Dorsal interossei of the hand

In human anatomy, the dorsal interossei (DI) are four muscles in the back of the hand that act to abduct (spread) the index, middle, and ring fingers away from the hand's midline (ray of middle finger) and assist in flexion at the metacarpophalangeal joints and extension at the interphalangeal joints of the index, middle, and ring fingers. == Structure == There are four dorsal interossei in each hand.

Source: Wikipedia — Dorsal interossei of the hand (CC BY-SA 4.0)