Diaphragm Action: Contraction:the dome moving downward,increases the volume of thoracic cavity which results in inspiration,at the same time the intra- abdominal pressure is increased assists in defecation,vomiting or child birth. Relaxation:the dome returns to the former position,reduces the volume to the thoracic cavity,resulting in expiration.Diaphragm Action: ❑ Contraction: the dome moving downward, increases the volume of thoracic cavity which results in inspiration, at the same time the intra￾abdominal pressure is increased assists in defecation, vomiting or child birth. ❑ Relaxation: the dome returns to the former position, reduces the volume to the thoracic cavity, resulting in expiration