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Module 8 > Structure of Eyeball > Flashcards

Structure of Eyeball Flashcards

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1
Q

what are the components of the eye

A
  1. eyeball
  2. adnexa (ocular muscles, eyelids, lacrimal apparatus)
  3. housed in orbit (bony margins, copious fat)
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2
Q

what are the orientation of the eyeball

A
  1. poles
  2. optic axis
  3. equator
  4. meridian
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3
Q

name the structures

A
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4
Q

what are the 3 tunics of the eyeball

A
  1. external fibrous tunic
  2. middle vascular tunic
  3. internal nervous tunic
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5
Q

what is the function of the external fibrous tunic

A

gives shape to eyeball

protective

complete

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6
Q

what are the functions of the middle vascular tunic

A

blood vessels

smooth muscle

nutrient supply

control lens and pupil shape and size

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7
Q

what is the function of the internal nervous tunic

A

translation of visual signal into nerve impulses and transmission to brain

functional –> where light is converted into nervous signals

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8
Q

what is the fibrous tunic made up of

A

dense, collagenous

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9
Q

what are the functions of the fibrous tunic

A

resist internal pressure of material in chambers

gives shape to eyeball

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10
Q

what are the two parts of the fibrous tunic

A
  1. cornea
  2. sclera

meet at limbus

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11
Q

what is the cornea made up of

A

connective tissue –> lamellar/layered arrangement

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12
Q

what is the main part of the cornea

A

substantia propria

anterior and posterior lining epithelium

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13
Q

where are is the anterior epithelium

A

continuous with conjunctival epithelium –> contains sensitive nerves

responsible for corneal reflex

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14
Q

what is the posterior epithelium

A

continuous with anterior surface of iris

supplies nutrients to cornea (no vessels)

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15
Q

what is the basement membrane of the cornea

A

descemet’s membrane

last barrier to penetration of cornea (ulceration)

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16
Q

what is the sclera made up of

A

opaque/white

collagenous and elastic fibres

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17
Q

what is the function of the sclera

A

entry points for nerves and vessels

attachments for ocular muscles anterior to equator

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18
Q

what is the thin membranous covering that separates the eyeball from retrobulbar fat and what does it allow

A

vagina bulbi

allows eyeball free movement in socket

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19
Q

what are the 3 parts of the vascular tunic

A
  1. choroid
  2. ciliary body
  3. iris
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20
Q

what is the choroid

A

lines sclera from optic nerve to limbus

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21
Q

what is the ciliary body

A

thickening of tunic area at level of limbus

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22
Q

what is the iris

A

projects into cavity behind cornea

easily visible

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23
Q

what are the functions of the vascular tunic

A
  1. vascular supply
  2. suspends lens and controls shape of lens and pupil
  3. vessels enter eyeball at posterior pole and around equator
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24
Q

name the structures

A
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25
what vessels are contained in the choroid
blood vessels in pigmented connective tissue posterior ciliary arteries and vorticose veins supplies nervous tunic via layer of capillaries vessels seen with opthalmoscope
26
where is the avascular layer in the choroid
dorsal avascular layer between capillaries and larger vessels
27
what is the tapetum lucidum
reflective area --\> sends light back through retina --\> increases sensitivity of eye to low light
28
what is the ciliary body
thickened ridged ring around lens
29
what are the ciliary processes
extend zonular fibres to lens --\> suspends lens
30
where is the smooth ciliary muscle and what is the function
between ciliary body and sclera alters lens shape and alters lens focusing
31
what is the iris and where does it attach to
flat ring of tissue peripheral attachment to sclera and ciliary body
32
what is the central opening of the iris
pupil
33
what muscles control the dilation/constriction of pupil
smooth spincter (constrictor --\> parasympathetic) and radial dilator (sympathetic) muscles control pupil size
34
what does the pupil divide
anterior and posterior chambers
35
what are iridic granules
projections from dorsal border across pupil horse, ruminant
36
what is part of the nervous tunic
retina
37
what does the retina line
choroid from optic nerve to pupillary margin
38
what are the parts of the retina that can be reached by light and what does it contain
posterior 2/3 contains receptor cells (pars optica retinae)
39
what part of the retina is not reached by light
anterior 1/3 has no receptors (pars ceca retinae) continues onto iris
40
what is the pigmentation of the retina
black appearance of pupil --\> absorbs light
41
what is the junction between optic and blind parts of the retina
ora serrata level of junction between ciliary body and choroid
42
what is the optic disc
extension of brain arising from optic nerve
43
what are the retinal layers of the nervous tunic
1. choroid 2. pigmented epithelium 3. neuroepithelial cells 3. bipolar ganglion cells 4. multipolar ganglion cells
44
what are the layers of the retina
45
where is the pigmented epithelium absent
no pigment over tapetum
46
what are the neuroepithelial cells
receptor cells 1. rods --\> B/W & night vision 2. cones --\> colour & day vision
47
what are the multipolar ganglion cells
axons pass to optic disc and form optic nerve
48
what inserts at the optic nerve
entry of optic nerve (CN II) no receptor cells --\> blind spot easily seen with opthalmoscope
49
what is the area of the dorsolateral to optic disc
optimal resolution macula
50
what is the visual axis
macula-centre of lens-object viewed
51
what is the refractive media
focussing of light through structure of eyeball
52
what are the components of the refractive media
1. cornea --\> major role in refraction of light 2. aqueous humor --\> anterior and posterior chambers 3. lens 4. virteous body --\> virteous chamber
53
what is the aqueous humor and its function
clear, watery maintains ocular pressure
54
what produces the aqueous humor
ciliary process cells --\> enter posterior chamber
55
how does the aqueous humor enter and exit
anterior chamber via pupil exits via iridocorneal (drainage)/angle (venous sinuses in sclera)
56
how is the aqueous humor drained and produced
drainage = production constant intracular pressure
57
what does failure to drain aqueous humor cause
glaucoma
58
what is the lens
elastic regularly arranged fibres --\> transparency outer capsule --\> attachment of zonular fibres around equator (thickest part of capsule)
59
what is lens accomodation
lens will be thick if no external force --\> circular ciliary muscle relaxed = wide circle )thin lens) 1. muscle contracts --\> relaxes zonular fibres (thick lens) --\> close vision 2. muscle relaxes --\> tightens zonular fibres (thin lens) --\> far vision
60
what is the process here (fibres involved, shape of lens)
61
what is the vitreous body
gel-like mass high water content = vitreous humor thin surface membrane
62
what is the function of the vitreous body
maintains contact between retina and choroid hyaline artery passes to lens in embryo --\> regresses after birth
63
what is the volume of the vitreous body
constant not reduced/drained --\> won't cause pressure buildup
64
how can the eye be imaged
1. opthalmoscope --\> direct 2. ultrasound (cheap, simple, allows assessment of retina) 3. CT and MRI may be useful but more for orbital disease
65
what is the function of the adnexa
protect and move eye
66
what are the components of the adnexa
1. orbit 2. orbital fasciae 3. ocular muscles 4. eyelids 5. conjunctiva 6. lacrimal apparatus
67
what is the orbit
"conical" cavity on the lateral side of skull
68
what bones are in the orbit
frontal, lacrimal and zygomatic bones
69
which species have orbital ligament
carnivores and pig
70
what is in the orbit in horse and ruminants
zygomatic process
71
what are the openings of the orbit
1. optic canal 2. orbital fissure 3. ethmoidal foraminae 4. lacrimal sac fossa (leads to nasolacrimal duct)
72
what is the orbit lined with
fibrous sheets (periorbita) and fatty connective tissue --\> allows free movement of eyeball
73
what are the structures of the orbit
74
what are the 4 rectus muscles
1. dorsal 2. ventral 3. medial 4. lateral
75
what are the 2 oblique muscles
1. dorsal 2. ventral
76
where do the ocular muscles originate from
optic canal area
77
what are the functions of oblique muscles
maintain orientation of visual axis
78
what are the functions of the ocular muscles
sheets of smooth muscle maintain eyeball protrusion and eyelid opening
79
what are the true eyelids called
palpebrae
80
what are the true eyelids
musculofibrous folds upper and lower lids meet at angles of eye (commissures)
81
what are the 3 layers of eyelids and conjunctiva
1. skin 2. musculofibrous 3. mucous membrane = palpebral conjunctiva
82
what are these structures
83
what are the layers of the eyelids
1. musculofibrous layer 2. tarsus - fibrous plate
84
what is the musculofibrous layer
orbicularis oculi orbital septum levator palpebrae superioris smooth muscles
85
what is the tarsus - fibrous plate
stabilizes edge of eyelid and gives shape to palpebral fissure tarsal (meibomian) glands and cilia (eyelishes) along margin (secrete part of tear film)
86
what are the structures of the eyelids
87
what are the components of the conjunctiva
1. palpebral conjunctiva --\> lines lids 2. bulbar conjunctiva --\> reflects over sclera, epithelium anterior to cornea
88
what is the conjunctival sac
the space between lids and eyeball (spot for foreign bodies)
89
what is the 3rd eyelid
conjunctival fold --\> central cartilage conjunctiva on both sides --\> not true eyelid
90
how is the 3rd eyelid retracted
by smooth muscle orbitalis covers eyeball when retracted into orbit
91
what is the function of the lacrimal apparatus
production of lacrimal fluid (tears) --\> protection, corneal nutrition
92
what are the glands in the lacrimal apparatus
1. lacrimal --\> dorsolateral wall or orbit 2. gland of 3rd eyelid --\> around base of 3rd eyelid cartilage, deeper gland in pigs and cattle (AKA nictitans/nictitating gland)
93
which lacrimal gland causes cherry eye
inflammation of nictitans/nictitating gland
94
what are the glands
95
where is the drainage of tear film in the lacrimal apparatus
puncta lacrimalia slits adjacent to caruncle feed into lacrimal sac --\> sacs drain into --\> nasolacrimal duct --\> runs through maxillan and drains into nasal cavity
96
where does the tear film pool at
at medial angle of eye --\> lacrimal lake fluid repelled from edge of lids by fatty secretion of tarsal glands
97
what are the 3 layers of the tear film
1. outer: lipid, from tarsal glands (even spread of tears and integrity of film) 2. middle: aqueous, from lacrimal glands (moisture, nourishment) 3. inner: mucinous from goblet cells in conjunctiva (maintains film contact with cornea)

Module 8 (43 decks)

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