The Human Eye Flashcards
describe the conjunctiva
mucous membrane, covering the front of eye 1/5
specifically state the functions of the conjunctiva
- produces lubrication mucous that prevents drying out.
2. pain receptors that reflexively cause eyelids to close from foreign objects
describe the sclera
tough, white inelastic and made of connective tissue and covers posterior 4/5
specifically state the functions of the sclera
- provides attachment for 6 extrinsic eye muscles,
2. it is inelastic so it keeps the posture right
describe the cornea
continuation of sclera in front of eye, transparent, curved to cause refraction
specifically state the functions of the cornea
protection of the eye, causes set converging refraction
name the structures of the outer fibrous coat
conjunctiva
cornea
sclera
describe the choroid
thin and dark straight below the SCELRA filled with blood vessels
functions of the choroid
absorbs light to prevent reflection which can cause blurriness and supply eye with nourishments of oxygen and food to retina cells
describe the ciliary body
muscular extension of CHOROID used to change the shape of the lens
function of the ciliary
controlling bulge of lens during accommodation
describe the iris
coloured extension of CHOROID used to adjust the amount of light entering the eye or how large the pupil is
definition of annular
ring
state the two involuntary muscles
- circular
2. radial
why are circular and radial muscles antagonistic
because the counteract each other one contracts while the other relaxes
describe the radial muscles
straight
contract (pull away) there’s a big pupil in DIM LIGHT
relax (longer) constricted pupil in BRIGHT LIGHT
describe the circular muscles
contract (move to the middle) there’s a smaller pupil in BRIGHT LIGHT
relax (they go away leaving a hole) dilated pupil in DIM LIGHT
describe the pupil
it is not a structure it is in fact just an opening and looks black because of the dark cavity, it is the point where light enters
how does brown affect the chances of iris colour
since brown is such a dominant colour, if you were to get a blue colour that means that there is no presence of brown pigment
function of the iris
controls the amount of light entering the eye by pupillary mechanism with the circular and radial muscles
name the structures of the middle vascular layer
choroid
iris
ciliary body
what is the pigment layer
it is a dark layer in the retina that absorbs light
describe the nervous layer
area of the retina that contains the photoreceptors, rods, and cones
function of photoreceptors
converts light stimulus into nerve impulses
describe rod cells
found in the PERIPHERAL of retina (edge)
function of the rods
give peripheral vision and respond to low light/night viand black and white
describe cone cells
responds to bright light and colour vision
function of the cones
detect colour , sharper and clearer vision
describe the neural layer
has photoreceptors synapses and axons of optic nerve
function of the neural layer
has neurons that carry impulses to optic nerve and the optic nerve carries it to the occipital lobe to cerebellum where it is interpreted as sight
describe the blind spot
no cones or rods, it is the place where the optic nerve and blood vessels and no vision is registered
function of blind spot
not sensitive to light
describe the yellow spot
centre of retina and it only has cones (macula lutea)
function of yellow spot
area of greatest clarity
name the structures of the retina (4)
pigment layer
nervous layer
blind spot
yellow spot
name the structures of the nervous layer (2)
photoreceptors
neural layer
what two cells are in the photoreceptors
rods and cones
what is the optic nerve
a collection of sensory neurons that go to cns
describe the lens
biconvexed, flexible transparent and refracts light (not set) and is held in place by the suspensory ligaments which are attached to the ciliary body
function of the lens
can change shape focusing of light on retina
describe the suspensory ligaments
works with the ciliary body to help lens bend light
describe the eye cavities
divided by the lens and suspensory ligaments into anterior and posterior
describe the anterior cavity
constantly refreshing/replenishing with nutrients
front of lens
watery fluid called aqueous humour
function of aqueous humour
carries away toxins
provides nutrients like oxygen
provides correct pressure in the front of the eye
describe the posterior cavity
jelly like which is called the vitreous humour
it is also formed when we are embryos and lasts a lifetime
functions of the vitreous humour
prevents eyeball from collapsing
and is holding retina against choroid
what is it when there is a bending of light
refraction
what is it called when the light rays move apart
diverge
what is it called when light rays move closer
converge
explain binocular vision
vision with 2 eyes with overlapping fields of view allowing good perception of depth and 3 dimensional images
explain pupillary mechanism
it is when the circular and radial muscles contract and relax to control the amount of light entering through pupil to retina in response to various light
explain accommodation
changing the shape of the lens to focus on images from different distances
what is myopia
short sightedness
condition
where people struggle to focus on object far
what hypermetropia
long sightedness
condition
where people struggle to see objects from a close to the eye
what causes myopia
too long eyeball
what is going on with the lens and cornea with short sightedness
they are TOO CONVEX (too much bulge)
remedy for myopia
conCAVED lenses! that will DIVERGE the light before the eye
what causes hypermetropia
too short eyeball
what is going on with the lens and cornea withlong sightedness
they are too FLAT (little bulge)
remedy for hypermetropia
conVEXED lenses! that will CONVERGE light before the eye
go into detail to explain binocular vision
each eye will get a slightly different view of object
as the image enters the posterior cavity it is upside down when it hits the back of the retina then is sent through the optic nerve to the occipital lobe to the cerebellum
then brain combines the 2 views to form a single 3D image
helps with depth perception and size of object
hereditary conditions that causes irregularly shaped cornea or lens
corneal astigmatism
lenticular astigmatism
corneal astigmatism which is bad and which is good
rugby ball
soccer ball
respectively
lenticular astigmatism which is bad and which is good
lens lands on 2 points of retina
one point on retina
respectively
what happens if you dont fix it
headaches and eye strain
what factors could cause it astigmatism
scratched, injury or could just be hereditary
remedies for astigmatism
glasses, contact lenses, or refractive LASER surgery
a condition where proteins in lens begin to clumps and clouds the vision and can lead to blindness
cataracts
what is the lens made of
water + protein
how can we diagnose cataracts
vision tests
check for colour change in the lens might turn yellowish
how can we diagnose cataracts
vision tests
check for colour change in the lens might turn yellowish
In accommodation explain what happens when there is something close
It is not natural for the lens to be bulged
Our ciliary contract and suspensory relaxes
In accommodation explains what happens when there’s something far
It is natural for the lens to be flat because there wouldn’t be a strain
Our ciliary relaxes and suspensory contracts
Flat lens + far object
Is it correct? And where does it land
Yes and it lands on the retina
Flat lens + close object
Is it correct? And where does it land
No
It goes past the retina, landing on 2 points making it blurry
Bilge lens + far object
Is it correct and where does it land?
No
It doesn’t land on the retina
state the 3 function of the eye
pathway of light rays and image formation
stimulation of photoreceptors
pathways of nerve impulses
explain the first step out of 4 for the pathway of light
light passes through air and all through the structures of the eye to stimulate photoreceptors
explain the second step out of 4 for the pathway of light AND ALSO DISCUSS WHAT HAPPENS DURING REFRACTION
refraction when light passes from one substance to another off different density and it’s rays are bent
explain the third step out of 4 for the pathway of light
the light rays converge to form a focused image on yellow spot of retina
explain the fourth step out of 4 for the pathway of light
the image shows up smaller than the object and upside down and reversed from left to right all inside the eye then optic nerve send it to the occipital lobe and them cerebellum to fix it, where it is interpreted as sight
