The teeth in the mouth cut, tear, and grind the food into smaller pieces so it can fit down the throat. The saliva is squirted into the food to moisten and soften the food. Remember, Saliva contains chemicals called enzymes, which break down the starches in the food. The enzyme in saliva that breaks down starch into sugar is called amylase.
The tongue is a muscle that works with the food & saliva to form a "ball" that can be swallowed. The tongue also contains taste buds that helps us tell the difference between salty, sour, sweet, & bitter foods.
The esophagus is a transportation tube from the mouth to the stomach. Remember, when we swallow, we're closing a trap door in our throat known as the epiglottis. This sends food down the esophagus and prevents food going down the trachea to our lungs. Food moves down the esophagus through a process called perilstalsis. Perilstalsis uses layers of muscle in your esophagus and intestines. The muscles relax and contract in a wave motion to pass food forward.
Once the food gets into the stomach from the esophagus, the stomach uses chemicals to make the food particles stronger. These chemicals include gastric juices and include enzymes that are chemicals that break down food. When the stomach is done moving the food, it's now a creamlike liquid called chyme. Finally a valve at the end of the stomach opens, sending the food past the liver.
The liver makes a chemical called bile, which is stored inside the gall bladder. When the gall bladder mixes the bile with the food, it breaks down the fat in the food.,
The pancreas releases more chemicals into the food, breaking down the carbohydrates and proteins.