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Biological Sciences > Review of ocular structure and function > Flashcards

Review of ocular structure and function Flashcards

1
Q

What are the 4 tissue types in the body

A
  • Nervous
  • Muscular
  • Epithelial
  • Connective
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2
Q

What are the three types of muscular tissue

A
  • Skeletal
  • Smooth
  • Cardiac
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3
Q

What are the two types of epithelial tissue

A
  • Covering

- Glandular

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4
Q

What are the two types of connective tissue

A
  • Loose

- Dense

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5
Q

What can glandular exocrine glands be split into

A
  • Unicellular glands

- Multicellular glands

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6
Q

What is example of unicellular gland

A

Goblet cells

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7
Q

What are multicellular glands divided into

A

Simple ( one duct )
Compound ( several ducts ) - bundles of secretory cells
Each duct has secretory units

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8
Q

What is meant by exocrine

A

secrete into duct

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9
Q

What is meant by endocrine

A

secrete into blood system

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10
Q

how many layers is tear film made of

A

3

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11
Q

what are layers of tear film

A
  • mucin layer - mucous - stick rest of tear film onto cornea
  • aqueous layer - serous secretions - bulk of tear - middle
  • lipid layer - sebaceous secretions - outer - stop rest of tear film evaporating
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12
Q

What is example of simple multicellular gland

A

tarsal gland - found in upper and lower eyelids

They open onto the ocular surface via pores at the eyelid margin

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13
Q

what part of tear film do tarsal glands secrete

A

Sebacceous - oily component

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14
Q

What forms the mucous part of tear film

A

Conjunctival goblet cells - cover posterior ( back )surface of eyelids and exposed surface of eye (limbus)

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15
Q

What does conjunctiva contain

A

mucous secreting goblet cells

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16
Q

What do goblet cells have

A

triangular nucleus + large lumen

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17
Q

What is example of multicellular compound gland

A

Lacrimal gland

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18
Q

what part of tear film does lacrimal glands secrete

A

Aqueous component - serous secretions

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19
Q

Process of blinking

A

Secrete tear film into conjucitval sac
All secretions spread over eye
Spreads tear film over eye’s exposed surface when we blink
Tears drained over puncta into lacrimal sac and then nose

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20
Q

What are tears drained through

A

Puncta

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21
Q

What are tears drained into

A

nasolacrimal duct

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22
Q

What are the main muscles involved in opening and closing the eye - movement of eyelids

A

Two skeletal muscles

Voulantary

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23
Q

Where do part of the muscles lie

A

Part of the muscle lies within the face and part within the eyelid

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24
Q

What are two muscles involved in moving eyelids

A
  • Orbicularis Oculi

- Levator palpebrae superioris

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25
Q

What does the Orbicularis Oculi

A 
Runs around the eye
Closes the eye
Orbit = round
Oculi - eye
Its contraction closes palpebral aperture ( eyelid )
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26
Q

What does Levator palpebrae superioris do

A

Runs along top of eye ball and sends tendons into eyelid

Opens eye and raises upper eyelid when it contracts

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27
Q

what is an example of a dense regular connective tissue

A

The corneal stroma

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28
Q

What is corneal stroma made of

A

collagen

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29
Q

is corneal stroma transparent or opaque and why

A

transparent

due to tightly packed and regularly arranged collagen fibres

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30
Q

What is outer corneal layer known as and where is it located

A

Corneal epithelium

Front of eye

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31
Q

What type of epithelium is it and why

A

Stratified squamous

Protects from dirt, eyelids,

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32
Q

What is the inner surface of the cornea known as

A

Corneal endothelium

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33
Q

What type of epithelium is corneal endothelium and why

A

Simple squamous
Single layer of flat cells = diffuse easily across barrier of minimal thickness
Ideal for areas where exchange of substances is required - allows avascular cornea to exchange substances with aqueous

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34
Q

Where does light enter after travelling across cornea

A

Anterior chamber - filled with aqueous humout
Lens
Vitreous humour
Impinges on retina

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35
Q

What does the light sensitive retina do

A

Converts photons to neurobiological activity

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36
Q

Where is posterior chamber

A

infront of lens, behind iris

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37
Q

what is the outer coat of eye known as

A

sclera

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38
Q

is sclera opaque or transparent and why

A

Opaque - white

collagen fibres irregularly arranged

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39
Q

What is the corneoscleral junction known as

A

Limbus

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40
Q

what is connective tissue proper made of

A
  • fibres ( collagen, elastic and reticular )
  • cells ( fibroblasts…)
  • ground substance
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41
Q

what are fibres

A

long stringy proteins in viscous brown substance

42
Q

what is connective tissue divided into

A

loose - adipose or aereolar
dense - regular - specific order, same diameter
or irregular - randomly arranged, varying diameters

43
Q

How many layers does cornea have and what are they

A 
5
epithelium
bowmans layer
stroma
descemets membrane
endothelium
44
Q

how many muscles does iris contain and what are they

A

2
iris sphincter
iris dilator

45
Q

what does iris sphincter do

A

circular muscle that constricts/closes pupil when sphincter contracts
parasympathetic pathway

46
Q

what does iris dilator do

A

opens the pupil when it contracts

sympathetic pathway

47
Q

what is ciliary body divided into

A
  • anterior ridge pars plicata- folded

- posterior smooth thinner pars plana - simple

48
Q

what are pars of plicata made up of

A

series of ridges - ciliary processes

49
Q

what does ora serata do

A

flat bit of ciliary body merges with retina here

50
Q

what is ciliary process covered with

A

2 layered epithelium

51
Q

what is outer pigmented epithelium part of

A

eye’s black box effect

52
Q

what is inner unpigmented epithelium part of

A

aqueous humour - produces it

53
Q

what is closest to inside of eye from inner unpigmented epithelium and outer pigmented epithelium

A

Inner unpigmented epithelium

54
Q

How does the black box effect work

A

stops stray light bouncing off retina = seeing detailed images
dont want light bouncing around inside of eye
open eye - black on inside - heavily pigmented

55
Q

What is uvea made up of

A

iris - forms pupil - merges with….
ciliary body
choroid

56
Q

What is choroid

A

a vascular layer - blood vessles sandwiched between sclera and retina

57
Q

function of choroid

A

main function to supply nutrients to outer retina

58
Q

why does outer retina need nutrients

A

it contains no nutrients itself - no blood vessels

59
Q

what is bruch’s membrane

A

separates choroid and retina

60
Q

what happens if bruch’s membrane is dusrupted

A

age related macular degeneration

61
Q

pars of plannner

A

flat/thin

62
Q

pars of plecata

A

folded/pleated

63
Q

where is choroid in histological section

A

to the left of anterior eye

64
Q

where is iris

A

coming of ciliary body - front of anterior eye

65
Q

What is iris

A

forms pupil
‘offshoot’ of ciliary body anteriorly
acts as aperture stop

66
Q

where does light go through in eye

A

pupil ONLY

67
Q

What is posterior surface of iris covered with and why

A

2 layered epithelium containing melanin

ensures the only light that enters eye is through pupil - light cant get through body of iris = aperture stop

68
Q

what is iris made of

A

loose areolar connective tissue - iris change size

69
Q

what is stroma example of and why

A

loose areolar connective tissue

change shape as pupil size changes by 2 muscles

70
Q

how is lens attached to ciliary body

A

by suspensory ligaments

71
Q

what are 3 layers of lens

A
  • elastic lens capsule covering entire surface - outer layer
  • simple epithelium underneath this
  • bulk of lens is made of elongated cells ( lens fibres ) - long thin cells
72
Q

what are lens fibres

A

long hexagonal cells that run from front to back surface of lens

73
Q

how are adjacent lens fibres joined

A

by gap junctions = allow flow of nutrients

74
Q

Aqueous production of inner epithelium of ciliary body

A

aqueous travels from ciliary body, past lens and supplies avascular lens and cornea with nutrients
it is drained through the trabecular meshwork into the canal of Schlemm at filtration angle

75
Q

what happens if aqueous is not drained

A

eye eventually explodes - glaucoma

76
Q

what is aqueous humour produced by and what does it do

A

inner epithelium

provides nutrients - need it because lens + cornea are avascular - no blood supply

77
Q

what does canal of schlemm do

A

takes in used aqueous and recycles it into avascular system

78
Q

summary of aqueous production

A
  • aqueous into anterior chamber
  • comes to filtration angle
  • trabecular framework - filters through aqueous humour and comes in canal of schlemm where it drains and recycled into vascular system
79
Q

what is bulk of ciliary body made of

A

smooth ciliary muscle

80
Q

what is bulk of ciliary body made of

A

smooth muscle - contracts - ciliary body moves inwards - towards lens - changes focus of eye

81
Q

what does inner layer of ciliary body do

A

produces aqueous

82
Q

what does outer layer of ciliary body do

A

black box effect

83
Q

what is the function of the lens capsule

A
  • elasticity - accommodation
  • selective barrier to substances - stopping large matter e.g. inflammatory cells entering lens, while allowing smaller necessary metabolites through
  • cataract surgery
84
Q

what happens in cataract surgery

A
  • the lens stoma is ‘ liquified ‘ by an ultrasound probe ( destroys lens fibres )and sucked out leaving capsule behind like empty bag which is then filled with an artificial lens
    i. e. replace damaged lens fibres with plastic lens = replacement lens - in capsule
85
Q

why is most of total refractive index provided by the cornea

A

due to the difference between the refractive index of air and the cornea

86
Q

role of lens

A

fine focus image through accommodation - change power

provides little refractive power

87
Q

where is majority of focusing of light done and why

A

at border of cornea

because its curved and the difference in refractive index between air and cornea

88
Q

when is eye usually emmetropic

A

at rest ( parallel light rays from distant objects focused on retina ) - light not refracted

89
Q

where are close objects focused

A

behind retina

90
Q

what is accommodation

A

bring close objects into focus - eye increase its refractive power - bend light more to refract more

91
Q

what happens in unaccommodated eye

A

lens is under tension and pulled flat

ciliary muscles relax and lens stretched

92
Q

what happens in accommodated eye

A

tension on lens released
rounder shape/fatter
ciliary muscles contracts
move closer to lens = more powerful

93
Q

what is presbyopia

A

loss of accommodative ability with age

94
Q

what is retina

A

lines back of eye
terminating anteroraly at ora serrata
made up of various neurons and glial cells
convert light into neurobiological activity

95
Q

what are outer layers of retina composed of

A
  • photoreceptors - convert optical image into nervous potentials ( phototransduction )
96
Q

what are cones sensitive to

A

high light levels

97
Q

what are rods sensitive to

A

low light levels

98
Q

what are the 5 main types of neurones the retina is made up of

A
  • photoreceptors
  • horizonal cells
  • bipolar cells
  • amacrine cells
  • ganglion cells
99
Q

what is the end result

A

action potential generated in ganglion cells

100
Q

what does light do

A

light traverses the inner retinal neurons before reaching photoreceptors
electrical signals leave via ganglion cell axons - make up optic nerve

101
Q

where is highest quality of image produce

A

fovea - because cones close together

102
Q

what are the 6 muscles attaching eyeball to skull

A
  • superior rectus
  • superior oblique
  • medial rectus
  • lacteral rectus
  • inferior oblique
  • inferior rectus

Biological Sciences (27 decks)

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