The muscles of the forearm can be divided into two groups: anterior (flexors) and posterior (extensors).
Both the flexors and extensors are further divided into superficial and deep layers.
The forearm muscles that control the movement of the hands are known as extrinsic hand muscles. These muscles originate outside the hand and insert on structures within it.
Shown here, the extrinsic hand muscles are the flexor carpi radialis, palmaris longis, flexor carpi ulnaris, and flexor digitorum superficialis.
These muscles move the wrist, hand, fingers and thumb.
The pronator teres inserts on the radius and pronates the forearm and hand.