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biology > the human eye > Flashcards

the human eye Flashcards

1
Q

how is the eyeball attached to the eye socket?

A

via rectus muscles

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2
Q

parts of the eye

hint: there are 13

A
  1. conjunctiva
  2. cornea
  3. sclera
  4. choroid
  5. retina
  6. optic nerve
  7. iris
  8. pupil
  9. lens
  10. suspensory ligament
  11. ciliary body
  12. vitreous humour
  13. aqueous humor

3,4,5 are also known as wall of the eye

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3
Q

structure and function of the conjunctiva

A
  • thin , transparent membrane (on surface of cornea)
  • protects cornea against friction
  • keeps eyeball moist
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4
Q

structure and function of cornea

A
  • part of sclera
  • small bulge at front of eye
  • transparent
  • reflects the most light into pupil
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5
Q

structure and function of sclera

A
  • tough, white outer layer
  • protects eyeball against mechanical injury
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6
Q

structure and function of choroid

A
  • has blood vessels that supply the retina with oxygen and nutrients
  • black, prevents internal reflection of light
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7
Q

structure and function of retina

A
  • innermost layer of eyeball which contain photoreceptors (rods and cones) that detect stimuli
  • has the most sensory receptors in body
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8
Q

structure and function of optic nerve

A

transmits nerve impulses from photoreceptors to brain

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9
Q

structure and function of iris

A
  • part of choroid (behind cornea)
  • controls size of pupil, hence controls amount of light that enters eye
  • 2 involuntary muscles : circular and radial
  • contains pigment which gives the eye its color
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10
Q

structure and function of pupil

A
  • hole in the centre of iris that allows light to enter eye
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11
Q

structure and function of lens

A
  • transparent, biconvex
  • elastic so it can change shape and thickness to refract light on retina
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12
Q

structure and function of suspensory ligaments

A
  • attaches lens to ciliary body to hold it in position
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13
Q

structure and function of ciliary body

A
  • (protruding parts attached to back of iris)
  • supports lens
  • contains muscles which control curvation of lens
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14
Q

structure and function of vitreous humor

A
  • transparent, jelly-like substance (found in main part of eyeball)
  • supports the lens
  • refracts light rays onto retina and keeps eyeball firm
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15
Q

structure and function of aqueous humor

A
  • transparent and watery fluid (found at front of eyeball)
  • refracts light rays into pupil and keeps eyeball firm
  • mantains shape of the anterior chamber (front) of the eyeball
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16
Q

what is the fovea?

A
  • part of retina that is most sensitive to light (dent, above of optic nerve)
  • images are usually focused here
  • contains only densely packed cones
17
Q

what is contained in the other parts of the retina

A

density of rods > density of cones

18
Q

what is the blind spot?

A
  • found immediately over the optic nerve
  • no photoreceptor cells, hence no vision
19
Q

specialty of rods

A
  • sensitive to low light intensity
  • blurry images in shades of gray
    (provides monochrome vision in dim light)
20
Q

specialty of cones

A
  • sensitive to high light intensity
  • red, blue, green cones responsible for color vision
    (provides acute (sharp) color vision in bright light)
21
Q

image formed on the retina is..?

hint : 3

A
  • inverted (upside down)
  • reversed (back to front)
  • diminshed (small)
22
Q

what is pupil reflex

A

an immediate change to the diameter of the pupil, in response to the intensity of light that falls on photoreceptors in the retina, without consious control

23
Q

how does the pupil adjust itself in bright light?

A
  • circular muscles of the iris contact
  • radial muscles of the iris relax
  • these reduce pupil size (pupil CONSTRICTS)， thus reducing amount of light entering the eye
  • which prevents damage to rods and cones

like closing a window when the sky is sunny

24
Q

how does the pupil adjust itself in dim light?

A
  • circular muscles of the iris relax
  • radial muscles of the iris contract
  • these enlarge pupil size (pupil DILATES)， thus allowing as much light as possible to enter the eye
  • let us see more clearly

like opening a window when the sky is dark

25
Q

what is focusing / accomodation?

A

adjustments of lens of the eye so that clear images of objects at different distances are formed on the retina

26
Q

focusing on distant object

A
  1. light reflected off object is parallel when it reaches eye
  2. cornea refracts light rays
  3. circular ciliary muscle relaxes
  4. suspensory ligament taut
  5. lens pulled out thin
  6. light focused on retina
27
Q

focusing on near object

A
  1. light reflected off object is diverging when it reaches eye
  2. cornea refracts light rays
  3. circular ciliary muscle contracted
  4. suspensory ligament slack
  5. lens more convex
  6. light focused on retina

biology (14 decks)

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