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MD1 Neuroscience > Orbit and Eyes > Flashcards

Orbit and Eyes Flashcards

1
Q

How can you get a blowout fracture to the orbit?

A

Blunt trauma to orbit

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2
Q

How is a broken bone in the orbit a protective measure?

A

Contents of orbit sink down into broken bone and are thus protected

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3
Q

What forms the supraorbital margin?

A

Frontal bone

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4
Q

What is the significance of the supraorbital notch?

A

Neurovascular structures pass through it

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5
Q

What forms the infraorbital margin?

A

Zgomatic bone laterally

Maxilla medially

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6
Q

Which bones break in a blowout fracture?

A

Thinnest and weakest bones

  • Lacrimal
  • More commonly, ethmoid in papyrus region
  • Or junction between 2
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7
Q

Which bones make up the roof of the orbit?

A

Frontal

Lesser wing of sphenoid

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8
Q

Which bones make up the floor of the orbit?

A

Maxilla - orbital plate of
Zygomatic
Palatine

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9
Q

Which bones make up the lateral wall of the orbit?

A

Zygomatic

Greater wing of sphenoid

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10
Q

Which bones make up the medial wall of the orbit?

A

Maxilla
Lacrimal
Ethmoid
Body of sphenoid

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11
Q

What colour is the sclera?

A

White

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12
Q

How much of the surface of the eyeball is the sclera?

A

5/6

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13
Q

What are the functions of the sclera?

A

Maintains shape of globe
Offers resistance to internal and external forces
Provides attachments for extraocular muscles

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14
Q

What is the sclera made of?

A

Collagen

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15
Q

What is the pattern of collagen in the sclera?

A

Laid down in whorls

Makes it very tough

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16
Q

How much of the surface of the eyeball is the cornea?

A

Anterior 1/6

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17
Q

Are the cornea and sclera continuous?

A

Yes

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18
Q

What is the principal refracting component of the eye?

A

Cornea

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19
Q

How much light does the cornea bend?

A

60%

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20
Q

What makes the cornea optimum for vision

A

Avascular
Transparent
Structure of collagen
Not many cell bodies

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21
Q

What are the five histological layers of the cornea, from outside to inside?

A 
Epithelium
Bowman's layer
Stroma
Descemet's membrane
Endothelium
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22
Q

What kind of layer is the epithelium?

A

Mucous membrane

Multiple cells

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23
Q

How many layers is the endothelium of the cornea?

A

1

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24
Q

Which part of the cornea is continuous with the sclera?

A

Stroma

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25
Q

How is collagen organised in the cornea?

A

Uniform in diameter
Evenly spaced
Run parallel to each other in bundles = lamellae
Adjacent lamellae at angles to each other

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26
Q

What does scleral opacity vary depending on?

A

Composition of stroma
Hydration
Size and distribution of collagen

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27
Q

How does the collagen of the cornea often heal?

A

Doesn’t grow back in ordered way
Scar formation
Loss of transparency

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28
Q

What is the anterior chamber?

A

Area just behind cornea

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29
Q

What is the anterior chamber angle?

A

Junction between iris and cornea

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30
Q

What are the key structures in the anterior chamber angle?

A

Cornea
Trabecular meshwork
Canal of Schlemm
Ciliary body

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31
Q

What is the trabecular meshwork?

A

Holes through which aqueous humour drains

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32
Q

What can happen if the trabecular meshwork is clogged?

A

Pressure in eye increases

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33
Q

What is the route of aqueous flow through the anterior chamber angle?

A

Past ciliary body
Through trabecular meshwork
Through canal of Schlemm

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34
Q

What are the three layers of the eye and what are their functions?

A
  1. Cornea and sclera > strength
  2. Uvea > nutrition
  3. Retina > sight
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35
Q

What are the functions of the ciliary body?

A

Formation of aqueous humour
Tethers lens
Accommodation

36
Q

What forms the aqueous humour?

A

Ciliary epithelium

37
Q

What tethers the lens?

A

Ciliary processes

38
Q

What is responsible for accommodation?

A

Ciliary muscle

39
Q

Where are the ciliary processes located?

A

Anteriorly only

40
Q

What is aqueous humour important for?

A

Maintaining health of lens and cornea

Creates intraocular pressure

41
Q

How many cell layers is the ciliary epithelium?

42
Q

Where is the ciliary epithelium?

A

On ciliary processes

43
Q

What does aqueous humour drain into?

A

Venous supply

44
Q

What structures does accommodation involve?

A

Lens
Ciliary muscle
Zonules attached to lens

45
Q

What are zonules?

A

Ligaments between ciliary processes and lens

Pull lens to change its shape

46
Q

Describe the ciliary muscle

A

Within ciliary body
Innervated by parasympathetic nervous system carried by CN III
Smooth muscle - like sphincter

47
Q

What does the ciliary muscle do to allow you to see things far away?

A

Relax > aperture of sphincter open > zonules stretch > lens becomes skinny

48
Q

What does the ciliary muscle do to allow you to see things close by?

A

Contract > aperture of sphincter smaller > zonules relax > lens becomes fat

49
Q

What is presbyopia?

A

Loss of accommodation with age

50
Q

Why does presbyopia happen?

A

Reduction in flexibility of lens and zonules

51
Q

What are the structures that make up the uvea?

A

Ciliary body

Iris

52
Q

What is the function of the iris?

A

Controls size of pupil > controls light entry

53
Q

Which muscles make up the iris?

A

Sphincter pupillae

Dilator pupillae

54
Q

What does the sphincter pupillae do?

A

Constrict pupil

55
Q

What is the sphincter pupillae innervated by?

A

Parasympathetic fibres of CN III

56
Q

What does the dilator pupillae do?

A

Dilate pupil

57
Q

What is the dilator pupillae innervated by?

A

Sympathetic nervous system

58
Q

Is the dilator pupillae a real muscle?

A

No, it’s specialised myoepithelium

59
Q

What is the choroid?

A

3 layers of blood vessels

60
Q

What is the most important layer of the choroid and where is it?

A

Choriocapillaris

Just below retina

61
Q

Where is the choroid?

A

Underneath retina

62
Q

What does the choroid supply?

63
Q

What are the parts of the retina?

A

Optic nerve head/optic disc
Fovea/foveola - in middle
Macula - around fovea, defined by pigment
Posterior pole - around macula
Ora serrata - retina joins rest of inside of eyeball

64
Q

What are the fovea and macula important for?

A

Central vision

65
Q

Describe the fovea?

A

High visual acuity
Avascular - gets nutrients from choroid
High density of cones
No rods

66
Q

What forms the optic nerve?

A

Axons of ganglion cells as they exit retina to pass visual information to higher cortical areas

67
Q

What is the lamina cribrosa?

A

1/3 of scleral collagen crosses optic nerve
Dense - 3-10 sheets
Sieve-hole transmitting nerve fibres
Provides some structure to optic nerve

68
Q

What happens to the lamina cribrosa when intraocular pressure increases?

A

Holes stretched
Press on axons of ganglion cells
Causes damage

69
Q

What are the four main arteries of the eye?

A 
Central retinal artery
Ciliary arteries
- Long posterior ciliary artery
- Short posterior ciliary artery
- Anterior ciliary artery
70
Q

Where is the central retinal artery from?

A

Internal carotid > ophthalmic > 1st branch

71
Q

What is the course of the central retinal artery?

A

Branches off ophthalmic nerve
Pierces optic nerve
Travels in optic nerve
Fans out on surface of retina

72
Q

What does the central retinal artery supply?

A

Inner retina

73
Q

What artery are the posterior ciliary arteries branches of?

A

Ophthalmic artery

74
Q

What is the course of the posterior ciliary arteries?

A

Branch off ophthalmic artery
Enter back of eye around optic nerve
Depending on how far they travel called short/long

75
Q

How many branchlets of posterior ciliary arteries are there?

76
Q

What do the long posterior ciliary arteries supply?

A

Travel in choroid all the way forward

  • Ciliary body
  • Iris
  • Some regions of retina via choroid
77
Q

What do the short posterior ciliary arteries supply?

A

Choroid around optic nerve

78
Q

What is the course of the anterior ciliary artery?

A

Ophthalmic artery > muscular artery > anterior ciliary artery
Travels on outside of globe towards front

79
Q

What does the anterior ciliary artery supply?

A

Anterior structures of eye

  • Conjunctiva
  • Some of sclera
  • Forms ring around cornea
80
Q

What supplies the outer retina - and the photoreceptors within it?

A

Posterior ciliary artery

81
Q

What structures make up the eyelid?

A 
Skin
- Glands
- Eyelashes
Muscles
- Orbicularis oculi
- Levator palpebrae superioris
Lacrimal apparatus
- Lacrimal gland and ducts
- Nasolacrimal sac and duct
82
Q

What is the function of orbicularis oculi?

A

Close eyelid

83
Q

Which nerve innervates orbicularis oculi?

84
Q

What is the function of levator palpebrae superioris?

A

In upper eyelid only

Opens eyelid

85
Q

Which nerve innervates levator palpebrae superioris?

MD1 Neuroscience (55 decks)

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