The Gastrointestinal System
The Gastrointestinal System is responsible for the breakdown and absorption of various foods and liquids needed to sustain life. Many different organs have essential roles in the digestion of food, from the mechanical disrupting of the teeth to the creation of bile (an emulsifier) by the liver. Bile production of the liver plays a important role in digestion: from being stored and concentrated in the gallbladder during fasting stages to being discharged to the small intestine. In order to understand the interactions of the different components we shall follow the food on its journey through the human body. During digestion two main processes occur at the same time. 1. Mechanical digestion: larger pieces of food get broken down into smaller pieces while being prepared for chemical digestion. Mechanical digestion starts in the mouth and continues into the stomach. 2. Chemical digestion: starts in the stomach and continues into the intestines. Several different enzymes break down macromolecules into smaller molecules that can be absorbed. The GI tract starts with the mouth and proceeds to the esophagus, stomach, small intestine (duodenum, jejunum, ileum), and then to the large intestine (colon), rectum, and terminates at the anus.