Muscles

Question 1

Extraocular muscles

Answer 1

Superior rectus =vertical top
Inferior rectus = vertical bot
Medial rectus = horizontal nasal
Lateral rectus = horizontal left
Superior oblique = above and across
Inferior oblique = below and across

Question 2

Rectus muscles origin

Answer 2

Arise from apex of orbit (annulus of zinn) which overlies optic foramen / medial superior orbital fissure

Question 3

Medial rectus innervation and use

Answer 3

innervated by Inf. Div. VN III (oculomotor)

Only used for adduction

Question 4

Lateral rectus innervation and use

Answer 4

Only muscle innervated by CN VI (abducens)

Only used for abduction

Question 5

Superior rectus innervation and use

Answer 5

Innervated by Sup. Div. CN III (oculomotor)

Primary elevation, secondary intorsion, tertiary adduction (as it attaches at an angle to optic axis)

Question 6

Inferior rectus innervation and use

Answer 6

Innervated by Inf. Div. CN III (oculomotor)

Primary Depression, secondary extorsion, tertiary adduction (as it attaches at an angle)

Question 7

Superior oblique innervation and use

Answer 7

Only muscle innervated by CN IV

Primary intorsion, secondary depression, tertiary abduction.

Question 8

Inferior oblique innervation and use

Answer 8

Innervated by Inf. Div. CN III (oculomotor)

Primary extorsion, secondary elevation, tertiary abduction.

Question 9

9 cardinal positions of gaze

Answer 9

Hashtag for people to focus eyes so you can see if their muscles work or nah

Question 10

Reflex eye movements

Answer 10

Vestibulo-ocular reflex = stabilized eye motion during head rotation.
Mediated by inner ear vestibular system.

Question 11

Oblique muscles origin

Answer 11

Insert posterior to equator of eye
Superior - Arise from sphenoid bone. tendon runs through trochlear, attached to trochlear fossa. Inserts under superior rectus
Inferior - arise from floor of orbit. Inserts under lateral rectus

Question 12

Annulus of zinn

Answer 12

Tendon ring around orbit apex where rectus muscle originates.
Overlies optic foramen (attached to sphenoid bone)
Overlies superior orbital fissure (attached to wing of sphenoid)

Question 13

Innervation of extraocular muscles

Answer 13

CN III = sup./inf./med. Rectus, inf. Oblique, leveator palpebrae superioris
CN IV = Sup. oblique
CN VI = lateral rectus

Question 14

Nerves that enter above or within annulus of Zinn

Answer 14

Lacrimal, frontal, trochlear = above

Sup./Inf. CN III, Nasociliary, Abducant = within

Question 15

Vasculature of extraocular muscles

Answer 15

Muscular branches of ophthalmic artery
Lateral B: lateral/superior rectus, superior oblique
Medial B: Inf./Medial rectus, inferior oblique
Lacrimal Artery: Lateral rectus
Infraorbital artery: Inferior oblique
These branches form ant. Ciliary arteries

Question 16

Muscle designation

Answer 16

Agonist: primary driver
Synergist: agonist assistor
Antagonist: agonist opposer
Yoke muscles: agonist of both eyes for binocular focus

Question 17

Law of muscle innervation for the eye

Answer 17

Hering’s law of equal innervation: each eyes’ agonist receive equal innervation
Sherrington’s law of reciprocal innervation: agonist and antagonist excitatory/inhibitory innervation is equal