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Neuroscience > Orbit and eyes > Flashcards

Orbit and eyes Flashcards

1
Q

Which bones form the orbital margins?

A

Supraorbital margin: frontal bone

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

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2
Q

What is the special feature of the supraoribtal margin?

A

Supraorbital notch

Frontal nerves pass through here

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3
Q

Which bones form the roof of the orbit?

A

Frontal bone

Lesser wing of sphenoid

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4
Q

Which bones form the floor of the orbit?

A

Maxilla

Zygomatic bone

Palatine (small contribution)

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5
Q

Which bones form the lateral wall of the orbit?

A

Zygomatic bone

Greater wing of sphenoid

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6
Q

Which bones form the medial wall of the orbit?

A

Maxilla

Lacrimal bone

Ethmoid

Body of sphenoid

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7
Q

Where are fractures most likely to occur in the orbit?

A

Medial wall

Lateral wall

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8
Q

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

A

Lacrimal and ethmoid bones

Very thin and fragile

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9
Q

How many layers does the eye consist of?

What is the composition of each?

A

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

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10
Q

Describe the sclera?

A

Posterior 5/6 of eyeball

Tough

Made up of collagen

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11
Q

What is the function of the sclera?

A

Maintains shape of eyeball

Provides resistance against forces

Provides attachments for EOMs

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12
Q

Why is the sclera so tough?

A

Due to squiggly arrangement of collagen

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13
Q

Describe the cornea?

A

Anterior 1/6 of eye

5 layers (including epithelium, stroma and endothelium)

Avascular

Transparent

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14
Q

What is the function of the cornea?

A

Principal refracting component of eye

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15
Q

Why is the cornea transparent?

A

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
Q

Why is the sclera opaque?

A

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

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17
Q

In which layer of the cornea is the collagen found?

A

Stroma

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18
Q

What is the anterior chamber angle?

A

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

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19
Q

What are the key structures in the anterior chamber angle?

A

Cornea

Trabecular meshwork

Canal of Sclemm

Ciliary body

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20
Q

Where does aqueous humour drain out of the eye?

A

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

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21
Q

What are the important structures in the ciliary body?

A

Ciliary processes (ciliary epithelium)

Ciliary muscle

22
Q

What are the functions of the ciliary body?

A

Formation of aqueous humour (ciliary epithelium)

Tethers lens (ciliary processes)

Accommodation (ciliary muscle)

23
Q

Where is aqueous humour produced?

Describe its pathway?

A

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

24
Q

Which eye structures are involved in accommodation?

A

Ciliary muscle

Zonules that attach to lens

25
Q

What is the function of the ciliary muscle?

A

Accommodation

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

26
Q

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

A

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

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

27
Q

What is presbyopia?

A

Condition in which we lose our ability focus

Lens becomes inflexible

Occurs with age

28
Q

What is the iris?

A

Aperture of the eye that forms the pupil

29
Q

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

What are their functions and innervation?

A

Sphincter pupillae: constricts pupil, parasympathetic innervation

Dilator pupillae: dilates pupil, sympathetic innervation

30
Q

What is the choroid?

What is its function?

A

Three layers of blood vessels in eye

Supplies nutrients to retina

31
Q

Where is the chorois located?

A

Between sclera and retina

32
Q

What are the major structures associated with the retina?

A

Optic nerve/disc

Macula and fovea

33
Q

What is the function of the macula and fovea?

A

Central vision

34
Q

Describe the fovea?

A

Avascular

High density of cones

35
Q

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

A

Choroid (beneath retina)

36
Q

What is the optic nerve formed by?

A

Axons of ganlgion cells as they exit the retina

37
Q

What is the lamina cribosa?

A

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

38
Q

Where is the blood supply to they eye derived from?

A

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

39
Q

What is the first branch of the opthalmic artery?

A

Central retinal artery

Pierces optic nerve to supply retina

40
Q

What are the three ciliary arteries?

A

Long posterior

Short posterior

Anterior

41
Q

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

A

Short posterior arteries stop at the optic nerve

Long posterior arteries travel all the way around the retina

42
Q

Where do posterior arteries pierce the eyeball?

A

Around the optic nerve

43
Q

Where do anterior ciliary arteries pierce the eyeball?

A

They don’t

Travel around to front of eyeball

44
Q

What are the vessels in the choroid fromed from?

A

Posterior ciliary artery

45
Q

What do the anterior ciliary arteries supply?

A

Anterior eye structures

46
Q

What do short posterior ciliary arteries supply?

A

Photoreceptors close to optic nerve and optic nerve head

47
Q

What does the central retinal artery supply?

A

Inner retinal layer

48
Q

What do the long posterior arteries supply?

A

Outer retina

Some anterior structures

49
Q

Describe the blood supply to the retina?

A

Central retinal artery supplies the inner retina

Long posterior ciliary artery supplies the outer retina

50
Q

Describe the eyelids?

A

Transition zone between skin and conjunctiva

Consist of glands, lashes, muscles and lacrimal apparatus

51
Q

Which muscles are associated with the eyelid?

Describe their actions and innervation?

A

Orbicularis oculi: depresses upper lid, innervated by CN VII

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

52
Q

What is special about the actions of th eyelid muscles?

A

Never work together

If one is contracted, the other is relaxed

Neuroscience (51 decks)

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