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anatomy and physio final > Lens > Flashcards

Lens Flashcards

1
Q

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
A

refract, transparency, accomodates

-protects

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2
Q

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

A

highest

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3
Q

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

A

cataract

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4
Q

the lens is avascular. what provides its nourishment

the ____ of the lens can affect the angle

A

aqueous

location

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5
Q

what are the 6 regions of the lens

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

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

A

corneal epithelium

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7
Q

the capsule is composed of …

A

collagenous fiber and fibrillin

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8
Q

____ confers elasticity to the lens

______ limits the ability to stretch

A

fibrillin

collagen

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9
Q

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

A

T. most molec except proteins move through the capsule

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10
Q

the zonules attach to the capsule. T or F

A

T.

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11
Q

when looking at near, the ciliary muscle ring ______, moving __________

  • zonules are _______
  • lens ______
A

contracts, forward and inward
-loosened
bulges

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12
Q

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

A

marfan’s syndrome

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13
Q

what is the only actively metabolizing area of the lens

A

anterior epithelium

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14
Q

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

A

90%

-anterior portion of the lens

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15
Q

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

A

90%

10%

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16
Q

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

A

pre-equatorial region

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17
Q

where si the region of active mitosis in the lens

A

pre-equatorial region

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18
Q

where is the pre-equatorial region located

A

under the iris from which it gains its protection

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19
Q

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

A

pre-equatorial region

boss ass region

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20
Q

cortex have hexagonal fibers because…….

A

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

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21
Q

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

these are zones of inconsistencies

A

center

peripheral

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22
Q

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

A

increase

increase

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23
Q

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

A

organelles

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24
Q

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

A

refractive power

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25
Q

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

A

hexagonal, regular, very little

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26
Q

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

A

the fibers are regularly spaced

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27
Q

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

A

destructive interference of light

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28
Q

the upright Y suture is ______

the upside-down Y suture is ____

A

anterior

posterior

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29
Q

the increased branching of the sutures produces better….

A

optical qualities

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30
Q

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

A

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

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31
Q

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

A

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

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32
Q

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

A

ball and socket

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33
Q

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

A

ball and socket junction

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34
Q

extensive intercellular communication exists via_____

A

the lens gap junction …

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35
Q

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

A

the lens - no room for lakes

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36
Q

what are lens fibers linked by

A

N-cadherin connections

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37
Q

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

A

neural tube

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38
Q

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

A

lens placode

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39
Q

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

the structure is now the optic cup

A

embryonic fissure

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

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40
Q

what start to form the vascular capsule of the lens

A

hyaloid vessels

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41
Q

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

A

posterior cells

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42
Q

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 _____
A
  1. embryonic optic vesicles
  2. lens placode, lens vesicle
  3. embryonic fissure
  4. hyaloid
  5. anterior epithelium
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43
Q

what is the area of nuclei of elongating fiber cells called

A

germinative zone

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44
Q

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

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

A

new fibers

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45
Q

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

A

basal ends

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46
Q

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
A
  1. sub-epithelial layers
  2. capsule, sutures
  3. basal ends
  4. mature fiber cells
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47
Q

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
A
  1. basal ends
  2. apical
  3. suture
  4. basal ends
  5. apoptosis
  6. light
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48
Q

organelle free zone:

  • diffrentiating fibers = outer ____% some organelles
  • mature fibers = inner ____%
A
  • 20%

- 80%

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49
Q

order of lens development from center to out is….

  1. ____ nucleus
  2. _____nucleus
  3. _____ nucleus
  4. cortex
  5. _____ capsule
A
  1. embryonal
  2. fetal
  3. adult
  4. cortex
  5. anterior capsule
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50
Q

what fibers from the posterior epithelium form the embryonic nucleus

A

primary lens fibers

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51
Q

where are secondary lens fibers formed? and by what

A

pre-equatorial region by mitosis

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52
Q

what fibers form the fetal nucleus

A

the fibers laid down before birth

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53
Q

between birth and sexual maturation form the ……

A

adult nucleus

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54
Q

what is formed by the fibers laid down after sexual maturation

A

cortex

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55
Q

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

A

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

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56
Q

variables affecting transparency

  1. ____ level
  2. ____ level
  3. water
  4. ____ remains
A
  1. cellular
  2. molecular
  3. water
  4. embryonic
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57
Q

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

A

transparency of the lens

58
Q

how is scatter related to the wavelength of light

A

independent or slightly dependent

59
Q

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

A

large

60
Q

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

A

closed angle glaucoma (high IOP)

contact lens over wear (lack of oxygen and buildup of osmotic pressure by lactate)

61
Q

what are factors that promote transparency

  1. ____ lens fibers
  2. _____ of lens fibers
  3. _____ of packing
  4. ______ of organelles
  5. _____
A
  1. small
  2. uniformity
  3. regularity
  4. paucity (lack of organelles)
  5. avascular
62
Q

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
A
  1. proteins
  2. small and uniform (90% crystallins)
  3. ordered
  4. high packing
63
Q

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

A

size and shape and their concentration

64
Q

why is water the destroyer?

A

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

65
Q

effects of water

  1. water produces ______
  2. ______in extracellular space
  3. disrupts ______
  4. pump/leak system:_____ pump maintains constant lens volume
A
  1. refractive lakes
  2. increase
  3. fibers
  4. anterior
66
Q

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

A

sodium

chloride

67
Q

what do the interdigitations and zonula occludens do to permeability

A

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

68
Q

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

A

mittendorf’s dot

69
Q

tunica vasculosa lentis-arises from the hyaloid artery

-regress during 2nd trimester

A

posterior lens

70
Q

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

A

anterior lens

71
Q

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

A

hypermature cataract

72
Q

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

A

secondary open angle glaucoma

73
Q

where is the mittendorf’s dot located

A

inferior nasal to posterior pole of lens

74
Q

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

A

bergmeister’s papilla

75
Q

what is the lens power at rest

lens w/ accomodation?

A

15D

15D MORE

76
Q

factors that affect refractoin are…

  1. _____ concentration is proportional to RI
  2. ________ polymerization ________ RI cuasing myopic shift in refraction
A
  1. protein

2. protein, increaes

77
Q

accommodation decreases by……..

A

1/4 age

78
Q

lens protects the retina from ________ by:

  1. _____ light < 400nm including blue, UVB and UVC light
  2. _____ o2 levels
  3. ____ lipids
  4. sloughing _______
A
  1. absorbs
  2. low
  3. saturated
  4. inwards
79
Q

99% of the lens energy is for…

A

pumping

80
Q

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

A

mucopolysaccharids (GAGs)

81
Q

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

______ replace tight junctions in the rest of the lens

A

anterior epithelium

interdigitations

82
Q

what are the 2 functions of actinomyosin and microtubulin

A
  1. control the lens fiber growth and migration

2. somehow involved in accomodation

83
Q

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

A

HARD. (like eveyrthing else to work)

-saturated and short chained

84
Q

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

A

yellowing

posterior

85
Q

what light is more scattered as pts dvelop catarcs

A

blue light

86
Q

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

A

center

87
Q

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

A

converged

obstructive

88
Q

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

A

dilated

constricted

89
Q

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

A

near than at distance

-bright

90
Q

a nucleosclerotic cataract (NSC) is located in the ______

  • the main problem with it is….
  • it is worse when the pupil is….
A

lens nucleus

  • scatters light
  • dilated
91
Q

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

A

90%
5%
5%

92
Q

what makes the lens very osmotically active

A

high protein content

93
Q

the urea soluble and insoluble proteins make up the…

A

cell membranes and nucleus of the lens

94
Q

what kind of proteins are urea soluble in lens

A

cytoskeletal and crystallin

95
Q

what kind of proteins are insoluble in lens

A

crystallin and membrane protein albuminoid

96
Q

what are the 3 different types of crystallins in humans?

-crystallins make up ___% of water soluble proteins of the lens

A

alpha, beta, gamma

-90%

97
Q

which crystallins act as chaperones?

A

alpha A and alpha B

98
Q

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

A

alpha A

99
Q

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

A

alpha B

100
Q

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

A

chaperones

101
Q

the location of the lens proteins

  • these decrease towards nucleus. 1. 2.
  • these increases towards nucleas. 1. 2.
A
  1. alpha
  2. beta
  3. gamma
  4. albuminoid
102
Q

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

A

oxidation, s-s bond formatoin

-oxidation

103
Q

the lens is more permeable anteriorly or posteriorly?

A

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

104
Q

how does water move from cell to cell ?

which surface does it move towards

A

through gap junctions and aqueous pore

-anterior surface

105
Q

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

A

impermeable

106
Q

where are most of the leaks located?

where are most of the pumps located?

A

posterior surface

anterior surface

107
Q

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

A

more
more
more
capsule has none

108
Q

anything detrimental to the pumps will lead to…..

anything that decreases ATP causes pump protein activity to…..

A

cataracts

decrease

109
Q

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

A

weaker

tight junctions

110
Q

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

A

anterior epithelium

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

111
Q

where does most of the osmolarity occur

A

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

112
Q

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

A

water movement into the lens

113
Q

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

A

posterior portion

anterior portion

114
Q

the electrolyte and water content resemble that of an….

the electrolyte and water content of aqueous and vitreous resumels that of…

A

intact cell

cerebrospinal fluid, plasma, or extracellular fluid

115
Q

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

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

A

K+ , Na+

K+, Na+

116
Q

most of the pumps are in the…

A

anterior epithelium

117
Q

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

A

saturated

118
Q

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

A

capsule

119
Q

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

A

high , low

120
Q

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 _____

A

vitreous, capsule, ant lens ep, aqueous

121
Q

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

A

vitreous

-concentration gradient, into

122
Q

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

A

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

  • inside
  • redox
  • aqueous humor, inside
123
Q

protein is very _____ inside the lens

A

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

124
Q

glutathion is made up of ____ aa

A

3

125
Q

the source of energy used to run the pumps is…

A

glucose

126
Q

glucose winds up in the lens cell as

A

glucose - 6-P

127
Q

an important reducing agent in the protection against superoxide

A

NADPH

128
Q

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

A

pentose shunts to take care of superoxide

129
Q

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

what percent ends up at pyruvate?

A

15%

85%

130
Q

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

A

80%

131
Q

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

A

passive diffusion
active transport
facilittated diffusion

132
Q

anaerobic atp generation, how many?

aerobic?

A

160

180

133
Q

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

A

energy
creatinine phosphate
CP
highest

134
Q

sorbitol pathway

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

2. fructose

135
Q

the highest productivity of any pathway lies in the…

A

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

136
Q

change in osmolarity causes changes in:

3 things

A
  1. thickness
  2. radius of curvature
  3. rx
137
Q

unusual changes in rx may indidcate…

A

diabetes

138
Q

superoxide production

  1. superoxide _______
  2. ___ wavelenths

superoxide reduction

  1. superoxide ____
  2. _____
A
  1. synthetase
  2. short
  3. dimutase
  4. glutathione
139
Q

how free radicals cause damage

  1. cross-linking of DNA =>
  2. corss-linking of lipids=>
  3. cross-linking of proteins=>
A
  1. gene mutations
  2. leaky membranes
  3. non-functional enzymes
140
Q

some pathways to cataracts (3)

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

anatomy and physio final (9 decks)

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