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Histology - Exam 4 > Sensory Systems - Eye > Flashcards

Sensory Systems - Eye Flashcards

1
Q

describe layers of orbit

A
  1. outer fibrous coat = cornea, sclera
  2. middle vascular (uveal) coat = iris, ciliary body, choroid
  3. inner retinal coat = retinal pigmented epithelium and neural retina
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2
Q

describe chambers of the eye

A

3 chambers:

  • anterior (b/w cornea and iris)
  • posterior (b/w back of iris and lens w/ attached fibers)
  • vitreous cavity (b/w lens and retina)
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3
Q

generally describe the cornea

A
  • transparent
  • convex
  • avascular (no blood or lymph in central portion)
  • 5 layers
  • can be transplanted w/o rejection
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4
Q

fxn of the convex shape of the cornea

A

aid in focusing light and images on retina

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5
Q

how do the central and peripheral parts of the cornea get nutrients?

A

central: diffusion from aqueous humor
peripheral: blood from limbus vessels

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6
Q

name the 5 layers of the cornea

A
  • epithelium
  • Bowman’s layer/membrane
  • stroma
  • Decemet’s membrane
  • corneal endothelium
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7
Q

describe epithelium of cornea

A
  • anterior layer
  • non-keratinized stratified squamous
  • small microvilli
  • pain receptors (trigeminal and oculomotors)
  • can regenerate
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8
Q

describe Bowman’s layer/membrane of cornea

A
  • layer of type 1 collagen
  • cannot regenerate
  • part of stroma
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9
Q

describe stroma of cornea

A
  • lattice of type 1 and type 5 collagen

- ECM rich in chondroitin and keratan sulfate

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10
Q

describe Decemet’s membrane of cornea

A
  • thick (5-10 um) basement membrane
  • contains type 7 collagen
  • produced by corneal endothelium
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11
Q

describe corneal endothelium

A
  • surface faces anterior eye chamber

- impermeable intercellular spaces that prevent fluid leakage into corneal stroma

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12
Q

generally describe the sclera

A
  • dense irregular CT

- opaque

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13
Q

function of sclera

A
  • protection and structural support

- insertion point for extraocular muscles

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14
Q

what is the limbus?

A

corneoscleral junction

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15
Q

what is adjacent to the limbus?

A

trabecular meshwork and canal of Schlemm

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16
Q

describe aqueous humor

A

fluid resembling plasma, but w/ less protein

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17
Q

what produces aqueous humor?

A

ciliary body epithelium

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18
Q

describe flow of aqueous humor

A

anterior chamber -> trabecular network -> canal of Schlemm -> aqueous veins -> episcleral veins

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19
Q

what does obstruction of aqueous humor flow lead to?

A

increased pressure in eye -> glaucoma

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20
Q

describe the choroid and fxn

A
  • highly vascular nutrient supplier to all eye layers
  • contains melanin
  • 3 layers
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21
Q

3 layers of the choroid

A
  • Bruch’s membrane
  • choriocapillaris (fenestrated caps-supply retina, fovea)
  • choroidal stroma
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22
Q

what does the ciliary body consist of?

A

uveal and neuroepithelial portions

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23
Q

describe uveal portion of ciliary body

A
  • outer layer of choroid (supraciliaris) + ciliary muscle attached to suspensory ligament
  • layer of fenestrated capillaries
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24
Q

describe neuroepithelial portion of ciliary body

A

2 layers of ciliary epithelium:

  • outer pigmented layer continuous w/ retinal pigmented epithelium
  • inner non-pigmented layer
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25
Q

what does the anterior portion of the ciliary body form?

A

it is folded to form ciliary processes

26
Q

what does epithelium in the ciliary processes produce?

A

aqueous humor

27
Q

what is the iris?

A
  • continuation of the ciliary body

- anterior part of middle coat (uvea)

28
Q

what controls size of pupil?

A

smooth muscle in iris

29
Q

describe smooth muscle in iris

A

2 layers:

  • circular (sphincter - parasympathetic)
  • radial (dilator - sympathetic)
30
Q

describe the lens

A
  • avascular
  • transparent
  • elastic
  • biconvex
31
Q

what encloses the lens?

A

capsule - thick basement membrane like material

32
Q

how does the lens change shape?

A

changes shape when tension on suspensory ligament fibers (zonular fibers) changes

33
Q

what is vitreous humor?

A
  • gel-like, transparent
  • water + hyaluronic acid
  • fills vitreous chamber
34
Q

function of vitreous humor

A

keeps lens and retina in place

35
Q

what is a cataract?

A

opacity of lens - associated with aging

36
Q

first two layers of retina

A
  1. retinal pigmented epithelium (RPE)

2. layer of rods and cones (photoreceptors)

37
Q

describe RPE fxns (3)

A
  • absorbs scattered light rays
  • phagocytosis of worn out discs shed from rods
  • stores and releases vitamin A to photo receptors
38
Q

what is the clinical significance of the RPE?

A

closely adhered to choroid - trauma can dislodge the retina at this site (where there is a space b/w RPE and rest of retina)

39
Q

what are rods: describe cells, contents, fxn?

A
  • tall cylindrical cells
  • outer segments = modified cilia
  • have discs from plasma membrane w/ rhodopsin pigment (transducer of light energy)
  • fxns in low light and peripheral vision
40
Q

what are cones: describe cells, contents, fxn?

A
  • shorter cone shaped cells
  • outer segments = modified cilia
  • have discs and pigments sensitive to red, green, and blue light
  • fxn in color vision and bright light
41
Q

where are cones found in relation to rods?

A

cones are located more centrally than rods

42
Q

what photoreceptors are found in the fovea?

A

only cones

43
Q

describe renewal of photoreceptors

A
  1. outer discs of old rods shed into space b/w outer segments and RPE, which phagocytoses them.
  2. new discs made from below, move upward, and replace old ones.

cone discs shed and replaced more slowly

44
Q

what are the posterior retina landmarks?

A

macula lutea and optic disc - viewed through the pupil by a scope

45
Q

what is the optic disc?

A

papilla where the optic nerve fibers exit retina

46
Q

does the optic disc have photoreceptors?

A

no

47
Q

fovea: what is it, fxn, describe photoreceptors?

A

what: a pit in the center of the macula
fxn: important for visual acuity
photoreceptors: only cones, very closely packed - highly represented in optic nerve and visual cortex = macular vision

48
Q

describe vessels around macula

A
  • no retinal vessels

- abundant choroid vessels on outside

49
Q

what is detached retina?

A

neural retina separated from RPE and from choroidal capillaries which feed photoreceptors, especially in fovea

50
Q

what is age related macular degeneration?

A

macular area and fovea lose function due to pigment epithelium behind retina degenerating and forming drusen (white spots) -> allowing fluid leakage behind fovea

51
Q

what type of vision loss does age related macular degeneration cause?

A

foveal cones die -> central vision loss -> cannot read or see fine detail

52
Q

what is a leading cause of blindness?

A

age related macular degeneration

53
Q

what is a common eye problem in aging?

A

glaucoma - increased pressure w/i eye

54
Q

what causes high intraocular pressure in glaucoma?

A

anterior chamber cannot exchange fluid properly by normal aqueous outflow

55
Q

what does the increased pressure in glaucoma lead to?

A

compromises blood vessels of optic nerve and axons of ganglion cells

56
Q

retinitis pigmentosa: what is it, what is first sign of disease, what develops eventually?

A
  • rods of peripheral retina degenerate in early stages of disease
  • first sign of disease = night blindness
  • eventually develop tunnel vision
  • black pigment in peripheral retina and thinned blood vessels at optic nerve head
57
Q

what is spared in retinitis pigmentosa?

A

only fovea

58
Q

how do you get retinitis pigmentosa?

A

hereditary

59
Q

how do you treat retinitis pigmentosa?

A

no cure

60
Q

what is diabetic retinopathy?

A

eye blood vessels become distorted and multiply

61
Q

how do you treat diabetic retinopathy?

A

laser treatment to stop blood vessel proliferation and fluid leakage

62
Q

what is hereditary retinal dystrophy?

A

inability of RPE to phagocytize worn out discs from rods

Histology - Exam 4 (5 decks)

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