EOMs origin, course, insertion

Question 1

what are muscle movements based on

Answer 1

movement of the muscle from its insertion towards its origin

Question 2

define origin and insertion

Answer 2

origin: fixed attachment
insertion: moves with contraction

Question 3

what is the common tendinous ring made of

Answer 3

oval band of connective tissue formed by the tendons of the recti muscles

Question 4

common tendinous ring origin

Answer 4

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

Question 5

superior rectus origin

Answer 5

attaches to upper limb of ring and dural sheath of ON

Question 6

medial rectus origin

Answer 6

attached to upper and lower limb of ring and dural sheath of ON

Question 7

lateral rectus origin

Answer 7

attaches to upper and lower limb of ring and prominence on greater wing of sphenoid.
spina recti lateralis - point of attachment

Question 8

inferior rectus origin

Answer 8

attaches to lower limb of ring

Question 9

medial rectus course

Answer 9

parallels medial orbital wall –> follows curve of globe until insertion.
sheath of medial rectus forms medial check ligament - holds globe in place

Question 10

lateral rectus course

Answer 10

parallels lateral orbital wall –> follows curve of globe until insertion.
sheath of lateral rectus forms lateral check ligament - holds globe in place

Question 11

superior rectus course

Answer 11

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.

Question 12

inferior rectus course

Answer 12

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

Question 13

when do recti muscles become tendons and what do they penetrate

Answer 13

become tendons prior to insertion.
penetrate tenon’s capsule to attach to sclera - tenon’s capsule covers the tendons for a short distance

Question 14

medial rectus insertion

Answer 14

anteromedial aspect of globe.
parallel to sagittal axis.
farthest forward.

Question 15

lateral rectus insertion

Answer 15

anterolateral aspect of globe.
parallel to sagittal axis.
least forward.

Question 16

superior rectus insertion

Answer 16

lateral anterosuperior aspect of globe.
forms 23 degree angle with visual axis

Question 17

inferior rectus insertion

Answer 17

lateral anteroinferior aspect of globe.
forms 23 degree angle with visual axis

Question 18

what do recti muscle insertions form

Answer 18

spiral of tillaux

Question 19

what do recti muscles + SO form

Answer 19

muscle cone - tip of cone at orbital apex

Question 20

oblique muscles

Answer 20

superior oblique muscle
inferior oblique muscle

Question 21

superior oblique muscle origin

Answer 21

lesser wing of sphenoid bone just above optic canal at orbital apex

Question 22

inferior oblique muscle origin

Answer 22

maxillary bone - just posterior to inferior medial orbital rim - only EOM to have origin in anterior orbit

Question 23

superior oblique muscle course

Answer 23

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

Question 24

what is the trochlea

Answer 24

u-shaped cartilage in trochlear fossa located in frontal bone medially

Question 25

inferior oblique muscle course

Answer 25

inferomedial wall of orbit to posterolateral aspect of globe

Question 26

superior oblique insertion

Answer 26

lateral posterosuperior aspect of globe.
forms 55 degree angle with visual axis

Question 27

inferior oblique insertion

Answer 27

lateral posteroinferior aspect of globe.
forms 51 degree angle with visual axis

Question 28

when do oblique muscles become tendons and what do they penetrate

Answer 28

prior to insertion.
penetrate tenon’s capsule to attach to sclera (tenon’s capsule covers tendons for short distance)