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Orbit and eyes Flashcards

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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?

Study These Flashcards
A

Ciliary processes (ciliary epithelium)

Ciliary muscle

22
Q

What are the functions of the ciliary body?

Study These Flashcards
A

Formation of aqueous humour (ciliary epithelium)

Tethers lens (ciliary processes)

Accommodation (ciliary muscle)

23
Q

Where is aqueous humour produced?

Describe its pathway?

Study These Flashcards
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?

Study These Flashcards
A

Ciliary muscle

Zonules that attach to lens

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
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
27
What is presbyopia?
Condition in which we lose our ability focus Lens becomes inflexible Occurs with age
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
32
What are the major structures associated with the retina?
Optic nerve/disc Macula and fovea
33
What is the function of the macula and fovea?
Central vision
34
Describe the fovea?
Avascular High density of cones
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
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
40
What are the three ciliary arteries?
Long posterior Short posterior Anterior
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
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
52
What is special about the actions of th eyelid muscles?
Never work together If one is contracted, the other is relaxed

Neuroscience (51 decks)

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