Final answer:
The posterior compartment of the forearm consists of the superficial and deep compartments, with muscles originating on different bones. The superficial compartment includes muscles that extend the wrist and move the hand sideways, while the deep compartment includes muscles that extend the thumb and move the hand sideways.
Step-by-step explanation:
The posterior compartment of the forearm consists of the superficial posterior compartment and the deep posterior compartment. In the superficial posterior compartment, the muscles originate on the humerus and include the extensor radialis longus, extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, and the extensor carpi ulnaris. These muscles are involved in extending the wrist and moving the hand sideways. In the deep posterior compartment, the muscles originate on the radius and ulna and include the abductor pollicis longus, extensor pollicis brevis, and extensor pollicis longus. These muscles are involved in extending the thumb and moving the hand sideways.