EOM Flashcards
What embryology origin is EOM?
Mesodermal
When does EOM development begin? When are they in their final anatomical positions?
- 3 weeks of gestation
- 6 months of gestation (continues enlarging throughout gestation)
How are EOMS different from other skeletal muscles?
EOM have denser blood supply
- connective tissue has more elastic fibers
- have fewer fibers per unit, so more fine movements
Due to a unique combination of white and red muscle fibers, what are EOMS?
Fast and fatigue resistant
What are the two layers of EOM?
- Orbital layer: superficially near the orbital wall (inserted on a pulley)
- Globar layer (located deeper, becomes contiguous with tendon to insert on the globe)
What is the primary action of medial rectus? Lateral rectus?
Medial:ADDuction
Lateral:ABDuction
List primary, secondary, and tertiary actions of SR
1: Elevation
2. Intorsion
3. ADDuction
List the primary, secondary, and tertiary functions of IR
1: depression
2. Extorstion
3. ADDuction
List the primary, secondary, and tertiary actions of SO
- Intorsion
- Depression
- ABDuction
List the primary, secondary, and tertiary actions of IO
- Extortion
- Elevation
- ABDuction
Where do all recti muscles originate?
Annulus of Zinn
List the annulus of Zinn tendon attachments
SR: upper limb annulus
MR: upper and lower limbs
IR: lower limb
LR: upper and lower limbs
Annulus encloses the oculomotor foramen, what passes through this?
- oculomotor nerve
- optic nerve
- ophthalmic artery
- abducens nerve
- nasociliary nerve
What is the spiral of tillaux?
-where recti muscles insert onto the sclera
Name the recti muscles in their order from closest to limbus to furthest
- Medial rectus
- inferior
- Lateral
- superior
What is the shortest muscle?
Inferior oblique
What is the longest and thinnest muscle?
Superior oblique
Where does the levator palpebrae superioris originate?
Orbital surface of lesser wing of sphenoid
What does the superior lamina of the lesser palpebrae superioris do? Inferior lamina?
Superior: voluntary to skin and upper eye lid
Inferior: involuntary to upper margin of superior tarsus
Name the superior muscles in order from superior to inferior
Levator
SR
SO
What is the strongest EOM and most eye turns are because of this?
Medial rectus
What is the only EOM to have it an atomic organ in the ANTERIOR orbit?
inferior oblique
What is the action of the check ligaments?
Provide stops to excessive movements
What are check ligaments?
Dense connective tissue network that connects EOM sheath to one another
