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Flashcards in Eye and orbit Deck (47)
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Which bone forms the roof of the orbit?

orbital plate of the frontal bone


Which bone forms the floor of the orbit?

orbital plate of the maxilla


Which bones form the lateral wall of the orbit?

zygoma and greater wing of sphenoid


Which bones form the medial wall of the orbit?

- front process of maxilla
- lacrimal bone
- orbital plate of ethmoid
- lesser wing of sphenoid


What are the 3 orbital foramina?

- optic canal
- inferior orbital fissure
- superior orbital fissure


What exits through the optic canal?

Optic nerve (II) and ophthalmic artery


What exits through the inferior orbital fissure?

Maxillary division of the trigeminal nerve (V2) and the infraorbital vessels


What exits through the superior orbital fissure?

- Ophthalmic division of the trigeminal nerve
- Oculomotor nerve
- Trochlear nerve
- Abducens nerve (VI)
- Ophthalmic vessels and Sympathetic fibres


How many extrinsic eye muscles are there and how are they divided?

4 recti
2 obliques


What are the 4 recti muscles?

Inferior, superior, medial and lateral


Where do the recti muscle originate and insert?

- Originate at the back of the obit, in the common tendinous ring
- Insert into the sclera, 5mm behind the corneal margin


What is the nerve supply to the recti muscles?

- Inferior, superior and medial recti supplied by oculomotor
- Lateral rectus supplied by abducens


What are the two oblique muscles?

inferior and superior


Where does the superior oblique originate, insert and what is its nerve supply?

- Originates in the body of the sphenoid
- Insert the globe in the posterior/superior quadrant, via the trochlear
- Nerve supply: trochlear


Where does the inferior oblique originate, insert and what is its nerve supply?

- Originates in the orbital surface of maxilla
- Insert the globe in the posterior/inferior quadrant
- Nerve supply: oculomotor


What are some symptoms of Horner's syndrome?

Ptosis (drooping upper eyelid), myosis (constriction) , aanhidrosis (inability to sweat)


What is the levator palpebrae superiosis?

muscle of the upper eyelid


Where does the levator palpebrae superiosis originate, insert and what is its nerve supply?

- Originates in the lesser wing of the sphenoid
- Inserts at the superior tarsal plate and skin of the eyelid
- Nerve supply: oculomotor (III) and sympathetic innervation to smooth muscle


If the muscles of the eye were working in isolation what would each of them do?

Lateral rectus: purely abduction action

Medial rectus: adducts towards midline

Superior oblique: depressor and abductor

Inferior oblique: elevator and abductor

Superior rectus: elevator and adductor

Inferior rectus: depressor and adductor


How can the eye muscles be tested (LR, MR)?

The lateral rectus: abducts in right eye, adducts in left

The medial rectus: adducts in left eye, adducts in right


How can IR and SO be tested for?

IR, SO are involved in depressing the eye. Therefore, asking a patient to look down will not test the function of any one muscle in isolation. To test function, you adduct or abduct the eye, before asking the patient to look down.

- When the eye adducts towards the midline, the only muscle contributing to depression then is the SO
- When the eye abducts away from the midline, the only muscle contributing to depression is the IR


What makes up the optic nerve?

The axons from the ganglion cells in the retina


What does the oculomotor nerve do?

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


What does the trochlear nerve do?

Motor fibres to SO


What does the abducens nerve do?

Motor fibres to LR


What are the nerves of the orbit?

- optic
- oculomotor
- trochlear
- opthalmic
- abducens


Describe the pathway of the opthalmic nerve

It travels laterally to the cavernous sinus and gives rise to the recurrent tentorial branch (which supplies the tentorium cerebelli).
It then exits the cranium via the superior orbital fissure, where it divides into its 3 branches.


What are the three branches of the opthalmic division of the trigeminal?
What do they do

- Frontal nerve, lacrimal nerve and nasociliary nerve
- Provide sensory innervation to the skin and mucous membranes of the structures derived from the frontonasal prominenc


Which nerves pass through the carvernous sinus (sits either side of the sphenoid)?

- trochlear
- oculomotor
- abducens
- maxillary division of trigeminal
- opthalmic division of trigeminal


Which artery passes through the sinus?

internal carotid