Fish have a digestive system that begins at the mouth and ends at the anus. It is usually comprised of a mouth, esophagus, stomach, pancreas and intestine. Not all species of fish, however, have a stomach, such as Cyprinidonts and Cyprinids, and herbivorous fish have longer digestive tracts than carnivorous fish.
Food is taken into the body through the mouth and then to the pharynx where it is ground with pharyngeal teeth before entering the esophagus. Layered with muscle, the walls of the esophagus can expand in order to accommodate large objects. Food is then broken down in the stomach by substances released from gastric glands. Some species of fish have a gizzard at the beginning of the stomach which begins the digestive process. Pyloric caeca are located at the end of the stomach in many species of fish and these continue the digestive process and expand the gut. Digestion is aided by the secretion of enzymes from the pancreas to the intestine where most of the food absorption occurs. The feces then leaves the body via the anus.