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Nervous System and Integument > 1.3 Special Sense Organs (Eye) > Flashcards

1.3 Special Sense Organs (Eye) Flashcards

1
Q

The eye:

A

Extremely complex organ

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2
Q

Where is the derived from?

A

both the ectoderm and mesoderm

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3
Q

Ectoderm =

A

Light structure
Ex: lens

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4
Q

Mesoderm =

A

Muscles that control eye movement

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5
Q

Explain What is happening in this diagram:
Part 1 of 4

A

The wall (optic sulci) of the diencephalon begins to extend toward the surface of the ectoderm

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6
Q

Explain What is happening in this diagram:
Part 2 of 4

A

-The optic sulcus deepens to become the optic vesicle

  • The optic vesicle continues to grow toward the ectoderm which is induced to thicken (forming the optic or lens placode) and later
  • The optic or lens placode will later begin to invaginate against the optic vesicle
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7
Q

Explain What is happening in this diagram:
Part 3 of 4

A
  • The optic or lens placode begins / continues to invaginate against the optic vesicle
  • The optic vesicle starts to undergo infolding and transforms from a single- wall to a double-walled optic cup
  • The inner and outer layers begin to behave differently
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8
Q

Explain What is happening in this diagram:
Part 4 of 4

A
  • The 2 layers of the optic cup differentiate
  • Outer layer: becomes thinner and starts to express melanin granules, later develops into pigmented layer of the retina
  • Inner layer: Thickens and develops into the sensory layer of the retina
  • ectoderm invaginates fully to form the lens vesicle
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9
Q

Where does the optic sulci develop from?

A

diencephalon

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10
Q

What structures​ are derived from the ectoderm?

A

lens and retina

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11
Q

What structures are derived from the mesoderm?

A

muscles that derive from the eye

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12
Q

What holds the lens of the eye in place?

A

Ciliary body

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13
Q

Accommodation​:

A

ability for light to focus on the retina

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14
Q

List the transparent media of the eye: What do​ these structures allow?

A
  1. conjunctiva
  2. cornea
  3. aqueous humour
  4. lens
  5. vitreous humour

Allow light to pass through all the way to retena

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15
Q

Conjuctiva

A
  • Continuous with the skin of eyelids
  • Stratified squamous epithelium
  • Goblet cells: secrete deepest, mucus, layer of tear film, which adheres tears to surface of globe
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16
Q

Sign of infection for Conjuctiva?

A

excessive mucous / stickyness on eyelids (conjungtivitious)

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17
Q

Conjunctiva function:

A

thin, clear, mucous membrane over cornea and sclera that lubricates eye

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18
Q

Does the cornea have blood cells?

A

no

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19
Q

Cornea:

A

transparent and avascular refracting light onto lens and focuses it on the retina

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20
Q

Where does the cornea get nutrition from?

A

It’s​ avascular so it gets its nutrition / O2 from aqueous layer and O2 from air

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21
Q

What does the aqueous humour do?

A

Provides nutrients for lens and cornea
- Maintains intraocular pressure
- Replaced several times a day

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22
Q

What are the stages of the aqueous humour?

A
  • Produced in ciliary body
  • flows from the posterior chamber via the pupil and comes out the anterior chamber
  • Then it drains through the vessels of the cornea and iris (canal of schlemm)
  • The remaining liquid drains out of the episcleral venous system
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23
Q

Lens:

A
  • This is the derivative of the optic placode
  • Onion structure of lens fibers​ - live cells
  • Cuboidal epithelium
  • Capsule, with rostral and caudal sutures
  • Softer cortex, firmer nucleus (firm/sclerotic with age)
  • No blood vessels or nerves
  • nutrients from aqueous
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24
Q

The vitreous humour:

A
  • exerts pressure​ inside eyeball, this maintains retia position
  • Secreted by ciliary up to the time of maturity
  • Gelatinous: water, hyaluronic acid and collagen
  • Hyaloid canal - remnant of blood vessels present during development
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25
Q

What does ​vitreous humour prevent?

A

Retinal detachment

26
Q

Rods vs. cones?

A

rods = night vision​
cones = daylight vision

27
Q

Macula:

A

ability to focus on high definition

28
Q

What is in the photoreceptor region of the eye?

A

cone and rod

29
Q

Once light hits the rods and cones but r​egion does it go to?

A

The Fovea and Macula region

30
Q

What are the 3 parts of the uveal tract?

A
  1. Choroid (forms majority of the inside eye
  2. Ciliary body
  3. Iris
31
Q

3 qualities of the Choroid:

A
  1. tapetum lucidum: refracts light inwards (inner: nearest retina
  2. vascular: blood supply
  3. black/connective (outer: nearest retina)
32
Q

Iridic granules: sympathetic vs. parasympathetic

A

Sympathetic: larger pupil
Parasympathetic: small pupil

33
Q

ciliary body

A

aqueous, vitreous, and lens accommodation​ ( ability for light to focus directly on retina)

34
Q

Iris

A

pupil size: center part = smooth muscle

35
Q

The sclera - outer wall

A
  • At the limbus – The sclera continuous with cornea.
  • The sclera is also continuous with dura at the optic stalk. (Recall that retina formation as an evagination of diecephalon).
36
Q

Extraocular muscles: pulls eye ​to midline

A

medial rectus

37
Q

Extraocular muscles: Pulls the eye outwards

A

lateral rectus

38
Q

Extraocular muscles: pulls eye ​down

A

ventral rectus

39
Q

Extraocular muscles: pulls the eye up

A

dorsal rectus

40
Q

oblique muscles

A

rotate eye within eye in globe

41
Q

retractor muscles:

A

pulls eye inwards when pressure is applied
- protective mechanism, 3rd eyelid may also pop out to prevent the eye from ​being destroyed

42
Q

What muscles is nerve III associated with?

A

-dorsal, medial, and vetral rectus
-ventral oblique

43
Q

The retractor muscle of the eyeball and lateral straight​ muscle are associated with which nerve?

A

Nerve VI

44
Q

The trochlea with the tendon of the dorsal oblique muscle is associsted with which nerve?

A

Nerve IV

45
Q

What do most of the rectus muscles do?

A

keep the eye straight or turn the eye within the globe

46
Q

Describe the structure of the adnexa: Deep mucous

A

from conjunctival goblet cells that adhere tears to conjunctiva

47
Q

Describe the structure of the adnexa: Middle aqueous layer

A

from main 3rd eyelid lacrimal glands that cleanse, have IgA, oxygenate, &fill optical defects

48
Q

Describe the structure of the adnexa: Superficial oily layer

A

from tarsal glands (modified sebaceous) that prevents evaporation

49
Q

Pupillary light -

A

(N. III) parasympathetic - pupil becomes smaller

50
Q

Pupil dilation​ -

A

sympathetic - pupil becomes​ larger

51
Q

Menace response -

A

VII, neck (involves cortex, cerebellum, and rostral colliculi

52
Q

Fixating response -

A

III, IV, VI

53
Q

Define Horner’s syndrome & symptoms often seen

A

disruption in the sympathetic nerve supply:
· partial ptosis (drooping or falling of upper eyelid)
· miosis (constricted pupil)
· facial anhidrosis (loss of sweating)
· decreased intraocular pressure

54
Q

Define Strabismus

A

Abnormal eye position caused by malfunction of nerve(s) controlling muscles involved with eye movements

55
Q

PTOSIS:

A

Unilateral - lesion of n.III to LPS or n.VII to face; sympathetic to smooth muscle (Horner’s)
Bilateral - often a lesion of VII nuclei

56
Q

MIOSIS

A

Unilateral - Orbital, e.g. Horner’s, pilocarpine or uveitis
Bilateral - tectal lesion, ‘UMN’ releasing higher inhibition of both E-W nuclei - guarded

57
Q

MYDRIASIS

A

Unilateral - Orbital, e.g. atropine or glaucoma
Bilateral - indicates central brainstem lesion affecting both Edinger-Westphal nuclei – grave

58
Q

What cranial nerves control extrinsic muscles?

A

Cranial nerves III, IV, VI

59
Q

What cranial nerves control autonomic control?

A

CN III and CCG

60
Q

Pathology may result from?

A

brainstem or individual nerve lesions

Nervous System and Integument (8 decks)

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