INTEROSSEI - Palmar Division: ORIGIN: Medial side, second metacarpal & Lateral side, fourth and fifth metacarpals INSERTION: Medial side, base first phalanx, index, ring, and little fingers & Tendon extensor digitorum ACTION: Adduct fingers, flex first phalanx, extend second and third Dorsal Division: ORIGIN: Adjacent sides, second through fifth metacarpals INSERTION: Lateral aspects of phalanges ACTION: Abduct fingers, flex first phalanx, extend second and third