Orbit and Eyes Flashcards Preview

MD1 Neuroscience > Orbit and Eyes > Flashcards

Flashcards in Orbit and Eyes Deck (85):
1

How can you get a blowout fracture to the orbit?

Blunt trauma to orbit

2

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

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

3

What forms the supraorbital margin?

Frontal bone

4

What is the significance of the supraorbital notch?

Neurovascular structures pass through it

5

What forms the infraorbital margin?

Zgomatic bone laterally
Maxilla medially

6

Which bones break in a blowout fracture?

Thinnest and weakest bones
- Lacrimal
- More commonly, ethmoid in papyrus region
- Or junction between 2

7

Which bones make up the roof of the orbit?

Frontal
Lesser wing of sphenoid

8

Which bones make up the floor of the orbit?

Maxilla - orbital plate of
Zygomatic
Palatine

9

Which bones make up the lateral wall of the orbit?

Zygomatic
Greater wing of sphenoid

10

Which bones make up the medial wall of the orbit?

Maxilla
Lacrimal
Ethmoid
Body of sphenoid

11

What colour is the sclera?

White

12

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

5/6

13

What are the functions of the sclera?

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

14

What is the sclera made of?

Collagen

15

What is the pattern of collagen in the sclera?

Laid down in whorls
Makes it very tough

16

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

Anterior 1/6

17

Are the cornea and sclera continuous?

Yes

18

What is the principal refracting component of the eye?

Cornea

19

How much light does the cornea bend?

60%

20

What makes the cornea optimum for vision

Avascular
Transparent
Structure of collagen
Not many cell bodies

21

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

Epithelium
Bowman's layer
Stroma
Descemet's membrane
Endothelium

22

What kind of layer is the epithelium?

Mucous membrane
Multiple cells

23

How many layers is the endothelium of the cornea?

1

24

Which part of the cornea is continuous with the sclera?

Stroma

25

How is collagen organised in the cornea?

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

26

What does scleral opacity vary depending on?

Composition of stroma
Hydration
Size and distribution of collagen

27

How does the collagen of the cornea often heal?

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

28

What is the anterior chamber?

Area just behind cornea

29

What is the anterior chamber angle?

Junction between iris and cornea

30

What are the key structures in the anterior chamber angle?

Cornea
Trabecular meshwork
Canal of Schlemm
Ciliary body

31

What is the trabecular meshwork?

Holes through which aqueous humour drains

32

What can happen if the trabecular meshwork is clogged?

Pressure in eye increases

33

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

Past ciliary body
Through trabecular meshwork
Through canal of Schlemm

34

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

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

35

What are the functions of the ciliary body?

Formation of aqueous humour
Tethers lens
Accommodation

36

What forms the aqueous humour?

Ciliary epithelium

37

What tethers the lens?

Ciliary processes

38

What is responsible for accommodation?

Ciliary muscle

39

Where are the ciliary processes located?

Anteriorly only

40

What is aqueous humour important for?

Maintaining health of lens and cornea
Creates intraocular pressure

41

How many cell layers is the ciliary epithelium?

2

42

Where is the ciliary epithelium?

On ciliary processes

43

What does aqueous humour drain into?

Venous supply

44

What structures does accommodation involve?

Lens
Ciliary muscle
Zonules attached to lens

45

What are zonules?

Ligaments between ciliary processes and lens
Pull lens to change its shape

46

Describe the ciliary muscle

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

47

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

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

48

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

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

49

What is presbyopia?

Loss of accommodation with age

50

Why does presbyopia happen?

Reduction in flexibility of lens and zonules

51

What are the structures that make up the uvea?

Ciliary body
Iris

52

What is the function of the iris?

Controls size of pupil > controls light entry

53

Which muscles make up the iris?

Sphincter pupillae
Dilator pupillae

54

What does the sphincter pupillae do?

Constrict pupil

55

What is the sphincter pupillae innervated by?

Parasympathetic fibres of CN III

56

What does the dilator pupillae do?

Dilate pupil

57

What is the dilator pupillae innervated by?

Sympathetic nervous system

58

Is the dilator pupillae a real muscle?

No, it's specialised myoepithelium

59

What is the choroid?

3 layers of blood vessels

60

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

Choriocapillaris
Just below retina

61

Where is the choroid?

Underneath retina

62

What does the choroid supply?

Retina

63

What are the parts of the retina?

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

What are the fovea and macula important for?

Central vision

65

Describe the fovea?

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

66

What forms the optic nerve?

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

67

What is the lamina cribrosa?

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

68

What happens to the lamina cribrosa when intraocular pressure increases?

Holes stretched
Press on axons of ganglion cells
Causes damage

69

What are the four main arteries of the eye?

Central retinal artery
Ciliary arteries
- Long posterior ciliary artery
- Short posterior ciliary artery
- Anterior ciliary artery

70

Where is the central retinal artery from?

Internal carotid > ophthalmic > 1st branch

71

What is the course of the central retinal artery?

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

72

What does the central retinal artery supply?

Inner retina

73

What artery are the posterior ciliary arteries branches of?

Ophthalmic artery

74

What is the course of the posterior ciliary arteries?

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

75

How many branchlets of posterior ciliary arteries are there?

7-11

76

What do the long posterior ciliary arteries supply?

Travel in choroid all the way forward
- Ciliary body
- Iris
- Some regions of retina via choroid

77

What do the short posterior ciliary arteries supply?

Choroid around optic nerve

78

What is the course of the anterior ciliary artery?

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

79

What does the anterior ciliary artery supply?

Anterior structures of eye
- Conjunctiva
- Some of sclera
- Forms ring around cornea

80

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

Posterior ciliary artery

81

What structures make up the eyelid?

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

82

What is the function of orbicularis oculi?

Close eyelid

83

Which nerve innervates orbicularis oculi?

CN VII

84

What is the function of levator palpebrae superioris?

In upper eyelid only
Opens eyelid

85

Which nerve innervates levator palpebrae superioris?

CN III

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