Muscle · Head

Levator palpebrae superioris

Musculus levator palpebrae superioris

The muscle that holds your upper eyelid open. It runs the length of the roof of the eye socket from the bone above the optic canal forward, widening into a broad flat tendon that fans down into the eyelid and grips the stiff fibrous plate inside it. It is unusual in being two muscles in one: the main sheet is ordinary voluntary muscle driven by the oculomotor nerve, but a thin deep layer within it is smooth, involuntary muscle driven by the sympathetic nervous system. That dual supply means how wide the eye opens has both a voluntary and an involuntary contribution, and it is why the eyes widen with alarm without any decision to open them.