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LCRS 2 - HNS Part 2 > The orbit > Flashcards

The orbit Flashcards

1
Q 
What make up the 
i. roof 
ii. Floor
iii. lateral wall 
of the orbit
A

Roof: orbital plate of the frontal bone
Floor: orbital plate of the maxilla
lateral wall: Zygoma and greater wing of sphenoid

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2
Q

What makes up the medial wall of the orbit

A

frontal process of maxilla, lacrimal bone, orbital plate of ethmoid bone, lesser wing of sphenoid

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3
Q

contents of Optic canal

A 
Optic nerve (II)
Ophthalmic artery (first branch of the internal carotid artery distal to the cavernous sinus)
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4
Q

Contents of inferior orbital fissure

A

V2, ifraorbital vessel

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5
Q

Superior orbital fissure

A

Cranial nerve 3, 4 and 6, and V1. Opthalmic vein and sympathetic fibres (running with vessels)

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6
Q

In which bones are the foramina found

A

Optic canal- lesser wing of sphenoid

Sup. orbital fissure- between the lesser and greater wings of the sphenoid bone

Inf. orbital fissure- sphenoid bone nad maxilla (posterior wall of the eye too, as the orbital plate of the maxilla runs back! (frontal process of maxlla is one of bones making up medial wall of orbit)

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7
Q

Where is the origin of the 4 recti, where do they insert

A

origin Common tendinous ring

insert Sclera, 5mm behind corneal margin

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8
Q

Nerve supply to rectus muscles

A

medial, super and infer = 3

lateral= 6

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9
Q

2 oblique muscles

A

inferior and superior

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10
Q

origin of oblique muscles

A

Inferior: orbital surface of maxilla
Superior: body of the sphenoid

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11
Q

Insertion of oblique muscles

A

Superior: posterior/superior quadrant, via trochlea (bony spur in the orbit!)

Inferior: post/inferior quadrant

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12
Q

Nerve supply of oblique muscles

A

inferior is 3, superior is 4

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13
Q

Origin, insertion and nerve supply of levator palpebrae superioris (LPS)

A

Origin=lesser wing of sphenoid

Insertion= superior tarsal plate and skin of eyelid

Nerve supply= III + sympathetic to smooth muscle

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14
Q

Why is synpathetic supply of LPS clinically important

A

Because in horners syndrome which involves loss of sympathetic ouput to head and neck, there is drooping of the eyelid (=ptosis)….. also lack of sweating, constricted pupil and endopthalmos in this condition

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15
Q

What is the trochlea

A

a small bony spur on the medial part of orbit

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16
Q

Contraction of superior oblique (isolated)

A

down and out depressor and abductor

17
Q

Contraction of inferior oblique (isolatesd)

A

up and out elevator and abductor

18
Q

Contraction of superior and inferior recti (isolated)

A

Superior elevatnes and adducts

Inferior depresses and adducts

19
Q

How to test lateral and medial rectus

A

Tracking (moving finger left and right), but remember that version will involve opposite muscle in each eye

20
Q

How to test function of superior oblique

A

they have to adduct that eye, and look down this removes the effect of the inferior rectus on depression of eye

21
Q

How to test function of inferior rectus

A

you have to abduct the eye and ask them to look down this removes the effect of the superior oblique on depression of the eye

22
Q

How to test the function of the inferior oblique

A

Adduct the eye and look up removes the effect of superior rectus

23
Q

How to test the function of the superior rectus

A

Abduct the eye and look up and up removes effect of inferior oblique

24
Q

Nerves of the orbit

A

Optic (retinal ganglion cell axons)

Oculomotor (2 rami, motor fibres to MR, SR IR, IO and LPS, parasymathetic fibres)…. oculomotor has superior brainch (innervates superior rectus and LPS, and inferior which does everything else. Sympathetic nerves from the internal carotid plexus travel with the superior branch to innervate the superior tarsal muscle , which helps maintain opened eyelid after LPS has opened it)

Trochlear (Motor fibres to SO)

Abducens (motor fibres to LR)

25
Q

Branches of the opthalmic division of the trigeminal nerve

A

Lacrimal, frontal and nasociliary

26
Q

Order of nerves in the lateral wall of the cavernous sinus (this is the area postero-medial to the orbit so it makes sense!)

A

This is where the nerves travel, after emerging from the brainstem, just before they’re about to go into the superior and inferior orbital fissure!

SO, in the order they emerge from the brainstem!

Oculomotor, trochlear (then more medially), abducens…..

Then opthalmic branch of trigeminal and maxillary branch of the trigeminal….

From here, oculomotor, trochlear, abducens and V1 go through the superior orbital fissure, but V2 then goes through the inferior orbital fissure!

27
Q

Which nerve runs near the internal carotid artery and is thus a bit furhter from the wall of the cavernus sinus

A

abducent

28
Q

Clinical relevance of the nerves in the cavernous sinus

A

Infection or cavernous sinus thrombosis can lead to problems with these nerves

29
Q

Branches of the lacrimal, frontal and nasociliary branch of V1

A

Lacrimal (none listed)

Frontal- supratrochlear and supraorbital (which emerges through supraorbital foramen to supply forehead!!!!!)

Nasociliary- branch to ciliay ganglion, ethmoidal and infratrochlear

30
Q

Outline the nerves in the preganglionic and post ganglionic parasynpathetic innervation to eye.

Which muscle(s) are innervated

A

Preganglionic= in the inferior rami of the 3rd cranial nerve

CILIARY GANGLION

Postganglionic= in short ciliary nerves

Innervating the ciliary muscle and the spinchter pupillae

31
Q

What does the opthalmic artery divide into

A 
central artery of the retina
muscular branches
ciliary
lacrimal
supratrochlear
supraorbital
32
Q

What do opthalmic veins divide into

A

drains back to superior (cavernous sinus)= ROUTE OF INFECTION

inferior (pterygoid plexus)

33
Q

What does papilloedema show

A

Its swelling at back of the eye showing inreased intracranial pressure

34
Q

State the innervation of the lacrimal gland

A

parasympathetic secretomotor fibres (CNVII) from pterygopalatine ganglion via zygomaticotemporal (which is a branch of V2) and finally lacrimal nerves

35
Q

Where is the lacrimal sac

A

medial canthas of the eye

36
Q

Where does the nasolacrimal duct drain

A

Into the internal meatus of the nose

37
Q

Outline the autonomic control of the eyelid….

What is the effect of the following:

  1. Damage to the oculomotor nerve
  2. Damage to sympathetic nerves
A

Both open the eyelid….

CN3 innervates levator palpabrae superioris…. damage to this nerve results in significant ptosis. This is skeletal muscle so has somatic input

Attached to the LPS is the superior tarsal muscle….
this muscle helps the eyelid to remain open once it has been opened by LPS. It is sometimes referred to as the smooth muscle component of LPS. It is innervated by sympathetic fibres and it will cause a slight ptosis if the sympathetic nerves are damaged e.g. in horners syndrome

LCRS 2 - HNS Part 2 (5 decks)

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