Final answer:
The deep anterior forearm contains the flexor pollicis longus and flexor digitorum profundus. These muscles are concerned with flexing the thumb and fingers respectively, with the third muscle being the pronator quadratus, which pronates the forearm.
Step-by-step explanation:
The three muscles in the deep anterior forearm are part of the group that controls the flexion of the fingers and wrist, as well as forming a fist. These muscles include the flexor pollicis longus, flexor digitorum profundus, and a third muscle which is not explicitly mentioned in the reference material provided, but can be identified as the pronator quadratus muscle due to its location and function in the forearm.
The flexor pollicis longus is responsible for flexing the thumb. The flexor digitorum profundus flexes the distal phalanges of the fingers. The pronator quadratus, although not mentioned in the provided material, is known as a deep anterior forearm muscle that pronates the forearm.