Exam 1 Koh- Aqueous Humor 2 Flashcards Preview

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Flashcards in Exam 1 Koh- Aqueous Humor 2 Deck (61):
1

What are the 3 outflow systems of the AH?

Corneoscleral meshwork, uveoscleral meshwork and episcleral vessels

2

What is the conventional outflow of the AH?

(65-90%) trabecular meshwork, Schlemm canal, collector vessels, intrascleral plexus, episcleral venous system

3

What is the uveoscleral outflow of the AH?

(Pressure insensitive) Pass across the face of ciliary muscle, into suprachoroid, and through scleral coat to end in the vortex system

4

What is the trabecular meshwork?

A specialized tissue at the chamber angle, is the major site for regulation of the normal bulk flow of the aqueous humor; superficial uveal meshwork, the deeper corneoscleral meshwork, and the juxtacanalicular connective tissue (JCT) adjacent to Schlemm's canal

5

How does the trabecular meshwork function?

Self-cleaning, unidirectional, pressure-sensitive, low- flow (2 micoliters/min/mmHg) biologic filter for the AH, and contributes thereby to control of the IOP

6

What is the trabecular meshwork outflow pathway?

Trabecular meshwork, Schlemm's canal, and the collector channels/aqueous veins

7

What is Schlemm's canal?

The inner wall endothelium, its basement membrane and the canal lumen

8

What are collector channels?

Collector channels and aqueous veins connect the canal lumen to the episcleral veins on the surface of the eye

9

How many collector channels are along the outerwall of Schlemm's canal?

30

10

What is the trabecular meshwork structure?

A lattice of connective tissue and endothelial cells embedded in GAG-like ground substance, then into the Schlemm canal and general venous circulation (episcleral vessels)

11

Why is there resistance in the trabecular meshwork?

In the vicinity of the inner wall endothelium of Schlemm's canal, its basement membrane, and the juxtacanalicular connective tissue

12

What are the tissue beams in the trabecular meshwork?

Or lamellae that have a core of collagenous and elastic fibers, and care covered by flat cells which rest on a basal lamina. The beams attach to one another in several layers and form a porous filter-like structure

13

What are the properties of the trabecular meshwork cells?

Have active phagocytic properties, high levels of cytoskeletal actin, lower levels of microtubules also contain vimetin and desmin = smooth muscle

14

Trabecular meshwork cells are specialized both for ______ transport of water and solutes and ______

Endocytic, contractility

15

Most of the matrix component in trabecular meshwork are synthesized and degraded by _______ cells

Endothelial

16

The phagocytic activity of TM cells is associated with what two things?

GAG-degrading enzymes and acid phosphatase

17

Each lamella or beam mostly contains what types of collagen?

1 and 3

18

The fine fibril contain what type of collagen?

6

19

The cells covering the trabecular meshwork beams is rich in collagen type ____ and ___

4 and laminin

20

The elastic fibers in collagen have a considerable amount of ____ ____ material

Electron dense

21

The spaces between the juxtaglomerular cells and extracellular maxtrix fibers contains what?

Ground substance, consisting of various proteoglycans and hyaluronan

22

What types of glycosaminoglycans (GAGs) are in the AH?

Hyaluronic acid, dermatan sulfate, and chondroitin sulfate

23

What are plaques?

Accumulation of extracellular matrix structures with age

24

What contributes to interstitial flow resistance?

Proteoglycans and GAGs

25

AH outflow resistance may be decreased by nearly 50% in bovine eyes after perfusion with _________

Hyaluronidase

26

Secreted ECM proteins influence cell function by modulating ______ ______

Cell-matrix interactions

27

What are the matrix proteins?

Elastin, fibronectin, versican, laminin, thrombospondin-1, SPARC (secreted protein, acidic and rich in cysteine), myocilin, optineurin

28

What 2 things are active in handling H2O2 and free radicals?

Catalase and a glutathione-dependent system

29

What is TGFb?

A member of a family of dimeric polypeptide growth factors

30

What are the isomers of IGF-b?

TGF-b1, TGF-b2, TGF-b3

31

What is the predominant isoform of TGFb as it is found at relatively high concentration in the AH of normal eyes?

TGF-b2

32

What are the effects of TGF-b?

Signaling does not only effect ECM turnover in the TM, but also acts on the TM actin cytoskeleton

33

The uveoscleral pathway accounts for what percentage of outflow?

10-35%

34

What is the resistance like in the uveoscleral outflow?

Minimal, main resistance is within the ciliary muscle

35

Which outflow has prostaglandin F2alpha analongs?

Uveoscleral

36

What is the uveoscleral flow rate?

Pev to be about 8mmHg, calculated uveoscleral outflow to be about 0.8 micoliters/min (36%)

37

What are the values for uveoscleral flow?

In normal eyes between 0.14 and 1.52 micoliters/min, constituting 12-54% of total aqueous outflow

38

Which outflow is more sensitive to pressure change?

Trabecular outflow

39

What is episcleral venous pressure?

Aqueous humor draining via the canal of Schlemm into a network of intrascleral collector channels that drain into the scleral veins

40

Uveoscleral drainage is possible owing to the fact that pressure in suprachoroid is _____ mmHg lower than in the anterior chamber

2-4

41

The difference from the suprachoroid and the anterior chamber can be reversed after _______ and can lead to hypotony and choroidal effusions

Trabeculectomy

42

What are glaucoma risk factors?

IOP, CCT, age, C/D ratio, VF loss, pseudoexfoliation

43

What is the glaucoma continuum?

Normal -> acceleration of apoptosis -> ganglion cell death/axon loss -> Retinal nerve fiber layer change (undetectable) -> Retinal nerve fiber layer change (detectable) -> short wavelength automated perimetry VF changes -> standard automated perimetry VF changes -> VF change (moderate) -> VF change (severe) -> blindness

44

What are features of primary open angle glaucoma?

Excessive depletion of meshwork cells, failure of phagocytosis, closure of Schlemm canal, progressive narrowing of the lumina of collector channels

45

What happens to the trabecular meshwork in primary open angle glaucoma?

Thickening and fusion of trabeculae, alterations in meshwork myocillin, accumulation of ECMs, GAGs, glycoproteins and small proteins in the JCT

46

What are 3 glucocorticoids used in the AH?

Dexamethasone, actin, and MMPs

47

What does dexamethasone do?

Increased deposition of extracellular matrix material in the outflow pathway, increased expression of myocilin

48

What does actin do?

Cause the formation of cross-linked actin networks in cultured HTM cells, less pliable and more likely to inhibit outflow

49

What do MMPs do?

Downregualtes matrix-metalloproteases (MMP2,3, and 14), less ECM turnover and less outflow, MMP3 to help degrade and remodel ECM

50

What are glucocorticoid effects on the trabecular meshwork?

TM cells have GC receptors and targets of GC activtiy, GCs alter the expression of hundreds of TM cells, genes, and proteins; GCs alter TM cell functions (decrease proliferation and phagocytosis), GCs increase extracellular matrix deposition, GC reorganize the actin cytoskeleton, GCs alter cellular junctions

51

What are the autonomic regulation steps for secretion of AH?

Ciliary body to posterior chamber: 1) uptake of solute and water at stromal surface by PE, 2) transfer from PE to NPE cells through gap junctions 3) transfer of solute and water by NPE cells into PC

52

Adrenergic receptors regulate IOP via ____ ____

Adenylate cyclase

53

What suppresses aqueous flow?

Beta blocker and alpha adrenergic agonists

54

Muscarinic receptors are linked to what?

PIP2 2nd messenger system (CB)

55

What 2 medications have good nocturnal efficacy?

Carbonic anhydrase inhibitor, prostaglandins (good but less than daytime)

56

What 2 medications cause a decrease in episcleral venous pressure?

Alpha-2- agonists and prostaglandins

57

What 3 medications increase uveoscleral outflow?

Adrenergic agents, alpha-2-agonists, prostaglandins

58

What medication decreases uveoscleral outflow?

Miotics

59

What 2 medications increase conventional out flow facility?

Miotics and prostaglandins

60

What 3 medications decrease aqueous humor flow?

alpha-2-agonists, beta-adreno-ceptor antagonists, carbonic anhydrase inhibitors

61

What 2 medications cause a slight increase in aqueous humor flow?

Miotics and adrenergic agents