Combined with the |extensor pollicis brevis| (thumb muscle), the |abductor pollicis longus| creates a narrow, triangular muscle form which wraps around the lower end of the |radius| (the bone of the forearm on the thumb side). The |abductor pollicis longus| originates on the back side of the |ulna| and |radius| and inserts at the base of the metacarpal bone of the thumb near the palm. This muscle extends the thumb away from the hand (abducts). It also rotates and flexes the hand at the wrist. The combination of the |abductor pollicis longus| and the |extensor pollicis brevis| forms the oblique carpal muscle group, which produces a small but important convexity three-fourths of the way down the forearm on its outer (radial) profile.
