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I. Ocular Physiology > Aqueous Outflow and Regulation (M2) > Flashcards

Aqueous Outflow and Regulation (M2) Flashcards

1
Q

Where does the trabecular meshwork begin?

A

Schwalbe’s line (end of Descemet’s)

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2
Q

What is at the posterior end of the trabecular meshwork?

A

bordered by scleral spur and infiltrated by ciliary muscle tendons

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3
Q

What are the layers of the trabecular meshwork?

A
  1. Uveal
  2. Corneoscleral
  3. Juxtacanalicular
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4
Q

What is the small, roundish branching trabeculae (~4μm diameter)?

A

uveal meshwork

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5
Q

How may layers thick is the uveal meshwork? 1. Corneoscleral meshwork? 2.

A
  1. 1-3

2. 8-15

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6
Q

Are the spaces in the corneoscleral meshwork larger or smaller than the uveal meshwork? 1. What is their shape? 2

A
  1. smaller

2. elliptical

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7
Q

What comprises of loose connective tissue with 2–5 layers of scattered cells that are embedded in a loosely arranged fibrillar extracellular matrix?

A

juxtacanalicular tissue

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8
Q

Does the juxtacanalicular tissue form the trabecular lamellae?

A

no

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9
Q

What is adjacent to juxtacanalicular tissue?

A

endothelial cells lining inner Schlemm’s canal

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10
Q

How is the juxtacanalicular tissue basement membrane arranged?

A

discontinuous

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11
Q

What are the uveal and corneal scleral lamellae lined with?

A

endothelial cells

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12
Q

What is the uveal meshwork continuous with?

A

corneal endothelium

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13
Q

What regulates the outflow for the trabecular meshwork?

A

mechanosensation of TM cells and elasticity of the ECM

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14
Q

How is mechanosensation of TM cells accomplished?

A

transmembrane integrin proteins

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15
Q

What is found between the first corneascleral lamellae and the subepithelial cells of the JCT?

A

elastic complex

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16
Q

What contributes to the elasticity of the trabecular meshwork?

A
  1. Fibrillar and non-fibrillar collagen
  2. Elastin
  3. Matricellular proteins
  4. GAGs/proteoglycans
  5. Proteins involved in proteoglycan turnover
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17
Q

What is the matricellular protein found in the trabecular meshwork?

A

Myocillin

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18
Q

What are the nerves that are found in the trabecular meshwork?

A
  1. afferent mechanoreceptors in scleral spur

2. para and sym

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19
Q

What is the circular structure that provides drainage for the aqueous humor and delivers it to venous return?

A

Schlemm’s canal

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20
Q

What is the mechanism of trabecular meshwork drainage into Schlemm’s canal?

A

Formation of giant vacuoles

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21
Q

Are there more intracellular pores in Schlemm’s canal or paracellular pores?

A

3-4 x more intracellular than paracellular pores

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22
Q

What causes a decrease in the number of pores in Schlemm’s canal?

A

POAG (primary open angle glaucoma)

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23
Q

What cells can get through the trabecular meshwork by deforming and changing shape?

A

RBCs and WBCs

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24
Q

What is an alternate to TM for entry into Schlemm’s canal?

A

Valve-like protrusions found emanating from inner wall of Schlemm’s canal (exit at distal end)

25
Q

How long does fluid movement into circulation take for uveoscleral AH outflow? 1. What is the rate of this outflow? 2

A
  1. about 2 hours

2. ~0.3 – 1.5 μl/minute

26
Q

What type of outflow is independent of IOP (unless significant drop)?

A

uveosceral outflow

27
Q

What is the driving force for the uveoscleral outflow?

A

pressure between the anterior chamber and the suprachoroidal space

28
Q

Which type of ciliary muscle fibers run along inside of sclera?

A

longitudinal fibers

29
Q

Which type of ciliary muscle fibers fan out from chamber angle toward ciliary processes?

A

radial fibers

30
Q

Which type of ciliary muscle fibers run parallel to schlemm’s canal?

A

circular fibers

31
Q

What happens to uveoscleral outflow when ciliary muscles contract?

A

reduced

32
Q

What happens to trebecular meshwork outflow when ciliary muscles contract?

A

increased

33
Q

What are the major contributors to resistance of AH through the trabecular meshwork?

A

JCT and surrounding ECM

34
Q

What is the mechanism of Laser trabeculoplasty?

A

Ablates TM tissue to allow less resistance and greater outflow to reduce IOP

35
Q

What is Peripheral Iridotomy typically used for? 1. What does it do? 2

A
  1. narrow angle glaucoma

2. Allows fluid to drain more directly to TM with a narrow angle

36
Q

What is a Muscarinic agonist that stimulates ciliary muscle, which pulls on trabecular meshwork and decreases resistance (increases facility)?

A

pilocarpine

37
Q

What is the mechanism of Echothiophate?

A

acetylcholinesterase inhibitor causing indirect stimulation of muscarinic receptors

38
Q

What adrenergic receptors are found in the ciliary body?

A

β2, α1, and α2 receptors

39
Q

What adrenergic receptors are found in trabecular meshwork endothelial cells?

A

β2 receptors

40
Q

What is the mechanism of adrenergic agonists?

A

increase facility of trabecular meshwork by activating cAMP cascade and reducing actin filaments forming the cytoskeleton (independent of ciliary body)

41
Q

What are examples of adrenergic agonists used to treat glaucoma?

A
  1. epinephrine
  2. Norepinephrine
  3. isoproterenol
42
Q

What is the mechanism of Brimonidine?

A

α2 agonist that relaxes ciliary smooth muscle and increases uveoslceral outflow

43
Q

What is the mechanism of Apraclonidine?

A

α2 agonist

44
Q

What drug can lower IOP by inhibiting cytoskeletal structure and relaxing cells inducing an increase in facility?

A

Rho-kinase inhibitor

45
Q

What are Latanoprost (Xalatan), travoprost (Travatan), unoprostone (Rescula), bimatroprost (Lumigan) examples of? 1. What is their mechanism? 2

A
  1. prostaglandin analogs
  2. Relaxes ciliary muscles and increase uveoscleral outflow.
    Also causes increase of MMP and degradation of collagen which reorganize scleral tissue and increases its permeability
46
Q

What is the most common glaucoma medication used?

A

prostaglandins

47
Q

What receptors are found in trabecular cells and cortisol induces sodium ion transport into aqueous (via NKA activation)?

A

glucocorticoid

48
Q

What is the mechanism of glucocorticoids in relation to the filtration of AH?

A

decrease facility due to a build up of ECM in trabecular meshwork and rearrangement of cytoskeleton in TM cells

49
Q

With advanced age, what happens to the trabecular meshwork?

A
  1. a loss of endothelial cells occurs which causes the inner uveal and corneal scleral tissue to become “glued” together
  2. Increased ECM
  3. Causes increased resistance
50
Q

What ligand is increased in POAG?

A

TGFβ

51
Q

Do pigmented cells of the iris, ciliary body, retina, and corneal endothelium assist or inhibit inflammation?

A

inhibit inflammation by suppressing activation of T-cells

52
Q

What causes uveitic glaucoma?

A

clog of trabecular meshwork with immune cells, proteins, debris, or fibrin due to inflammation

53
Q

What are pharm. treatments aimed to influence in the fluid mechanics of outflow equation?

A

aimed at reducing Fin or by increasing Ctrab and Fu

54
Q

How much can a heart pulse influence IOP?

A

1-2 mmHg

55
Q

How does laying down or head below level of heart impact IOP?

A

increases IOP

56
Q

How does eyelid closure impact IOP?

A

increases IOP

57
Q

How does eyelid opening impact IOP?

A

increases IOP

58
Q

What are the etiologies of primary closed angle glaucoma?

A
  1. hyperopia
  2. old age
  3. women
59
Q

What is the process in which dendritic cells avoid immune effectors in ocular tissues (T-cells) that would otherwise stimulate immunogenic inflammation called?

A

Anterior Chamber Associated Immune Deviation (ACAID)

I. Ocular Physiology (20 decks)

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