Sentence:  Microscopic studies of the gastrocnemius , pectoralis major , transversus abdominis , <WSD>biceps</WSD> brachii , and diaphragm showed atrophy as well as varying degrees of injury ranging from swelling and vacuolization to focal necrosis of the muscle fibers . 
Meaning of the word marked with <WSD> tags:  a muscle that flexes and supinates the forearm