Anatomy of the eye Flashcards
1
Q
What is the orbit?
A
Cavity that contains the eye and its associated structures
2
Q
Where is the orbit located?
A
Upper part of facial skeleton
3
Q
What shape is the orbit?
A
Pyramid shaped
4
Q
What are the parts of the orbit? What are their relative positions?
A
Apex - posteriorly
Base - anteriorly
Walls
5
Q
What is located at the apex of the orbit?
A
Superior orbital fissure
inferior orbital fissure
Optic canal
6
Q
What forms the margins of the base of the orbit?
A
Orbital rim
7
Q
What are the walls of the orbit?
A
Roof
Floor
Medial
Lateral
8
Q
What forms the roof of the orbit?
A
The frontal bone
9
Q
What forms the floor of the orbit?
A
The maxilla
10
Q
What forms the medial wall of the orbit?
A
Ethmoid bone
11
Q
What forms the lateral wall of the orbit?
A
Zygomatic bone
12
Q
What is located above the roof the orbit?
A
Anterior cranial fossa
frontal lobe
13
Q
Which walls of the orbit are the weakest?
A
Medial wall
Floor
14
Q
Why is the medial wall of the orbit relatively weaker?
A
Because it is mostly made up of the ethmoid bone which contains the ethmoidal air sinuses
15
Q
Why is the floor of the orbit relatively weaker?
A
Because it is mostly made up of the maxillary bone which contains the maxillary air sinus
16
Q
What are the contents of the orbital cavity?
A
Eye
Extrinsic ocular muscles
Neurovascular supply
Lacrimal apparatus
Orbital fat
17
Q
What is another term for palpabrae?
A
Eyelids
18
Q
What are the functions of the palpabrae?
A
Protect the eye from drying out
Protect eye when palpebral fissure is closed
19
Q
What are the palpabrae made up of?
A
Tarsal plates
Muscles
20
Q
What are tarsal plates made up of?
A
Fibrous connective tissue
Mebomian glands at edges
21
Q
What is the function of the tarsal plates?
A
Make eyelids firm
Give shape to eyelids
22
Q
What lies between the orbital contents and the orbicularis oculi?
A
Orbital septum
23
Q
What is the orbital septum?
A
Sheet of fibrous tissue
24
Q
What does the orbital septum attach to?
A
Orbital rim
Tarsal plates
Tendon of levator palpabrae superioris muscle
25
What is the pre-septal space?
Tissues in front of the orbital septum
26
What is the post-septal space?
Tissues behind the orbital septum
27
What are the muscles of the eyelids?
Levator palpabrae superioris
28
What is the function of the Mebomian glands?
Produce oily secretion
29
What is the purpose of the oily secretion produced by the Mebomian glands?
Lubricates edge of eyelids
Mix with tear film over eye
prevent tears from evaporating too quickly
prevent tear spillage
30
What part of the eye does the conjunctiva cover?
Sclera
Inner surface of eyelid
31
What does the conjunctiva lining the sclera and the inner surface of the eyelid form?
The conjunctival sac
32
What part of the eye does the conjunctiva not cover?
Cornea
33
What is the conjunctiva made up of?
Mucous membrane
34
What are the functions of the conjunctiva?
Produces mucous and tears
| to lubricate the cornea
35
What is the relative blood supply of the conjunctiva?
Good blood supply
| lots of small blood vessels supplying it
36
What are the parts of the lacrimal apparatus?
Lacrimal gland
Lacrimal sac
Nasolacrimal duct
37
Where is the lacrimal gland located?
Fossa in superolateral orbit
38
What is the function of the lacrimal gland?
Produce tears
| lubricate conjunctiva and cornea of eye, prevent them drying out
39
What happens to fluid from the lacrimal gland?
Passes into conjunctival sac
travels to medial angle of eye
drains into lacrimal sac
drains into nasolacrimal duct into nasal cavity
40
What is the innervation of the lacrimal gland?
Parasympathetic
via greater petrosal nerve of CN7 facial nerve
then opathalmic branches of CN5 trigeminal nerve
41
What is the role of blinking in lubrication of the surface of the eye?
Washes tear film across conjunctiva and cornea
moves any particles to medial angle of eye to be removed
42
What is the blood supply of the eye?
Internal carotid artery
| opthalmic artery
43
What is the venous drainage of the eye?
Superior and inferior opthalmic veins
| into cavernous sinus, pterygoid venous plexus
44
What innervates the eye?
General sensory - opthalmic branch of CN5 trigeminal
Special sensory - CN2 optic nerve
Motor - CN3 oculomotor, CN4 trochlear and CN6 abducens
45
What is the position of the eyeball in the orbital cavity?
Suspended in the orbital cavity
| not resting on the floor of the orbital cavity
46
What suspends the eyeball in the orbital cavity?
Suspensory ligament
Rectus muscles
Orbital fat
47
How does the suspensory ligament of the orbital cavity relate to the eyeball?
Suspensory ligament runs inferiorly to the eyeball
48
How many layers of the eyeball are there?
Three
49
What are the layers of the eyeball?
Sclera, cornea
Choroid, ciliary body, iris
Retina
50
What is the sclera of the eye?
White of the eye
51
What is the sclera made up of?
Fibrous connective tissue
52
What are the functions of the sclera?
Give shape to eyeball
Attachment for extra-ocular muscles
53
What is the relationship between the sclera and cornea?
Sclera continues anteriorly as cornea
54
What is the sclera continuous with apart from the cornea?
Dura surrounding optic nerve
55
What is the cornea of the eye?
Transparent part of the eye anteriorly
56
What is the relative blood supply of the cornea?
It is avascular
57
What is the importance of the cornea being transparent and avascular?
So light can pass through
58
How are the choroid, ciliary body and iris related to each other?
Choroid continues anteriorly as ciliary body and iris
| ciliary body connects the choroid and the iris together
59
What is the relative blood supply of the choroid and ciliary body?
Good blood supply
60
What is the iris made up of?
Contains smooth muscle
- sphincter pupillae
- dilator pupillae
Contains pupil
61
What is the pupil?
Hole in the middle of the iris
62
What is the function of the pupil?
Light rays pass through it onto lens
63
What is the ciliary body made up of?
Ciliary muscle
Ciliary processes
64
What does the ciliary body attach to?
Choroid, iris
Lens
65
How does the ciliary body attach to the lens?
Suspensory ligaments
66
What is the lens?
Transparent biconvex structure
67
What surrounds the lens?
Capsule
68
What is the blood supply of the lens?
Avascular
69
What is the importance of the lens being transparent and avascular?
So light rays can pass through it
70
What effect does contraction of the ciliary muscle have on the lens?
Moves towards middle
decreases tension on suspensory ligaments
lens thickens
71
What effect does relaxation of the ciliary muscle have on the lens?
Moves outwards
increases tension on suspensory ligaments
lens thins
72
How many layers is the retina made up of?
Two
73
What are the layers of the retina?
Inner photosensitive layer
Outer pigmented layer
74
What is the inner photosensitive layer of the retina made up of?
Rod and cone cells
75
What is the outer pigmented layer of the retina made up of?
Cells that contain melanin
76
What is the function of the rod and cone cells?
Detect and respond to light
77
What is the function of melanin in the outer pigmented layer of the retina?
Absorbs scattered light passing into the eye
| focussing light on the retina
78
Where are cone cells most concentrated on the retina?
Macula
79
If the eye looks directly at an object, what part of the retina is light focussed onto?
Macula
80
What does the macula look like on a fundoscope?
Darker area of retina
81
How do rod and cone cells respond to light?
Generate action potentials
82
What are the relative positions of the macula and the optic disc?
Macula is lateral to optic disc
83
What is the middle of the macula called?
The fovea
84
Where are rod cells most concentrated on the retina?
Towards the peripheries
85
What features of vision are the cone cells responsible for?
High visual acuity
Colour vision
86
What features of vision are the rod cels responsible for?
Vision in low-intensity light
87
What is the fovea made up of?
Only cone cells, no rod cells
88
Where are action potentials generated by rod and cone cells carried to?
Ganglion cells to optic disc
| at optic disc is optic nerve
89
What is the optic disc commonly known as? Why?
Blind spot
| no cone or rod cells at this point, because all action potentials collect here
90
What is the optic disc cup?
Central depression on optic disc
92
What is deep to the inner photosensitive layer of the retina?
Vitreous chamber
93
What does the vitreous chamber of the eyeball contain?
Vitreous humour
94
What are the other chambers of the eyeball apart from the vitreous chamber?
Anterior chamber
Posterior chamber
95
What is the anterior chamber of the eyeball?
Space between cornea and iris
96
What is the posterior chamber of the eyeball?
Space between iris and lens
97
How do the anterior and posterior chambers relate to each other?
Continuous with each other through the pupil
98
What do the anterior and posterior chambers of the eyeball contain?
Aqueous humour
99
What produces the aqueous humour in the anterior and posterior chambers?
Ciliary processes of ciliary body
100
What is the direction of flow of the aqueous humour from the ciliary processes?
Into the posterior chamber
through the pupil
into the anterior chamber
to the irido-corneal angle
trabecular meshwork
canal of Schlemm
101
What are the functions of the aqueous humour in the anterior and posterior chambers?
Nourishment to lens and cornea
| because they don't have a blood supply
102
What is the irido-corneal angle?
Space between anterior surface of iris and posterior of cornea
in the upper corner
103
What is the canal of Schlemm?
Venous channel
104
What is light focussed on to in the eyeball?
Retina
105
How is light focussed onto the retina?
Refraction of light
106
What is refraction?
Change in direction of light
| as it passes from one medium to another of a different density
107
Where does refraction in the eyeball occur?
Air to liquid tear film
Through cornea
Lens
Aqueous, vitreous humour
108
Where does most refraction in the eyeball occur?
Cornea
109
What happens to light rays hitting the eye from objects at different distances from the eye?
As object gets closer to the eye
| light rays become more divergent
110
What is the significance of light rays hitting the eye from nearer objects being more divergent?
Need more refraction to focus them onto the retina
111
What is responsible for changing the amount of refraction of light rays to focus them onto the retina?
Accommodation reflex
112
What information does the optic nerve carry in the accommodation reflex?
Out of focus image
113
What motor information does the CN3 oculomotor nerve carry in the accommodation reflex?
Sphincter pupillae muscle constricts pupil
Ciliary muscle thickens lens
Medial recti muscles converge the eyes
114
What is the purpose of the eyes converging in the accommodation reflex?
So that the image is focussed on the same point of the retina in both eyes
115
What cranial nerves are involved in the accommodation reflex?
Sensory - CN2 optic nerve
Motor - CN3 oculomotor nerve including its autonomic parasympathetic fibres
116
What is the purpose of the pupil constricting in the accommodation reflex?
So light rays pass through the centre of the lens
117
What does the optic disc look like on a fundoscope?
Pale area on retina
118
What other structures enter and leave at the optic disc apart from the optic nerve?
Retinal artery
Retinal vein
119
What is the accommodation reflex?
Looking at object closer to eye makes pupil constrict, eyes converge and lens become more biconvex
