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Ocular Anatomy quiz #3 > Retina > Flashcards

Retina Flashcards

1
Q

what is the main function of the retina

A

where light energy is transformed into a neural signal and sent to the visual pathway

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2
Q

what is phototransduction

A

process of transforming light energy into a neural signal

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3
Q

what are the first 3 cells of the visual pathway

A

photoreceptors, bipolar cells, and ganglion cells

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4
Q

which interneurons modify the signal as it passes through the retina

A

amacrine cells, horizontal cells, and interplexiform cells

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5
Q

what do the neuroglial Muller Cells do

A

they maintain the physiologic environment of the retina

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6
Q

what are microglia

A

neuroglial cells that are wandering phagocytic cells

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7
Q

what are astrocytes

A

star-shaped cells that are in the nerve fiber layer/ganglion layer to support blood vessels and fibers

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8
Q

what are the innermost 9 layers of the retina called

A

the Sensory or Neural Retina

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9
Q

what is the 10th layer of the retina

A

the retinal pigmented epithelium (RPE)

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10
Q

what is the function of the RPE

A

to phagoctize the shed photoreceptor discs

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11
Q

what type of cells are in the RPE

A

a monolayer of cuboidal cells

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12
Q

what extends from the RPE to the photoreceptor layer (PR)

A

microvilli processes

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13
Q

which layer is the outermost neural layer

A

the photoreceptor layer (PR)

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14
Q

what does the PR layer contain

A

photopigment, rods and cones

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15
Q

what are the PR cells highly specialized to do

A

convert light energy into neural messages

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16
Q

which part of the PR layer is for capturing light

A

the outermost part

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17
Q

which part of the PR layer is for transmitting the neural signal

A

the innermost part

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18
Q

what parts are common between rods and cones

A

outer segment, cilium, inner segment, outer fiber, cell body, inner fiber, and synaptic terminal

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19
Q

what is the outer segment (OS)

A

a stack of membranous discs that are enclosed by the plasmalemma of the cell

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20
Q

where is photopigment located

A

inside the outer segment discs of the photoreceptors

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21
Q

where does the apex of the outer segment face

A

the RPE

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22
Q

where do the mircovilli from the RPE extend to in the PR layer

A

the distal third of the outer segment (OS)

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23
Q

what is the cilium

A

a connecting stalk between the OS and inner segment

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24
Q

what is the inner segment

A

two regions: ellipsoid and myoid region

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25
Q

what is in the ellipsoid region of the IS

A

mitochondria, power house

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26
Q

what does the myoid region of the IS contain

A

endoplasmic reticulum and golgi apparatus for synthesizing proteins

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27
Q

what is the outer fiber

A

extends from the inner segment to the cell body

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28
Q

what is inside the cell body

A

the nucleus of the photoreceptor

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29
Q

what is the inner fiber

A

the axon of the photoreceptor (forms the synaptic vesicles)

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30
Q

how many rods are there

A

92-120 million

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31
Q

what is another name for dim light

A

scotopic vision

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32
Q

what photopigment do rods contain

A

rhodopsin

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33
Q

where does the density of rods peak

A

in a ring about 4.5mm from the fovea

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34
Q

are there rods in the fovea

A

no only cones

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35
Q

how many discs are there in the rod outer segment

A

600-1000 discs

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36
Q

where is the photoreceptor rhodopsin located in the rod

A

in the disc membrane

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37
Q

when are the rod discs shed/phagocytized

A

early in the mornings

38
Q

what is the specialized terminal of the rod inner fiber called

A

a spherule

39
Q

what does the rod spherule contain

A

synapses with bipolar dendrites and horizontal processes

40
Q

how many cones are there for bright vision and color

A

5 million

41
Q

what is another term for bright vision

A

photopic vision

42
Q

how many different opsins (photopigments) are there for regions of the light spectrum

A

3

43
Q

what are S-cones

A

blue cones (420nm)

44
Q

what are M-cones

A

green cones (531nm)

45
Q

what are L-cones

A

red cones (588nm)

46
Q

how is the cone discs shape different from the rod discs

A

they are wider at the base and taper toward the apex

47
Q

when are the cone discs shed

A

in the evening

48
Q

what is different about the cone nuclei from the rod nuclei

A

the cone nuclei are larger

49
Q

what is the terminal structure of the cone called

A

pedicle

50
Q

what is the external limiting membrane (ELM)

A

a dark line (dots) of zonule adherens which hold the photoreceptors to each other and to Mullers cells

51
Q

what do the zonule adherens act as in the ELM

A

a barrier to large molecules into and out of the retina

52
Q

what is the outer nuclear layer (ONL)

A

contains the nuclei of the photoreceptor cells

53
Q

what is the outer plexiform layer (OPL)

A

where the synaptic terminals of the photoreceptors will synapse with the dendrites of the bipolar and horizontal cells

54
Q

what does the outer plexiform layer a demarcation of

A

the inner retinal layers that are supplied by the central retinal artery and the outer layers supplied by the choroid

55
Q

why is the outer plexiform layer a discontinuous membrane

A

there are many desmosome-like attachments (synaptic densities) between the processes

56
Q

what is the inner nuclear layer (INL)

A

where cell bodies of bipolar cells, horizontal cells, amacrine cells, interplexiform cells and Muller cells are located

57
Q

what does the internal nuclear layer mark/separate

A

the deepest part of the retina that is supplied by the central retinal vasculature

58
Q

what is the inner plexiform layer (IPL)

A

the dendrites of the ganglion cells and the axons of the bipolar cells

59
Q

what is the ganglion cell layer (GCL)

A

usually one cell layer thick (thicker in the macula)

60
Q

where do the ganglion cells communicate with

A

with the central visual system structures

61
Q

what is the nerve fiber layer (NFL)

A

unmyelinated nerve fibers (axons of ganglion cells) also the central retinal vessels

62
Q

what is the internal limiting membrane (ILM)

A

closest to the vitreous, formed by the footplates of the Muller cells, covered by basement membranes

63
Q

anteriorly, the internal limiting membrane is continuous with what other internal limiting membrane

A

in the ciliary body

64
Q

posteriorly, at the optic disc, what are the footplates replaced with

A

processes from astrocytes that form the internal limiting membrane of the disc

65
Q

what 3 things does the central retina contain

A

macula, fovea, and foveola

66
Q

how big is the diameter of the macula

A

5.5mm

67
Q

how far from the edge of the optic disc is the macula

A

3.5mm and 1mm below

68
Q

why is the macula darker in color

A

the PRE cells are taller and contain more pigment

69
Q

why does the macula have a yellow hue

A

it has increased amount of lutein and zexanthin in the ganglion and bipolar cells

70
Q

what is the fovea centralis (fovea)

A

the part of the retina that provides the best visual acuity (only cones are found here)

71
Q

how wide is the fovea

A

1.5mm diameter

72
Q

what is the sloping down of the walls of the fovea called

A

clivus

73
Q

is the fovea avascular

A

yes

74
Q

which retinal layers are present in the fovea

A

only the outer layers (no inner)

75
Q

which cells are found in the fovea

A

only photoreceptors (cones)

76
Q

what direction are the inner fibers of the photoreceptors in the outer plexiform of the fovea oriented

A

horizontal (vertical in the rest of the retina)

77
Q

what is the Nerve Fiber Layer of Henle

A

the layer in the fovea region where the photoreceptor fibers are horizontal

78
Q

how wide is the foveola

A

0.35mm in diameter

79
Q

what retinal layers are not present in the foveola

A

the inner, but it still has an internal limiting membrane and muller cells

80
Q

what is often seen in the center of the foveola

A

a reflex (umbo)

81
Q

what is present in the extereme peripheral retina

A

the rods are replaced by malformed cones near the ora serrata

82
Q

what blood supplies the inner retina

A

the central retinal vasculature

83
Q

what blood supplies the outer retina

A

the choriocapillaries

84
Q

what does the central retinal artery split into

A

a superior and inferior retinal artery and then nasal and temporal branches to feed their quadrants

85
Q

what are the two capillary beds in the retina

A

superficial and deep capillary plexus

86
Q

where is the superficial capillary plexus

A

in the nerve fiber layer

87
Q

where is the deep ciliary plexus

A

in the internal neuron layer

88
Q

are the capillaries fenestrated in the retina

A

no, they are in the blood-retinal barrier

89
Q

what is the ciliretinal artery

A

15-20% of population has it, derived from the short posterior ciliary arteries

90
Q

is the blood supply of the retina neuroregulated or autoregulated

A

autoregulated

91
Q

what veins drain the retina

A

central retinal vein

Ocular Anatomy quiz #3 (4 decks)

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