The Eye Flashcards
1
Q
role of lacrimal gland
A
produce secretions (tears) that lubricate, clean and protect the surface of the anterior eye
2
Q
route of tears
A
pass medially over the eye towards the puncta on upper and lower eyelids where they drain down the nasolacrimal duct which passes through the skull into the nasal cavity
3
Q
role of anterior eye
A
protect sensitive inner eye and focus and funnel light inwards
4
Q
what is the cornea?
A
transparent layer over iris and pupil
5
Q
transparent layer of eye
A
cornea
6
Q
role of cornea
A
light enters the eye
7
Q
white of the eye
A
sclera
8
Q
sclera role
A
tough outer protective layer
gives shape to eyeball
9
Q
sclera is covered by what?
A
conjunctiva
10
Q
conjunctiva
A
transparent mucous membrane covering the sclera and internal eyelid
doesn’t cover cornea
11
Q
bulbar conjunctiva
A
(superficial to sclera (on top of))
○ Protective
○ Small blood vessels
12
Q
(palpebral conjunctiva)
A
○ Continuous with the bulbar conjunctiva
○ Makes the conjunctival fornix (fold)
13
Q
common damage to conjunctiva
A
inflammation and infection - conunctivitis
14
Q
Palpebral fissures
A
gap between the upper and lower eyelids (where the eyeball is)
- Palpebri = eyelids
15
Q
Where the palpebral fissures meet in the corner of the eyes are called…
A
the canthus/palpebral commissures:
○ Medial canthus/palpebral commissure (inner corner of eye).
○ Lateral canthus/palpebral commissure (outer corner of eye).
16
Q
Epicanthic fold
A
fold of skin upon the canthus
17
Q
CN for sclera
A
CNI
18
Q
nutrient supply to cornea
A
aqueous humor
19
Q
iris
A
- Pigmented epithelia laying on the lens
- Deep in the cornea
- Diaphragm with a pupil on top
- Iris changes the diameter of the pupil
- Contains intrinsic eye muscles which constrict and dilate the pupil to change its diameter and therefore the amount of light that enters the eye
20
Q
lens
A
- Bends and focus light onto the back of the eye
- Acted on by ciliary muscles attached by suspensory ligaments
- Less malleable and more cloudy as you get older (ability to see up close deteriorates)
○ Cloudy = cateracts
21
Q
cloudy lens indicates…
A
cateracts
22
Q
retina
A
- Has photosensitive cells called rods and cones which detect light and colour respectively
○ Convert light into neural activity which is transmitted via the optic nerve to the occipital lobe- At the centre is the macula focuses the most light and the centre is the fovea (focuses central vision)
23
Q
centre of retina is…
A
- At the centre is the macula focuses the most light and the centre is the fovea (focuses central vision)
24
Q
fluids filling the eye
A
2 fluids called humors filling the eye and maintain the shape and pressure of the eyeball
- Anterior to the lens is the water like one which is aqueous humor
- Gel like vitreous humour posterior
- Pathology of either of these puts pressure on the optic nerve and causes conditions like glycoma
25
how is diameter of pupil adjusted?
by sphincter and dilated pupillae muscles
26
what happens to pupil in bright light or to focus on near objects and how?
contraction of sphincter pupillae reduces pupil aperture
27
what happens to pupil in dark light or in response to fright?
dilator pupillae increases pupil diameter
28
innervation of sphincter muscles
parasympathetic
29
innervation of dilator pupillae
sympathetic
30
shape of lens at rest
bulges
31
shape of lens when contracted
flattens
32
what changes the shape of the lens
contraction of the ciliary body causes pulling on the suspensory ligaments attached to the lens
33
shape change of the lens is called what?
accommodation
34
what does accommodation allow?
eye to focus on near or far objects by focusing incoming light
35
where is lens
posterior ro pupil
36
where is the anterior chamber
between cornea and iris
37
what is between cornea and iris
anterior chamber
38
where is posterior chamber
between iris and lens
39
what is between iris and lens
posterior chamber
40
what are the anterior and posterior chambers filled with?
aqueous humour
41
where is aqueous humour produced?
by ciliary body
42
where does aqueous humour drain
between cornea and sclera
43
ciliary muscle
ring of smooth muscles surrounding the lens inside the eye
- Autonomic muscle
- Can contract (smaller ring)
○ Zonular fibres relax so lens can shrink and become fact
○ Focus on near objects
- Can relax (larger ring)
○ Fibres under tension and pull the lens thin
○ Focus on distant objects
- Lens sits inside the ring and is strung from it by zonular fibres
- Parasympathetic innervation via cranial nerve 3 - oculomotor nerve
44
sphincter pupillae
smooth muscle cells in iris
- Contraction causes pupil to be smaller so less light into eye
- Innervated by parasympathetic fibres from cranial nerve 3
- Constriction of the pupil is called miosis
45
pupillae light reflex
- If lots of light goes into the eye and falls on the retina, this is carried to the midbrain by cranial nerve 2 (optic nerve) and the reflex arc says lots of light is coming in and then the cranial nerve 3 (parasympathetic fibres) tell sphincter pupillae to contract and constrict the pupil so less light goes into the eye.
- Happens to both eyes at the same time regardless of which eye the light is going into
- If cranial nerve 3 is damaged or compressed or if midbrain is injured then the reflex may be absent
- Need 2 muscles: this one does the opposite
○ Dilator pupillae - dilator muscles (smooth muscle cells in the iris)
§ Pull on edge of iris to make pupil bigger to let more light in
§ Innervated by sympathetic fibres - mediated by noradrenaline so the fight or flight response can cause pupil dilation (some drugs can also cause this as they contain noradrenaline)
□ Spinal nerves in chest so damage in chest or neck may affect this function and only on one side maybe.
§ Mydriasis = dilation of the pupil
46
main chamber of eye
vitreous chamber
47
vitreous chamber
main chamber of eye lined by retina
48
lights path through the eye
enters through pupil
projected via lens onto retina where there are Rods and cones
nerve fibres from the retina combine to form an optic nerve in the optic disk (blind spot)
49
rod cells
in retina
black and white vision
50
cone cells
in retina
colour vision
51
retina is supported by...
choroid layer providing oxygenated blood and nutrients via BV
52
optic nerve innervates the...
optic disk
53
choroid layer
(posterior to the retina) - rich blood filled layer that stops light bouncing around in the eye
54
rod and cone cells wiring
Rod and cone cells are wired so that the neurons pass in front but where the nerves join in the optic disk means there is a blind spot
55
macula lutea
high-res focus area of eye
56
high-res focus area of eye
macula lutea
57
central part of macula
fovea
58
fovea
central part of macula with the highest density of cones
59
Macula lutea with fovea centralis
centre of focus. (the macula contains the fovea)
60
which cranial nerves are eye related?
2
3
4
6
61
fibres from retina converge to create....
CNII - optic nerve
62
what forms the optic nerve
fibres from retina
63
optic nerve route
optic nerve travels through optic canal of the orbit tor enter the cranial cavity.
left and right optic nerves join to form the optic chiasm
here, some nerve fibres decussate to opposite side of brain
2 nerve structures again form, a left and right optic tract which pass posteriorly to the lateral geniculate nucleus of the thalamus and project onto occipital lobe where image is processed
64
where is optic chiasm
posterior to pituitary gland
65
pituitary tumours and the optic chiasm
tumours can compress the chaism, causing a pattern of visual loss called bitemporal hemianopia
66
damage at optic chiasm results in...
bitemporal hemianopia
67
bitemporal hemianopia
damage to optic chiasm
loss of lateral field of vision (see medial vision only)
tunnel vision
68
damage to optic nerve from one eye results in...
blindness in eye
69
damage to optic tract results in...
homonymous hemianopia
70
homonymous hemianopia
damage to optic tract
loss of vision on the same side of each eye
71
where is the damage if bilndess of the eye is the result
optic nerve of that eye
72
how many extraocular muscles
6-7
73
2 types of extraocular muscle
rectus
oblique
74
rectus muscles
travel straight backwards posteriorly alongside the eye
75
oblique muscles
more obtuse insertion (rotate eye)
76
4 rectus muscles
superior
inferior
medial
lateral
77
2 oblique muscles
superior
inferior
78
small cinnective tissue that the superior oblique runs through
trochlear
79
which eye muscle runs through the trochlear
superior oblique
80
nerve innervating the superior oblique
trochlear nerve (CNIV)
81
shape of the orbit
conical
82
direction of eye at rest
forwards
83
upwards gaze
elevation
84
downwards gaze
depression
85
outwards gaze
abduction
86
inwards gaze
adduction
87
inward rotation
intorsion
88
outward rotation
extorsion
89
superior rectus movement
elevation and adduction
90
medial rectus movement
adduction
91
inferior rectus movement
depression
92
inferior oblique movement
depression and adduction
93
superior oblique movement
depression and abduction
94
lateral rectus movement
abduction
95
muscle for elevation and adduction
superior rectus
96
muscle for adduction
medial rectus
97
muscle for depression
inferior rectus
98
muscle for depression and adduction
inferior oblique
99
muscle for depression and abduction
superior oblique
100
muscle for abduction
lateral rectus
101
nerve innervation for superior rectus
oculomotor
102
nerve innervation for medial rectus
olucomotor
103
nerve innervation for inferior rectus
oculomotor
104
nerve innervation for inferior oblique
oculomotor
105
nerve innervation for superior oblique
trochlear nerve
106
nerve innervation for lateral rectus
abducens nerve
107
oculomotor nerve innervates which eye muscles
superior, medial and inferior rectus
inferior oblique
108
trochlear nerve innervates which eye muscles
superior oblique
109
abducens nerve innervates which eye muscles
lateral rectus
110
what is conjugate eye movement?
e.g. as one eye adducts, the other abducts simultaneously
111
3 ways conjugate eye movement occurs
scanning
tracking
compensation
112
scanning
from one visual target to another at high speed (saccades)
113
tracking
eyes follow a slow-moving object across your vision
114
compensation
eyes remain on target despite body moving
vestibular ocular reflex (VOR)
115
vestibular ocular reflex (VOR)
compensation - eyes remain on target despite body moving
116
what are gaze centres/nuclei and what do they do?
found in brainstem (midbrain and pons)
conjugating eye movements
vertical and horizontal gaze centres activated either consciously or automatically
117
gaze centres in pons
left and right horizontal gaze centre
paramedian pontine reticular formation (PPRF) - signals CN to fire for conjugation
118
horizontal scanning/saccades
- muscles
- gaze centres
- nerves
medial and lateral rectus muscles on opposite sides are linked
nerves controlling these muscles are wired to each other via horizontal gaze centre
CNIII and CNVI
119
midbrain and gaze centres
paired upward gaze centre in median longitudinal fasciculus (MLF)
paired downward gaze centre ventral to this
nuclei pair of elevators or depressions conjugate eye movements
120
automatic scanning/smooth pursuit and the brain
visual info from the eye activates the superior colliculus, which activates the nuclei of corresponding gaze centres to initiate rapid eye movement - accuracy fine-tuned by the cerebellum
121
voluntary ocular saccades and the brain
frontal eye fields in motor cortex initiate signal for eyes to move (conscious signal)
signal decussates to the opposite, side of the brainstem where it stimulates a gaze centre
122
tracking and the brain
in addition to gaze centres, other nucleus in pons (nucleus prepositus hypoglossi) triggers head movement
labyrinth and cerebellum fine tune eye movements to keep focus on target
