The Orbit Flashcards
location of bony orbit relative to the cranial fossae?
Inferior to the anterior cranial fossa
Anterior to the middle cranial fossa
apex and base of orbit
Apex points posteromedially
Base opens on to the face
what is contained in the pyramid shaped orbit?
Eyeball
Extraocular muscles
Lacrimal apparatus
bones of the orbit
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)
what runs through the optic canal?
optic nerve
ophthalmic artery
what runs through the superior orbital fissure?
III, IV, V1, VI
Superior ophthalmic vein
Sympathetic fibres
what runs through the inferior orbital fissure?
1) Maxillary branch of the trigeminal (v2) AFTER it passes through the foramen rotundum
2) Infra-orbital vessels
i. e. inferior ophthalmic vein
what are the intrinsic muscles of the eye involved in?
changing the size of the pupil and shape of the lens
what are the 3 intrinsic muscles of the eye?
1) Dilator pupillae - sympathetic [radial muscles]
2) Sphincter pupillae - parasympathetic [circular muscles of iris]
3) Ciliary muscle - parasympathetic [accomodation of lens]
what are the extrinsic muscles of the eye involved in?
elevating the eyelid and moving the eyeball
what are the extrinsic muscles of the eye?
1) 4 recti
2) 2 obliques
3) Eyelid muscles – Levator palpebral superioris (LPS) and orbicularis oculi
which muscles surrounds the eye on the face?
what nerve innervates it?
orbicularis oculi
facial nerve (temporal and zygomatic motor branches)
what is the effect of VII lesion on the eye? [3]
inability to shut eye tightly
tear spillage
dry eye
what does the LPS connect to in the eyelid?
tarsus: plate of dense connective tissue
what is the origin and insertion of LPS?
origin: lesser wing of sphenoid above optic foramen
insertion: tarsus
innervation of LPS
clinical relevance?
dual innervation
- mostly by III oculomotor
- sympathetic fibres innervates the superior tarsal muscle
in Horner’s Syndrome
adduction
movement towards midline
abduction
movement laterally
where do the four recti muscles originate and insert?
origin: common tendinous ring
insertion: 5mm behind the corneal margin
innervation of superior rectus
oculomotor (superior division of III)
innervation of medial rectus
oculomotor (inferior division )
innervation of inferior rectus
oculomotor (inferior division)
innervation of lateral rectus
abducens (VI)
action of lateral rectus
ABDuction
[abd- abducens]
action of medial rectus
adduction
action of superior rectus
elevation and adduction
action of inferior rectus
depression and adduction
innervation of superior oblique?
trochlear (IV)
innervation of inferior oblique?
oculomotor (III)
origin and insertion of inferior oblique ?
innervation?
Origin: Orbital surface of maxilla
Insertion: Posterior/inferior quadrant of eyeball
Innervation: III
function of inferior oblique
Extorsion (up and out)
Elevation and abduction
origin and insertion of superior oblique?
innervation?
Origin: Body of sphenoid
Insertion: posterior/superior quadrant of eyeball via trochlea
innervation: IV
function of superior oblique?
Intorsion (down and out)
Depression and abduction
what do all recti supplied by the oculomotor do?
which recti are they?
they all adduct (towards the midline)
superior, medial and inferior recti
which muscles intort?
superior oblique and superior rectus (into the eye)
what muscles extort?
inferior oblique and inferior rectus
extorsion
up and out
down and in
[extinct- DIe]
intorsion
up and in
down and out
fibres of ophthalmic branch of trigeminal
only sensory
However both parasympathetic and sympathetic nerve fibres hitchhike here
fibres of oculomotor
Motor fibres to MR, SR, IR, IO &LPS
parasympathetic motor component to the sphincter pupillae and ciliary body
how do sympathetic fibres reach the dilator pupillae
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.
individual nerves and muscles
Trochlear nerve (IV) - SO Abducens nerve (VI) - LR
where does the opth branch of V leave?
superior orbital fissure
3 branches of the opth branch of V
1) Lacrimal nerve
2) Frontal nerve;
- Supratrochlear
- Supraorbital
3) Nasociliary nerve:
- Ciliary branches
- Ethmoidal
- Infratrochlear
the two efferents components of oculomotor?
1) Motor to eye muscles
2) Parasympathetic motor to the sphincter pupillae and ciliary body
2 nuclei from which the oculomotor fibres emerge from?
1) oculomotor (GSE)
2) Edinger Westphal (GVE)
journey of CNIII
Leaves brain from the interpeduncular fossa
Passes along Cavernous sinus
divisions of CNIII
superior and inferior divisions (made just before entering orbit)
what is contained only in the inferior division of CNIII?
PNS component
through what structure do the inferior and superior divisions of CNIII go?
common tendinous ring in the superior orbital fissure
which muscles does the superior branch of CNIII innervate?
superior rectus and LPS
which muscles does the inferior branch of the CNIII innervate?
middle and inferior rectus
inferior oblique
where do the PNS fibres carried in the inferior branch of CNIII go to?
ciliary ganglion
where do the CNIII fibres go from the ciliary ganglion?
along ciliary nerves of V1 with T1 SNS fibres go to the sphincter pupillae and ciliary body
contraction leads to pupil constriction
do the sympathetic fibres that go along with the ciliary nerves originate form CNIII?
no, they originate from T1
they are hitchhikers
synapse at superior cervical ganglion at C2
where do the postganglionic fibres travel to?
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)
lacrimal nerve of CNVII
facial nerve parasympathetic fibres (VII) from the pterygopalatine ganglion use the lacrimal nerve to travel to the lacrimal gland
ciliary branches of nasocillary nerve (V1)
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
sympathetic fibres summary
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
parasympathetic fibres summary
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
journey of IV
middle cranial fossa
cavernous sinus
sup orbital fissure
superior oblique
journey of VI
posterior cranial fossa
middle cranial fossa
cavernous sinus alongside ICA
sup orbital fissure
lateral rectus
[lats, abs –> abducens for lateral rectus]
what two things meet at the cavernous sinus?
ICA and oculomotor nerve
3 branches of ophthalmic branch of V
1) frontal
2) lacrimal
3) nasociliary
hitchhiker nerves
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
what do the sympathetic fibres innervate?
superior tarsal muscle
dilator pupillae and blood vessels of the eye travelling along the ciliary nerves
testing motor function of CNIII
move eyeball in certain directions
testing PNS function of CNIII
- light reflex
- accommodation reflex
why is clinical testing for eye movement different to the anatomical movements?
you need to isolate the muscle by eliminating horizontal movement
the opposite horizontal movement is done first before testing elevation and depression
testing the the SR and IR
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]
testing the obliques
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]
testing the MR and LR
adduct and abduct
what are the 3 effects of CNIII lesion?
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)
how is the orbicularis oculi tested (VII)
screw eyes shut
how is the ophthalmic branch of V tested?
V1 is purely sensational therefore test dermatome and corneal reflex
what is the result of impaired SNS innervation?
Horner’s Syndrome ue to lesion in the upper symp trunk
what usually causes a lesion in the upper sympathetic trunk?
apex lung tumour (Pancoast’s tumour)
3 effects of upper sympathetic trunk lesion
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)
what is the effect of lesion to the entire oculomotor?
complete ptosis
arterial supply of the eye
ophthalmic artery (branch of the internal carotid artery)
6 branches of the ophthalmic artery
1) Supratrochlear
2) Muscular branches
3) Ciliary
4) Supraorbital
5) Lacrimal
6) Central artery of the retina
[Some Men Cut Soldiers Like Cheese]
venous drainage of orbit
2 channels
Superior ophthalmic vein
Inferior ophthalmic vein
superior ophthalmic vein pathway
1) through sup orbital fissure
2) into cavernous sinus
inferior ophthalmic vein pathway
1) joins the superior OV
2) passes through the sup. orbital fissure
3) into the inferior orbital fissure
4) joins pterygoid plexus
pupillary light reflex afferent
- 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)
pupillary light reflex efferent
- 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)
direct and consensual response to light
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.
what is the result of damage to the afferent (input) pathway in the light reflex?
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
corneal reflex afferent and efferent arms
Afferent: Sensation to touch is conducted via the ophthalmic Nerve (V1)
Efferent: Facial motor nucleus (VII) –> along facial nerve to orbicularis oculi
drainage of tears
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
innervation of lacrimal glands
PNS fibres from CNVII from pterygopalatine ganglion via zygomaticotemporal
then into lacrimal nerves
which nucleus do the PNS fibres to the lacrimal glands come from?
pathway to lacrimal gland?
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
