CBSE Class 10 Answered

The diaphragm is a sheet of muscles that lies across the bottom of the chest cavity. Breathing occurs with the help of diaphragm and other muscles in the chest and abdomen. When diaphragm is pulled down, it leaves more space for the lungs to expand and also lowers the internal air pressure. Due to this pressure difference between inside and the outside environment, air is sucked in when we inhale. This air then expands the lungs. When diaphragm relaxes, the chest cavity inside the body gets smaller again. The lungs begin to collapse as the air is pushed up and out of the body in an exhale.Thus diaphragm and other chest and abdomen muscles change the space and pressure inside the body to accomodate breathing.