Exam 1 Koh- Cornea Biochem 2 Flashcards Preview

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Flashcards in Exam 1 Koh- Cornea Biochem 2 Deck (98):
1

What are the types of collagen in the basal lamina?

4, 7, 9, 16

2

What 3 things are included in the basal lamina?

Collagen, fibronectin, Heparan sulfate

3

What proteoglycans are included in the stroma?

Keratan sulfate, dermatan sulfate, chondroitan sulfate

4

What types of collagen are in the stroma?

1 and 6 (major), 3 and 5 (minor)

5

What 3 things included in Descemet's membrane?

Collagen, laminin, fibronectin

6

What types of collagen are in Descemet's membrane?

4 and 8

7

What are MMPs?

A family of Zn2+ dependent enzymes

8

What do MMPs do?

Degrade ECM components (proteoglycans/collagens)

9

How many members of MMPs? What is found in a healthy cornea?

>26 members, only MMP2 found in healthy cornea

10

What MMPs are synthesized after corneal injury?

MMP1, MMP3 and MMP9

11

What is the physiological function of MMPs?

Neurite growth, cell migration, would healing, vessel growth, ovulation

12

What is the pathological function of MMPs?

Tumor growth and migration, fibrosis, glaucoma, arthritis, lupus, etc.

13

What are MMP substrates?

Most of the ECM components (fibronectin, vitronectin, laminin, entactin, tenascin, aggrecan, myelin, basic protein, etc.) and collagens (1, 2, 3, 4, 5,6, 7, 8, 9, 10, 14)

14

What are the tissue inhibitors of metallo proteinases?

TIMP 1-4, differentially expressed in tissues, and temporally follow the influx of MMPs, TIMP-2 is constitutively produced as is MMP-2

15

What are keratocytes?

Major cell type of the stroma and are involved in maintaining the ECM environment

16

What are some stromal problems?

Granular dystrophy, keratoepithelin (ECM, adhesion differentiation), lattice dystrophy, herpetic stromal keratitis

17

How think is Descemet's membrane?

~10 micrometers thick

18

What secreted Descemet's membrane?

Endothelium

19

What type of collagen is most abundant in Descemet's membrane?

4

20

What collagens are included in Descemet's membrane?

4, 5, 8, 9, 12

21

What is the function of Descemet's membrane?

Provides elasticity and deformability, imparts strength and resilience, the main resistance to normal intraocular pressure

22

What are 2 Descemet/Endothelial Problems?

Vogt's striae, decreased central corneal thickness

23

What type of cells are in the endothelium?

Polygonal cells 20 micometers in diameter

24

What is the cell density in the endothelium?

About 3000/ mm^2

25

What type of junctions are in the endothelium?

Tight

26

What do the pumps do in the endothelium?

Maintain a partially dehydrated state

27

What happens to the endothelium in aging?

Endothelial cells decreases with aging, a concomitant spreading and thinning of the remaining cells

28

Where is water pumped into?

Aqueous humor

29

What type of aquaporin is in the epithelium?

5

30

What type of aquaporin is in the endothelium?

1

31

Oxygen from the _____ _____ for aerobic glycolysis

Aqueous humor

32

What type of antiport is in the cornea?

Na+/H_ antiport: Na+ (in) with H+ (out), maintain intracellular pH

33

What are 2 pumps in the cornea?

Na+ movement (tears -> epithelium), passive diffusion; Na+ movement (epithelium -> stroma) active Na+/K+ ATPase

34

How does transport of fluid occur in the cornea?

Transport of fluid out of the cornea (HCO3-/Cl- pump), outward extrusion of Cl-, inward transport of Na+ and HCO3-

35

What is corneal transparency due to?

Individual fibrils are ineffective scatterers because of their small diameter and their refractive index is relatively close to the surrounding ground substance, destructive interference, cornea is thin and avascular

36

What does destructive interference do?

Reduces the scattering by a factor of ~10 over that which would occur if the fibrils scattered independently of one another

37

What percentage of the cornea is hydrated?

80

38

What percentage of the sclera is hydrated?

70

39

The corneal stoma ____ water

Imbibes

40

How do GAGs contribute to hydration?

Hydrophilic

41

What is the cornea analogous to?

A slice of water stabilized in 3D by a meshwork of fibrils and soluble polymers

42

What can cause corneal swelling?

Abrasion, high IOP, swelling pressure is > metabolic pump rate

43

Swelling pressure generates a level of ____ ____

Interfibrillar tension

44

Swelling disrupts normal ___ arrangement

Fibril

45

Contact lens effects are predominantly affect the function of the ______

Epithelium

46

What are 4 CLs effects?

CLs shift from aerobic to anaerobic metabolism, lactate levels in the cornea are doubled with CL wear, induced stromal acidosis impairing deturgescence, neovascularization

47

What does the epithelium receive oxygen from?

Tears

48

The epithelium receives glucose from the circulation via the _____

Aqueous

49

What are the factors underlying transparency loss in the edematous cornea?

Increased light scattering, disordered fibrillar distributions and regions "lakes" where fibrils are missing, lakes would cause large fluctuations in the refractive index, increasing light scattering

50

How does the corneal epithelium regenerate?

Constantly regenerates by mitotic activity in the basal layer of cells at the limbus

51

Aster injury to the epithelium, there is migration of a single-cell layer across the _____ to close the defect

Stroma

52

What reforms in epithelial repair?

Hemidesmosomes and intercellular contacts

53

In epithelial repair, single cell layer is restored to a ___ layered architecture

6

54

What is migration in epithelial healing?

Marked cytoskeletal and cell shape changes involving redistribution of actin-myosin fibrils

55

Intracellular signaling via ___ ___ ____

Cell surface integrins

56

How does the epithelium adhere to the BM and Bowman's layer?

Hemidesmosomes

57

Many _____ elapse before anchoring fibrils reappear in adhesion

Days

58

Many _____ pass before full ultrastructural integrity is restored

Months

59

Recurrent Corneal Erosion

Damage to the superficial stromal layers

60

How does stromal repair occur?

Immediate imbibition of water from the tears by the GAGs, causes localized opacification (light scatter), initiates deposition of fibrin within the wound, rapid epithelialization of the wound incision, and finally activation of the keratocytes to divide and synthesize collagen and GAGs

61

Opacity

Irregular size and arrangement of fibrils

62

In extensive wounds, there is _____ opacification

Irreversible

63

What are the stages of stromal wound healing

After wounding, transparent keratocytes differentiate into migratory fibroblasts, fibroblasts migrate into the wound margin, at the wound margin fibroblasts differentiate into nonmotile, contractile myofibroblasts, after wound closure, myofibroblasts disappear

64

Every 10 micrometers in LASIK and PRK is equal to how many diopters of myopia?

1

65

For hyperopia, the anterior stromal tissue in LASIK and PRK is removed from the _____

Periphery

66

What are characteristics of PRK-induced haze?

Corneas frequently develop anterior light scattering that causes a hazy appearance following photorefractive keratectomy, variable levels of collagen 4 after surgery; rate of re-epithelialization; keratocyte apoptosis; and relationship between TGF-beta and myofibroblast transformation

67

PRK-induced haze peaks when?

2-6 months postsurgery in humans, after which it diminishes

68

What are the 3 unhealed wounds of LASIK?

Small flap scar, weak flap, eye banks reject

69

What are some advantages of Small Incision Lenticule Extraction (SMILE)?

Simple, all femtosecond procedure; no tissue ablation; environmental conditions do not affect treatment outcomes; no flap-related risks; enables correction of higher myopia; low impact on corneal nerves, less postop "dry eye" than LASIK; preserves strong anterior stromal tissue; less biomechanical impact; flap-less minimally invasive "keyhole" procedure attractive to patients

70

What is the future of SMILE?

Lenticule profiles for hyperopia, presbyopia, and custom (wavefront-or topography-guided) correction; inserting donor lenticules into corneal pockets for refractive correction

71

What is the corneal wound healing cascade for a clear eye?

Epithelial injury -> keratocyte apoptosis -> keratocyte proliferation and migration -> Normal basement membrane regeneration -> NO myofibroblast generation

72

What is the corneal wound healing cascade for a hazy eye?

Epithelial injury -> keratocyte apoptosis -> keratocyte proliferation and migration -> inflammatory cell infiltration -> defective basement membrane regeneration -> myofibroblast generation

73

Endothelial repair does not undergo ____ in humans

Mitosis

74

What happens to the endothelium with age?

A decline in number, an increase in size and variable morphology, cornea imbibes water (decompensates) and becomes opaque

75

Normal corneal endothelium has no type___ collagen, after injury, fibroblastic cells express type ___ collagen

1, 1

76

What is the immune privilege of the cornea?

Devoid of both blood and lymphatic vessels, TGFb

77

What compounds are anti-angiogenesis in the cornea?

PEDF, thrombospondin, angiostatin, endostatin, soluble VEGFR1

78

What compounds are pro-angiogenesis in the cornea?

VEGF, hypoxia inducible factor-1alpha, interleukin-8, tumor necrosis factor-alpha, angiogenin

79

What is interleukin-1?

A master regulator that stimulates keratocytes to secrete secondary cytokines

80

What are 3 reasons vascularization occurs?

Injury, infection, contact lens wear (20-30%)

81

What are types of infiltrates?

Neutrophils, basophils, eosinophils, monocytes, lymphocytes, RBCs, Langerhans cells

82

What 3 entities affects corneal transparency?

Inflammation, neovascularization, endothelial pums

83

A deficiency in vitamin A leads to what?

Impaired cornea and conjunctial epithelial function, loss of goblet cells in the conj, 'keratinization' of the corneal epithelium, corneal opacity, Bitot's spots, punctate erosions, xerophthalmia

84

What commonly gathers in the epithelium?

Iron

85

When does a horizontal Hudson-Stahli line form?

After 50, iron

86

What is the Fleischer ring?

Peripheral rings in the cornea made of iron, 50% keratoconus

87

What is the Stocker line?

Iron deposition, in the epithelium ahead of pterygium

88

What is Ferry's line?

Corneal epithelium iron line at the edge of filtering blebs

89

What is Kayser-Fleischer ring made of?

Copper

90

Within Descemet's membrane, there is a pigmented copper ring at the periphery of the cornea in ____ _____

Wilson's disease

91

How do you get silver and gold deposition in the cornea?

After prolonged topical application of silver-containing eye drops, prolonged gold therapy for RhA

92

What are oxidative products?

Superoxide, H2O2, free radicals

93

What are ocular effects of oxidative damage?

Actinic keratosis, pingueculum, pterygium, endothelial changes, age-related cataract

94

What is the tear film made of?

Mucins, superoxide dismutase, ascorbic acid, glutathione, Cys, Tyr, uric acid

95

What antioxidants is the aqueous humor made of?

Cys, AA, GSH (glutathione), UA, Tyr

96

What antioxidants is the lens made of?

Cys, AA, GSH, UA, Tyr

97

What happens to the cornea in diabetes?

Altered tear chemistry, decreased corneal sensitivty, increased epithelial fragility, corneal thickened, endothelial polymegathism, slower wound healing, long-term contact lens wear

98

What are the age-related changes in the cornea?

Thickening of epithelial basement membrane, decrease in nerve density, decrease in stromal cell density, thickening of Descemet's membrane, appearance of Hassall-Henle Bodies, decrease in number of corneal endothelial cells