Role of Epiglottis- It is a Flap tissue which seals off the trachea when swallow the food . But at the time of Respiration it remains open .

Role of Diaphragm- It main function is to pump out the CO₂  and take back O₂ in the lungs. When we breathe in it flattens and when we breathe out it comes to it's stationary position.