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A - MSRA Ophthalmology [14] > [15] Anatomy of the Orbit, Eye, and Lacrimal Apparatus > Flashcards

[15] Anatomy of the Orbit, Eye, and Lacrimal Apparatus Flashcards

1
Q

What is the orbit?

A

A pyramidal shaped bony cavity within the facial skeleton

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2
Q

What does the orbit contain and protect?

A
  • The eyeball
  • Its muscles
  • Nerves
  • Vessels
  • Most of the lacrimal apparatus
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3
Q

What nerve does the orbit contain?

A

The optic nerve

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4
Q

How does the optic nerve enter the eye?

A

It enters the back of the eye via the optic canal at the apex of the pyramid

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5
Q

What are the layers of the optic nerve?

A
  • Pia mata
  • Arachnoid mata
  • Dura mata
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6
Q

Why does brain inflammation lead to photophobia?

A

Because the layers of the optic nerve also become inflamed

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7
Q

Which walls of the orbit are thin and vulnerable to injuries to the face or eye?

A

Inferior and medial walls

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8
Q

What is the apex of the orbit?

A

The optic canal

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9
Q

What makes up the superior boundary of the orbit?

A

The frontal and sphenoid bone

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10
Q

What makes up the lateral boundary of the orbit?

A

Zygomatic and sphenoid

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11
Q

What makes up the medial boundary of the orbit?

A

Ethmoid, maxillary, lacrimal. sphenoid

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12
Q

What makes up the inferior boundary of the orbit?

A

Maxillary, zygomatic

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13
Q

What holes does the orbit have?

A
  • Optic canal
  • Superior orbital fissure
  • Inferior orbital fissure
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14
Q

What does the optic canal transmit?

A
  • Optic nerve
  • Opthalmic artery
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15
Q

What does the superior orbital fissure transmit?

A
  • Trochlear nerve
  • Frontal branch of opthalmic nerve
  • Lacrimal branch of opthalmic nerve
  • Abducent nerve
  • Superior branch of oculomotor nerve
  • Nasociliary branch of opthalmic nerve
  • Inferior branch of oculomotor nerve
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16
Q

What does the inferior orbital fissure transmit?

A

Inferior opthalmic vein

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17
Q

What are the different parts of the eyeball?

A
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18
Q

What holds the lens in place?

A

Suspensory ligaments

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19
Q

What does the lens act to do?

A

Focus light onto the back of the retina

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20
Q

What is the area of the most accurate vision?

A

Macula/fovea

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21
Q

Why is the macula/fovea the site of the most accurate vision?

A

Because it has the most amount of cells, so convert most light energy to nerve signals

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22
Q

What is the optic disc?

A

The location at which the optic nerve enters the retina, and thus the blind spot

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23
Q

What are the layers of the eyeball?

A
  • Outer fibrous layer
  • Middle vascular layer
  • Inner layer
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24
Q

What does the outer fibrous layer of the eyeball comprise of?

A

Tough, fibrous sclera

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25
Q

How is the outer fibrous layer of the eyeball continuous anteriorly?

A

As the transparent cornea

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26
Q

What is the function of the outer fibrous layer of the eyeball?

A
  • Provides attachment for the extra-ocular muscle
  • Gives shape to the eyeball
  • Protective
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27
Q

What is the outer fibrous layer of the eyeball continuous with posteriorly?

A

The dural sheath covering the optic nerve at the back of the eye

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28
Q

What covers the sclera of the eyeball?

A

A thin, transparent layer of cells called the conjunctivae

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29
Q

Where does the conjunctivae extend?

A

Up to the edge of the cornea (the limbus), and is reflected onto the inner surface of the upper and lower eyelids

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30
Q

What runs through the conjunctivae?

A

Blood vessels

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31
Q

What does the middle vascular layer of the eyeball consist of?

A
  • Choroid
  • Ciliary body
  • Iris
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32
Q

What is the function of the ciliary body?

A

Connects the choroid with the iris

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33
Q

What are the properties of the ciliary body?

A
  • Vascular
  • Muscular
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34
Q

Where does the iris lie?

A

Just anteriorly to the lens

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35
Q

What is the iris?

A

A thin contractile diaphragm with a central aperture, the lens

36
Q

What is the purpose of the central aperture of the iris?

A

Allows for transmission of light

37
Q

What forms the iris?

A
  • Sphincter muscle
  • Dilator pupillae muscle
38
Q

What are the muscles forming the iris under the control of?

A

The autonomic nervous system

39
Q

Why does the middle vascular layer of the eyeball need a rich network of blood vessels?

A

To help supply nutrients to avascular area of eyeball

40
Q

What does the inner layer of the eyeball consist of?

A

Retina

41
Q

What does the retina consist of?

A
  • Optic parts
  • Non-visual parts
42
Q

What are the chambers of the eyeball?

A
  • Anterior
  • Posterior
  • Vitreous
43
Q

What is the anterior chamber of the eyeball filled with?

A

Transparent liquid aqueous humour

44
Q

Where is the anterior chamber of the eyeball found?

A

Between the cornea and the iris

45
Q

How does the anterior chamber of the eyeball communicate with the posterior chamber?

A

Through the pupil

46
Q

What is the posterior chamber of the eyeball filled with?

A

Transparent liquid aqueous humour

47
Q

Where is the posterior chamber of the eye found?

A

Between the iris and the lens

48
Q

What does the posterior chamber of the eye contain?

A

The ciliary body and processes

49
Q

What is the function of the ciliary body and processes?

A

Secretes aqueous humour

50
Q

What is the aqueous humour of the eye important for?

A
  • Supporting the shape of the eyeball (along with vitreous humour)
    Providing nourishment to the lens and cornea
51
Q

How does the aqueous humour support the shape of the eyeball?

A

Because of the pressure it exerts

52
Q

Why is the aqueous humour required to provide nourishment to the lens and cornea?

A

Because they do not have their own blood supply

53
Q

Where does the aqueous humour of the eye drain through?

A

The irido-corneal angle, into the canal of Schlemm

54
Q

What is the irido-corneal angle?

A

The space between the anterior surface of the iris and the posterior extremity of the cornea

55
Q

Where does the aqueous humour drain from the canal of Schlemm?

A

Via a trabecular meshwork, back into the venous circulation

56
Q

What is the vitreous chamber filled with?

A

Transparent, jelly-like vitreous humour

57
Q

What is the lens?

A

Transparent biconvex structure

58
Q

Where does the lens lie?

A

Posterior to the iris

59
Q

What is the lens enclosed in?

A

A capsule

60
Q

What is the lens attached to?

A

Ciliary body

61
Q

How is the lens attached to the ciliary body?

A

By the circular suspensory ligament

62
Q

What is the nerve and blood supply to the lens?

A

It does not have any

63
Q

How does the lens recieve its nutrients?

A

Entirely from the aqueous humour that surrounds and bathes it

64
Q

What is the effect of contraction of the ciliary msucle fibres?

A

It alters the tension of the suspensory ligaments, and so allows for a change in the shape of the lens

65
Q

What does a change in the shape of the lens do?

A

Changes its refractive power

66
Q

What is the front of the eye exposed to?

A

The eyelids and the lacrimal glands

67
Q

What kind of role to the eyelids and the lacrimal glands have?

A

Have an important protective role

68
Q

How to the eyelids and the lacrimal glands protect the eye?

A

They prevent the surface of the eye from drying out, or being injured by small particles

69
Q

What happens when the cornea becomes dry?

A

The eye blinks reflexively, and the eyelids carry a film of fluid over the cornea while also sweeping any dust and foreign material across the medial angle of the eye to be removed

70
Q

How are the eyelids strengthened and given their shape?

A

By tarsal playes

71
Q

What are tarsal plates?

A

Dense bands of connective tissue

72
Q

What do tarsal plates contain?

A

Tarsal glands (Meibomian glands)

73
Q

What is the purpose of the Meibomian glands?

A

They secrete an oily substance

74
Q

What is the purpose of the oily secretion of the Meibomian glands?

A
  • Lubricate the edge of eyelids
  • Mix with the tear film over the surface of the eye
75
Q

Why do the oily secretions from the Meibomian glands mix with the tear film over the surface of the eye?

A

To prevent tears from evaporating too quickly

76
Q

What does the lacrimal apparatus consist of?

A
  • Lacrimal glands
  • Lactimal ducts
  • Lacrimal canaliculi
77
Q

What do the lacrimal glands do?

A

Secrete the lacrimal fluid (tears)

78
Q

Where do the lacrimal glands lie?

A

In a fossa on the superolateral part of the orbit

79
Q

What happens to the lacrimal fluid after it has been secreted by the lacrimal glands?

A

It enters the conjuctival sac through the lacrimal ducts, and from the ducts pass into the lacrimal lake at the medial angle of the eye

80
Q

Where does the lacrimal fluid go from the lacrimal lake?

A

Fluid drains into the lacrimal sac before passing into inferior meatus of the nasal cavity via the nasolacrimal duct

81
Q

What is the passage of the lacrimal fluid into the inferior meatus of the nasal cavity the reason for?

A

You getting a runny nose when you cry

82
Q

What innervates the structures of the orbit?

A

The optic nerve and several branches of the opthalmic division of the trigeminal nerve

83
Q

What supplies blood to the muscles and tissues of the orbit?

A

Branches of the opthalmic artery

84
Q

What supplies blood to the retina?

A

The central retinal artery, a branch of the opthalmic artery

85
Q

How is the orbit and related structures drained of blood?

A

Venous drainage is via tributaries into the opthlamic veins

A - MSRA Ophthalmology [14] (16 decks)

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