Relier Pairs Muscle Actions Part One (D)Version en ligne muscles par Jennifer Jennings 1 pectoralis major 2 biceps brachii 3 rectus abdominis 4 flexor carpi radialis and ulnaris 5 sternocleidomastoid 6 triceps brachii 7 trapezius 8 deltoid 9 levator scapulae 10 latissimus dorsi elevates scapula if cervical vertebrae are fixed., flexes neck laterally when scapula is fixed. extends and laterally flexes the neck. flexes, adducts, and medially rotates humerus elbow flexion, forearm supination. rotates head left and right. bilaterally draws head forward and down. flexes waist and compresses abdominal viscera flexes wrist anteriorly ant. fibers flex and medially rotate arm, lat. fibers abduct the arm, post. fibers extend and laterally rotate the arm extends elbow adducts and medially rotates humerus, extends the shoulder joint