BCSC Pediactrics (Anatomy of the Extraocular Muscles and Their Fasca

Question 1

Name the seven extraocular muscles.

Answer 1

Superior rectus, inferior rectus, medial rectus, lateral rectus, inferior oblique, superior oblique, and levator palpebrae superioris

Question 2

Which extraocular muscle is not involved with eye movement?

Answer 2

Levator palpebrae superioris

Question 3

What cranial nerves innervate the extraocular muscles?

Answer 3

CN III (oculomotor), CN IV (trochlear), and CN IV(abducens)

Question 4

CN III (oculomotor) innervates which extraocular muscles?

Answer 4

Superior rectus, inferior rectus, medial rectus, inferior oblique, levator palpebrae superioris

Question 5

CN IV (trochlear) innervates which extraocular muscles?

Answer 5

Superior oblique

Question 6

CN VI (abducens) innervates which extraocular muscles?

Answer 6

Lateral rectus

Question 7

What muscles are innervated by the superior division of CN III?

Answer 7

Superior rectus and levator palpebrae superioris

Question 8

What muscles are innervated by the inferior division of CN III?

Answer 8

Medial rectus, inferior rectus, and inferior oblique

Question 9

The parasympathetic innervation to the sphincter pupillae and ciliary muscle reach their final destination by traveling with which cranial nerve? (Be specific)

Answer 9

Inferior division of CN III that supplies the inferior oblique.

Question 10

Describe primary position.

Answer 10

The eyes and head are directed straight ahead.

Question 11

What constitutes the primary action of an extraocular muscle?

Answer 11

The major effect on the position of the eye when the muscle contracts while the eye is in primary position.

Question 12

Are the eyes and head in primary position with regards to describing an extraocular muscles secondary and tertiary actions?

Answer 12

Yes. The secondary and tertiary actions of a muscle are the additional effects on the position of the eye when in primary position.

Question 13

Approximately how many degrees can the globe be rotated in each direction from primary position?

Answer 13

50°

Question 14

Under normal conditions, how many degrees from primary position does the eye move before head movement occurs?

Answer 14

15-20°

Question 15

Describe the origin and course of the medial rectus muscle?

Answer 15

It arises from the annulus of Zinn and courses along the medial wall of the orbit

Question 16

Which extraocular muscle is at risk of injury during ethmoid sinus surgery? Why?

Answer 16

The medial rectus due to it course along the medial wall of the orbit.

Question 17

Describe the origin and course of the lateral rectus muscle?

Answer 17

It arises from the annulus of Zinn and courses along the lateral wall of the orbit

Question 18

Which extraocular muscle does not have an oblique muscle running tangential to it?

Answer 18

The medial rectus.

Question 19

What is the clinical significance of the medial rectus being the only extraocular muscle without an oblique running tangentially to it?

Answer 19

This generally makes surgery on the medial rectus less complicated, but means that there is no point of reference if the surgeon becomes disoriented nor a point of attachment if the muscle is lost.

Question 20

Describe the origin and course of the superior rectus muscle?

Answer 20

It arises from the annulus of Zinn and courses anteriorly, upward over the eyeball, and laterally forming a 23° angle with the visual axis of the eye in primary position.

Question 21

Describe the origin and course of the inferior rectus muscle?

Answer 21

It arises from the annulus of Zinn and courses anteriorly, downward over the eyeball, and laterally forming a 23° angle with the visual axis of the eye in primary position.

Question 22

Describe the origin and course of the superior oblique muscle?

Answer 22

It arises from the orbital apex above the annulus of Zinn and courses anteriorly and upward along the superomedial wall of the orbit. It becomes tendinous before passing through the trochlea which redirects the tendon inferiorly, posteriorly, and laterally, forming a 51° angle with the visual axis of the eye in primary position.

Question 23

True or false? The superior oblique tendon penetrates the Tenon capsule.

Answer 23

True

Question 24

Describe the insertion of the superior oblique in relation to the insertion of the superior rectus?

Answer 24

The superior oblique tendon inserts 2 mm nasally and 5 mm posteriorly to the superior rectus.

Question 25

Where does the trochlea arise?

Answer 25

It arises from the frontal bone in the superior nasal orbit.

Question 26

Is the trochlea made of cartilage or collagen?

Answer 26

Cartilage

Question 27

True or false? The trochlea contains a bursa-like structure?

Answer 27

True

Question 28

Describe the origin and course of the inferior oblique muscle?

Answer 28

It arises from the periosteum of the maxillary bone, just posterior to the orbital rim and lateral to the orifice of the lacrimal fossa. It courses laterally, superiorly, and posteriorly, going inferior to the inferior rectus muscle and inserting under the lateral rectus muscle in the posterolateral portion of the globe, in the area of the macula, forming a 51° angle with the visual axis of the eye in primary position.