Sentence:  Microscopic studies of the gastrocnemius , pectoralis major , transversus abdominis , biceps brachii , and <WSD>diaphragm</WSD> 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:  (anatomy) a muscular partition separating the abdominal and thoracic cavities; functions in respiration