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I. Ocular Physiology > Aqueous Humor Composition and Formation (M2) > Flashcards

Aqueous Humor Composition and Formation (M2) Flashcards

1
Q

What secretes the aqueous humor?

A

ciliary epithelium lining the ciliary processes

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2
Q

What drives aqueous flow in the anterior chamber?

A

convection (heat and cod from iris vasculature)

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3
Q

What are the aqueous humor pathways?

A
  1. conventional route

2. Uveoscleral/unconventionial route

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4
Q

Describe the conventional route to aqueous outflow:

A

trabecular meshwork -> inner wall of Schlemm’s canal into its lumen -> collector channels -> deep scleral -> intrascleral -> episcleral plexus (aqueous veins) -> episcleral vein

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5
Q

Describe the uveoscleral/unconventional route to aqueous outflow

A

Across the iris root -> uveal meshwork -> anterior face of the ciliary muscle -> CT between muscle bundles -> suprachoroidal space -> through the sclera

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6
Q

What percentage of drainage is through the uveoscleral route? 1. Does it increase or decrease with age? 2

A
  1. 35-55%

2. decreases

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7
Q

What are the major sources of the blood-aqueous barrier?

A
  1. nonpigmented ciliary epithelium and posterior epithelium

2. nonfenestrated blood vessels of the iris

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8
Q

What are the major differences in composition of the blood plasma and the aqueous?

A
  1. protein content (plasma>AH)
  2. Ascorbic acid (AH>plasma)
  3. Lactate (AH>plasma)
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9
Q

What make up the majority of ions in the AH?

A

sodium and chloride

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10
Q

What are the organic molecules found in the AH?

A
  1. Urea
  2. ascorbic acid
  3. lactate
  4. amino acids/proteins
  5. glutathione
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11
Q

What is the average pO2 in the AH?

A

55mmHg

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12
Q

Which ions are greater in the AH than the plasma? 1. Lesser in the AH than plasma? 2

A
  1. H+ and Cl-

2. bicarbonate

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13
Q

What is the source of the proteins in the AH?

A

fenestrated capillaries of the ciliary body

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14
Q

What are the proteins found in the AH?

A
  1. Albumin
  2. IgGs
  3. cytokines
  4. carbonic anhydrase
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15
Q

What are the fibrinolytic and pro-coagulation proteins found in the AH?

A
  1. plasminogen

2. plasminogen proactivator

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16
Q

Where are the tight junctions in the ciliary processes epithelium?

A

non-pigmented epithelium

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17
Q

What is dialysis in the presence of hydrostatic pressure called?

A

ultrafiltration

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18
Q

What is when a solution of protein and salt is separated from plain water by a membrane permeable to the salt and water but not to the protein, there will be a net movement of water to the protein side by diffusion and a movement of salt away from the protein side called?

A

dialysis

19
Q

What is the primary source of aqueous humor?

A

ultrafiltration of plasma from capillaries

20
Q

What must occur in order for ultrafiltration to occur?

A

hydrostatic pressure must be larger than the sum of the IOP + Oncotic pressure

21
Q

What drives the NKCC pump? 1. What is the location of this pump in the formation of aqueous? 2

A
  1. High Na+ in stroma

2. basolateral pigmented epithelium

22
Q

What does the NKCC transport?

A
  1. 2 Cl-
  2. Na+
  3. K+
23
Q

What converts available CO2 into hydrogen ions and bicarbonate? 1. What is the location of this in the formation of aqueous? 2

A
  1. carbonic anhydrase

2. pigmented epithelium cytoplasm

24
Q

What causes NHE and AE2 transport to occur readily? 1 What is the location of these pumps in the formation of aqueous? 2

A
  1. build up of H+ and HCO3- AND the availability of Na+ and Cl- in the stroma
  2. basolateral pigmented epithelium
25
Q

What does the NHE transport?

A

Na+ into cell and H+ out

26
Q

What does the AE2 transport?

A

Cl- into cell and HCO3- out

27
Q

What draws water through aquaporin water channels in aqueous production? 1. What is the location of the aquaporin? 2

A
  1. Build up of sodium and chloride ions in the PE

2. basolateral pigmented epithelium

28
Q

What drives the NKA pump in aqueous formation? 1. What is the location of this pump in the formation of aqueous? 2

A
  1. ATP and the available intracellular sodium

2. basolateral nonpigmented epithelium

29
Q

What does the NKA pump transport?

A

3 Na+ out and 2 K+ in

30
Q

What facilitates basolateral transport of Cl- through chloride channels into the aqueous humor?

A

positive charge of Na+ in aqueous humor AND available intracellular Cl-

31
Q

What drives water being drawn basolaterally and transcellularly into the aqueous humor?

A

Na+ AND Cl- in aqueous

32
Q

What is the aqueous formation rate?

A

2.5 microliters/min

33
Q

Is aqueous production increase or decreased during sleep?

A

decrease

34
Q

What things regulate aqueous production?

A
  1. NKCC pump can moves ions both ways
  2. circadian rhythm
  3. autonomic/adrenergic (sympathetic) control
  4. Timolol (a β-adrenergic antagonist)
35
Q

What transports glucose into cells from the ciliary process stroma? 1. What does it use to drive this process? 2

A
  1. SGLT/Sodium Glucose transporter

2. Na+ concentration gradient

36
Q

What helps glucose exit cells through facilitated diffusion?

A

GLUT

37
Q

What is ascorbate essential for? 1. What secretes it? 2. What inhibits ascorbic acid transport? 3

A
  1. limiting ultraviolet radiation (UVR) and anti-oxidant
  2. ciliary body epithelium
  3. Blocking sodium channels
38
Q

What do Dorzolamide and brinzolamide do?

A

inhibit Carbonic anhydrase

39
Q

Do SVCT/Sodium vitamin C transporter require ATP? 1. Where are these found? 2

A
  1. yes

2. pigmented epithelium

40
Q

What are the afferent nerves found in the CB? 1. Efferent nerves? 2

A
  1. sensory peptidergic neurons

2. Sympathetic and Parasympathetic

41
Q

What is the mechanism of increased secretion of AH with sympathetic innervation?

A

Catecholamine (NorE) bind to Beta receptor -> formation of cAMP -> indirectly activates chloride channels -> AH production

42
Q

What is the mechanism of stimulation of A3 adenosine receptors increasing AH production?

A

A3 adenosine receptor activated -> cAMP increase -> indirectly activates chloride channels -> AH production

43
Q

What can stimulate NKCC co-transporter?

A

Catecholamines that stimulate the β-adrenergic receptor

44
Q

What is the mechanism of aproclonidine?

A

α2-adrenergic agonists to decrease aqueous humor formation and IOP

I. Ocular Physiology (20 decks)

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