Extraocular Muscles Flashcards
What are the extraocular muscles
- Levator palpebrae superioris
- 4 Recti
- Superior oblique muscle
- Inferior oblique muscle
Levator palpebrae superioris origin
Orbital roof in front of optic foramen
Levator palpebrae superioris insertion
Under orbital roof into tarsus and skin of upper eyelid
Superior conjunctival fornix
Levator palpebrae superioris nerve supply
Oculomotor 3rd cranial nerve
Levator palpebrae superioris action
Elevates upper eyelid
Muscle deep part (muller’s muscle) is smooth and supplied by sympathetic fibers
4 Recti origin
- Common tendinous ring surrounding optic foramen and medial part of superior orbital fissure
- Each arises from ring corresponding side
- Lateral rectus has head from superior orbital fissure
4 Recti insertion
Each passes forward to be inserted into sclera short distance behind corneoscleral junction (51/2-71/2mm)
MR: 51/2 mm
IR: 61/2 mm
LR: 7 mm
Sr: 71/2 mm
4 Recti nerve supply
Oculomotor 3rd cranial nerve
Except lateral rectus: abducent 6th cranial nerve
Lateral rectus muscle action
Moves eyeball lateral (abduction)
Medial rectus muscle action
Moves eyeball medial (adduction)
Movements of abduction and adduction occur around on…
Imaginary vertical axis
Superior rectus muscle action
Moves eyeball upwards (elevates) and medial (adducts) with slight intorsion
Inferior rectus muscle action
Moves eyeball downwards (depresses) and medial (adducts) with slight extorsion
Movements of intorsion and extorsion occur around…
Imaginary anteroposterior diameter
Movements of upwards and downwards occur around…
Imaginary transverse axis
Superior oblique muscle origin
- Orbital roof above and medial to optic foramen
- Lies just above and medial superior rectus origin
Superior oblique muscle insertion
Tendon passes forwards through Trochlea then curves backwards and downwards and lateral to insert into sclera behind eyeball equator
Superior oblique muscle nerve supply
Trochlear 4th cranial nerve
Superior oblique muscle action
Moves eyeballs downwards (depresses) and lateral (abducts) with intorsion
Inferior oblique muscle origin
Floor of orbit just lateral to Nasolacrimal groove
Inferior oblique muscle insertion
Muscle passes backwards and upwards and lateral below eyeball to insert into sclera behind eyeball equator
Inferior oblique muscle nerve supply
Oculomotor 3rd cranial nerve
Inferior oblique muscle action
Moves eyeball upwards (elevates) and lateral (abducts) with extorsion
