400
When you breathe in, the diaphragm _____________, pulling downward and making the space inside the chest _____________. More space allows the lungs to expand and pull in air. As the diaphragm ____________, the space inside the chest gets _______________and the air is pressed out.
When you breathe in, the diaphragm contracts, pulling downward and making the space inside the chest larger. More space allows the lungs to expand and pull in air. As the diaphragm relaxes, the space inside the chest gets smaller and the air is pressed out.