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MBBS2/Anatomy~HEAD & NECK > Gross anatomy of the eyeball > Flashcards

Gross anatomy of the eyeball Flashcards

1
Q

where is the eyeball embedded

A

in orbital fat

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2
Q

the eyeball is separated from the orbital fat by what

A

fascial sheath of the eyeball

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3
Q

what are the 3 layers (tunics) of the eye

A

-outer fibrous coat
-middle vascular pigmented coat i.e. the uvea
-inner nervous coat i.e. the retina

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4
Q

what is the outer fibrous coat like

A

its an inelastic coat

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5
Q

what makes up the outer fibrous coat

A

-cornea (anteriorly)
-opaque sclera (posteriorly)

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6
Q

what makes up the uvea

A

-choroid
-ciliary body
-iris

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7
Q

where does the retina extends to

A

forwards to within 6mm of the limbus

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8
Q

the opaque sclera is composed of what

A

dense fibrous tissue

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9
Q

what colour is the sclera

A

white

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10
Q

what pierces the sclera posteriorly

A

optic nerve

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11
Q

the sclera is fused with what

A

dural sheath of the optic nerve

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12
Q

what do you call the area of the sclera that is pierced by the nerve fibers of the optic nerve

A

lamina cribrosa

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13
Q

what other things pierce the sclera

A

ciliary arteries and nerves and their associated veins

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14
Q

the sclera is directly continuous with what in front

A

with the cornea at the corneoscleral junction/ limbus

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15
Q

whats at the junction of the sclera and cornea

A

an opening i.e. the scleral venous sinus

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16
Q

what colour is the cornea

A

transparent

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17
Q

what does the cornea do

A

it refracts the light entering the eye

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18
Q

what is the cornea in contact with posteriorly

A

the aqueous humor

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19
Q

whats the blood supply of the cornea

A

it is avascular and devoid of lymphatic drainage.

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20
Q

how is the cornea nourished

A

by diffusion from the aqueous humor and from the capillaries at its edge

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21
Q

whats the nerve supply of the cornea

A

long ciliary nerves from the ophthalmic division of the trigeminal nerve

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22
Q

why are cornea transplants common and successful

A

because the cornea has no blood vessels therefore there are no antibodies to cause rejection

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23
Q

whats the limbus

A

the junction between the cornea and the sclera

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24
Q

what does the limbus nourish

A

peripheral cornea

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25
Q

how is a cornea nourished in a cornea transplant

A

by tears and aqueous humor

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26
Q

what does the limbus assist in

A

corneal wound healing

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27
Q

the limbus has the pathway for what

A

aqueous outflow

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28
Q

whats the conjunctiva

A

the translucent mucous membrane that joins the eyeball to the lids ( it lines the posterior surface of the eyelids and anterior aspect of the eyeball)

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29
Q

whats the normal conjunctiva like

A

-pink
-smooth
-thin
-transparent

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30
Q

what runs within conjunctiva

A

large deep blood vessels that run vertically

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31
Q

what does the conjunctiva form at the upper and lower reflections between the eyeball and eyelid

A

2 sacs i.e. the superior and inferior fornices

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32
Q

whats the function of the conjunctiva

A

it helps lubricate the eye by producing mucus and tears (but a small volume of tears compared to the lacrimal gland)

it contributes to the immune surveillance and helps to prevent the entrance of microbes into the eye

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33
Q

what are the 3 parts of the conjunctiva

A

-bulbar conjunctiva
-palpebral conjunctiva
-forniceal conjunctiva

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34
Q

what does the conjunctiva contain

A

-stroma ( has no adenoid tissues until 3 months after birth)
-follicles and papillae

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35
Q

what are some conditions of the conjunctiva

A

-conjunctival injection
-chemosis

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36
Q

describe the palpebral conjunctiva

A

its richly vascular, extremely thin and strongly bound to the tarsal plate

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37
Q

the palpebral conjunctiva is subdivided into what

A

-marginal
-tarsal
-orbital

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38
Q

whats the extension of the marginal conjunctiva

A

it extends from the lid margin to about 2mm back of the lid upto the sulcus subtarsalis

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39
Q

whats the marginal conjunctiva

A

its actually a transitional zone between skin and the conjunctiva proper

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40
Q

what opens in the marginal zone

A

lacrimal puncta

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41
Q

whats the bulbar conjunctiva

A

its transparent and lies loose over the underlying structures ( so can be moved easily)

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42
Q

what separates the bulbar conjunctiva from the anterior sclera

A

episcleral tissue and tenons capsule

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43
Q

whats the blood supply of the conjunctiva

A

-marginal arcade of the eyelid
-peripheral arterial arcade of the eyelid
-anterior ciliary artery

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44
Q

what supplies the palpebral conjunctiva and the fornices

A

branches from the marginal and peripheral arcades of the artery

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45
Q

where do veins of the conjunctiva drain into

A

venous plexus of the eyelids which then drain into the superior and inferior ophthalmic veins

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46
Q

where does the cicumcorneal zone of the limbus drain into

A

the anterior ciliary veins

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47
Q

the lateral side of the conjunctiva drains into what lymph nodes

A

the periauricular lymph nodes

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48
Q

the medial side of the conjunctiva drains into what lymph nodes

A

the submandibular lymph nodes

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49
Q

whats the nerve supply of the bulbar conjunctiva

A

long ciliary nerve branches of nasociliary nerve from the ophthalmic division of the trigeminal nerve

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50
Q

whats the nerve supply of the superior palpebral and forniceal conjunctiva

A

frontal and lacrimal branches of V1

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51
Q

what are clinical correlates of the conjunctiva

A

-conjunctivitis
-malignant lymphoma
-conjunctival papilloma

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52
Q

what does the middle layer of the eye contain

A

blood vessels

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53
Q

what is the small opening in front of the middle layer

A

pupil

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54
Q

what is the choroid

A

its the vascular layer of the eye containing connective tissues

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55
Q

where does the choroid lie

A

between the retina and sclera

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56
Q

what is the choroid composed of

A

an outer pigmented layer and an inner highly vascular layer

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57
Q

what does the choroid do

A

provides oxygen and nourishment to the outer layers of the retina as well as the ciliary body and iris

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58
Q

whats the blood supply of the choroid

A

branches of the ophthalmic artery (which enter the eyeball without passing with the optic nerve)

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59
Q

what is the ciliary body continuous with

A

posteriorly with the choroid and anteriorly it lies behind the peripheral margin of the iris

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60
Q

what is the ciliary body composed of

A

-ciliary ring
-ciliary processes
-ciliary muscles

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61
Q

whats the ciliary ring

A

its the posterior part of the body and its surface has shallow grooves i.e. the ciliary striae

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62
Q

what are the ciliary processes

A

are radially arranged folds which are connected to the suspensory ligaments of the lens

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63
Q

whats the ciliary muscle composed of

A

meridional and circular fibers of smooth muscle

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64
Q

how do meridional fibers run

A

backward from the limbus to the ciliary processes

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65
Q

where do the circular fibers of the ciliary body lie

A

internal to the meridional fibers

66
Q

whats the nerve supply of the ciliary body

A

-the ciliary muscle is supplied by parasympathetic fibers from the oculomotor nerve

67
Q

whats the action of the ciliary body

A

contraction of the ciliary muscle especially the meridional fibers pulls the ciliary body forward, which relieves tension in the suspensory ligament causing the elastic lens to become more convex, increasing the refractive power of the lens

68
Q

the tension on suspensory ligaments does what

A

changes the shape of the lens depending on the distance of the object being viewed, this process is called accommodation

69
Q

whats the iris

A

its the coloured part of the eye and is the most anterior portion of the vascular tunic

70
Q

what makes up the iris

A

radial and circular muscles

71
Q

what does the iris do

A

controls the amount of light entering the eye

72
Q

whats the opening in the middle of the iris

A

pupil

73
Q

what happens to the iris in bright light

A

the parasympathetic nervous system causes the circular muscles to contract and the radial muscles to relax, causing the pupil to constrict and less light enters the eye.

74
Q

what happens to the iris in dim light

A

the sympathetic nervous system causes the circular muscles to relax and radial muscles to contract, which causes the pupil to dilate and more light enters eye

75
Q

what causes constriction of the pupils

A

contraction of the circular fibers because of parasympathetic control through the short ciliary nerves

76
Q

what causes dilation of the pupils

A

contraction of the radial fibers because of sympathetic control through the long ciliary nerves

77
Q

what does the drug atropine do

A

it inhibits the parasympathetic nervous system causing the pupil to dilate

78
Q

what are the 3 chambers of the eye

A

-the anterior chamber
-the posterior chamber
-the vitreous cavity

79
Q

where is the anterior and posterior chamber located

how do these 2 chambers communicate

what fills these 2 chambers

A

infront of iris and behind iris respectively

communicate through pupil

are filled with clear aqueous humour

80
Q

what fills the vitreous cavity

A

a gel like structure i.e. the vitreous fluid

81
Q

what makes aqueous humor

A

ciliary body

82
Q

aqueous humor is continually drained by what

A

scleral venous sinus/ canal of schlemm

83
Q

how often is aqueous humor replaced

A

90 mins

84
Q

what is a glaucoma

A

its increased intraocular pressure that can cause blindness due to compression of the retina and its blood supply. It is caused by problems with drainage of aqueous humor

85
Q

whats aqueous humor

A

its a clear liquid produced by the ciliary body and secreted onto the posterior chamber

86
Q

how does the aqueous humor get into the anterior chamber

A

through the pupil

87
Q

where is the scleral venous sinus located

A

junction between the cornea and the iris

88
Q

what maintains the pressure within the eye

A

by continuous formation and drainage of aqueous

89
Q

whats the normal intraocular pressure (IOP)

A

10-21mmHg

90
Q

what causes high IOP

A

obstruction of aqueous outflow

91
Q

whats the function of the aqueous humor

A

-supplies nutrients to avascular cornea and lens
-maintains intraocular pressure

92
Q

what part of the eyeball is continuously growing throughout life

A

crystalline lens

93
Q

what do lens do

A

-separates the anterior 1/5 of the eyeball and posterior 4/5
-its a changeable refractive media i.e. focuses image on retina

94
Q

what controls the lenswhat is the lens composed of

A

-capsule
-epithelium
-lens fibers

95
Q

what disease affects the lens

A

cataracts (opacity of the lens)

96
Q

what controls the lens to focus images on the retina

A

suspensory ligaments and ciliary muscles

97
Q

whats accommodation

A

it refers to the ability of the eye to alter its focus so that clear images of both close and distant objects can e formed on the retina

98
Q

what are the light rays like for distant objects

A

they are almost parallel so dont need much refraction to focus on the retina

99
Q

what should the lens for a distant object be like

A

thin and weak (have long focal length)

100
Q

what are the light rays for a close object like

A

they are diverging so need more refraction to focus them onto the retina

101
Q

what should the lens for close objects be like

A

thick and strong ( have a sort focal length)

102
Q

what is the posterior cavity filled with

A

vitreous humor (its jelly like)

103
Q

what does the posterior cavity do

A

holds retina in place

104
Q

how often is vitreous humor formed

A

once during embryonic life

105
Q

what are floaters

A

debris in vitreous of older individuals

106
Q

the retina makes up what of the eye

A

posterior 3/4 of eyeball

107
Q

anterior margin of retina contains what

A

ora serrata retina (rods only)

108
Q

whats the optic disc

A

its where theres attachment of the optic nerve/ its the blind spot

109
Q

optic disc has no what

A

photoreceptors

110
Q

where is the fovea centralis

A

near the middle of the retina

111
Q

whats does the fovea centralis contain

A

has high conc of cones

112
Q

the fovea centralis is a region of high what

A

visual acuity

113
Q

whats the blood supply of the retina

A

-central retinal artery
-choroid

114
Q

how do the retinal vessels enter and leave the eye

A

through the optic nerve and run in the nerve fibre layer

115
Q

what supplies each of the retinal quadrants

A

major arterial and venous branch that form an arcade

116
Q

the retina has a superficial layer of what

A

pigment epithelium (melanin)

117
Q

what is the superficial layer of pigment epithelium

A

-its a non visual portion
-it absorbs stray light and helps keep image clear

118
Q

what are the layers of the retina

A

-photoreceptor layer
-bipolar neuron layer
-ganglion cell layer

119
Q

what do rods do

A

-they are for nocturnal vision i.e. black and white vision, so give great sensitivity in dim light
-they discriminate shapes and movements distributed along the periphery retina

120
Q

whats visual transduction

A

its when light initiates a nerve impulse

121
Q

whats the structure of a rod cell

A

-it has an inner segment made up of synapse, nucleus, mitochondria
-outer segment made up of membrane disks

122
Q

in visual transduction detection of light is carried out on what

A

the membrane disks

123
Q

what do membrane disks contain

A

rhodopsin

124
Q

what is rhodopsin

A

its a pigment of the photoreceptor cells in the retina

125
Q

what does rhodopsin do

A

its responsible for the first events in the perception of light

126
Q

what rhodopsin comprised of

A

-opsin
-retinal

127
Q

retinal is made from what

A

vitamin A

128
Q

which part of rhodopsin is the light sensitive part

A

retinal

129
Q

retinal exists in what 2 forms

A

cis and trans

130
Q

in the dark retinal is in what form

A

cis

131
Q

what happens for retinal to switch to the trans form

A

it absorbs a photon of light and the shape of the opsin protein changes- a process called bleaching

132
Q

what is the reverse reaction i.e. from trans to cis like

A

-its very slow
-it requires an enzyme reaction
- it requires ATP as rhodopsin has to be resynthesised

133
Q

in visual transduction how does the impulse reach the brain

A
  1. there is bleaching of the rhodopsin in a rod cell
  2. this will alter the permeability of the membrane to Na+
  3. this will create an nerve impulse that will travel down the sensory neuron in the optic nerve to the brain
134
Q

what does rhodopsin control

A

sodium channels

135
Q

which rhodopsin opens sodium channels

A

the rhodopsin with cis retinal (absence of light)

136
Q

which rhodopsin closes sodium channels

A

the rhodopsin with trans retinal (light)

137
Q

in visual transduction what happens in the dark

A

the cannel is open and Na+ flows in which causes rod cells to depolarise (so when in total darkness the membrane of a rod cell is polarised)

138
Q

what do rod cells release in the dark

A

neurotransmitter

139
Q

in visual transduction ,when in the dark, the synapse with bipolar cells is what

A

an inhibitory synapse (the neurotransmitter stops the impulse)

140
Q

in visual transduction what happens in the light

A
  1. cis retinal is converted to trans retinal and the Na+ channels begin to close
  2. less neurotransmitter is produced , but if the threshold is reached the bipolar cell will be depolarised
  3. this will then create an impulse which is then passed to the ganglion cells and then to the brain
141
Q

what is the outer segment like for rods and cons

A

R- rod shaped
C- con shaped

142
Q

where do you find rods and cones and what are they used for

A

R- are distributed throughout the retina so are for peripheral vision
C- are found mainly in the fovea, so they only detect images in the centre of retina

143
Q

what is the sensitivity like for rods and cones

A

R- have good sensitivity
C- have poor sensitivity

144
Q

what are the types of rods and cones and what vision do they provide

A

R- is only 1 type and gives monochromatic vision

C- has 3 types (R,G,B) and gives colour vision

145
Q

what do rods and cones connect to

A

R- many of them connect to one bipolar cell, which results in poor acuity= poor resolution

C- each con is connected to 1 bipolar cell, which results in good acuity= good resolution

146
Q

con cells have different what

A

forms of opsin but have the same retinal

147
Q

red light stimulates which cones

A

R cones

148
Q

yellow light stimulates which cones

A

R and G cones equally

149
Q

cyan light stimulates which cones

A

B and G cones equally

150
Q

white light stimulates which cones

A

all 3 cones equally

151
Q

how are objects in the periphery of our field viewed

A

they are not seen in colour or detail

152
Q

whats the pathway of light

A

ganglion cells- bipolar cells- photoreceptor cells

153
Q

what is the pathway for visual impulses

A

photoreceptor cells- bipolar cells- ganglion cells- optic nerve

154
Q

the optic nerve behind the eyeball is surrounded by what

A

CSF

155
Q

behind the eyeball the optic nerve is protected by what

A

the meninges

156
Q

what makes up the optic nerve

A

axons of the retinal ganglion cells

157
Q

what 3 neurons make up the visual pathway and where do they lie

A
  1. bipolar cell which lies within the retina
  2. ganglion cell synapse in lateral geniculate body
  3. the 3rd neuron terminates in the visual cortex
158
Q

the left occipital lobe receives visual images from what

A
  • nasal 1/2 of the right eye
    -temporal 1/2 of the left eye
159
Q

the right occipital lobe receives visual images from where

A

-nasal 1/2 of the left eye
- temporal 1/2 of the right eye

160
Q

What’s the importance of the tear film

A

It maintains the normal environment for the corneal epithelial cells

MBBS2/Anatomy~HEAD & NECK (4 decks)

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