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Anatomy Head And Spine > The Orbit > Flashcards

The Orbit Flashcards

1
Q

location of bony orbit relative to the cranial fossae?

A

Inferior to the anterior cranial fossa

Anterior to the middle cranial fossa

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2
Q

apex and base of orbit

A

Apex points posteromedially

Base opens on to the face

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3
Q

what is contained in the pyramid shaped orbit?

A

Eyeball
Extraocular muscles
Lacrimal apparatus

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4
Q

bones of the orbit

A

1) sphenoid (greater makes lateral wall and lesser wing makes medial wall)
2) frontal bone (roof-orbital plate)
3) ethmoid (medial wall- orbital plate)
4) lacrimal (medial wall)
5) maxilla (floor- orbital plate, medial wall- frontal process)
6) zygoma (lateral wall-orbital plate)

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5
Q

what runs through the optic canal?

A

optic nerve

ophthalmic artery

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6
Q

what runs through the superior orbital fissure?

A

III, IV, V1, VI
Superior ophthalmic vein
Sympathetic fibres

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7
Q

what runs through the inferior orbital fissure?

A

1) Maxillary branch of the trigeminal (v2) AFTER it passes through the foramen rotundum

2) Infra-orbital vessels
i. e. inferior ophthalmic vein

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8
Q

what are the intrinsic muscles of the eye involved in?

A

changing the size of the pupil and shape of the lens

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9
Q

what are the 3 intrinsic muscles of the eye?

A

1) Dilator pupillae - sympathetic [radial muscles]
2) Sphincter pupillae - parasympathetic [circular muscles of iris]
3) Ciliary muscle - parasympathetic [accomodation of lens]

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10
Q

what are the extrinsic muscles of the eye involved in?

A

elevating the eyelid and moving the eyeball

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11
Q

what are the extrinsic muscles of the eye?

A

1) 4 recti
2) 2 obliques
3) Eyelid muscles – Levator palpebral superioris (LPS) and orbicularis oculi

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12
Q

which muscles surrounds the eye on the face?

what nerve innervates it?

A

orbicularis oculi

facial nerve (temporal and zygomatic motor branches)

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13
Q

what is the effect of VII lesion on the eye? [3]

A

inability to shut eye tightly
tear spillage
dry eye

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14
Q

what does the LPS connect to in the eyelid?

A

tarsus: plate of dense connective tissue

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15
Q

what is the origin and insertion of LPS?

A

origin: lesser wing of sphenoid above optic foramen
insertion: tarsus

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16
Q

innervation of LPS

clinical relevance?

A

dual innervation

  • mostly by III oculomotor
  • sympathetic fibres innervates the superior tarsal muscle

in Horner’s Syndrome

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17
Q

adduction

A

movement towards midline

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18
Q

abduction

A

movement laterally

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19
Q

where do the four recti muscles originate and insert?

A

origin: common tendinous ring
insertion: 5mm behind the corneal margin

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20
Q

innervation of superior rectus

A

oculomotor (superior division of III)

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21
Q

innervation of medial rectus

A

oculomotor (inferior division )

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22
Q

innervation of inferior rectus

A

oculomotor (inferior division)

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23
Q

innervation of lateral rectus

A

abducens (VI)

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24
Q

action of lateral rectus

A

ABDuction

[abd- abducens]

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25
Q

action of medial rectus

A

adduction

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26
Q

action of superior rectus

A

elevation and adduction

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27
Q

action of inferior rectus

A

depression and adduction

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28
Q

innervation of superior oblique?

A

trochlear (IV)

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29
Q

innervation of inferior oblique?

A

oculomotor (III)

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30
Q

origin and insertion of inferior oblique ?

innervation?

A

Origin: Orbital surface of maxilla

Insertion: Posterior/inferior quadrant of eyeball

Innervation: III

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31
Q

function of inferior oblique

A

Extorsion (up and out)

Elevation and abduction

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32
Q

origin and insertion of superior oblique?

innervation?

A

Origin: Body of sphenoid

Insertion: posterior/superior quadrant of eyeball via trochlea

innervation: IV

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33
Q

function of superior oblique?

A

Intorsion (down and out)

Depression and abduction

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34
Q

what do all recti supplied by the oculomotor do?

which recti are they?

A

they all adduct (towards the midline)

superior, medial and inferior recti

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35
Q

which muscles intort?

A

superior oblique and superior rectus (into the eye)

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36
Q

what muscles extort?

A

inferior oblique and inferior rectus

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37
Q

extorsion

A

up and out
down and in

[extinct- DIe]

38
Q

intorsion

A

up and in

down and out

39
Q

fibres of ophthalmic branch of trigeminal

A

only sensory

However both parasympathetic and sympathetic nerve fibres hitchhike here

40
Q

fibres of oculomotor

A

Motor fibres to MR, SR, IR, IO &LPS

parasympathetic motor component to the sphincter pupillae and ciliary body

41
Q

how do sympathetic fibres reach the dilator pupillae

A

These hitchhike onto the oculomotor nerve to reach the superior tarsal muscle and onto V1 to reach the dilator pupillae and blood vessels of the eye.

42
Q

individual nerves and muscles

A 
Trochlear nerve (IV) - SO
Abducens nerve (VI) - LR
43
Q

where does the opth branch of V leave?

A

superior orbital fissure

44
Q

3 branches of the opth branch of V

A

1) Lacrimal nerve
2) Frontal nerve;
- Supratrochlear
- Supraorbital

3) Nasociliary nerve:
- Ciliary branches
- Ethmoidal
- Infratrochlear

45
Q

the two efferents components of oculomotor?

A

1) Motor to eye muscles

2) Parasympathetic motor to the sphincter pupillae and ciliary body

46
Q

2 nuclei from which the oculomotor fibres emerge from?

A

1) oculomotor (GSE)

2) Edinger Westphal (GVE)

47
Q

journey of CNIII

A

Leaves brain from the interpeduncular fossa

Passes along Cavernous sinus

48
Q

divisions of CNIII

A

superior and inferior divisions (made just before entering orbit)

49
Q

what is contained only in the inferior division of CNIII?

A

PNS component

50
Q

through what structure do the inferior and superior divisions of CNIII go?

A

common tendinous ring in the superior orbital fissure

51
Q

which muscles does the superior branch of CNIII innervate?

A

superior rectus and LPS

52
Q

which muscles does the inferior branch of the CNIII innervate?

A

middle and inferior rectus

inferior oblique

53
Q

where do the PNS fibres carried in the inferior branch of CNIII go to?

A

ciliary ganglion

54
Q

where do the CNIII fibres go from the ciliary ganglion?

A

along ciliary nerves of V1 with T1 SNS fibres go to the sphincter pupillae and ciliary body

contraction leads to pupil constriction

55
Q

do the sympathetic fibres that go along with the ciliary nerves originate form CNIII?

A

no, they originate from T1
they are hitchhikers
synapse at superior cervical ganglion at C2

56
Q

where do the postganglionic fibres travel to?

A

carotid plexus and ophthalmic artery

from the carotid plexus:

1) Superior tarsal muscle (via superior branch of the oculomotor nerve*)
2) Dilator pupillae (via the ciliary nerves of V1)
3) Blood vessels of the eye (via the ciliary nerves of V1)

57
Q

lacrimal nerve of CNVII

A

facial nerve parasympathetic fibres (VII) from the pterygopalatine ganglion use the lacrimal nerve to travel to the lacrimal gland

58
Q

ciliary branches of nasocillary nerve (V1)

A

1) Oculomotor parasympathetic fibres (III) to inferior branch of III to the ciliary ganglion. From here, the fibres leave III and hitchhike onto the ciliary branches of V1 to travel to the:
Sphincter pupillae and the ciliary body

2) Sympathetic fibres (T1) from the superior cervical ganglion travel to the carotid plexus and then use the ciliary branches of V1 to travel to the
Dilator pupillae
Blood vessels of the eye

59
Q

sympathetic fibres summary

A

T1
superior cervical ganglion (at C2)
Carotid plexus
1) fibres hitchhike onto the superior branch of the oculomotor nerve to reach the superior tarsal muscle
2) fibres hitchhike onto the ciliary branches of the nasociliary nerve (V1) to reach the dilator pupillae and blood vessels of the eye

60
Q

parasympathetic fibres summary

A

1) Edinger Westphal nucleus (III)
Oculomotor nerve inferior branch
ciliary ganglion:
ciliary branches of the nasociliary nerve (V1) to reach the sphincter pupillae and ciliary body.

2) Facial nerve fibres (VII) eventually hitchhike onto the lacrimal nerve (V1) to reach the lacrimal gland

61
Q

journey of IV

A

middle cranial fossa
cavernous sinus
sup orbital fissure

superior oblique

62
Q

journey of VI

A

posterior cranial fossa
middle cranial fossa
cavernous sinus alongside ICA
sup orbital fissure

lateral rectus

[lats, abs –> abducens for lateral rectus]

63
Q

what two things meet at the cavernous sinus?

A

ICA and oculomotor nerve

64
Q

3 branches of ophthalmic branch of V

A

1) frontal
2) lacrimal
3) nasociliary

65
Q

hitchhiker nerves

A

Parasympathetic GVE fibres from the facial nerve (VII) hitchhike on V2 (zygomatic) and then the lacrimal branch of V1
From here they travel to the lacrimal gland

Parasympathetic GVE fibres from the oculomotor nerve (III) travel to the ciliary ganglion and then hitchhike on the short ciliary nerve to the sphincter pupillae and ciliary body

Sympathetic fibres (T1) from the superior cervical ganglion travel to the carotid plexus and then hitchhike onto the ciliary nerves –> dilator pupillae and the blood vessels of the eye

66
Q

what do the sympathetic fibres innervate?

A

superior tarsal muscle

dilator pupillae and blood vessels of the eye travelling along the ciliary nerves

67
Q

testing motor function of CNIII

A

move eyeball in certain directions

68
Q

testing PNS function of CNIII

A
  • light reflex

- accommodation reflex

69
Q

why is clinical testing for eye movement different to the anatomical movements?

A

you need to isolate the muscle by eliminating horizontal movement

the opposite horizontal movement is done first before testing elevation and depression

70
Q

testing the the SR and IR

A

The superior and inferior recti adduct the eye, and therefore, to test them, you need to abduct the eye first

SR–> look laterally and up
LR–> look laterally and downward
[look laterally as they normally would adduct]

71
Q

testing the obliques

A

The obliques abduct the eye, and therefore, to test them, you need to adduct the eye first.

IO–> look medially and up
SO–> look medially and down
[look medially as both normally abduct]

72
Q

testing the MR and LR

A

adduct and abduct

73
Q

what are the 3 effects of CNIII lesion?

A

1) Loss of movement of ocular muscles except LR and SO.
- Eye in ‘down and out’ position

2) Loss of innervation to the levator palpabrae superioris
- Complete ptosis

3) Loss of parasympathetic function
- Dilated pupil (mydriasis)
(The sympathetic nerves travel to the dilator pupillae by hitchhiking and therefore are not affected in an oculomotor palsy)

74
Q

how is the orbicularis oculi tested (VII)

A

screw eyes shut

75
Q

how is the ophthalmic branch of V tested?

A

V1 is purely sensational therefore test dermatome and corneal reflex

76
Q

what is the result of impaired SNS innervation?

A

Horner’s Syndrome ue to lesion in the upper symp trunk

77
Q

what usually causes a lesion in the upper sympathetic trunk?

A

apex lung tumour (Pancoast’s tumour)

78
Q

3 effects of upper sympathetic trunk lesion

A

1) Partial ptosis:
only the superior tarsal muscle is affected, not the levator palpebrae superioris

2) Miosis (constricted pupil):
As the dilator pupillae is affected

3) Anhydrosis (reduced sweating)

79
Q

what is the effect of lesion to the entire oculomotor?

A

complete ptosis

80
Q

arterial supply of the eye

A 
ophthalmic artery 
(branch of the internal carotid artery)
81
Q

6 branches of the ophthalmic artery

A

1) Supratrochlear
2) Muscular branches
3) Ciliary
4) Supraorbital
5) Lacrimal
6) Central artery of the retina

[Some Men Cut Soldiers Like Cheese]

82
Q

venous drainage of orbit

A

2 channels
Superior ophthalmic vein
Inferior ophthalmic vein

83
Q

superior ophthalmic vein pathway

A

1) through sup orbital fissure

2) into cavernous sinus

84
Q

inferior ophthalmic vein pathway

A

1) joins the superior OV
2) passes through the sup. orbital fissure
3) into the inferior orbital fissure
4) joins pterygoid plexus

85
Q

pupillary light reflex afferent

A
  • Nasal and temporal fibres leave the eye and nasal fibres cross at the optic chiasm
  • Firing occurs down both left and right optic tracts
  • The relevant neurones exit and synapse with neurones in the pretectal nucleus
  • There is then communication with the EW nucleus

afferent input in one eye caused efferent in both (direct and consensual)

86
Q

pupillary light reflex efferent

A
  • Preganglionic parasympathetic fibres from E-W nuclei (III) travel in the inferior branch of the oculomotor nerve (III)
    [inferior branch only carried PNS]
  • Synapse in ciliary ganglion.
  • Postganglionic parasympathetic fibres carried in the ciliary nerves (V1) to innervate
  • Both sphincter pupillae (direct and consensual)
87
Q

direct and consensual response to light

A

When the pretectal nucleus receives an afferent input, it communicates with both Edinger-Westphal nuclei such that there is an efferent response in the ipsilateral (direct response) and contralateral (consensual response) eyes.

88
Q

what is the result of damage to the afferent (input) pathway in the light reflex?

A

Relevant Afferent Pupillary Defect (RAPD)

  • light in undamaged eye causes constriction in both eyes
  • light in damaged eye, no afferent response therefore no efferent so eye stop constriction and dilate to neutral
89
Q

corneal reflex afferent and efferent arms

A

Afferent: Sensation to touch is conducted via the ophthalmic Nerve (V1)

Efferent: Facial motor nucleus (VII) –> along facial nerve to orbicularis oculi

90
Q

drainage of tears

A

1) Lacrimal gland secretes tears
2) Washed inferomedially on blinking
3) Drain via the lacrimal canaliculi into the lacrimal sac
4) down nasolacrimal duct
5) into anterior part of inferior meatus

91
Q

innervation of lacrimal glands

A

PNS fibres from CNVII from pterygopalatine ganglion via zygomaticotemporal

then into lacrimal nerves

92
Q

which nucleus do the PNS fibres to the lacrimal glands come from?

pathway to lacrimal gland?

A

superior salivatory nucleus

into internal auditory meatus eventually to pterygopalatine ganglion, travel to lacrimal gland alongside the zygomaticotemporal nerve

meets the lacrimal nerve of V

Anatomy Head And Spine (5 decks)

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