Extraocular muscle Anatomy

Question 1

What do the extraocular muscles consist of?

Answer 1

medial and lateral rectus, the superior and inferior rectus and the superior and inferior oblique.

Question 2

What is the funciton of the extraocular muscles?

Answer 2

They move the eye and are innerveted by cranial nerves 3,4,6

Question 3

What is the lateral rectus innervated by the abducens nerve?

Answer 3

CN VI

Question 4

What is the superior oblique innervated by?

Answer 4

The trochlear nerve (CN IV)

Question 5

What are all other muscles besides the lateral rectus, the abducens and superior oblique innervated by?

Answer 5

oculomotor nerve (CN III)

Question 6

What are the two primary axes of rotation of the eyeball?

Answer 6

The horizontal axis is at the level of the pupil that produces elevation and depression
The vertical axis through the middle of the eyeball that produces abduction (away from the nose) and adduction (toward the nose)

Question 7

To test lateral rectus what should you ask the pt to do?

Answer 7

look lateral

Question 8

to test medial rectus what should you ask the pt to do?

Answer 8

look medial

Question 9

to test superior rectus?

Answer 9

look lateral and up, innervation CN III

Question 10

to test inferior rectus?

Answer 10

look lateral and down, CN III

Question 11

What does asking the pt to first look laterally take away?

Answer 11

it takes away the ability of these muscles to adduct. These muscles are then only left with only the second of their functions available- elevation or depression

Question 12

to test inferior oblique

Answer 12

look medial and up, innervation CN III

Question 13

to test superior oblique

Answer 13

look medial and down, CN IV

Question 14

Asking the pt to first look medially takes away what?

Answer 14

ability of muscles to abduct. These muscles are then left with only the second of their functions-elevation or depression.

Question 15

How can all three cranial nerves be tested?

Answer 15

By asking the pt to follow your finger as you trace and H in front of your eye.

Question 16

Describe an occulomotor injury (CN III)

Answer 16

The affected eye drift down and out compared to normal eye when you ask pt to look straight ahead.
The muscle supplied by the trochelar nerve is intact which ddepresses and abducts the eye and abductens nerve (lateral rectus) which abducts they eye.
***The individual will also have drooping of the eyelid (ptosis) and pupil dilation (mydriasis)

Question 17

Describe a trochelar nerve injury CN IV

Answer 17

The eye drifts upward copared to the normal eye when asked to look straight ahead.
The muscles supplied by the occulomotor and abducens are intact which results in some loss of depression of the eye. Abduction and adduction are normal.

Question 18

Describe an abducens (CN VI) nerve injury

Answer 18

Eye drifts medially compared to normal eye when pt asked to look straight ahead.
Strong adductor of the eye is intact, the medial rectus.