2.37 understand the role of the intercostal muscles and the diaphragm in ventilation

2.37 •breathing in: •intercostal muscles and diaphragm contract 

                                         •thorax volume increases

                                                   •this decrease in pressure draws in air 

         •breathing out: •intercostal muscles and diaphragm relax

                                           •thorax volume decreases

                                                    •air is forced out