When you flex your muscles you are contracting them. When your muscle fibers gain tension through Actin and Myosin crossbridge cycling they may shorten due to the tension. This is called muscle contraction
Answer:
Oxygen passes from inside the alveoli through the thin walls and dif- fuses into the blood. At the same time, carbon dioxide waste passes from the blood into the alveoli.
Explanation:
Answer:
it depends with the quality but in most cases they are flushable
