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Anatomy and Physio Final > Cornea and Sclera > Flashcards

Cornea and Sclera Flashcards

1
Q

why is the sclera opaque

A

irregular array of collagen fibers and water content

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2
Q

the sclera is avascular except for the…

A

superficial vessels of the episclear and intrascleral vascular plexus

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3
Q

what type of collagen is the sclera 90% of

A

type 1

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4
Q

which collagen is expansible tissue.
which is control of fibril dimension.
which is the ability to resist tension

A

type 3
type 5
type 1

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5
Q

the large change in the refractive index of the cornea compared to air and by the corneal curvature produes the……

A

refracting element

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6
Q

which is the most prominent interface w/in the cornea

A

the interface btwn the basal cells and the basement membrane

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7
Q

which wavelenths are absored more in the cornea

A

shorter

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8
Q

in wound healing, the goal is to promote_______ and not ______ by controlling fibroblast activatoin

A

regeneration

fibrosis

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9
Q

to maintain cell regularity in corneal epithelial transparency, the cornea must prevent _______ from acculmualting and causing________ of cells and fibers

A

prevent water from accumulating and causing swelling/disorganization of cells and fibers

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10
Q

the cornea contains large concentrations of glycosaminoglycans which created an environment with a ______

A

high osmotic pressure

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11
Q

what maintain a barrier to fluid and ion transport in the cornea

A

tight junctions

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12
Q

what tight junction protein is at the site of the suprabasal epithelium

A

claudin

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13
Q

what is the basment membrane adhered to the basal cells by

A

hemidesmosomes and trans-plasma membrane collagen

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14
Q

the corneal epithelium has relatively low ________ through its _______cell membrane

A

ionoic conductance

apical

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15
Q

the movement of sodium from the tears into the epithelium is by ______ but ______is required to move it into the stroma

A

diffusion

active transport

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16
Q

what is ion transport into the cornea mediated by

A

NA/K ATPase and CA/Mg ATPase

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17
Q

what is the inward flux of sodium from the tears balnced out by

A

the outward movment of chloride into the tears

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18
Q

What is the driving force for the transport of chloride into the tears

A

the movemnt of sodium into the stroma by the pump

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19
Q

what pump in the basolateral membrane maintains the sodium gradient for the NaCl co-transport

A

Na/K pump

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20
Q

how does chloride move into the cell against an electrochemical gradient

A

the Na-K-Cl co-transport

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21
Q

stimulation of the beta adrenergic receptors and serotonergic receptors increases ……

A

apical chloride conductance

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22
Q

the K channel is under _____ via _____ mediated pathway

A

parasympatheic control

cGMP

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23
Q

what channel is mechano-senstivie

A

K channel

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24
Q

what causes an increase in current through the K channels as the cornea swells

A

hyposmotic solutions

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25
Q

what channel acts as a regulatory channel controlling osmolarity and cell volume

A

K channel

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26
Q

the K channel is sensitive to ___ changes

A

pH

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27
Q

what is intracellular pH regulated by

A

lactate-H co tranport and Na H exchange

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28
Q

epithelial transport of water is ____ compared to endothelial pump

A

HELLA SMALL

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29
Q

what is the water transporter that is important for the maintenance of normal corneal stromal thickness

A

aquaporin 5

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30
Q

what kind of innervation do the chloride channels do?

A

sympatheitc innervation

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31
Q

what kind of innervation do the potassium channels do?

A

parasympatheic innervation

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32
Q

where do the new basal cells originate from

A

stem cells at limbus

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33
Q

what is maintained by the shedding of superficial cells and proliferation of cells

A

epithelium

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34
Q

there is no cell ______ in surface epithelial cells or wing cells

A

division

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35
Q

wehre do the basal cells migrate towards

A

center of cornea (123 mM per week)

36
Q

how much basal cell division occurs per day

A

10-15%

37
Q

when do hemidesmosomes form during in a invasion-abrasion response

A

early period (18 hours)

38
Q

the release of epidermal growth factor (EGF) initiates the production of fibronectin to cover the damaged area when what is damaged

A

basement membrane

39
Q

what serves as a temporary matrix for cell adhesions

A

fibronectin

40
Q

in the stroma, which collage is the one that regulates fibril thickness? which collagen is < 5nm in diameter?

A

type 5

type 1

41
Q

which types of collagen are found in the normal basement membrane

A

4 and 7

42
Q

why does the stroma need type 1 collagen filaments to be < 5 nm

A

corneal transparency. narrow diameter fibers dont cause light to scatter

43
Q

type 1 collagen fibers make up ____% of collagen fibers in the stroma

A

50-55%

44
Q

in addidtion to types 4 and 7, what other unique collagen types are found in bowmans and descemets membrane

A

5, 8, 11, 12

45
Q

in size theory of transparency, the fibril size is _____ and interfibril distance is less than ______

A

<30 nm

less than half the wavelenth of light

46
Q

light scattered by fibrils of uniform diameter is cancelled by ______

A

destructive interference

47
Q

do collagen fibrils have to be of equal diameter and equidistant from each other?

A

NOPE

48
Q

what is the principle that says when a wave passes through an opening the waves nearest the opening margins are slowed and the wavefront becomes curved

A

huygen’s-fresnel principle

49
Q

waht maintins the regular spacing and packing of the collagen fibrils

A

proteoglycans

50
Q

what do corneal GAGs exist in the native state as

A

proteoglycans

51
Q

how does the cornea maintain fibril spacing

A

GAGs connect their next nearest neighbor collagen fibrils and form a ring like structure around each fibril

52
Q

what is involved in regulating collagen fiber diameter

A

keratan sulphate

53
Q

what is involved in regulating interfibrillar spacing

A

dermatan sulphate

54
Q

collagen abnormalities and its relationship to proteoglycans can result in the loss of…

A

transparency

55
Q

what is does abnormal keratan sulphate synthesis result in

A

macular dystrophy

56
Q

what % is the cornea hydrated?

what % is the sclera hydrated

A

80%

70%

57
Q

why will the cornea absorb more water if it is placed in saline

A

bc of the high concentration of GAGs

58
Q

what does the swelling pressure produce?

A

inter-fibril tension that helps to maintain regular arrangemnt of fibrils

59
Q

what is swelling pressure related to

A

thickness

60
Q

what is the name for specialized fibroblasts residing in the stroma

A

corneal keratocytes (fibroblasts)

61
Q

what are speciliized fibroblasts found in the stroma important in (3 things)

A
  1. maintaining transparency
    2 wound healing
  2. synthesizing matrix components
62
Q

keratocytes remain _____ until required

A

dormant

63
Q

what do keratocytes express

A

corneal crystallins

64
Q

what are responsible for the production and maintenance of the extracellular matrix of the stroma

A

keratocytes

65
Q

tensile strength of keratocytes increases up to the ….

A

fourth postoperative year

66
Q

______ incisions heal more slowly than _____ incisions

A

central

peripheral

67
Q

____ is a form of controlled cell death w/o the release of lysosomal enzymes or other intracellular components that could damage surrounding tissue

A

keratocyte apoptosis

68
Q

when do the dying stromal cells undergo necrosis

A

after the initial wave of apoptosis

69
Q

are metabolic processes temperature dependent

A

duh

70
Q

the metabolic pump moves what?

A

ions NOT WATER

71
Q

what balance does transparency depend on

A

leak/ion pump balance

72
Q

why do cells enlarge w/ aging

A

w/ the loss of cells, cells from surrounding areas spread to fill the space

73
Q

when are the pump and barrir restored in endothelial wound healing

A

when the single layer is restored

74
Q

which pump sites are increased w/ endothelial wound healing

A

Na K ATPase

75
Q

where is oxygen obtained from

A

tears, small amonts from aqueous and limbal vasculatoure

76
Q

glucose, amino acids, and vitamins are obtained from…

A

aqueous

77
Q

the inflammatory response in contact lens inhibits the….

A

Na/K ATPase

78
Q

what can contribute to epithelial thinning associted w/ long term contact lens use

A

decreased mitosis rates

79
Q

reduction in ______ is thought to be the result of prolonged epithelial edema in long term CL use

A

desmosomes

intercellular hemi-desmosomes

80
Q

what causes keratinization of the ocular surface epithelium

A

vit a deficiency

81
Q

the ionic barrier in the corneal epithelium generates a transepithelial potential of _________

A

25 - 35 mV

82
Q

what is the xyz hypothesis of cell maintenance of epithelial wound healing

A 
X = proliferation of basal cells
Y = Centripetal movement of cells
Z = Cell loss from the surface
83
Q

How long would it take for a 6mm corneal would to heal?

A

48 hours

84
Q

How many different types of collagen have been detected in the eye?

A

22

85
Q

light scatter only occurs when the distance between two regions of different refractive index become greater than ______

A

200 nm

86
Q

The stroma represents about _______ % of corneal thickness

A

85 - 90%

Anatomy and Physio Final (9 decks)

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