[TA] three intrinsic muscles in the hand; origin, first: ulnar side of second metacarpal; second and third: radial sides of fourth and fifth metacarpals; insertion, first: into ulnar side of index; second and third: into radial sides of ring and little fingers; action, adducts fingers toward axis of middle finger; nerve supply, ulnar.flexor pollicis brevis (muscle). SYN: musculus interosseus palmaris [TA], musculus interosseus volaris.