Muscles of orbit

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File:Eyemuscles.jpg
Muscles of the orbit from Gray's Anatomy

There are seven muscles of the orbit; one controls the movement of the upper eyelid, and six others control the movement of the eye.

Muscle Innervation Primary function Secondary function Tertiary function
Levator palpebrae superioris Oculomotor nerve Elevation of the superior (upper) eyelid . .
Superior rectus Oculomotor nerve Elevation Intorsion Adduction
Inferior rectus Oculomotor nerve Depression Extorsion Adduction
Lateral rectus Abducens nerve Abduction . .
Medial rectus Oculomotor nerve Adduction . .
Superior oblique Trochlear nerve Intorsion Depression Abduction
Inferior oblique Oculomotor nerve Extorsion Elevation Abduction

A good mnemonic to remember which muscles are innervated by what nerve is to paraphrase it as a molecular equation: LR6SO4R3.
Lateral Rectus - Cranial Nerve VI,
Superior Oblique - Cranial Nerve IV,
the Rest of the muscles - Cranial Nerve III.

Another way to remember which nerves innervate which muscles is to understand the meaning behind all of the Latin words. The fourth cranial nerve, the trochlear, is so named because the muscle it innervates, the superior oblique, runs through a little fascial pulley that changes its direction of pull. This pulley exists in the superiomedial corner of each orbit, and "trochl-" is Latin for "pulley." The sixth cranial nerve, the abducens, is so named because it controls the lateral rectus, which abducts the eye (rotates it laterally) upon contraction. All of the other muscles are controlled by the third cranial nerve, the oculomotor, which is so named because it is in charge of the movement (motor) of the eye (oculo-).

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