The gastrointestinal (GI) system is made up of the GI tract plus accessory organs that include salivary glands, pancreas, liver, digestive enzymes and gallbladder. The function of the GI system is to process nutrients and energy from food and fluids that you ingest. In people with GI problems, these functions are impaired. GI conditions include irritable bowel syndrome (IBS), inflammatory bowel diseases (IBD) such as Crohn's and ulcerative colitis, gastroesophageal reflux disease (GERD), celiac disease, anal disorders, diverticular disease, colon polyps and cancer and colitis.