Exhalation is a passive process during which the intercostal muscles and the diaphragm relax. The ribs move downward and inward, while the diaphragm rises. This movement causes the chest to decrease in size and positive pressure to build inside the chest cavity. The positive pressure pushes air out of the lungs.
The two main types of exocrine secretory cells of the stomach are parietal cells and chief cells. Parietal cells secrete hydrochloric acid and chief cells secrete digestive enzymes such as pepsin
