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Year 2 - LCRS - Anatomy of the Head, Neck and Spine > Session 5: Orbit > Flashcards

Session 5: Orbit Flashcards

1
Q

What bones make up the orbit?

A
  • Maxilla
  • Lacrimal bone
  • Zygomatic bone
  • Spheniod bone
  • Ethmoid Bone
  • Frontal Bone
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2
Q

What makes up the roof of the orbit?

A

the orbital plate of the frontal bone

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3
Q

What makes up the floor of the orbit?

A

orbital plate of maxilla

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4
Q

What makes up the lateral wall of the orbit?

A
  • zygoma

- greater wing of the sphenoid

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5
Q

What makes up the medial wall of the orbit?

A
  • Frontal process of maxilla
  • Lacrimal bone
  • Orbital plate of ethmoid
  • Lesser wing of sphenoid
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6
Q

What are the foramina in the orbit?

A
  • optic canal (quite round?)
  • inferior orbital fissure
  • superior orbital fissure
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7
Q

What passes through the optic canal?

A
  • Optic nerve (II)

- ophthalmic Artery

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8
Q

What passes through the inferior orbital fissure?

A
  • maxillary nerve (V2)

- infraorbital vessles

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9
Q

What passes through the superior orbital fissure?

A
  • ophthalmic nerve (V1)
  • oculomotor nerve (III)
  • trochlear nerve (IV)
  • abducens nerve (VI)
  • ophthalmic vessles
  • sympathetic fibres
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10
Q

What is a blowout fracture?

A
  • The floor of the orbit can be fractured e.g. squash game injury.
  • the eye drops slightly
  • causes problems like double vision
  • sometimes it has to be surgically fixed
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11
Q

What are the extrinsic eye muscles divided into?

A

Recti and obliques

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12
Q

What are the 4 recti muscles of the eye?

A
  • superior
  • inferior
  • medial
  • lateral
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13
Q

Where do the recti muscles originate from?

A

common tendinous ring

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14
Q

Where do the recti muscles insert?

A
  • sclera

- 5mm behind corneal margin

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15
Q

What is the nerve supply to the recti muscles?

A
  • superior, inferior and medial are supplied by CN3 (oculomotor)
  • lateral is supplied by CN VI (abducens)
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16
Q

What are the 2 oblique muscles of the eye?

A

Superior and inferior

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17
Q

Where does the superior oblique originate?

A

Body of sphenoid (at tendinous ring)

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18
Q

Where does the superior oblique insert?

A

posterior/superior quadrant via trochlea

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19
Q

Where does the inferior oblique originate?

A

orbital surface of maxilla

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20
Q

Where does the superior oblique insert?

A

post/inferior quadrant

21
Q

What is the nerve supply of the superior oblique?

A

CNIV (trochlear)

22
Q

What is the nerve supply of the inferior oblique?

A

CNIII (oculomotor)

23
Q

Levator palpebrae superioris (LPS)

A
  • Muscle of upper eyelid
  • Origin: Lesser wing of sphenoid
  • Insertion: Superior tarsal plate and skin of eyelid
  • Nerve supply: III + sympathetic to smooth muscle
24
Q

What is the muscle of the upper eyelid?

A

Levator palpebrae superioris (LPS)

25
Q

trochlea

A

bony spur in the medial aspect of the orbit

26
Q

Why is the levator palpebrae clinically important?

A
  • It receives sympathetc innervation

- in Horners Syndrome there is drooping of the eyelid

27
Q

What eye movement does the contraction of the superior oblique cause?

A
  • away from the midline and down
28
Q

What eye movement does the contraction of the inferior oblique cause?

A

out and up

29
Q

What eye movements do the lateral and medial recti muscles cause?

A

Medial: adduction towards midline
lateral: abduction away from the midline

30
Q

What eye movements do the superior and infeior recti cause?

A
  • apart from the elevation / depression they cause adduction and move the eye towards the midline
    (BUT: this is re anatomy, not IRL because IRL they do not work in an isolated fashion but together)
31
Q

How do you test eye muscle (and CN) function?

A
  • lateral and medial rectus: follow finger on horizontal line
  • superior oblique: ask the patient to move the eye in and down (this is how you test the trochlear nerve)
32
Q

Why is following a vertical line not useful for testing the function of the superior and inferior recti muscles?

A

Because they are not the only ones moving the eye up and down, the obliques do that to. You are not isolating the muscles that way.

-> ask the patient to adduct/abduct the eye to test the function of the superior / inferior ***

33
Q

optic nerve

A
  • made up of axons from the ganglion cells in the retina

- CNII

34
Q

Oculomotor Nerve

A
  • CN3
  • 2 rami
  • motor fibres to: MR, SR, IR, IO & LPS
  • parasympathetic fibres
35
Q

Trochlear nerve

A
  • CNIV

- motor fibres to SO

36
Q

Abducens nerve

A
  • motor fibres to LR

- CNVI

37
Q

What are all the nerves of the orbit?

A
  • CNII (optic)
  • CNIII (oculomotor)
  • CNIV (trochlear)
  • CNVI (abducens)
  • V1 (ophthalmic, brach of trigeminal): lacrimal and frontal and nasociliary branches
  • ciliary ganglion
    => CNs run through the cavernous sinus (not II)
38
Q

Which nerves run through the cavernous sinus?

A
  • III
  • IV
  • V1 (ophthalmic)
  • V2 (maxillary)
  • VI
39
Q

Which nerve in the cavernous sinus tends to run along the internal carotid artery rather than along the wall?

A

Abducens (CNVI)

40
Q

What are the branches of the ophthalmic (V1) nerve?

A
  • lacrimal
  • frontal (-> supratrochlear and supraorbital (-> this supplies i.e. forehead))
  • nasociliary (-> branch to the ciliary ganglion, ethmoidal, infratrochlear branches)
41
Q

Ciliary ganglion

A
  • parasympathetic
  • preganglionic fibres in inferior ramus of oculomotor
  • postganglionic fibres in short ciliary nerves
  • sphincter pupillae & ciliary muscle
42
Q

What are the blood vessles of the orbit?

A
  • ophthalmic artery

- opthalmic vein

43
Q

Ophthalmic artery

A
  • central artery of the retina
  • muscular branches
  • ciliary
  • lacrimal
  • supratrochlear
  • supraorbital
44
Q

Ophthalmic veins

A
  • superior (drains into the cavernous sinus, potential route of infection of the cranial cavity)
  • inferior (drains into the pterygoid plexus)
45
Q

Where is the lacrimal gland?

A

In the anterolateral superior orbit

46
Q

What makes up the lacrimal system?

A
  • lacrimal gland
  • lacrimal sac (medial canthus of the eye, drains into nose into the inferior meatus of the nose via: )
  • nasolacrimal duct
47
Q

Control of lacrimation

A
  • parasympathetic secretomotor fibres (CNVII) from pterygopalatine ganglion (behind the cheek) via zygomaticotemporal and finally lacrimal nerves
  • tears have a protective function (cornea)
48
Q

What might you suspect if a patient complains of dry eyes?

A
  • problems with the parasympathetic system - no production of tears

Year 2 - LCRS - Anatomy of the Head, Neck and Spine (6 decks)

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