Goldfish
Once food is in the goldfish’s mouth, it’s pushed to the back of the throat where a set of teeth grind and crush it. The ground down food passes down a tube called the oesophagus, which squeezes out excess water.  The oesophagus is lined with taste buds and cells that produce mucus to keep things moving on. The oesophagus empties into an expandable section of the goldfish’s digestive which is not to be confused with the stomach. It is simply a buffer zone to hold excess food as needed. Just before this expanded section, chemicals from the gallbladder and pancreas are pumped in with the food.  The ones from the gallbladder make up bile, which is used to break down fats; the ones from the pancreas contain enzymes that are used to break down proteins. All along the digestive tract are cells that secrete enzymes that act on carbohydrates, breaking them down into sugars. From the expanded section to the goldfish’s anus, lots of mucus is produced and as much useful material as possible is absorbed into the bloodstream to be used for energy, growth, protection and repair.