Anatomy of the Orbit, Eye, and Lacrimal Apparatus Flashcards Preview

ESA 4 - Head and Neck > Anatomy of the Orbit, Eye, and Lacrimal Apparatus > Flashcards

Flashcards in Anatomy of the Orbit, Eye, and Lacrimal Apparatus Deck (85):
1

What is the orbit? 

A pyramidal shaped bony cavity within the facial skeleton 

2

What does the orbit contain and protect? 

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

 

3

What nerve does the orbit contain? 

The optic nerve

4

How does the optic nerve enter the eye? 

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

5

What are the layers of the optic nerve? 

  • Pia mata
  • Arachnoid mata
  • Dura mata

 

6

Why does brain inflammation lead to photophobia? 

Because the layers of the optic nerve also become inflamed 

7

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

Inferior and medial walls 

8

What is the apex of the orbit? 

The optic canal

9

What makes up the superior boundary of the orbit? 

The frontal and sphenoid bone

10

What makes up the lateral boundary of the orbit? 

Zygomatic and sphenoid

11

What makes up the medial boundary of the orbit? 

Ethmoid, maxillary, lacrimal. sphenoid

12

What makes up the inferior boundary of the orbit?

Maxillary, zygomatic

13

What holes does the orbit have? 

  • Optic canal
  • Superior orbital fissure
  • Inferior orbital fissure

 

14

What does the optic canal transmit? 

  • Optic nerve
  • Opthalmic artery

 

15

What does the superior orbital fissure transmit? 

  • 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

 

16

What does the inferior orbital fissure transmit? 

Inferior opthalmic vein

 

17

What are the different parts of the eyeball? 

18

What holds the lens in place? 

Suspensory ligaments

19

What does the lens act to do? 

Focus light onto the back of the retina

20

What is the area of the most accurate vision? 

Macula/fovea

 

21

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

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

22

What is the optic disc? 

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

23

What are the layers of the eyeball? 

  • Outer fibrous layer
  • Middle vascular layer
  • Inner layer

 

24

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

Tough, fibrous sclera

25

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

As the transparent cornea

26

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

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

 

27

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

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

28

What covers the sclera of the eyeball? 

A thin, transparent layer of cells called the conjunctivae

29

Where does the conjunctivae extend? 

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

30

What runs through the conjunctivae? 

Blood vessels

31

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

  • Choroid
  • Ciliary body
  • Iris

 

32

What is the function of the ciliary body? 

Connects the choroid with the iris

33

What are the properties of the ciliary body? 

  • Vascular
  • Muscular

 

34

Where does the iris lie? 

Just anteriorly to the lens

35

What is the iris? 

A thin contractile diaphragm with a central aperture, the lens

36

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

Allows for transmission of light

37

What forms the iris? 

  • Sphincter muscle
  • Dilator pupillae muscle

 

38

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

The autonomic nervous system

39

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

To help supply nutrients to avascular area of eyeball

40

What does the inner layer of the eyeball consist of? 

Retina

41

What does the retina consist of? 

  • Optic parts
  • Non-visual parts

 

42

What are the chambers of the eyeball? 

  • Anterior 
  • Posterior
  • Vitreous

 

 

43

What is the anterior chamber of the eyeball filled with? 

Transparent liquid aqueous humour

44

Where is the anterior chamber of the eyeball found? 

Between the cornea and the iris

45

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

Through the pupil

46

What is the posterior chamber of the eyeball filled with?

Transparent liquid aqueous humour

47

Where is the posterior chamber of the eye found?

Between the iris and the lens

48

What does the posterior chamber of the eye contain? 

The ciliary body and processes

49

What is the function of the ciliary body and processes? 

Secretes aqueous humour

50

What is the aqueous humour of the eye important for? 

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

 

51

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

Because of the pressure it exerts

52

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

Because they do not have their own blood supply

53

Where does the aqueous humour of the eye drain through?

The irido-corneal angle, into the canal of Schlemm

54

What is the irido-corneal angle?

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

55

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

Via a trabecular meshwork, back into the venous circulation

56

What is the vitreous chamber filled with?

Transparent, jelly-like vitreous humour

57

What is the lens?

Transparent biconvex structure

58

Where does the lens lie? 

Posterior to the iris

59

What is the lens enclosed in? 

A capsule

60

What is the lens attached to? 

Ciliary body

61

How is the lens attached to the ciliary body? 

By the circular suspensory ligament

62

What is the nerve and blood supply to the lens?

It does not have any 

63

How does the lens recieve its nutrients?

Entirely from the aqueous humour that surrounds and bathes it

64

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

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

65

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

Changes its refractive power

66

What is the front of the eye exposed to? 

The eyelids and the lacrimal glands

67

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

Have an important protective role

68

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

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

69

What happens when the cornea becomes dry? 

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

How are the eyelids strengthened and given their shape? 

By tarsal playes

71

What are tarsal plates? 

Dense bands of connective tissue

72

What do tarsal plates contain? 

Tarsal glands (Meibomian glands)

73

What is the purpose of the Meibomian glands? 

They secrete an oily substance

74

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

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

 

75

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

To prevent tears from evaporating too quickly

76

What does the lacrimal apparatus consist of? 

  • Lacrimal glands
  • Lactimal ducts
  • Lacrimal canaliculi

 

77

What do the lacrimal glands do? 

Secrete the lacrimal fluid (tears)

78

Where do the lacrimal glands lie? 

In a fossa on the superolateral part of the orbit

79

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

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

Where does the lacrimal fluid go from the lacrimal lake?

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

81

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

You getting a runny nose when you cry

82

What innervates the structures of the orbit? 

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

83

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

Branches of the opthalmic artery 

84

What supplies blood to the retina?

The central retinal artery, a branch of the opthalmic artery 

85

How is the orbit and related structures drained of blood?

Venous drainage is via tributaries into the opthlamic veins