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Anatomy and Physio Final > Lens > Flashcards

Flashcards in Lens Deck (140):
1

function of the lens is to
-____ light onto the retina while maintaining ______ and at the same time undergoing various degrees of deformation as it ______
-_____ the retina from UV light by absorbing the higher energy shorter wavelength light

refract, transparency, accomodates
-protects

2

the lens is a thick tissue and has the _________ protein concentration of any tissue in the body :O!

highest

3

the lens can only get sick one way and that is through a ......

cataract

4

the lens is avascular. what provides its nourishment
the ____ of the lens can affect the angle

aqueous
location

5

what are the 6 regions of the lens

1. capsule
2. anterior epithelium
3. equatorial region
4. cortex
5. nucleus
6. sutures

6

the basement membrane of the capsule is homologous to that of the ...

corneal epithelium

7

the capsule is composed of ...

collagenous fiber and fibrillin

8

____ confers elasticity to the lens
______ limits the ability to stretch

fibrillin
collagen

9

the capsule is not much of a barrier to protection. T or F

T. most molec except proteins move through the capsule

10

the zonules attach to the capsule. T or F

T.

11

when looking at near, the ciliary muscle ring ______, moving __________
-zonules are _______
-lens ______

contracts, forward and inward
-loosened
bulges

12

a fibrillin disease where the lens is dislocates due to weak zonules

marfan's syndrome

13

what is the only actively metabolizing area of the lens

anterior epithelium

14

the anterior epithelium comprises ____% of all metabolism that occurs w/in the lens.
-this is good bc the highest oxygen concentration is at the _____

90%
-anterior portion of the lens

15

the anterior epithelium contains ___% of all the pumps of the lens. the other ___% are in the posterior-intermediate area

90%
10%

16

what is the region of greatest energy use because of pumps, area of mitosis
=>which makes it the maximum synthetic area

pre-equatorial region

17

where si the region of active mitosis in the lens

pre-equatorial region

18

where is the pre-equatorial region located

under the iris from which it gains its protection

19

what area contains all the mitotic elements of the lens including DNA
-in danger of mitotic cell damage by UV

pre-equatorial region

boss ass region

20

cortex have hexagonal fibers because.......

it can be packed to its maxiumum.
more cells per unit area
more proteins per cell
=> more proteins total

21

the older lens cells are located in the ....
the younger ones are in the .......region

these are zones of inconsistencies

center
peripheral

22

in the cortex,
______ in protein concentration towards nucleus
_____ in refractive power towards the nucleus

increase
increase

23

fibers lose all of their ______ as they are pushed into the interior of the lens

organelles

24

the protein concentration ramps upward in the center of the lens, which increases....

refractive power

25

the nucleus has ____ fibers, packed in a ____ array with ______ extracellular space located btwn them

hexagonal, regular, very little

26

why will the scattered light be reflected and scattered in a regular manner

the fibers are regularly spaced

27

the explanation of transparency of the lens is because of the....... of light

destructive interference of light

28

the upright Y suture is ______
the upside-down Y suture is ____

anterior
posterior

29

the increased branching of the sutures produces better....

optical qualities

30

which suture are where the lens fibers meet inside the lens?
what do they do to water in the lens?
how do they radiate?

the y-sutures
keep the water out so the lens is dry
outward

31

what is a reason that water does not flow through the center of the lens

there are less interdigitations in the periphery of the lens than in its center

32

as fibers reach the sutures, the membranes become progressively more interlocked, forming interlocking__________ junctions

ball and socket

33

these junctions may stabilize the lateral membranes of the fiber cells and ensure the cells remain tightly connected during accommodation

ball and socket junction

34

extensive intercellular communication exists via_____

the lens gap junction ...

35

where is the smallest extracelllular substance located in any tissue of the body

the lens - no room for lakes

36

what are lens fibers linked by

N-cadherin connections

37

the embryonic optic vesicles form as an ____ of the neural tube connected to it by stalks

neural tube

38

as the optic vesicle approaches the surface ectoderm, it induces the formation of the...

lens placode

39

the sides of the vesicle grow down reducing the gap to a narrow cleft called the...

the structure is now the optic cup

embryonic fissure

aka choroidal fissure, ocular fissure, optic fissure. thanks for all the fucking names T__T

40

what start to form the vascular capsule of the lens

hyaloid vessels

41

early lens vesicle develops.....which cells elongate to reach the anterior epithelium

posterior cells

42

lens development
1. _______ form as an extension of the neural tube
2. as these approach the surface ectoderm the ______ and _____ form
3. narrow cleft called the _______ forms in the walls of the optic cup
4. _____ vessels start to form the vascular capsule of the lens
5. early lens vesicle devleops w/ post cells elongating to reach the _____

1. embryonic optic vesicles
2. lens placode, lens vesicle
3. embryonic fissure
4. hyaloid
5. anterior epithelium

43

what is the area of nuclei of elongating fiber cells called

germinative zone

44

(transcript) mitosis in the pre-equatorial layer produces...

(mitosis occurs in the sub-epithelial layer in slides).....................wtf

new fibers

45

once the fibers reach the sutures, they stop elongating and their _______ detach from the capsule

basal ends

46

lens fiber growth
1. mitosis occurs in the ____
2. new fibers migrate along the _____, elongating to reach to _____
3. _____ detach from capsule at sutures
4. _____ are buried deeper in the lens w/ successive generations

1. sub-epithelial layers
2. capsule, sutures
3. basal ends
4. mature fiber cells

47

pattern of movement
1. _____of fibers move along capsule surfcae
2. _____ ends slide beneath epithelium until they meet elongating cell from other side near midline
3. stop elongating = _________
4. _____ ends detach from capsule
5. organelles then degrade by ______
6. _____ scatter declines

1. basal ends
2. apical
3. suture
4. basal ends
5. apoptosis
6. light

48

organelle free zone:
-diffrentiating fibers = outer ____% some organelles
-mature fibers = inner ____%

-20%
-80%

49

order of lens development from center to out is....
1. ____ nucleus
2. _____nucleus
3. _____ nucleus
4. cortex
5. _____ capsule

1. embryonal
2. fetal
3. adult
4. cortex
5. anterior capsule

50

what fibers from the posterior epithelium form the embryonic nucleus

primary lens fibers

51

where are secondary lens fibers formed? and by what

pre-equatorial region by mitosis

52

what fibers form the fetal nucleus

the fibers laid down before birth

53

between birth and sexual maturation form the ......

adult nucleus

54

what is formed by the fibers laid down after sexual maturation

cortex

55

the lens in a child is _____
the adults is ____
why does the lens change with age?

clear
cloudy
reflect both migration inward and changes in protein synthesis rates

56

variables affecting transparency
1. ____ level
2. ____ level
3. water
4. ____ remains

1. cellular
2. molecular
3. water
4. embryonic

57

what is dependent on the regularity of the lens fibers as well as their contructive/destructive interferenece properties

transparency of the lens

58

how is scatter related to the wavelength of light

independent or slightly dependent

59

the scatter produced by disruption of the regular array takes place when scattering particles are very _____ compared to the wavelength of light

large

60

water in the cornea can be a sign of....( 2 things)

closed angle glaucoma (high IOP)
contact lens over wear (lack of oxygen and buildup of osmotic pressure by lactate)

61

what are factors that promote transparency
1. ____ lens fibers
2. _____ of lens fibers
3. _____ of packing
4. ______ of organelles
5. _____

1. small
2. uniformity
3. regularity
4. paucity (lack of organelles)
5. avascular

62

molecular level or transparency
1. fibers accumulate large amounts of _____ as they elongate x2 other cells
2. lens proteins are ____ and _____
3. _____ arrangement
4. ________ density

1. proteins
2. small and uniform (90% crystallins)
3. ordered
4. high packing

63

scatter at the MOLECULAR level is dependent on the ................. of their proteins

size and shape and their concentration

64

why is water the destroyer?

disrupts fibers and destroys the regular array, creating refractive lakes bc of the difference in refractive index

65

effects of water
1. water produces ______
2. ______in extracellular space
3. disrupts ______
4. pump/leak system:_____ pump maintains constant lens volume

1. refractive lakes
2. increase
3. fibers
4. anterior

66

the pump/leak system in transparency osmoregulates by pumping out ____ ions and passive efflux of _____ is accompanied by water

sodium
chloride

67

what do the interdigitations and zonula occludens do to permeability

decrease it. they impose a barrier to water flow btwn cells especially in the center of the lens

68

what is the disease from congenital origin that arose from the posterior lens attachment of the hyaloid artery

mittendorf's dot

69

tunica vasculosa lentis-arises from the hyaloid artery
-regress during 2nd trimester

posterior lens

70

anterior pupillary membrane-arises from the developing iris stroma
-regress during 2nd trimester

anterior lens

71

the lens proteins leak and the body reacts to the foreign proteins w/ an antigen-antibody response

hypermature cataract

72

the antigetn-antibody response occurs and the preceipatates can clog the angle leading to

secondary open angle glaucoma

73

where is the mittendorf's dot located

inferior nasal to posterior pole of lens

74

what is the remnant of hyaloid artery at the center of the optic disk that has a small tuft of fibrous tissue

bergmeister's papilla

75

what is the lens power at rest
lens w/ accomodation?

15D
15D MORE

76

factors that affect refractoin are...
1. _____ concentration is proportional to RI
2. ________ polymerization ________ RI cuasing myopic shift in refraction

1. protein
2. protein, increaes

77

accommodation decreases by........

1/4 age

78

lens protects the retina from ________ by:
1. _____ light < 400nm including blue, UVB and UVC light
2. _____ o2 levels
3. ____ lipids
4. sloughing _______

1. absorbs
2. low
3. saturated
4. inwards

79

99% of the lens energy is for...

pumping

80

the lens fibers need lubrication to slide which is provided for by the...

mucopolysaccharids (GAGs)

81

the tight junctions or barrier is located in the.....

______ replace tight junctions in the rest of the lens

anterior epithelium
interdigitations

82

what are the 2 functions of actinomyosin and microtubulin

1. control the lens fiber growth and migration
2. somehow involved in accomodation

83

the sphingomyelin need to be ____ inorder to allow the lens to smoothly accommodate in different stages
-the lipids are _____ and ____chained

HARD. (like eveyrthing else to work)

-saturated and short chained

84

the scatter of light creates the _____ of the lens and there is NO _____yellowing

yellowing
posterior

85

what light is more scattered as pts dvelop catarcs

blue light

86

where are anterior pole and post pole cataracs located at in the lens

center

87

light is _______by the lens and this means that the posteriror subcapsular catarct is more _____ to light than the anterior

converged
obstructive

88

in the posterior catarct:
more light will pass through if pupil is ______
less light will pass through if pupil is _____

dilated
constricted

89

a pt w/ a post cataract will have a worse VA at ______ bc the pupil will constrict during accommodation.

-pt will have more problems in ____light

near than at distance

-bright

90

a nucleosclerotic cataract (NSC) is located in the ______
-the main problem with it is....
-it is worse when the pupil is....

lens nucleus
-scatters light
-dilated

91

the major lens proteins are...
water soluble ___%
urea soluble ____%
insoluble _____%

90%
5%
5%

92

what makes the lens very osmotically active

high protein content

93

the urea soluble and insoluble proteins make up the...

cell membranes and nucleus of the lens

94

what kind of proteins are urea soluble in lens

cytoskeletal and crystallin

95

what kind of proteins are insoluble in lens

crystallin and membrane protein albuminoid

96

what are the 3 different types of crystallins in humans?
-crystallins make up ___% of water soluble proteins of the lens

alpha, beta, gamma
-90%

97

which crystallins act as chaperones?

alpha A and alpha B

98

which crstyallin is importnat for the normal function of lens epithelial cells and fiber cells?

alpha A

99

which crystallin has cataracs and myopathy when a mutation in it occurs

alpha B

100

what is a protein that stabilizes other proteins, preventing them from aggregating

chaperones

101

the location of the lens proteins
-these decrease towards nucleus. 1. 2.
-these increases towards nucleas. 1. 2.

1. alpha
2. beta

1. gamma
2. albuminoid

102

albuminoid is thought to arise via ______ and ____ bond formation.
-how do alpha, beta, and gamma convert to albuminoid?

oxidation, s-s bond formatoin
-oxidation

103

the lens is more permeable anteriorly or posteriorly?

posteriorly so that the ions enter and water follows in the back

104

how does water move from cell to cell ?
which surface does it move towards

through gap junctions and aqueous pore
-anterior surface

105

the nucleus of the lens is relatvively ______ so that motion of ions and water is mainly cortical

impermeable

106

where are most of the leaks located?
where are most of the pumps located?

posterior surface
anterior surface

107

anterior epithelium has ____ pumps than the intermediate layers of the lens, which has _____ than the nucleus and then ____ than the capsule

more
more
more
capsule has none

108

anything detrimental to the pumps will lead to.....
anything that decreases ATP causes pump protein activity to.....

cataracts
decrease

109

the cells in the posterior portion of the lens have _____ membrane and lack ______

weaker
tight junctions

110

the _____ barrier exists across the anterior epithelium. the next strongest barrier is the .....

anterior epithelium
nucleus of the lens bc firmly packed and very impermeable to water

111

where does most of the osmolarity occur

in the front of the lens. stronger osmotic gradients across the front

112

in the osmotic gradient: anything that will increase the osmolarity inside the lens will increase....

water movement into the lens

113

cataracts caused by leaky membranes will be in the .....portion of the lens while those caused by osmotic gradients will be located in the .........

posterior portion
anterior portion

114

the electrolyte and water content resemble that of an....
the electrolyte and water content of aqueous and vitreous resumels that of...

intact cell

cerebrospinal fluid, plasma, or extracellular fluid

115

the inside of the lens is high in....and low in....

the outside of the lens is low in....and high in...

K+ , Na+

K+, Na+

116

most of the pumps are in the...

anterior epithelium

117

facilitated diffusion is passive. but it is carrier mediated and can become...

saturated

118

permeable to small molecular weight proteins including low molecular weight crystallins but prevents diffusion of large molecules

capsule

119

water tends to move into the lens bc the protein content inside the cell is ___ and the water content is-____

high , low

120

in the na/k atpase pump it exchanges sodium pumped out for k pumped in:
-Na passive diffuses down a concentration gradient in the _____, across the ____ into the lens, and diffuses to the ______ epithelium where it is pumped out into the _____

vitreous, capsule, ant lens ep, aqueous

121

potassium diffuses the the other direction of na towards the....
-tend to diffuse down its _____ out of the lens but is pumped back _____ the lens

vitreous
-concentration gradient, into

122

Cl: ____ down its concentration gradient into the cell
Ca: moves _____ its conc. gradidnet
glucose: supplied by the _____so there is higher concentration ______ the cell
-passes through the cell membrane through ....

-lactate: higher concentration ____ the cell so it
leaks
-ascorbic acid: ___ element
-inositol: high concentration in ____ and ____ the cell

diffuses
down
aqueous humor, outside
-facilitated diffusion and passive diffusion

-inside
-redox
-aqueous humor, inside

123

protein is very _____ inside the lens

high. cell membrane is not permeable to proteins proteins synthesized inside the cell from aa

124

glutathion is made up of ____ aa

3

125

the source of energy used to run the pumps is...

glucose

126

glucose winds up in the lens cell as

glucose - 6-P

127

an important reducing agent in the protection against superoxide

NADPH

128

the lens has no turnover of cells and needs the pathway....

pentose shunts to take care of superoxide

129

what percent of glucose-6-p enters the pentose shunt to produce ribose-5-p and NADPH?

what percent ends up at pyruvate?

15%

85%

130

majority of glucose is used to make lactate, even though only produces a small amount of ATP. what percent.
minor used for aerobic pathway

80%

131

movements of ions and water from aqueous and vitreous: (3 things)

passive diffusion
active transport
facilittated diffusion

132

anaerobic atp generation, how many?
aerobic?

160
180

133

nucleus requires _____ for pumps
nucleus uses ______ phosphate
conc. of _____ highest in nucleus
protein content ____ in nucleus

energy
creatinine phosphate
CP
highest

134

sorbitol pathway
1. conversion of glucose to ______
2. conversion of sorbitol to _____

1. sorbitol
2. fructose

135

the highest productivity of any pathway lies in the...

pre-equatorial epithelium bc it is the area of active mitosis

136

change in osmolarity causes changes in:
3 things

1. thickness
2. radius of curvature
3. rx

137

unusual changes in rx may indidcate...

diabetes

138

superoxide production
1. superoxide _______
2. ___ wavelenths

superoxide reduction
1. superoxide ____
2. _____

1. synthetase
2. short

1. dimutase
2. glutathione

139

how free radicals cause damage
1. cross-linking of DNA =>
2. corss-linking of lipids=>
3. cross-linking of proteins=>

1. gene mutations
2. leaky membranes
3. non-functional enzymes

140

some pathways to cataracts (3)

1. sunlight
2. posterior inflammations (uveitis)
3. diabetes