Orbit and eyes Flashcards Preview

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Flashcards in Orbit and eyes Deck (52):
1

Which bones form the orbital margins?

Supraorbital margin: frontal bone

Infraorbital margin: zygomatic bone (lateral) and maxilla (medial)

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2

What is the special feature of the supraoribtal margin?

Supraorbital notch

Frontal nerves pass through here

3

Which bones form the roof of the orbit?

Frontal bone

Lesser wing of sphenoid 

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4

Which bones form the floor of the orbit?

Maxilla

Zygomatic bone

Palatine (small contribution)

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5

Which bones form the lateral wall of the orbit?

Zygomatic bone

Greater wing of sphenoid 

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6

Which bones form the medial wall of the orbit?

Maxilla

Lacrimal bone

Ethmoid

Body of sphenoid

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7

Where are fractures most likely to occur in the orbit?

Medial wall

Lateral wall

8

Which bones are most likely to fracture in the orbit? Why?

Lacrimal and ethmoid bones

Very thin and fragile

9

How many layers does the eye consist of?

What is the composition of each?

3

Outer layer: sclera and cornea; for stucture and protection

Middle layer: uvea, ciliary body, iris, choroid; vascular supply and nutrition

Inner layer: retina; vision

10

Describe the sclera?

Posterior 5/6 of eyeball

Tough

Made up of collagen 

11

What is the function of the sclera?

Maintains shape of eyeball

Provides resistance against forces

Provides attachments for EOMs

12

Why is the sclera so tough?

Due to squiggly arrangement of collagen 

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13

Describe the cornea?

Anterior 1/6 of eye

5 layers (including epithelium, stroma and endothelium)

Avascular

Transparent 

 

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14

What is the function of the cornea?

Principal refracting component of eye

15

Why is the cornea transparent?

Due to the collagen being laid down in order; collagen fibrils of same diameter laid down in parallel, at equal distances 

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16

Why is the sclera opaque?

Collagenfibrils are different diameters, lengths, and lay at different angles to each other 

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17

In which layer of the cornea is the collagen found?

Stroma

 

18

What is the anterior chamber angle?

Junction between iris and cornea, where aqueous humour drains out of eye

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19

What are the key structures in the anterior chamber angle?

Cornea

Trabecular meshwork

Canal of Sclemm

Ciliary body

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20

Where does aqueous humour drain out of the eye?

In anterior chamber angle, via trabecular meshwork and Canal of Schlemm

21

What are the important structures in the ciliary body?

Ciliary processes (ciliary epithelium)

Ciliary muscle

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22

What are the functions of the ciliary body?

Formation of aqueous humour (ciliary epithelium)

Tethers lens (ciliary processes)

Accommodation (ciliary muscle)

23

Where is aqueous humour produced?

Describe its pathway?

Formed in the ciliary epithelium of the ciliary processes

Then travels forward through pupil to drain via the trabecular meshwork of the anterior chamber angle 

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24

Which eye structures are involved in accommodation?

Ciliary muscle

Zonules that attach to lens

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25

What is the function of the ciliary muscle?

Accommodation 

Contracts and relaxes to change tension of zonules and therefore alter the shape of the lens

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26

Describe the configuration of the ciliary muscle, zonules and lens for vieiwng both close and distant objects?

Close object: ciliary muscle contracted, zonules relaxed, lens bulgy

Distant object: ciliary muscle relaxed, zonules taught, lens thin

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27

What is presbyopia?

Condition in which we lose our ability focus

Lens becomes inflexible 

Occurs with age 

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28

What is the iris?

Aperture of the eye that forms the pupil

29

What are the two muscles that are associated with the iris?

What are their functions and innervation?

Sphincter pupillae: constricts pupil, parasympathetic innervation 

Dilator pupillae: dilates pupil, sympathetic innervation

30

What is the choroid?

What is its function?

Three layers of blood vessels in eye

Supplies nutrients to retina

31

Where is the chorois located?

Between sclera and retina

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32

What are the major structures associated with the retina?

Optic nerve/disc

Macula and fovea

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33

What is the function of the macula and fovea?

Central vision

34

Describe the fovea?

Avascular

High density of cones

 

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35

If the macula and fovea are avascular, where do they derive their nutrients from?

Choroid (beneath retina)

36

What is the optic nerve formed by?

Axons of ganlgion cells as they exit the retina 

37

What is the lamina cribosa?

Band of dense connective tissue formed by 1/3 of the scleral fibres as they continue across where the optic nerve is

Sieve-hole that transmits nerve fibres 

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38

Where is the blood supply to they eye derived from?

Tributaries of the opthalmic artery, which is a branch of the internal carotid artery 

 

39

What is the first branch of the opthalmic artery?

Central retinal artery

Pierces optic nerve to supply retina

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40

What are the three ciliary arteries?

Long posterior 

Short posterior 

Anterior 

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41

What is the difference between long and short posterior ciliary arteries?

Short posterior arteries stop at the optic nerve

Long posterior arteries travel all the way around the retina 

42

Where do posterior arteries pierce the eyeball?

Around the optic nerve

43

Where do anterior ciliary arteries pierce the eyeball?

They don't

Travel around to front of eyeball

44

What are the vessels in the choroid fromed from?

Posterior ciliary artery

45

What do the anterior ciliary arteries supply?

Anterior eye structures

46

What do short posterior ciliary arteries supply?

Photoreceptors close to optic nerve and optic nerve head 

47

What does the central retinal artery supply?

Inner retinal layer

48

What do the long posterior arteries supply?

Outer retina

Some anterior structures

49

Describe the blood supply to the retina?

Central retinal artery supplies the inner retina

Long posterior ciliary artery supplies the outer retina 

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50

Describe the eyelids?

Transition zone between skin and conjunctiva

Consist of glands, lashes, muscles and lacrimal apparatus 

51

Which muscles are associated with the eyelid?

Describe their actions and innervation?

Orbicularis oculi: depresses upper lid, innervated by CN VII

Levator palpebrae superiosis: elevates upper lid, innervated by CN III

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52

What is special about the actions of th eyelid muscles?

Never work together

If one is contracted, the other is relaxed

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