The following parts are involved in breathing process, except

The part that is not involved in the breathing process is the mouth. The breathing process involves inhaling air through the nostrils, which passes through the nasal cavity, and then enters the lungs. During inhalation, the ribs and the diaphragm expand to create more space for the lungs to fill with air. Then, during exhalation, the ribs and the diaphragm relax and contract to push the air out of the lungs. Therefore, the correct answer is "mouth".