A thenar muscle (an intrinsic hand muscle) that moves the thumb away from the first finger. It originates in the flexor retinaculum and on the tubercles of the scaphoid and trapezium wrist bones. It attaches to the outside (lateral) base of the proximal phalanx of the thumb. It abducts the thumb and together with the other thenar muscles it opposes the thumb against the little finger. It is innervated by the recurrent branch of the median nerve (C8, Tl).