The normal function of the digestive tract is marvelously coordinated. Food and fluids enter at the top for digestion and absorption. The waste moves smoothly down the digestive tract for timely elimination. Not surprisingly, in some people a certain amount of incoordination in this process occurs. These people do not have changes in their anatomy as a cause of this difficulty, nor do they have ulcer, tumor, or inflammation. This may involve the colon (the large intestine). The change is in function; hence it is called functional bowel disease. Other names are irritable colon syndrome, irritable bowel syndrome, and mucous colitis.