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Diagram of the muscles of the arm in action. Labels: 1, humerus; 2, ulna, 3, biceps muscle; 4, attachment to the humerus; 6, triceps muscle; 7, tendon; 8, a ball to be moved. 9, 10, 11, direction the ulna moves when the biceps muscle contracts. When the triceps muscle contracts, the forearm extends.

Arm Muscles in Action

Diagram of the muscles of the arm in action. Labels: 1, humerus; 2, ulna, 3, biceps muscle; 4, attachment…