Cornea and Sclera Flashcards Preview

Anatomy and Physio Final > Cornea and Sclera > Flashcards

Flashcards in Cornea and Sclera Deck (86):
1

why is the sclera opaque

irregular array of collagen fibers and water content

2

the sclera is avascular except for the...

superficial vessels of the episclear and intrascleral vascular plexus

3

what type of collagen is the sclera 90% of

type 1

4

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

type 3
type 5
type 1

5

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

refracting element

6

which is the most prominent interface w/in the cornea

the interface btwn the basal cells and the basement membrane

7

which wavelenths are absored more in the cornea

shorter

8

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

regeneration
fibrosis

9

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

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

10

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

high osmotic pressure

11

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

tight junctions

12

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

claudin

13

what is the basment membrane adhered to the basal cells by

hemidesmosomes and trans-plasma membrane collagen

14

the corneal epithelium has relatively low ________ through its _______cell membrane

ionoic conductance
apical

15

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

diffusion
active transport

16

what is ion transport into the cornea mediated by

NA/K ATPase and CA/Mg ATPase

17

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

the outward movment of chloride into the tears

18

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

the movemnt of sodium into the stroma by the pump

19

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

Na/K pump

20

how does chloride move into the cell against an electrochemical gradient

the Na-K-Cl co-transport

21

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

apical chloride conductance

22

the K channel is under _____ via _____ mediated pathway

parasympatheic control
cGMP

23

what channel is mechano-senstivie

K channel

24

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

hyposmotic solutions

25

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

K channel

26

the K channel is sensitive to ___ changes

pH

27

what is intracellular pH regulated by

lactate-H co tranport and Na H exchange

28

epithelial transport of water is ____ compared to endothelial pump

HELLA SMALL

29

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

aquaporin 5

30

what kind of innervation do the chloride channels do?

sympatheitc innervation

31

what kind of innervation do the potassium channels do?

parasympatheic innervation

32

where do the new basal cells originate from

stem cells at limbus

33

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

epithelium

34

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

division

35

wehre do the basal cells migrate towards

center of cornea (123 mM per week)

36

how much basal cell division occurs per day

10-15%

37

when do hemidesmosomes form during in a invasion-abrasion response

early period (18 hours)

38

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

basement membrane

39

what serves as a temporary matrix for cell adhesions

fibronectin

40

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

type 5
type 1

41

which types of collagen are found in the normal basement membrane

4 and 7

42

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

corneal transparency. narrow diameter fibers dont cause light to scatter

43

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

50-55%

44

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

5, 8, 11, 12

45

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

<30 nm
less than half the wavelenth of light

46

light scattered by fibrils of uniform diameter is cancelled by ______

destructive interference

47

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

NOPE

48

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

huygen's-fresnel principle

49

waht maintins the regular spacing and packing of the collagen fibrils

proteoglycans

50

what do corneal GAGs exist in the native state as

proteoglycans

51

how does the cornea maintain fibril spacing

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

52

what is involved in regulating collagen fiber diameter

keratan sulphate

53

what is involved in regulating interfibrillar spacing

dermatan sulphate

54

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

transparency

55

what is does abnormal keratan sulphate synthesis result in

macular dystrophy

56

what % is the cornea hydrated?
what % is the sclera hydrated

80%
70%

57

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

bc of the high concentration of GAGs

58

what does the swelling pressure produce?

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

59

what is swelling pressure related to

thickness

60

what is the name for specialized fibroblasts residing in the stroma

corneal keratocytes (fibroblasts)

61

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

1. maintaining transparency
2 wound healing
3. synthesizing matrix components

62

keratocytes remain _____ until required

dormant

63

what do keratocytes express

corneal crystallins

64

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

keratocytes

65

tensile strength of keratocytes increases up to the ....

fourth postoperative year

66

______ incisions heal more slowly than _____ incisions

central
peripheral

67

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

keratocyte apoptosis

68

when do the dying stromal cells undergo necrosis

after the initial wave of apoptosis

69

are metabolic processes temperature dependent

duh

70

the metabolic pump moves what?

ions NOT WATER

71

what balance does transparency depend on

leak/ion pump balance

72

why do cells enlarge w/ aging

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

73

when are the pump and barrir restored in endothelial wound healing

when the single layer is restored

74

which pump sites are increased w/ endothelial wound healing

Na K ATPase

75

where is oxygen obtained from

tears, small amonts from aqueous and limbal vasculatoure

76

glucose, amino acids, and vitamins are obtained from...

aqueous

77

the inflammatory response in contact lens inhibits the....

Na/K ATPase

78

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

decreased mitosis rates

79

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

desmosomes
intercellular hemi-desmosomes

80

what causes keratinization of the ocular surface epithelium

vit a deficiency

81

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

25 - 35 mV

82

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

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

83

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

48 hours

84

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

22

85

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

200 nm

86

The stroma represents about _______ % of corneal thickness

85 - 90%