Digestion

The three phases of digestion are cephalic, gastric, and intestinal. During the cephalic phase, food has not entered the body but smell and thought of food stimulates the central nervous system to start preparing the body for the injestion of food. The salivatory glands begin to salivate. During the gastric phase, food begins to enter the stomach and there is a strech in the stomach that triggers hormonal and neural signals. Mechanical and chemical digestion begin to take place in the stomach. An increased pH stimulates G cells to release gastrin, which stimulates stomach activity. The intestinal phase begins when food passes through the pyloric sphincter and into the small intestine. There is mechanical, endocrine, and neural control.