BCSC Pediactrics (Anatomy of the Extraocular Muscles and Their Fasca Flashcards
Name the seven extraocular muscles.
Superior rectus, inferior rectus, medial rectus, lateral rectus, inferior oblique, superior oblique, and levator palpebrae superioris
Which extraocular muscle is not involved with eye movement?
Levator palpebrae superioris
What cranial nerves innervate the extraocular muscles?
CN III (oculomotor), CN IV (trochlear), and CN IV(abducens)
CN III (oculomotor) innervates which extraocular muscles?
Superior rectus, inferior rectus, medial rectus, inferior oblique, levator palpebrae superioris
CN IV (trochlear) innervates which extraocular muscles?
Superior oblique
CN VI (abducens) innervates which extraocular muscles?
Lateral rectus
What muscles are innervated by the superior division of CN III?
Superior rectus and levator palpebrae superioris
What muscles are innervated by the inferior division of CN III?
Medial rectus, inferior rectus, and inferior oblique
The parasympathetic innervation to the sphincter pupillae and ciliary muscle reach their final destination by traveling with which cranial nerve? (Be specific)
Inferior division of CN III that supplies the inferior oblique.
Describe primary position.
The eyes and head are directed straight ahead.
What constitutes the primary action of an extraocular muscle?
The major effect on the position of the eye when the muscle contracts while the eye is in primary position.
Are the eyes and head in primary position with regards to describing an extraocular muscles secondary and tertiary actions?
Yes. The secondary and tertiary actions of a muscle are the additional effects on the position of the eye when in primary position.
Approximately how many degrees can the globe be rotated in each direction from primary position?
50°
Under normal conditions, how many degrees from primary position does the eye move before head movement occurs?
15-20°
Describe the origin and course of the medial rectus muscle?
It arises from the annulus of Zinn and courses along the medial wall of the orbit
Which extraocular muscle is at risk of injury during ethmoid sinus surgery? Why?
The medial rectus due to it course along the medial wall of the orbit.
Describe the origin and course of the lateral rectus muscle?
It arises from the annulus of Zinn and courses along the lateral wall of the orbit
Which extraocular muscle does not have an oblique muscle running tangential to it?
The medial rectus.
What is the clinical significance of the medial rectus being the only extraocular muscle without an oblique running tangentially to it?
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.
Describe the origin and course of the superior rectus muscle?
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.
Describe the origin and course of the inferior rectus muscle?
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.
Describe the origin and course of the superior oblique muscle?
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.
True or false? The superior oblique tendon penetrates the Tenon capsule.
True
Describe the insertion of the superior oblique in relation to the insertion of the superior rectus?
The superior oblique tendon inserts 2 mm nasally and 5 mm posteriorly to the superior rectus.
