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Histology II > The Eye > Flashcards

The Eye Flashcards

1
Q

what is the arrangement of the neural retina?

A

arranged into three cell body layers = “nuclear” separated by two synaptic layers = “plexiform”

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1
Q

what is the lacrimal gland?

A

a compound tubuloalveolar serous gland lacking striated ducts and heavilty infiltrated with adipocytes and plasma cells

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2
Q

what causes the aqueous humor to flow between the iris and the lens?

A

fluid pressure in the posterior chamber

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2
Q

what are the layers of the cornea?

A

ABCDC: Anterior Corneal Epithelial Bowman’s layer Corneal stroma Descemet’s membrane Corneal endothelium

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2
Q

how is the sclera different from the cornea?

A

sclera is a dense irregular CT (cornea has different layers); it is opaque (cornea = transparent) and it is vascularized (cornea = avascularized)

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2
Q

where is the pigmented epithelium of the iris located? what is its histology?

A

on the posterior surface of the iris; contains two layers of pigmented cells continuous with the two layers of epithelium of the ciliary body

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3
Q

what is the ora serrata?

A

the area where the cilliary body and retina join

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3
Q

what is found in the plexiform layers of the retina?

A

synaptic contacts

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3
Q

where are meiobian glands found? what do they produce? what is their function in eye?

A

found on the tarsal plate (CT); they are a sebaceous gland that secretes oil forming a hydrophobic ring around the eye to prevent loss of the tear fluid

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4
Q

what is the function of the cornea? is it avascular?

A

cheif refractive component of the eye; it is avascular and normally free of WBC

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4
Q

can the corneal be transplanted? why?

A

yes, it is avascular so there is a decreased likelihood of graft rejection

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5
Q

what is the retina derived from?

A

the brain (neural ectoderm)

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6
Q

what is the palpebral conjunctiva continuous with?

A

thin skin of the eyelid; it continues through an arch (fornix) and reflects back onto the surface of the eye at the bulbar conjunctiva

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8
Q

what are the three tunics/layers of the eye?

A

superficial to deep: 1. fibrous outer layer = sclera + cornea 2. vascular middle layer = choroid, ciliary body, iris 3. sensory inner layer = retina = pigment epithelium + neural retina

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9
Q

what is bulbar conjunctiva’s histological relevance? ie: what type of tissue/cells?

A

stratified epithelium containing goblet cells that covers the anterior sclera and is continuous with the anterior corneal epithelium

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9
Q

what photopigment do rods contain? what type of vision does this photopigment allow for?

A

rhodopsin = provides highly sensitiy but poor acuity and no color discrimination

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10
Q

what is the main function of the vascular layer of the eye?

A

to supply adjacent structures (iris, retina, sclera, ciliary muscles) with oxygen and nutrients

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10
Q

what are choriocapillaris?

A

a layer of fenestrated capillaries produced by the choroid that are next to the pigment epithelium of the retina

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10
Q

what happens due to diabetic retinopathy?

A

blood-retina barrier leakage and capillary loss are prominent

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11
Q

what forms the blood-aqueous barrier? what is its function?

A

formed by: occluding zonules of the blood vessels of the iris, ciliary body, and corneal endothelial cells.; it isolates the aqueous humor from the blood

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11
Q

What are the layers of the retina?

A

from the choriocapillaris to the vitreous chamber: Retinal pigment epithelium Photoreceptors (inner and outer segments) Outer nuclear layer (nuclei of photoreceptors) Outer plexiform layer (synaptic contacts Inner nuclear layer (nuclei of bipolar and other cells) Inner plexiform layer (synaptic contacts) Ganglion (cells sending axons our of retina) Optic Nerve fiber layer: ganglion cell axons

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11
Q

what is responsible for relaying signals from the photorecepts to the innermost cell layer of the retina? in what layer are these cells found?

A

bipolar cells; found in inner nuclear layer

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12
Q

How is the histology of the trabecular meshwork significant for its function?

A

it is composed of sieve-like squamous (vascular) endothelium-lined channels in the wall of the anterior chamber adjacent to the peripheral rim of corneal endothelium

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13
Q

what portion of the pohotoreceptor captures photons to produce visual signal?

A

outer portion

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14
Q

where is the limbus region?

A

circular region where the sclera joins the cornea

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14
Q

Sooo tears that surface of the eye contain what?

A

lacrimal tear fluid, mucus from conjunctival goblet cells + oil from the meibomian glands to retard evaporation

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15
Q

what is the function of the retina?

A

initial coding of visual information

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15
Q

what is presbyopia? what is the treatment?

A

when the lens becomes resisitant to accomodative changes (during middle age); treatment = bifocals

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17
Q

what are the three chambers of the eye?

A

anterior, posterior, vitreous

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17
Q

where is the retinal pigment epithelial cells located?

A

next to Bruch’s membrane and the choriocapillaris

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18
Q

the ora serratus signifies transition of what orbital layers?

A
  1. transition from multi-layer retina to bi-layered ciliary epithelium 2. where the choroid transitions into the ciliary body, muscle, and stroma NOTE: retinal pigment epithelium trnasitions into the pigmented (outer) ciliary epithelial while the multilayered neural retina transitions into non-pigmented (inner ciliary epithelial cells) therefore the ora serratus secretes aqueous humor
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19
Q

where is the choroid located?

A

between the sclera and the retina

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20
Q

do the endothelial cells lining the iris vessels posses occludens zonules?

A

yes

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21
Q

what is the function of the fibrous layer of the eye?

A

(the sclera + cornea); functions for protection and support of the eye

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21
Q

what are the layers of the retina?

A

neural retina + retinal pigment

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22
Q

What type of cells make up the corneal endothelium? is it ever regenerated?

A

layer of simple squamous to cuboidal cells; NOT PART OF THE VASCULATURE (even though ‘endothelial’ layer); part of the blood aqueous barrier regenerates poorly

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23
Q

What are Drusen? what do they cause? when do they arise?

A

drusen = opaque nodules accumulating between Bruch’s membrane and the pigment epithelium; can hinder transfer of oxygen and nutrients from th echoriocapillaris to the retina. Appear during age-related macular degeneration (losing of vision)

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25
Q

what promotes clarity of the cornea?

A

the arrangement of type I collagen fibrils in the corneal stroma layer; the lamellae of fibrils are oriented perpendicularly with respect to those above and below; fibrils have uniform diamter and interfibrillar spacing

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26
Q

what type of skin is found on the eyelids? what types of glands etc do they have?

A

thin skin; has sebacceous glands, sweat glands and fine hairs

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27
Q

what is the stroma composed of?

A

loose, pigmented, highly vascularized connectived tissue

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28
Q

what is the function of the cells in the inner (nonpigmented) epithelial layer of the ciliary body?

A
  1. secrete aqueous humor 2. anchor the collagen fibers of the suspensory ligaments 3. join the occluding zonules
30
Q

how does the corneal endothelium layer contribute to the blood aqueous barrier?

A

it has occluding zonules; regulates the ion content of the corneal stroma to help maintain approriate hydration of the corneal stroma;

30
Q

what does the lends have to promote clarity? where is it found?

A

high concentration of lens crystallins protein in the lens fiber cells

31
Q

where is the retina located?

A

found in the posterior 2/3 of the eye, extending from the ora serrata to the optic disk

31
Q

where does the central retinal artery/nerve run? how does it enter/exit the eye?

A

runs in the intraorbital section of the optic nerve; enters/exits the eye through the blind spot (optic disk)

33
Q

what produces aqueous humor?

A

ciliary body

35
Q

where is bulbar conjunctiva found

A

a mucous membrane covering the anterior surface of the eyeball around the cornea

37
Q

how is hydration of the cornea maintained?

A

via regulation of the ion content by the zonula occludens of the conreal endothelial layer

38
Q

how is aqueous humor drained/flow?

A

produced by the ciliary body (in the nonpigmented epithelial cells) in the posterior chamber of the eye, and flows to the anterior chamber; it is directed into the limbus region, down the trabecular meshwork and then through the schlemm’s canal to exit out the angle of the anterior chamber to the venous system

39
Q

what is found in the outer nuclear layer of the retina? inner nuclear layer?

A

outer = nuclei of photoreceptros i = nuclei of bipolar and other cells

40
Q

what does the inner segment of the photoreceptors contain?

A

organelles

42
Q

what is aqueous humor?

A

similar in composition to CSF (high Na low K) but contains very little protein

43
Q

What type of cells make up the Bowman’s layer? is it ever regenerated?

A

ACELLULAR condensation of underlying collagenous layer that resists penetration and slows bacterial invasion. The layer DOES NOT regenerate if damaged

44
Q

what is responsible to absorbing light as it passes through the retina?

A

melanin-containing cells (choroid melanocytes)

45
Q

what happens in the fovea? what is the fovea made up of?

A

made up of entirely cones (colors+ visual acuity); it is a depression in the macula where light falls directly on the photoreceptors resulting in high visual acuity

47
Q

what causes corneal opacity?

A

damage to endothelium, disrupted ion balance in stroma, or invasion of white blood cells due to infection

49
Q

what forms the blood-retinal barrier?

A

formed by blood vessels of retina and occluding zonules of retinal pigment epithelium

49
Q

what is the function of the limbus region? is it vascularized?

A

highly vascularized; supplies nutrients and cells for the cornea and drains the aqueous humor

49
Q

what is the ciliary body bound by?

A

ora serrata and iris

51
Q

what is myopia? what is it caused by?

A

nearsightedness (can’t see far away); caused by thinning of the sclera which leads to axila elongation of the vitreous chamber and then image is then focused in front of the retina

52
Q

what is the optic papilla/optic disk? what does it contain?

A

located where the optic nerve fibers leave the eye; have NO RECEPTORS = blind spot

53
Q

what supplies the retina with blood?

A

inner 2/3 of retina = central retinal artery outer 1/3 = choriocapillaris of the choroid

55
Q

what is the function of vitreous humor?

A

support the shape of the eye and maintain the position of the retina to prevent detachment

57
Q

what is the anterior surface of the iris composed of?

A

discontinous layer of fibroblasts

58
Q

what is glaucoma caused by? symptoms? treatment?

A

caused by collagen deposition in the trabecular meshowk during aging that can block the aqueous outflow channels, producing INCREASED INTRAOCULAR pressure; can lead to blindness if not treated; treatments = carbonic anhydrase inhibitors to slow aqueous production and laser surgery

60
Q

does vitreous humor regenerate?

A

yes, but poorly (unlike aqueous humor which is constantly being produced to nourish the lens and other structures

62
Q

what produces vitreous humor?

A

hyalocytes

63
Q

what is the composition of the fibrous layer?

A

sclera + cornea + associated regions (limbus, lamina cribrosa)

65
Q

what is the content inside each chamber of the eye?

A

anterior: aqueous humor posterior: aqueous humor vitreous: vitreous humor

66
Q

what is the function of the lens?

A

to focus the eye to maintain a sharp image of the visual field on the retina

67
Q

what is the lens capsule?

A

a thick basal lamina that all of the lens cells contirbute to; it anchors the suspensory ligaments, which in turn are anchored to ciliary epithelium of the ciliary process

68
Q

what is another name for the vascular layer? what does it contain?

A

uvea; contains the choroid, ciliary body, iris

69
Q

describe the muscles bundling the iris

A
  1. corcimferentially arranges pupillary constrictor muscle (adjacent to the pupillary margin) 2. radially arranged pupillary dilator muscle (adjacent to the constrictor)
70
Q

what photopigment do cones contain? what type of vision does this photopigment allow for?

A

iodopsin = color vision and fine acuity (due to less convergence in connections)

70
Q

what types of cells make up the lens? is it vascularized? innervated?

A

lens made up of: epithelial cells, lens fiber cells, lens capsule; avascular and aneural

72
Q

How does the aqueous humor drain?

A

through a circumferential drainage network (trabecular meshwork) then the aqueous humor makes its way to the canal of schlemm and then drained into the venous system

73
Q

what is the function of the iris?

A

to regulate the amount of light falling on the retina ALSO acts as a fate for the flow of aqueous humor between the anterior and posterior chambers

75
Q

what type of cells are in the pigmented epithelium? what do they have? why is it significant?

A

simple cuboidal epithelilum; contain melanin; important for absorption of any light that is not captured by photoreceptors

76
Q

what is a cataract?what is it caused by? what is the treatment?

A

increased opacity in the lens; occurs in older people but can appear prematurely due to UV radiation, steroids, toxins and trauma; treatment = surgical removal of the lens and replace it with a plastic lens of fixed focus

77
Q

is the lens a cellular?

A

no; only on the anterior of lens is there simple cuboidal cells, the rest of the lens undergoes mitosis to become elongated lens fiber cells but as they elongate (and do so throughout human life), they lose their nuclei and most organelles;

78
Q

what are the components of the sclera (it is a connective tissue so it has cell, ground substance, fibers)

A

cells = fibroblasts ground substance = keratan sulfate + chondroitan sulfate (not rich in corneal proteglycan like the corneal stroma) fibers = type I collagen varying in diambeter and interfibril spacing (unlike corneal stroma)

79
Q

where does bulbar conjunctiva reflect?

A

onto the inner surface of the eyelids (palpebral conjunctiva)

80
Q

what phagocytizes the used up tips of the photoreceptors?

A

retinal pigment epithelium

81
Q

What type of cells make up the Descemet’s membrane? is it ever regenerated?

A

thickened basal lamina of underlying corneal endothelium DOES regenerate

82
Q

where is the pigmented retinal epithelium layer located?

A

on Bruch’s membrane (basal lamina reinforced by collagen adn elastic fibers)

84
Q

what does the ciliary body contain?

A

smooth muscles (for accomodation) vacualrized CT beneath epithelium two layered epithelium (outer = pigmented)

86
Q

what is vitrous humor composed of?

A

a thick gelatinous fluid containing hyaluronic acid and collagens (type I and type II)

87
Q

what is the iris?

A

fibromuscular flap of tissue containing pigmented cells, vacularized connective tissue, and smooth muscle; has a free margin that forms the pupil;

89
Q

what are the boundaries of each chamber of the eye?

A

anterior: inside surface of the cornea, anterior surface of the iris, and part of the anterior lens posterior: epithelium of the iris, ciliary process, zonule fibers, and anterior lens vitreous:retina, osterior ciliary body, zonule fibers, posterior lens

90
Q

what is found in the ganglion layer of the retina?

A

cells sending axons out of retina

91
Q

what is the function of aqueous humor?

A

to nourish the lens and other structures bordering on the anterior and posterior chambers

92
Q

what supplies the vascular layer? what drains it?

A

ciliary arteries = supply vortex = veins

93
Q

what mediates the signal transduction for sight?

A

G-Protein cascade

94
Q

What type of cells make up the corneal stroma? is it ever regenerated?

A

dense irregular CT; thickest layer of the cornea; cells = keratinocytes ground substance = corneal proteoglycan rich keratan and chondroitin sulfates fibrils = type I collagen arrangement( perpendicular DOES NOT REGEN. (damage = scarring)

95
Q

what do tears contain in order to combat infection?

A

IgA and lysozyme

96
Q

what is the lamina cribrosa? where is it located? what is its function?

A

sieve like opening in the posterior sclera allows exiting retinal ganglion cell axons to form the optic nerve

97
Q

What type of cells make up the anterior corneal epithelium? is it ever regenerated? is it innervated?

A

stratified squamous non-keratinized cells; epithelium is renewed ~ once a week, so if it is damaged, repair is possible; contains MANY sensory free nerve endings

98
Q

what is found in the optic nerve fiber layer?

A

ganglion cell axons

99
Q

what is bruch’s membrane? (lamina vitrea)

A

a thin elastic membrane that lies between the choriocapillaris and the retinal pigment epithelium

100
Q

what type of epithelium is found on the fornix and bulbar conjunctiva?

A

stratified with goblet cells

101
Q

what is LASIK eye surgery?

A

permanent refractive changes produced surgically that reshape the cornea to increase or decrease its power

Histology II (4 decks)

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