Sentence:  Microscopic studies of the gastrocnemius , <WSD>pectoralis</WSD> major , transversus abdominis , biceps 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 skeletal muscle that adducts and rotates the arm