Muscles Of The Globe

Question 2

How many extraocular muscles control eye movement?

Answer 2

6 muscles — 4 recti (superior, inferior, medial, lateral) and 2 obliques (superior, inferior)

Question 3

Which nerve innervates the lateral rectus muscle?

Answer 3

Abducens nerve (CN VI)

Question 4

Which nerve innervates the superior oblique muscle?

Answer 4

Trochlear nerve (CN IV)

Question 5

What nerve innervates the remaining four eye muscles (superior, inferior, medial recti + inferior oblique)?

Answer 5

Oculomotor nerve (CN III)

Question 6

What is the primary action of the superior rectus?

Answer 6

Elevation, adduction, and medial rotation (intorsion)

Question 7

What is the primary action of the inferior rectus?

Answer 7

Depression, adduction, and lateral rotation (extorsion)

Question 8

What is the primary action of the medial rectus?

Answer 8

Adduction (moves eye medially)

Question 9

What is the primary action of the lateral rectus?

Answer 9

Abduction (moves eye laterally)

Question 10

What is the primary action of the superior oblique?

Answer 10

Depression, abduction, and medial rotation (intorsion)

Question 11

What is the primary action of the inferior oblique?

Answer 11

Elevation, abduction, and lateral rotation (extorsion)

Question 12

What is the mnemonic for eye muscle innervation?

Answer 12

LR6 SO4 R3 (Lateral Rectus – CN VI, Superior Oblique – CN IV, Rest – CN III)

Question 13

Where do the rectus muscles originate from?

Answer 13

Common tendinous ring (annulus of Zinn) at the back of the orbit

Question 14

Where does the superior oblique originate and insert?

Answer 14

Origin: sphenoid bone above the common ring → trochlea → inserts on superior posterolateral sclera

Question 15

Where does the inferior oblique originate and insert?

Answer 15

Origin: maxilla (anteromedial orbit floor) → inserts on inferior posterolateral sclera

Question 16

Which muscles are responsible for elevation of the eye?

Answer 16

Superior rectus and inferior oblique

Question 17

Which muscles are responsible for depression of the eye?

Answer 17

Inferior rectus and superior oblique

Question 18

Which muscles cause intorsion of the eye?

Answer 18

Superior rectus and superior oblique

Question 19

Which muscles cause extorsion of the eye?

Answer 19

Inferior rectus and inferior oblique

Question 20

Which muscle is the primary elevator of the eye when it is abducted?

Answer 20

Superior rectus

Question 21

Which muscle is the primary elevator of the eye when it is adducted?

Answer 21

Inferior oblique

Question 22

Which muscle is the primary depressor of the eye when it is abducted?

Answer 22

Inferior rectus

Question 23

Which muscle is the primary depressor of the eye when it is adducted?

Answer 23

Superior oblique

Question 24

Which extraocular muscle does not originate from the common tendinous ring?

Answer 24

Inferior oblique

Question 25

What is the anatomical pulley structure associated with the superior oblique muscle?

Answer 25

Trochlea

Question 26

What is the effect of a CN III lesion on eye movement?

Answer 26

Eye looks down and out (due to unopposed lateral rectus and superior oblique); ptosis and mydriasis may also occur

Question 27

What is the effect of a CN IV lesion on eye movement?

Answer 27

Difficulty looking down and in; may cause vertical diplopia, especially when going down stairs

Question 28

What is the effect of a CN VI lesion on eye movement?

Answer 28

Inability to abduct the affected eye (lateral rectus paralysis)

Question 29

Which eye muscle is tested by asking the patient to look laterally then upward?

Answer 29

Superior rectus

Question 30

Which eye muscle is tested by asking the patient to look laterally then downward?

Answer 30

Inferior rectus

Question 31

Which eye muscle is tested by asking the patient to look medially then upward?

Answer 31

Inferior oblique

Question 32

Which eye muscle is tested by asking the patient to look medially then downward?

Answer 32

Superior oblique

Question 33

Which two extraocular muscles are involved in pure vertical eye movement?

Answer 33

Superior rectus (elevation) and inferior rectus (depression), but only when the eye is abducted

Question 34

Which two extraocular muscles are involved in pure horizontal eye movement?

Answer 34

Medial rectus (adduction) and lateral rectus (abduction)

Question 35

What is the functional test for the lateral rectus muscle?

Answer 35

Ask the patient to look directly outward (abduct the eye)