anatomy of the extraocular muscles Flashcards
what are the 4 rector muscles?
superior
inferior
medial
lateral rectus
what are the 2 oblique muscles?
superior
inferior
what are the 7 extraocular skeletal muscles?
4 rectus muscles
2 oblique muscles
levator palpebrae superioris
what are the rectus and oblique muscles responsible for?
eye movement
what is the role of levator palpebrae superioris?
superior eyelid movement
where do all the rectus muscles originate?
common tendinous ring
where do all the rectus muscles insert?
onto sclera
where do the oblique muscles insert?
onto eyeball at oblique angle
where does the superior oblique muscle originate from?
sphenoid bone
where does the inferior oblique muscle originate from?
orbital plate of maxilla
before inserting onto the eyeball, where does the tendon of the superior oblique pass through?
a trochlea (loop of connective tissue)
what is the only muscle involved in raising the superior eyelid?
LPs
where is the origin of the LPA?
lesser wing of sphenoid
where does LPS insert?
skin and tarsus of superior eyelid
what is Mueller’s muscle?
a collection of smooth muscle fibres in the superior tarsal muscle
what does Mueller’s muscle assist with?
LPS in opening the eyelid
what is the difference in innervation between Mueller’s muscle and LPS?
Mueller’s muscle - sympathetic fibres from superior cervical ganglion
LPS - CN III (oculomotor)
what causes ptosis in Horner’s syndrome?
sympathetic innervation of Mueller’s muscle is compromised as Mueller’s muscle assists in opening eyelid
which direction does the lateral rectus look?
laterally
what supplies lateral rectus?
CN VI (abducent nerve)
which direction does the superior oblique look?
medial, down
what is superior oblique supplied by?
CN IV (trochlear nerve)
what are all other muscles of the eye supplied by?
CN III (oculomotor)
which two muscles don’t have secondary movements?
medial and lateral rectus
where do all movements occur from?
primary position e.g. gaze directed forward
what do we have to do to test movements of individual muscles?
line up gaze plane of muscles being tested to isolate muscle movements
how do we test superior rectus muscle (oculomotor)?
ask patient to look laterally and upward
how do we test inferior rectus muscle (oculomotor)?
ask patient to look laterally and downward
how do we test lateral rectus muscle (abducent)?
ask patient to look laterally
how do we test medial rectus muscle (oculomotor)?
ask patient to look medially
how do we test inferior oblique muscle (oculomotor)?
ask patient top look medially and upward
how do we test superior oblique muscle (trochlear)?
ask patient to look medially and downward
what is the only movement lateral rectus can do?
abduct eyeball
when in abduction, what is the only thing the superior rectus muscle can do?
elevate eyeball
when in abduction, what is the only thing the inferior rectus can do?
depress eyeball
what is the only thing the medial rectus muscle can do?
adduct eyeball
when in adduction, what is the only thing the inferior oblique can do?
elevate eyeball
when in adduction, what is the only thing the superior oblique can do?
depress eyeball
what muscles are involved in pure elevation of the eye?
superior rectus and inferior oblique
how do superior rectus and inferior oblique synergistically elevate eyes?
work as antagonistic rotators
what muscles are involved in pure depression of the eye?
superior oblique and inferior rectus
how do superior oblique and inferior rectus synergistically depress eyes?
work as antagonistic adductors/abductors
