how many EOMs and IOMs are there? Name them and the associated EOM
EOM:
**levator palp superioris
IOM:
ciliary msc, dilator pup, sphinter pupillae
descibe the structure of EOMs
striated
dont tire
voluntary and involuntary actions
small diamter fibres
rich nerve supply = controlled mvts
rich bld supply
sheath = high degree of elasticity
Where do the rectus msc originate from and attach to? What are the distances from the limbus?
Annulus of Zinn
attached anterior to equator
MR>IR>LR>SR
MR = closest to limbus so more powerful
Primary actions of recti msc
SR= elevation
IR= depression
LR= abduction (out)
MR= adduction (in)
Where does each oblique msc originate and attach to?
insert into eyeball at 90 degrees (compared to recti)
attach posterior to equator
SO originate at sphnoid bone, just outside the annulus of Zinn
reaches fibrous ring (trochlea)
msc after trochlea = tendon
SO passes under SR
IO originate at medial orbital wall (prone to trauma)
passes over IR
Action of oblique msc
Primary actions
SO- incyclotorsion
IO- excyclotorsion
eye abducted: SR - elevation
IR- depression
eye adducted: IO- elevation
SO- depression
What is the annulus of Zinn and which nerves pass thru it?
fibrous tendinous ring
Cr. N.II, III, IV, VI
innervation of the EOM
1. III- oculomotor
SR, LPS, IR, MR, IO, cill msc, sphincter pup
IV- Tochlear- SO
VI- Abducens- LR
desribe the eye movemnet terminology
Ductions- mono
Versions- binocular
w/ versions, angle btwn direction of gaze x change. AKA conjugate mvts
RIght= dextroversion - R eye = ABducted. L eye = ADducted
Left= Laevoversion
Up= supraversion
down= infraversion
Vergence - maintain bino vision
w/ vergence, angle changes for near and far vision. AKA disconjugate mvts
Divergence- increase angle - for far vision
Convergence- decrease angle - for near vision
**same msc from each eye contracts
WHich msc acts in each cardinal psn of gaze?
obliques come towards nose
Summary of EOM mvts in primary position
in primary psn - eye moves 23’ inwards
When eye is adducted, obliques change primary action to depression / elevation
Recti= max pri action with ABduction- used for DV
Obliques= max sec action with ADduction- used for NV
what are contralateral synergists
pair of msc in each eye, contract at same time
oposite msc= antagonists
R and L EOMS superimposed
Px right gaze = my left gaze
desribe trochlear nerve (IVth)
long and thin - prone to closed head trauma
crossed nerve- only CN whose fibres come from contralateral nucleus
describe the 3rd nerve pathway
post cerebral art & sup cerebellar art at the back of COW. close to ICA
risk of damage from aneurysm
divides into sup and inf branch before entering orbit via superior orbital fissure via cavernous sinus
VIth nerve pathway
Bends over petrous tip of palatine bone
Prone to trauma
Order of cr. Nerve at risk of aneurysm
3, 6, 4
Last changed8 months ago
