Which cranial nerves innervate the six extraocular muscles?

Which cranial nerves innervate the six extraocular muscles?

• A. CN III, CN IV, CN VI
• B. CN II, CN IV, CN VI
• C. CN I, CN II, CN III
• D. CN IV, CN V, CN VI

Answer: (A)

Six extraocular muscles receive motor input from three cranial nerves: oculomotor, trochlear, and abducens. The oculomotor nerve supplies four of the six muscles—the medial, superior, and inferior rectus, plus the inferior oblique—and also lifts the eyelid via levator palpebrae superioris. The trochlear nerve innervates the superior oblique, and the abducens nerve supplies the lateral rectus. This combination is why the six muscles are innervated by CN III, CN IV, and CN VI. Options that include other nerves aren’t correct because those nerves don’t innervate the extraocular muscles. The optic nerve (CN II) handles vision, and the trigeminal nerve (CN V) doesn’t innervate these muscles.

Six extraocular muscles receive motor input from three cranial nerves: oculomotor, trochlear, and abducens. The oculomotor nerve supplies four of the six muscles—the medial, superior, and inferior rectus, plus the inferior oblique—and also lifts the eyelid via levator palpebrae superioris. The trochlear nerve innervates the superior oblique, and the abducens nerve supplies the lateral rectus. This combination is why the six muscles are innervated by CN III, CN IV, and CN VI.

Options that include other nerves aren’t correct because those nerves don’t innervate the extraocular muscles. The optic nerve (CN II) handles vision, and the trigeminal nerve (CN V) doesn’t innervate these muscles.