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Ocular Anatomy quiz #2 > Crystalline Lens > Flashcards

Crystalline Lens Flashcards

1
Q

what is the crystalline lens

A

all cells, transparent, biconvex structure

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2
Q

what is the posterior curvature

A

5-8mm radius of curvature

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3
Q

what is the anterior curvature

A

8-14mm

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4
Q

which side, anterior or posterior of the lens is steeper

A

the posterior side

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5
Q

how far away from the pars plicata is the lens equator

A

about 0.5mm away from the ciliary processes

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6
Q

what are the dimensions of an adult lens (unaccommodated)

A

10mm in diameter and 4mm thick

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7
Q

what changes as we age, the diameter or thickness of the lens

A

the thickness, increases about 0.02mm per year

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8
Q

what keeps the lens in place on the posterior surface to the anterior surface of the vitreous

A

the hyaloid capsular ligament

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9
Q

how much of the total power of the eye is the lens power

A

about 15 to 20 D (the cornea accounts for the rest)

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10
Q

what are the 3 parts to the lens

A

an elastic capsule, lens epithelium, and lens fibers

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11
Q

what is the thickest basement in the body

A

the elastic capsule of the lens

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12
Q

where is the thickest part of the lens

A

just anterior and posterior to the equator

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13
Q

where is the lens the thinest

A

at the posterior pole

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14
Q

does the posterior side have an epithelium

A

no

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15
Q

how is the lens capsule secreted anteriorly

A

by the anterior lens epithelium

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16
Q

how is the lens capsule secreted posteriorly

A

by the superficial lens fibers

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17
Q

which side of the lens capsule thickens with age, posterior or anterior

A

the anterior side does

18
Q

what are the two functions of the lens capsule

A

act as a diffusion barrier that is freely permeable to low-molecular weight compounds and to make the lens more pliable in response to the pull of the zonular fibers during accommodation

19
Q

where do the zonules attach to the lens capsule

A

between the equator and the poles

20
Q

why is there no posterior epihelium

A

it was used to form the primary lens fibers during embryonic development

21
Q

where do cells proliferate

A

the pre-equatorial (germanative zone) near the equator

22
Q

what happens to the cell after it is created

A

it transitions into an elongated columnar shape and arranged in meridional rows and will become secondary lens fibers

23
Q

do any of the fibers die off as we age

A

no, they become compacted and make the lens less pliable

24
Q

how does the lens receive nutrients

A

the central anterior epithelium is involved in the transport of substances from the aqueous humor (the lens is avascular)

25
Q

what is the bulk of the lens

A

the secondary fibers

26
Q

where is the nucleus located in the secondary lens fibers

A

it is anterior, it gradually disintergrates and the fiber will lose contact with the basement membrane

27
Q

what are lens Y sutrures

A

the place where anterior and posterior end of fibers meet

28
Q

how long and what shape are the lens fibers

A

they are 10mm long and U-shaped to fit in the lens (4-5mm thick)

29
Q

which side, anterior or posterior is the Y suture upright

A

the anterior side

30
Q

how are the lens fibers held together

A

by interlocking adjacent plasma membranes (ball and socket)

31
Q

what type of junction is present in the fibers

A

gap junctions to permit the deeper fibers with nutrients from the aqueous humor

32
Q

besides suppling nutrition what else to the gap junctions aid with

A

helping the lens to act like a single cell

33
Q

what is the epithelium-fiber interface

A

the border of the apical portion of the anterior epithelium and the apical portion of the secondary lens fiber

34
Q

after the nuecli are lost in the fibers, what happens to them

A

they become specialized to form crystallins (alpha and beta): the bulk of the lens fiber 40%

35
Q

why is the lens so refractive

A

due to the specialization of the fibers forming crystallins

36
Q

what is the earliest fiber mass called

A

the embryonic nucleus (center of lens)

37
Q

when is the embryonic nucleus formed

A

first 2 months of embryonic development (doesn’t increase in size)

38
Q

what fibers are formed before birth that have the Y sutures

A

the fetal nucleus

39
Q

what nucleus has the fibers formed between birth and sexual maturation, that increases throughout life

A

the adult nucleus

40
Q

is there blood supply to the crystalline lens

A

not after embryologic development

Ocular Anatomy quiz #2 (8 decks)

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