Since the perch is often used to describe the typical internal anatomy of a fish, let's assume the fish on the end of your line is one of this species. If you were to open the mouth of your catch, you would find a mouth cavity with a number of small, pin-like teeth used for holding food. At the end of the stomach, a valve regulates the passage of food into a coiled intestine which opens to the exterior through the anus . Some fish that must 'chew' their food have 'teeth' located in the pharynx. These 'teeth' serve to mash the food so there is no danger of food bits being washed into the gills.
Extra room is required to digest the fibre found in plant matter.
Attached at the upper end of the intestine, close to the stomach, are finger-like projections called pyloric caeca . These aid in the absorption of food in the intestine and serve as a temporary storage space. Since they are definite in number for each species, they are sometimes used to determine the fish species. The liver is located in front of the stomach and connected to the liver is a gall bladder . Both function in the digestion of food by secreting necessary digestive enzymes.