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Ocular Anatomy quiz #1 > Cornea > Flashcards

Cornea Flashcards

1
Q

what is included in the outermost fibrous tunic of the eye

A

the transparent cornea and the opaque sclera

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2
Q

how much of the eyeball does the cornea contribute

A

1/6th

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3
Q

what is the corneoscleral limbus

A

the area of the merging of the cornea and the sclera

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4
Q

how much refractive power does the cornea contribute

A

(43.1 to 48.8D) 3/4

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5
Q

how thick is the central and peripheral part of the cornea

A

the center is about 0.52mm and increases to 0.70mm

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6
Q

how big is the optical zone

A

the central 1/3 of the cornea or 4mm

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7
Q

what are the 5 layers of the cornea

A

epithelium, bowman’s layer, stroma, descemets membrane, endothelium

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8
Q

what cells make up the corneal epithelium

A

stratified nonkeratinized, nonsecretory, squamous epithelium

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9
Q

is the corneal epithelium regularly or irregularly arranged

A

regular to permit light to enter

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10
Q

what cells are absent in the center of the corneal epithelium that are present in the periphery

A

melanocytes and immunocompetent dendritic cells

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11
Q

what is the most superficial layer of the corneal epithelium

A

the apical layer

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12
Q

what does the apical layer of the epithelium secrete

A

glycocalyx- also has microvilli and ridges to increase the surface area to stabilize the tear film

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13
Q

how are the apical cells joined together

A

tight junctions along the lateral walls to prevent passage of fluid between the cells and excessive uptake of fluid from the tear film

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14
Q

what layer is directly below the apical layer

A

wing cell layer

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15
Q

how do the wing layer connected

A

via desmosomes and communicate gap junctions

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16
Q

what shape are wing cells

A

polyhedral , anterior surface is convex/posterior concave to fit over the basal cells

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17
Q

what is the basal cell layer (basement membrane) made of

A

columnar cells, stand in perfect alignment

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18
Q

how do the basal cells attach to the basement membrane (basal lamina)

A

hemidesomosomes, communicate with gap junctions

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19
Q

how is the basement membrane formed for the basal cell layer of the epithelim

A

secreted by the basal cells, anchored by fibrils pass through the basement membrane and bowmans layer

20
Q

how are the basal cells and the wing cells connected

A

via desmosomes

21
Q

when the basal cells are migrating toward the center of the cornea, where do they originate from peripherally

A

the Palisades of Vogt

22
Q

what are the Palisades of Vogt

A

located in the radial folds of the epithelium of the limbus, may harbor stem cells

23
Q

which layer of the corneal epithelium undergoes mitotic division

A

the basal cells

24
Q

what is the second layer of the cornea

A

bowman’s layer

25
Q

why is bowman’s layer not a membrane

A

It is PAS -

26
Q

can bowman’s layer regenerate?

A

No, it is produced pre-natally, lacks keratocytes (fibroblast) cells

27
Q

what replaces bowman’s layer if it is damaged

A

the epithelium thickens in its place

28
Q

which layer of the cornea is the thickest, about 90%

A

the stroma (substantia propria)

29
Q

what is the stroma made of

A

an extracellular matrix of arranged collagen fibers

30
Q

how far apart must the collagen fibrils be to keep the cornea transparent

A

must be less than one half the wavelength of visible light (400-700nm)

31
Q

where is descemet’s membrane

A

lies on the posterior surface of the stroma (substantia propria) serving as a basement membrane for the corneal endothelium

32
Q

which layer of the cornea thickens from birth to adult

A

Descemet’s membrane

33
Q

can descemet’s membrane be reformed if damaged

A

yes

34
Q

what is Schwalbe’s line

A

the anterior border ring of the trabecular meshwork- where Descemet’s membrane abruptly stops at the corneal margin

35
Q

what are Hassall-Henle Bodies

A

small transparent growths, that increase with age, on the posterior surface of Descemet’s membrane at the periphery of the cornea, they protrude the anterior chamber

36
Q

what is corneal guttata

A

when Hassall-Henle Bodies occur in the central cornea instead of the periphery

37
Q

what is the corneal endothelium comprised of

A

single layer of flat, hexagonal arranged cells, uniform size, with the apical end facing the anterior chamber and basal ends apposed to Descemet’s membrane

38
Q

what type of barrier does the corneal endothelium provide

A

a leaky barrier allowing nutrients from the aqueous humor to enter the avascular stroma

39
Q

what junctions are connecting the corneal endothelium cells

A

macula occludens, dont completely encircle the cells to allow a leaky barrier

40
Q

what is the corneoscleral limbus

A

junction of the cornea and the sclera, encircles the peripheral cornea, external scleral sulcus is here

41
Q

where are the trabecular meshwork and canal of schlemm located

A

in the internal scleral sulcus

42
Q

at the corneal periphery, which structures are continuous with others

A

corneal epithelium- conjunctival epithelium, corneal stroma- scleral stroma, corneal endothelium- endothelial cells of trabecular meshwork

43
Q

which layers terminate at the corneal periphery

A

Bowmans layer and Descemet’s membrane

44
Q

what is the sensory innervation to the cornea

A

long ciliary nerves from the ophthalmic division of the trigeminal nerve

45
Q

where do the long ciliary nerves travel to reach the cornea

A

through the perichoroidal space between the sclera and the choroid

46
Q

which layers of the cornea do not have innervation

A

Descemet’s layer and corneal endothelium

Ocular Anatomy quiz #1 (8 decks)

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