The abductor pollicis brevis is one of the muscles forming the thenar eminence, the muscle mass of the thumb. The abductor pollicis brevis is the largest of the thenar eminence muscle group and is flat, elongated and triangular in shape. It lies just below the skin and slightly overlaps the flexor pollicis brevis and mostly covers the opponens pollicis. The abductor pollicis brevis originates from the tubercle of the trapezium and from the flexor retinaculum. It inserts in the proximal phalanx of the thumb. This muscle is innervated by the median nerve and supplied by palmar branches of the radial artery. It moves the metacarpal bone of the thumb away from the palm. Research Abductor Pollicis Brevis