What are the three groups of intrinsic muscles of the hand, and what are their general functions?

The three groups are the thenar muscles of the thumb's ball, the hypothenar muscles of the little finger's ball, and the midpalmar muscles. They control precise finger movements, with thenar and hypothenar groups flexing, abducting, and opposing their digits, while the midpalmar lumbricals and interossei extend the fingers and the interossei also adduct and abduct the fingers.

The intrinsic muscles of the hand lie entirely within the palm and are divided into the thenar eminence group, the hypothenar eminence group, and the midpalmar group. The thenar and hypothenar groups each contain a small flexor, an abductor, and an opponens muscle, moving the thumb and little finger respectively. The midpalmar muscles consist of the lumbricals and interossei, which extend the fingers at the interphalangeal joints, while the interossei also act as the main abductors and adductors of the fingers. Together these muscles control the most delicate and precise finger movements, such as opposition of the thumb, while powerful gripping movements are left to the forearm muscles.