EOMs origin, course, insertion Flashcards
what are muscle movements based on
movement of the muscle from its insertion towards its origin
define origin and insertion
origin: fixed attachment
insertion: moves with contraction
what is the common tendinous ring made of
oval band of connective tissue formed by the tendons of the recti muscles
common tendinous ring origin
apex of orbit - slightly nasal, posterior portion of orbit.
anterior to optic canal and inferior part of the superior orbital fissure.
divide into upper and lower thickened bands
superior rectus origin
attaches to upper limb of ring and dural sheath of ON
medial rectus origin
attached to upper and lower limb of ring and dural sheath of ON
lateral rectus origin
attaches to upper and lower limb of ring and prominence on greater wing of sphenoid.
spina recti lateralis - point of attachment
inferior rectus origin
attaches to lower limb of ring
medial rectus course
parallels medial orbital wall –> follows curve of globe until insertion.
sheath of medial rectus forms medial check ligament - holds globe in place
lateral rectus course
parallels lateral orbital wall –> follows curve of globe until insertion.
sheath of lateral rectus forms lateral check ligament - holds globe in place
superior rectus course
courses forward beneath levator muscle - sheaths enclosing these 2 muscles are connected; connect eyelid movement with eye movement (UL elevates on upgaze).
parallels orbital roof –> follows curve of globe until insertion.
inferior rectus course
courses forward above inferior oblique - sheaths enclosing these 2 muscles form capsulopalpebral fascia; connects eyelid movement with eye movement (LL lowers on downgaze and elevates on upgaze).
parallels orbital floor –> follows curve of globe until insertion
when do recti muscles become tendons and what do they penetrate
become tendons prior to insertion.
penetrate tenon’s capsule to attach to sclera - tenon’s capsule covers the tendons for a short distance
medial rectus insertion
anteromedial aspect of globe.
parallel to sagittal axis.
farthest forward.
lateral rectus insertion
anterolateral aspect of globe.
parallel to sagittal axis.
least forward.
superior rectus insertion
lateral anterosuperior aspect of globe.
forms 23 degree angle with visual axis
inferior rectus insertion
lateral anteroinferior aspect of globe.
forms 23 degree angle with visual axis
what do recti muscle insertions form
spiral of tillaux
what do recti muscles + SO form
muscle cone - tip of cone at orbital apex
oblique muscles
superior oblique muscle
inferior oblique muscle
superior oblique muscle origin
lesser wing of sphenoid bone just above optic canal at orbital apex
inferior oblique muscle origin
maxillary bone - just posterior to inferior medial orbital rim - only EOM to have origin in anterior orbit
superior oblique muscle course
anteriorly along medial wall.
muscle changes to tendon near superior medial orbital wall.
longest EOM bc of tendon.
passes through trochlea.
courses posterolaterally beneath superior rectus
what is the trochlea
u-shaped cartilage in trochlear fossa located in frontal bone medially
inferior oblique muscle course
inferomedial wall of orbit to posterolateral aspect of globe
superior oblique insertion
lateral posterosuperior aspect of globe.
forms 55 degree angle with visual axis
inferior oblique insertion
lateral posteroinferior aspect of globe.
forms 51 degree angle with visual axis
when do oblique muscles become tendons and what do they penetrate
prior to insertion.
penetrate tenon’s capsule to attach to sclera (tenon’s capsule covers tendons for short distance)
