The mouth breaks up food particles. This is where mechanical digestion starts; the food is broken down into smaller pieces. And chemical digestion occurs when the food mixes with the saliva. In the mouth the lipids/fats are broken down by lingual lipase, and complex carbohydrates are broken down by salivary amylase.
The esophagus transports food to the stomach. The esophagus produces no digestive enzymes but does produce mucus for lubrication.
The stomach stores and churns food. Pepsin digests protein. It is produced by the stomach cells called "chief cells" in its inactive form pepsinogen.Pepsinogen is then activated by the stomach acid into its active form, pepsin.
The liver digests food by producing bile to break down fats, removing toxins and breaking down and storing some vitamins and minerals.
The gallbladder is a small pouch that sits just under the liver. bile is then stored in the gallbladder. After meals, the gallbladder is empty and flat, like a deflated balloon. Before a meal, the gallbladder may be full of bile and about the size of a small pear.