lecture 8 - EOM Flashcards
how many EOM per eye
7
name the muscle that controls the eyelid
levator palpebrae superioris
which cranial nerve supplies the:
Superior Rectus
LPS
3rd (cranial) - superior divison
which cranial nerve supplies the:
medial rectus
inferior rectus
inferior oblique
3rd (cranial) - inferior division
which cranial nerve supplies the superior oblique
4th (trochlear)
which cranial nerve supplies the lateral rectus
6th (abducens)
what is the anatomical origin of the recti muscles?
annulus of Zinn
where is the mechanical origin of the recti muscles?
10mm posterior to the equator of globe
as the muscle contracts, the cornea rotates …. the body of the muscle itself
(fill in the gap)
towards
what is the primary action of the medial rectus?
inwards
what is the primary action of the lateral rectus?
outwards
what is the primary action of the Superior Rectus?
upwards
what is the primary action of the inferior rectus?
downwards
what is the anatomical origin of superior oblique
annulus of zinn
what is the anatomical origin of inferior oblique
anterior infero-nasal corner
where is the mechanical origin superior oblique?
anterior supero-nasal corner of orbital rim
where is the mechanical origin of the inferior oblique ?
anterior and inferior to globe, copies to IR tendon
what is the primary action of superior oblique
the cornea moves away from the body of the muscle therefore
downwards
what is the primary action of the inferior oblique?
the cornea moves away from the body of the muscle and therefore
upwards
downwards movement is known as
depression
upwards movement is known as
elevation
which 2 recti are concentric with limbus
MR and LR
which 2 recti are tilted slightly nasally
SR and IR
list the insertions of the muscles, starting with closest to limbus to furthest
MR (5.5mm away)
IR (6.5mm)
LR (7mm)
SR (7.5mm)
which muscle inserts underneath the LR
IO
which muscle inserts under the SR
SO
in primary position where is the centre of rotation location in relation to the apex of the cornea?
13.5mm
if the eye is abducting and adducting, which of Fick’s axis is the eye moving alone?
Z axis
if the eye is elevating or depression, which of Fick’s axis is the eye moving along?
X axis
if the eye is cycle-rotating or displaying torsion, which of Fick’s axis is the eye moving along?
Y axis
what is duction movements limited by?
length of muscle + tendon
edge of orbit
soft tissue of orbit
what movement is adduction
inwards
what movement is abduction?
outwards
what is elevation known as (in terms of duction)
supraduction
what is depression known as (in terms of duction)
infraduction
what is extorsion known as (in terms of duction)
excycloduction
what is intorsion known as (in terms of duction)
incycloduction
where does the muscle contract if it’s axis of rotation coincides with one of Fick’s axes of rotation?
purely around that axis
where is a muscles axis of rotation in terms of its muscle plane?
perpendicular
what is the muscle plane?
point where the muscle first touches the globe and the centre of rotation
what does RADSIN stand for?
R - recti
AD - adduct
S - superiors
IN - intort
in primary position does the Superior Rectus muscles axis coincide with one of ticks axes ?
no
what is the primary action of the superior rectus
elevation
what is the secondary action of the Superior Rectus
incycloduction
what is the tertiary action of the Superior Rectus?
adduction
what is the primary action of the inferior rectis?
depression
what is the secondary action of the inferior rectus?
excycloduction
what is the tertiary action of the inferior rectus?
adduction
which muscles form angles of about 23 degrees with x axis and 67 degrees with y axis
SR
IR
which muscles form angles of about 36 degrees with the y axis and 54 degrees with the x axis ?
SO
what is the primary action of superior oblique?
incycloduction
what is the secondary action of superior oblique?
depression
what is the tertiary action of the superior oblique?
abduction
what is the tertiary action of the superior oblique?
abduction
when the eye is adducted which muscle produces depression?
superior oblique
when the eye is adducted which muscles produces elevation?
inferior oblique
when the eye is abducted which muscle produces elevation?
superior rectus
when the eye is abducted which muscle produces depression?
inferior rectus
what actions does the SR have in primary position?
elevation
adduction
intorsion
what deviation in primary position would your px have if they had a large right SR weakness?
right hypotropia
right exotropia
right extorsion
what action does the inferior oblique have in primary position?
extorsion
elevation
abduction
what deviation in primary position would your px have if they had a large right IO weakness?
left hypotropic
left intorsion
left esotropia
