27
Q

What is xeroderma pigmentosum?

What are the symptoms?

A

A rare genetic disorder caused by DNA exinuclease deficiency.

Symptoms: skin damage (increased risk of cancer), eye lid scarring, corneal ulcerations

Ocular Physiology (8 decks)

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