Digestion

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