The portion of the alimentary canal from the stomach to the intestines
Some references consider mouth and anus as parts of the gastrointestinal tract. However, the literal meaning of gastrointestinal pertains to the gastro– (from gastric) for stomach and intestinal for intestines, thus, only to stomach and the intestines.
Human gastrointestinal tract is divided into upper and lower: the upper consists of the stomach and duodenum (others include the esophagus and mouth) while the lower is comprised of the small intestine (except duodenum) and large intestine (others include the anus).
Word origin: Gastrointestinal + tract
Abbreviation: GI tract