The muscles that move the hand and fingers are divided into two groups — the anterior and the posterior compartment muscles. The anterior compartment muscles flex the wrists, digits, and thumbs and pronate the hand. The superficial layer of the anterior compartment is made up of the flexor carpi radialis, palmaris longus, and flexor carpi ulnaris muscles. The flexor digitorum superficialis lies under these three muscles and is the largest of the superficial muscles. The anterior deep layer comprises the flexor pollicis longus and flexor digitorum profundus muscles. The posterior compartment muscles extend the wrists, fingers, and thumbs and supinate the hand. The superficial layer of the posterior compartment is made up of the extensor carpi radialis longus , extensor carpi radialis brevis , extensor digitorum , extensor digiti minimi and extensor carpi ulnaris . The posterior deep layer is made up of the abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis.