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Ocular Anatomy quiz #2 > Iris > Flashcards

Iris Flashcards

1
Q

what is the function of the iris

A

it acts as a mobile diaphragm separating the aqueous compartment into anterior and posterior chambers

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2
Q

what is the normal size of the iris

A

1-8mm

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3
Q

why does the iris change size (not the pupil)

A

it regulates the amount of light entering/illuminating the retina

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4
Q

what is the average diameter of the iris

A

12mm

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5
Q

where is the iris the thickest

A

at the iris collarette (0.6mm thick)

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6
Q

where is the iris collarette located

A

1.5mm from the pupillary margin

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7
Q

where is the iris the thinest

A

near its insertion into the ciliary body, the root of the iris (0.5mm thick)

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8
Q

what does the iris collarette separate

A

it is a circular ridge that separates the iris into a pupillary zone and a ciliary zone

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9
Q

what determines the iris color

A

it is due to stromal absorption, whatever light waves are not absorbed are reflected back and that is the eye color

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10
Q

if the iris was blue, what wavelengths would be absorbed

A

the longer wavelengths, allowing shorter (blue) to be reflected back

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11
Q

what is the pupillary ruff

A

where the pupillary zone starts

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12
Q

what are fuch’s crypts

A

depressions on the anterior surface of the iris, along the collarette

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13
Q

what are the radial ridges

A

formed by the underlying stromal vasculature in the ciliary region that can be seen

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14
Q

how is the posterior side of the iris different from the anterior side

A

it is more smooth and uniform

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15
Q

how many layers does the iris have

A

5: anterior border layer, stroma, muscle layer, dilator muscle and anterior pigment epithelium, and posterior pigmented epithelium

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16
Q

where does the anterior border layer come from

A

it is a condensation of the underlying stroma

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17
Q

how is the collagen arranged in the anterior border layer of the iris

A

in radial columns appearing as white fibers in light-colored irises

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18
Q

what is an iris process

A

after the anterior border layer terminates at the iris root, the iris may extend in a spoke-like fashion at schwalbes line

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19
Q

what is absent in the anterior border layer

A

the oval shaped Fuch’s crypts

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20
Q

what is the collagen the most abundant in the stroma

A

around the blood vessels

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21
Q

where are the arteries derived from that supply the iris

A

the major circle of the iris (located in the ciliary body)

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22
Q

what arteries supply the MAC (major arterial circle)

A

2 long posterior ciliary arteries and 7 anterior ciliary arteries

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23
Q

where is the minor arterial circle located

A

near the collarette

24
Q

what keeps the blood vessels from kinking during mydriasis and miosis

A

collagen fibers that surround and anchor the blood vessels

25
Q

where do the veins drain for the iris

A

into the vortex veins

26
Q

are iris capillaries fenestrated or nonfenestrated

A

they are non-fenestrated

27
Q

how are the iris stroma endothelial cells joined together

A

by zonula occludens (tight junctions) to form the blood-aqueous barrier

28
Q

what is the iris freely permeable to

A

aqueous humor

29
Q

where is the sphincter muscle located

A

within the stroma

30
Q

what type of muscle is the sphincter muscle

A

spindle-shaped smooth muscle cells joined by gap junctions

31
Q

what shape is the sphincter muscle

A

it is circular, within the pupillary zone of the iris

32
Q

how wide is the sphincter muscle

A

about 0.75-0.1mm wide

33
Q

does the sphincter muscle remain functional if it is severed

A

yes

34
Q

if the sphincter muscle contracts, what happens to the pupil

A

it will constrict (miosis)

35
Q

what innervates the sphincter muscle

A

postgagnlionic parasympathetic fibers from the short posterior ciliary nerves

36
Q

what layer is posterior to the iris stroma

A

the myoepithelial layer: 2 portions- muscular basal portion and the epithelial apical portion

37
Q

where is the muscular portion of the myoepithelial layer

A

adjacent to the stroma- make up the iris dilator muscle

38
Q

how is the dilator muscle arranged

A

it starts from the iris root and extends radially toward the pupil, overlapping manor

39
Q

what happens when the dilator muscle contracts

A

the pupil will dilate

40
Q

what innervates the dilator muscle

A

long posterior ciliary nerves (nasociliary branch of ophthalmic, trigeminal nerve 5)

41
Q

what signals do the nerves carry to the dilator muscle

A

postganglionic sympathetic innervation from the superior ganglion

42
Q

is the pupil maintain a constant size

A

no it is always in hippus, due to struggle between the sympathetics and parasympathetic innervation

43
Q

why do you think LSD for the dilator muscle

A

Long, sympathetic, Dilator

44
Q

how does the anterior pigmented iris epithelium face the posterior pigmented epithelium

A

apex to apex

45
Q

how are the twwo pigemented epithelial layers connected

A

via tight intercellular junctions and desmosomes

46
Q

which layer of pigemented epithelium is move heavily pigmented

A

the posterior pigment epithelium

47
Q

what type of cells are the anterior pigement epithelium

A

they are cuboidal shaped

48
Q

what type of cells are the posteior pigement epithelium

A

columnar shaped

49
Q

why does the posterior pigmented epithelium have tight junctions and desmosomes

A

prevent macromolecules from entering the posterior chamber from the anterior chamber

50
Q

Does the posterior or anterior pigmented epithelium lose its pigment

A

the posterior does as it becomes the NPE of the ciliary body

51
Q

does the posterior pigmented epithelium have a basement membrane

A

yes, it covers the basal side of the cell, giving the posterior chamber a lining

52
Q

how does the iris get blood supply

A

by 2 long posterior ciliary arteries and the 7 short anterior ciliary arteries

53
Q

what do the 2 long posterior ciliary arteries and the 7 short anterior ciliary arteries merge to form

A

the MAC

54
Q

is the MAC a plexus

A

yes, not a single vessel

55
Q

what are the “Thick Walled Vessels”

A

the arteries that extend out radially from the MAC towards the pupillary margin, lined with collagen

Ocular Anatomy quiz #2 (8 decks)

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