Structure of Skeletal Muscle
Skeletal muscle is made of thousands of muscle fibers, which are long, multinucleated cell. Each muscle fiber is composed of smaller units called myofibrils. Myofibrils are made up of contractile units called sarcomeres, which are the basic units of muscle contraction. Sarcomeres contain thick (myosin) and thin (actin) filaments that slide past each other to cause muscle contraction.