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vanessa special senses > anatomy of vision > Flashcards

anatomy of vision Flashcards

1
Q

what is the function of eyelids?

A
  1. closes and protects the eye
  2. spreads tear
  3. upper eyelid is supplied by levator palpebrae, cranial nerve 3)
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2
Q

what is the function of eyelash

A

to protect the eye from dust

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3
Q

what is the function of tarsal gland ?

A

it is sebaceous glands that lubricate the eye

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4
Q

what is conjuntiva ?

A

it lines the eyeld and cover the outer sclera (white par) of the eyeball
it is accessory structure of the eye

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5
Q

what is lacrimal glands?

A

they are located above each eye and secretes tears

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6
Q

what is lacrimal canaliculi ?

A

tears flush across the eyeball medially into canaliculli and into caniculli sacs and into nasolacrimal duct in the nasal cavity

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7
Q

what are the extrinsic eye muscles ?

A

6 extrinsic eye muscles

  • superior oblique
  • inferior oblique
  • superior rectus
  • inferior rectus
  • medial rectus
  • lateral rectus
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8
Q

what is the function n of the extrinsic eye muscles ?

A

they control the movement of each eye ball
allow eyes to follow a moving object
help maintain the shape of eyeball and hold it in orbit

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9
Q

what is the clinical issue of extrinsic eye muscles?

A

diplopia
the movement of external muscles of the two eye are not perfectly coordinated and person cannot focus the images of the same area of the visual field = double images

result from the weakness of extrinsic muscle

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10
Q

what are the intrinsic eye muscles ?

A

they are smooth muscles inside the eye

  1. iris
  2. cillary body

involuntary muscles that help to dilate e the pupil

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11
Q

what is the outermost layer of the eye made up of?

A

fibrous layer (avascular) that consist of

  1. sclera
  2. cornea
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12
Q

what is the sclera layer ?

A

it is the white part of the eye

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13
Q

what is the function of sclera?

A

it protects and shapes the eyeball and provides a sturdy anchoring site for the extrinsic muscles

posteriorly pierced by optic nerve and is continuous with the dura mater of the brain

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14
Q

what is cornea?

A

central anterior window that allows eye into the eye and is continuous with the sclera

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15
Q

what is the function of cornea ?

A

it is the window that allow light to enter the eye and filter UV light and has a major role for light bending.

It is avascular and is well supplied with nerve endings (Pain receptors)

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16
Q

what is the vascular layer of the eye ?

A

it is the middle coat of the eye (uvea) and it consist of:

  1. choroid (inner most layer)
  2. cillary body
  3. iris
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17
Q

what is the choroid? what is its fucntion

A

it is a blood vessel rich layer that nourishes all eye layer

has brown pigment produced by melanocytes to help absorb light preventing it from scattering and reflecting within the eye

posterior openting where the optic nerve leave the eye

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18
Q

what is the cillary body?

A 
cillary muscles (smooth muscles that control the lens shape )
cillary processes (secrete fluid that fills the cavity of the anterior segment of the eye)
clillary zonule (suspensory ligament that extend from the ciliary process to the lens and it transmits tension from the ciliary muscle to the lens )
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19
Q

what is iris ? what is its structure

A

it consist of pigmented cells and is a flattened doughnut between the cornea and the lens
it is continuous with the cillary body

muscles in iris allow the pupil to change size

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20
Q

what is pupil?

A

he pupil is the opening at the center of the iris through which light passes.

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21
Q

for close and and bright vision how does the iris change its shape?

A

the sphincter pupillae ( circular muscles) contract and constrict the pupil

parrasympathetic control it

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22
Q

for distant and dim vision how does the iris change its shape

A

the dilator pupillae (radial pupillae) contracts and pupils dilates allowing more light to enter

sympathetic control it

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23
Q

what is the inner most layer of the eye?

A

retina (develops from an extension of the brain)
outer layer : pigmented layer
inner layer : neural layer

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24
Q

what is the retina made up of ?

A

millions of photoreceptor that convert light energy and neurons involved in processing light

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25
Q

what is the outer layer of the retina ? structure

A

pigmented layer that is next to the choroid and extends anteriorly to cover the cilliary body and posterior face of the iris

26
Q

what is the function of the outer layer of retina

A

the pigmented layer absorbs light and prevent it from scattering in the eye

it also acts as phagocytes participating in photoreceptor call renewal
it stores vit A needed by photoreceptor cells

27
Q

what is the inner layer of the retina called and what is its structure?

A

it is the inner neural layer and contains millions of receptor cells, the rods and cones, which are called photoreceptors because they respond to light.

28
Q

what is the function of the inner layer of retina ?

A

It receives light from an image we are looking at, and converts that light into electrical impulses which are sent through the fibres of the optic nerve to the brain.

29
Q

who supplies the retina ?

A

outer third: choroid plexus
inner two thirds : central artery and central vein

only part where arterioles are visible

30
Q

what is optic disc?

A

it is where optic nerve exits the eye and it is also called the blind spot as it lacks photoreceptors

31
Q

what is macula ?

A

it is yellowish pigmented spot on the temporal side of the optic disc where there re maximum concentration of cones (NO RODS)

32
Q

what is fovea ?

A

The fovea centralis is located in the center of the macula lutea, a small, flat spot located exactly in the center of the posterior portion of the retina.

visual acuity is greatest at this part and it provides a colour vision whatever we wish to view is found on the fovea

33
Q

what is rods ?

A

they are dim light visual receptors
numerous in the body
more sensitive than cones
do not provide sharo images or colour vision

34
Q

what are cones

A

receptors for bright light and provide high quality vision

35
Q

what are the chamber of the eye?

A 
anterior chamber ( between the cornea and the iris  )
posterior chamber (iris and lens )
vitreous chamber
36
Q

where is the aqueous humor secreted at?

A

secreted by cillary process in posterior chamber

37
Q

what is the chamber infront of the lens (anterior and posterior chamber)?

A

filled by aqueous humor

supplies nutrients and oxygen to the lens and cornea and to some cells of retina and carries away metabolic waste

forms and drains continually

38
Q

what is the vitreous chamber? made up of and location

A

it is between the lens and retina

filled with clear gel, vitreous humor

39
Q

what is the function of vitreous humor?

A

it supports the posterior surface of the lens and holds the neural layer of iretna firmly against pigmented layer

contributes to intraocular pressure and helping to counteract the pulling force of extrinsic eye muscle

maintain the shape of the eyeball

40
Q

what is the clinical problem of the anterior chamber?

A

glaucoma
where drainage of aqueous humor is blocked and fluid backs up. the pressure within the eye may rise to dangerous levels and compress the retina
might result in blindness

41
Q

what is the structure of lens ?

A

convex on both sides and is a transparent, flexible structure that can change shape to focus light on retina

held in place by zonule capsule and nourished by the aqueous humor

42
Q

what is the clinical of the lens

A

cataract

clouding of lens that causes the world to appear distorted like seeing through frosted glass

43
Q

what is the refractive media made up of?

A

made up of
aqueous humor
lens
viteous humor

44
Q

what is optic nerve ?

A

it is where bipolar cells receive impulses from the receptors and passed on to ganglion cells
( axons of the ganglion cells are collected at the optic disc)
they continue ass optic nerve by exiting the eye

45
Q

what is optic chiasma ?

A

it is where the two optic nerves mix and cross over

46
Q

which cortex does visual image get send to?

A

primary visual cortex where it receives, integrates and proceses visual information relayed from retina

located in occipital lobe

47
Q

how are images formed?

A

they are formed as light passes from form air to the eye, moves in cornea, aqueous humor, lens, vitus humor, neural layer of retina and excite photoreceptors

light ray are focused on retina (by refraction of light)
and image that is formed is smaller and inverted

48
Q

what is refraction of light?

A

bending of light rays when they pass from one medium to another at an oblique angle to produce a focused image at the retina

49
Q

where does the light bend at?

A

entering the cornea
entering the lens
leaving the lens

50
Q

how does the eye adapt for distant vision?

A

sympathetic input will relax the cilliary muscle and it tighens the cillary zonule

this flattens the lens and thins the lens

eyes are best adapted for this and it at its lowest refractory power

51
Q

how does eye adapt for close vision?

A

parasympathetic output contracts the cillary muscle
cillary zonule has low tension
allow the lens to buldge and thicken

in addition active adjustment is needed

52
Q

what is the active adjustment needed for close vision?

A
  1. accomodation of lens (increase in refractory power of lens and lens thickens to provide a shorter focal length need ed to focus the image of a close object on the retina)
  2. constriction of pupil (sphincter pupillae muscle reduces the size of the pupil toward 2mm to prevent most of the divergent light rays from entering the eye)
  3. convergence of eyeball (eyes will converge and deviate to the nasal side so that images will fall on the macula)
53
Q

what is myopia ?

A

Nearsightedness

when distant object focus in front of the retina rather than on it

54
Q

what is hyperopia ?

A

farsighedness

parallel rays from distant object focus behind the retina

55
Q

what is astigmatism ?

A

unequal curvature in different parts of the cornea or lens

56
Q

macula vs fovea

A
57
Q

what are rods

A

have photosensitive pigments in rods (rhodopsin which consist of opsin and retinal)

they are highly sensitive to light and have a large amount of photopigment

it is for night vision

it is loacted outside the fovea

100million per eye

58
Q

what are cones?

A

consist of retinal and 3 kind of opsin (red blue and green)

low sensitivity to light 
small amount of pigment present 
photopic (day vision)
concentrated in fovea 
6 million per eye
59
Q

how are colours seen ?

A

the key light absorbing molecules is retinal
they combine with opsin (proteins) to form 4 type of visual pigments

there are only 3 colours, the cones spectra overlap (more than 1 activated at same time)

60
Q

how are white seen?

A

when all the cones are stimulated

61
Q

can see colours in dark?

A

no colour discrimination in dark because dim light cannot stimulate cones

vanessa special senses (3 decks)

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