Review of ocular structure and function Flashcards
1
Q
What are the 4 tissue types in the body
A
- Nervous
- Muscular
- Epithelial
- Connective
2
Q
What are the three types of muscular tissue
A
- Skeletal
- Smooth
- Cardiac
3
Q
What are the two types of epithelial tissue
A
- Covering
- Glandular
4
Q
What are the two types of connective tissue
A
- Loose
- Dense
5
Q
What can glandular exocrine glands be split into
A
- Unicellular glands
- Multicellular glands
6
Q
What is example of unicellular gland
A
Goblet cells
7
Q
What are multicellular glands divided into
A
Simple ( one duct )
Compound ( several ducts ) - bundles of secretory cells
Each duct has secretory units
8
Q
What is meant by exocrine
A
secrete into duct
9
Q
What is meant by endocrine
A
secrete into blood system
10
Q
how many layers is tear film made of
A
3
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
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
13
Q
what part of tear film do tarsal glands secrete
A
Sebacceous - oily component
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)
15
Q
What does conjunctiva contain
A
mucous secreting goblet cells
16
Q
What do goblet cells have
A
triangular nucleus + large lumen
17
Q
What is example of multicellular compound gland
A
Lacrimal gland
18
Q
what part of tear film does lacrimal glands secrete
A
Aqueous component - serous secretions
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
20
Q
What are tears drained through
A
Puncta
21
Q
What are tears drained into
A
nasolacrimal duct
22
Q
What are the main muscles involved in opening and closing the eye - movement of eyelids
A
Two skeletal muscles
Voulantary
23
Q
Where do part of the muscles lie
A
Part of the muscle lies within the face and part within the eyelid
24
Q
What are two muscles involved in moving eyelids
A
- Orbicularis Oculi
- Levator palpebrae superioris
25
What does the Orbicularis Oculi
```
Runs around the eye
Closes the eye
Orbit = round
Oculi - eye
Its contraction closes palpebral aperture ( eyelid )
```
26
What does Levator palpebrae superioris do
Runs along top of eye ball and sends tendons into eyelid
| Opens eye and raises upper eyelid when it contracts
27
what is an example of a dense regular connective tissue
The corneal stroma
28
What is corneal stroma made of
collagen
29
is corneal stroma transparent or opaque and why
transparent
| due to tightly packed and regularly arranged collagen fibres
30
What is outer corneal layer known as and where is it located
Corneal epithelium
| Front of eye
31
What type of epithelium is it and why
Stratified squamous
| Protects from dirt, eyelids,
32
What is the inner surface of the cornea known as
Corneal endothelium
33
What type of epithelium is corneal endothelium and why
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
34
Where does light enter after travelling across cornea
Anterior chamber - filled with aqueous humout
Lens
Vitreous humour
Impinges on retina
35
What does the light sensitive retina do
Converts photons to neurobiological activity
36
Where is posterior chamber
infront of lens, behind iris
37
what is the outer coat of eye known as
sclera
38
is sclera opaque or transparent and why
Opaque - white
| collagen fibres irregularly arranged
39
What is the corneoscleral junction known as
Limbus
40
what is connective tissue proper made of
- fibres ( collagen, elastic and reticular )
- cells ( fibroblasts...)
- ground substance
41
what are fibres
long stringy proteins in viscous brown substance
42
what is connective tissue divided into
loose - adipose or aereolar
dense - regular - specific order, same diameter
or irregular - randomly arranged, varying diameters
43
How many layers does cornea have and what are they
```
5
epithelium
bowmans layer
stroma
descemets membrane
endothelium
```
44
how many muscles does iris contain and what are they
2
iris sphincter
iris dilator
45
what does iris sphincter do
circular muscle that constricts/closes pupil when sphincter contracts
parasympathetic pathway
46
what does iris dilator do
opens the pupil when it contracts
| sympathetic pathway
47
what is ciliary body divided into
- anterior ridge pars plicata- folded
| - posterior smooth thinner pars plana - simple
48
what are pars of plicata made up of
series of ridges - ciliary processes
49
what does ora serata do
flat bit of ciliary body merges with retina here
50
what is ciliary process covered with
2 layered epithelium
51
what is outer pigmented epithelium part of
eye's black box effect
52
what is inner unpigmented epithelium part of
aqueous humour - produces it
53
what is closest to inside of eye from inner unpigmented epithelium and outer pigmented epithelium
Inner unpigmented epithelium
54
How does the black box effect work
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
What is uvea made up of
iris - forms pupil - merges with....
ciliary body
choroid
56
What is choroid
a vascular layer - blood vessles sandwiched between sclera and retina
57
function of choroid
main function to supply nutrients to outer retina
58
why does outer retina need nutrients
it contains no nutrients itself - no blood vessels
59
what is bruch's membrane
separates choroid and retina
60
what happens if bruch's membrane is dusrupted
age related macular degeneration
61
pars of plannner
flat/thin
62
pars of plecata
folded/pleated
63
where is choroid in histological section
to the left of anterior eye
64
where is iris
coming of ciliary body - front of anterior eye
65
What is iris
forms pupil
'offshoot' of ciliary body anteriorly
acts as aperture stop
66
where does light go through in eye
pupil ONLY
67
What is posterior surface of iris covered with and why
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
what is iris made of
loose areolar connective tissue - iris change size
69
what is stroma example of and why
loose areolar connective tissue
| change shape as pupil size changes by 2 muscles
70
how is lens attached to ciliary body
by suspensory ligaments
71
what are 3 layers of lens
- 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
what are lens fibres
long hexagonal cells that run from front to back surface of lens
73
how are adjacent lens fibres joined
by gap junctions = allow flow of nutrients
74
Aqueous production of inner epithelium of ciliary body
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
what happens if aqueous is not drained
eye eventually explodes - glaucoma
76
what is aqueous humour produced by and what does it do
inner epithelium
| provides nutrients - need it because lens + cornea are avascular - no blood supply
77
what does canal of schlemm do
takes in used aqueous and recycles it into avascular system
78
summary of aqueous production
- 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
what is bulk of ciliary body made of
smooth ciliary muscle
80
what is bulk of ciliary body made of
smooth muscle - contracts - ciliary body moves inwards - towards lens - changes focus of eye
81
what does inner layer of ciliary body do
produces aqueous
82
what does outer layer of ciliary body do
black box effect
83
what is the function of the lens capsule
- elasticity - accommodation
- selective barrier to substances - stopping large matter e.g. inflammatory cells entering lens, while allowing smaller necessary metabolites through
- cataract surgery
84
what happens in cataract surgery
- 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
why is most of total refractive index provided by the cornea
due to the difference between the refractive index of air and the cornea
86
role of lens
fine focus image through accommodation - change power
| provides little refractive power
87
where is majority of focusing of light done and why
at border of cornea
| because its curved and the difference in refractive index between air and cornea
88
when is eye usually emmetropic
at rest ( parallel light rays from distant objects focused on retina ) - light not refracted
89
where are close objects focused
behind retina
90
what is accommodation
bring close objects into focus - eye increase its refractive power - bend light more to refract more
91
what happens in unaccommodated eye
lens is under tension and pulled flat
| ciliary muscles relax and lens stretched
92
what happens in accommodated eye
tension on lens released
rounder shape/fatter
ciliary muscles contracts
move closer to lens = more powerful
93
what is presbyopia
loss of accommodative ability with age
94
what is retina
lines back of eye
terminating anteroraly at ora serrata
made up of various neurons and glial cells
convert light into neurobiological activity
95
what are outer layers of retina composed of
- photoreceptors - convert optical image into nervous potentials ( phototransduction )
96
what are cones sensitive to
high light levels
97
what are rods sensitive to
low light levels
98
what are the 5 main types of neurones the retina is made up of
- photoreceptors
- horizonal cells
- bipolar cells
- amacrine cells
- ganglion cells
99
what is the end result
action potential generated in ganglion cells
100
what does light do
light traverses the inner retinal neurons before reaching photoreceptors
electrical signals leave via ganglion cell axons - make up optic nerve
101
where is highest quality of image produce
fovea - because cones close together
102
what are the 6 muscles attaching eyeball to skull
- superior rectus
- superior oblique
- medial rectus
- lacteral rectus
- inferior oblique
- inferior rectus
