Anatomy of the Orbit and the Eye Flashcards
(142 cards)
1
Q
what bones are part of the bony orbit?
A
-frontal, zygomatic, maxilla, nasal, sphenoid, ethmoid, lacrimal
2
Q
what are the 2 important notch/foramen in the bony orbit?
A
supraorbital notch/foramen and the infraorbital foramen
3
Q
what is the difference between a notch and a foramen?
A
a foramen is a complete circle and a notch is more āCā shaped
4
Q
what is the apex if the bony orbit?
A
optic canal
5
Q
what shape is the bony orbit?
A
pyramidal
6
Q
what is the base of pyramid known as clinically?
A
orbital rim
7
Q
what creates the orbital rim?
A
combined superior, inferior, medial and lateral orbital margins
8
Q
what protects the eye from a direct blow?
A
the orbital rim
9
Q
why do smaller objects cause a direct blow to the eye?
A
they are smaller than the orbital rim and orbital rim doesnt protect it
10
Q
which part(s) of the orbit are commonly affected by blowout fractures?
A
medial wall and orbital floor
11
Q
why are the medial wall and orbital floor more commonly affected by blowout fractures?
A
they are extremely thin
12
Q
what can happen after a blow out fracture and what NVB can be damaged?
A
orbital contents can become trapped, infraorbital NVB can be damaged
13
Q
what bone does the infraorbital NVB pass through before passing through the infraorbital foramen?
A
the maxillary
14
Q
what is th outcome of the infraorbital NVB being damaged?
A
general sensory deficit of facial skin
15
Q
what is the external layer of the eyelid?
A
orbicularis oculi muscle
16
Q
what are the 2 parts of the orbicularis oculi?
A
orbital part and palpebral part
17
Q
what is just deep the orbicularis oculi?
A
the orbital septum
18
Q
what is the orbital septum?
A
a sheet of fascia
19
Q
what does the orbital septum do?
A
helps prevent spread of infection from superficial to deep
20
Q
how many tarsi is the around the eye?
A
2 - superior and inferior
21
Q
what are the tarsi?
A
plates of fibrous connective tissue
22
Q
why is the superior tarsus important?
A
gives shape and support to the eye and is an attachment point for muscles
23
Q
what are embedded in the tarsi?
A
tarsal glands
24
Q
what is the function of the tarsal glands?
A
secrete lipid substance
25
what is the function of the lipid secreted by the tarsal glands?
stops tears from overflowing and stops eyes sticking together when we blink
26
what is the limbus?
the junction between the cornea and the sclera
27
what is the sclera covered by?
conjunctiva
28
what is the coloured part of the eye called?
iris
29
in conjuctivitis, what is it that becomes dilated and inflamed?
conjuctival vessels
30
what is the tiny black dot on the inferior medial aspect of the lower lid known as?
inferior lacrimal papilla and punctum
31
what is the function of the inferior papilla and punctum?
it is an opening which tears go through to get into nasolacrimal duct
32
where is the location of the lacrimal gland?
superior lateral aspect of eyelid
33
what is located in the medial angle of the eye?
lacrimal lake
34
what CN gives the parasympathetic control to the lacrimal gland to produce tears?
CN VII
35
where does the nasolacrimal duct drain into?
inferior meatus
36
what is corneal reflections used to test?
the symetry of bilateral eye positions/movements
37
what are the 3 layers of the eye?
fibrous, uvue and retina
38
what is the outer layer of the eye?
fibrous layer
39
what are the 2 parts to the fibrous layer?
sclera and cornea
40
what is the sclera important for?
muscle attachment
41
what is meant by refractive power?
the ability to focus light
42
how much of the refractive power is the cornea responsible for?
2/3rd
43
what is the middle layer of the eye?
the uvea (vascular layer)
44
what are the 3 parts to the uvea?
the iris, the ciliary body and the choroid
45
what is the function of the iris?
control pupil diameter. moves to adjust amount of light coming through the cornea
46
what is the function(s) of the ciliary body?
help control iris, controls the shape of the lens, and secretes aqueous humour
47
what is the photosensitive layer of the eye?
the retina
48
what is the inner layer of the eye?
the retina
49
what are the segments of the eye?
anterior and posterior segments
50
what is classed as the anterior segment the eye?
infront of the lens
51
what chambers is the anterior eye divided in to?
anterior and posterior chamber
52
where is the anterior chamber of the anterior segment found?
between the cornea and the iris
53
what does the anterior segment contain?
aqueous humour
54
what is the posterior chamber of the anterior segment of the eye between?
between the iris and suspensory ligaments
55
what does the posterior chamber contain?
aqueous humour
56
what is the function of the aqueous humour?
to provide nutrition to the iris and cornea as they dont have a blood supply
57
where is the posterior segment of the eye?
everything posterior to the lens
58
what does the posterior segment of the eye contain?
vitreous body
59
what is within the vitreous body?
virtreous humour
60
what is vitreous humour?
gel-like liquid
61
where is a common location for 'floaters' in the eye and what causes them?
in the vitreous body, caused when the gel starts to solidify a bit and clump together with collagen fibres
62
where does the circulation of the aqueous begin?
in the ciliary body
63
what secretes the aqueous?
ciliary processes
64
after the ciliary processes has secreted the aqueous, where does it circulate and why?
within the posterior lens, to nourish lens
65
how does the aqueous pass into the anterior chamber?
through the pupil
66
when the aqueous passes through the pupil, what does it nourish?
the cornea
67
where is the aqueous reabsorbed?
into scleral venous sinus
68
what else is the scleral venous sinus known as?
canal of Schlemm
69
where abouts is the canal of schlemm?
at iridocorneal angle
70
what are the 3 parts of the retina? (there is more but only need to learn these)
the optic disc, the macula and the fovea
71
where is the point of formation of CN II?
optic disc
72
what is the function of the optic disc?
point of formation of CN II, only point of exit/entry for blood vessels and axons of CN II
73
why does the optic disc give rise to a blind spot?
there is no cones or rods, nothing to pick up light
74
where in the retina has the greatest density of cones?
the macula
75
what are cones and rods?
photoreceptors
76
which type of photoreceptor is more active during daylight?
cones
77
what photoreceptors do we use in dim light?
rods
78
where is the fovea?
the centre of macula
79
how deep is the depression in the macula that creates the fovea?
1.5mm depression
80
what is important about the fovea?
area of most acute vision
81
what is the arterial supply to the retina?
the central artery of the retina
82
what is the clinical importance of the central artery of the retina?
it is an end artery so it it gets blocked the retina dies
83
where do the retina artery and vein enter the retina?
through the optic disc
84
what does light have to pass through in the retina before it reaches the retina?
the axons of the ganglion cells, the ganglian cells and also the blood vessels
85
what is in the most posterior layer of the retina?
the photoreceptors
86
what lies anterior to the photoreceptor cells in the retina?
the ganglion cells
87
what lies anterior to the gnaglion cells in the retina?
the axons of the ganglion cells
88
where do the retinal veins and arteries lie in relation to the retina?
anterior to the retina
89
where is light from the right visual field processed?
left primary visual cortex
90
where is light from the lower visual filed processed by?
by the superior part of the primary visual cortex
91
where does light from the right visual field hit the retina?
the right nasal retina
92
how does light recieved by the right nasal retina, move to be processed by the left primary visual cortex?
it crosses at the optic chiasm
93
if light hits the temporal retina, does it cross at the optic chiasm or remain on the same side?
stay on same side
94
arterial supply to the orbit?
ophthalmic artery
95
what artery does the ophthalmic artery branch from?
the internal carotid artery
96
what does the internal carotid pass through before giving off the ophthalmic artery?
passes through the carotid canal and through the cavernous sinus.
97
what different branches does the ophthalmic artery give rise to?
- nasal cavity branches
- forehead (scalp) branches
- ciliary arteries
- the central artery of the retina
98
where does the ciliary branches supply?
the middle layer of the eye- uvea
99
what is the only vein that drains the retina?
the central vein of the retina
100
what is the main venous drainage of the orbit?
the superior ophthalmic vein
101
what will the superior ophthalmic vein eventually drain to?
cavernous sinus
102
what does the superior ophthlamic vein go through to reach the cavernous sinus?
the superior orbital fissure
103
where else can the orbit drain to anteriorly other than the superior ophthalmic vein?
facial vein
104
where does the inferior ophthalmic artery mainly drain in to?
the superior ophthalmic vein
105
where is the danger triangle on the face?
from the corners of the lips to the root of the nose
106
why is the danger triangle considered dangerous?
it is thought that if a spot is squeezed here a vein can be easily squeezed which leaves it susceptible to bacteria getting into the vein and due to the facial veins having communications through the orbit and canvernous sinus, then infection could spread to here
107
how many extraocular skeletal muscles are there?
7
108
what are the 7 extraocular skeletal muscles?
- superior, inferior, medial and lateral rectus
- superior and inferior oblique
- levator palpebrae superiosis
109
where do the 4 rectus muscles all originate from?
the common tendinous ring
110
where is the common tendinous ring?
around the optic canal
111
where do all 4 rectus muscles insert onto?
the sclera
112
where do the 2 oblique muscles attach onto?
the sclera
113
what is the function of the levator palpebrae superiosis?
lifts the upper lid
114
what does the superior oblique muscle pass through before attaching to the sclera?
the trochlear
115
what does the trochlear do?
it is basically a pulley, makes a turn in the tendon of the superior oblique muscle so it attaches to sclera at an oblique angle.
116
what nerve supplies the somatic motor innervation to the lateral rectus muscle?
CN VI - abducent nerve
117
what nerve supplies the superior oblique muscle with somatic motor innervation?
CN IV - trochlear nerve
118
exluding the lateral rectus and superior oblique, what is the motor innervation to all the other extraocular muscles?
CN III - oculomotor nerve
119
what are the 3 different axis' of the eyeball?
vertical axis, transverse axis, anteroposterior axis
120
if the eye moves in the vertical axis, what movements can it be doing?
adduction and abduction
121
which movements can the eye do if it is moving in the transverse axis?
elevation/depression
122
where is the anteroposterior axis running through?
runs straight through the direction of the gaze
123
what movements can the eye undertake if it is moving along the anteroposterior axis?
intorsion/extorsion
124
what is meant by intorsion of the eyeball?
medial rotation
125
what is meant by extorsion?
lateral rotation of the eyeball
126
where is the apex of the orbit (optic canal) located relative to the rest of the orbit?
medially located
127
what causes the difference in the orbital axis and the optical axis?
the orbital axis points out at an angle due to medially positioned apex of orbit
128
most of the extrocular muscles have secondary movements on top of their primary movements, except which 2 muscles?
medial and lateral rectus
129
what is meant by the primary position of the eyeball?
gaze directed forward
130
to test the function of a particular muscle (and its nerve) what must you do?
line up gaze to the plane of muscles being tested and isolate muscle movement
131
what is the only function of the lateral rectus?
abduct eyeball
132
when the eyeball is abducted, it brings the line of gaze into the same plane as what?
superior and inferior rectus
133
in what position should the eyeball be in to assess superior rectus and why?
in abduction as in abduction the superior rectus can only elevate
134
why should the eyeball be abducted when assesing inferior rectus?
inferior rectus can only depress when eyeball is abducted so assessing its individual function
135
what is the only function of the medial rectus?
adduct the eyeball
136
when the eyeball is adducted, what planes is in now in line?
same plane as superior oblique and inferior oblique attachments
137
in what posision should the eyeball be to test inferior oblique?
in adduction
138
if the inferior oblique is working correctly, how will it move the eyeball in adduction?
it will elevate the eyeball
139
when eyeball is in adduction, what is the only function of the superior oblique?
can only depress the eyeball
140
what muscles are responsible for pure elevation?
superior rectus and inferior oblique
141
what muscles are responsible for pure depression?
inferior rectus and superior oblique
142
what is meant by yolk movement?
cant just move one eye at a time
