A tubular organ in animals that is divided into a series of zones specialized for the ingestion, digestion, and absorption of food and for the elimination of indigestible material (see illustration). In most animals the canal has two openings, the mouth (for the intake of food) and the anus (for the elimination of waste). Simple animals, such as cnidarians (e.g. Hydra and jellyfish) and flatworms, have only one opening to their alimentary canal, which must serve both functions.

The human alimentary canal