What are common digestive system diseases?

Quick med school!: Wow, that's like a whole semester of med school. Maybe more. Diseases can be self limited, like viruses or GI bugs; or functional, like GERD and irritable bowel syndrome; or inflammatory, like Crohn's disease and ulcerative colitis, or diverticulitis; or structural, like strictures, or cancers. There are a host of others, too many to add here. Go to reputable website to read more.