Respiration is the process used in all living things for gaining energy. Energy is needed for keeping the vital organs working and generally staying alive. It is also needed for moving muscles. Keeping a constant body temperature is important to. Cell division, reproduction and other important processes in the body all need energy to work.

Breathing:
Breathing in >>> Inspiration
Diaphragm lowers and the ribs raise to increase the volume of the thorax. The pressure decreases so air is drawn into the lungs.

Breathing out >>> Expiration
Diaphragm raises and ribs lower which decreases the volume of the thorax. The pressure increases and air is forced out of the lungs