No chemical digestion occurs in the esophagus. The esophagus is used in order to move food into the stomach using peristaltic motion.

Amylase is introduced in the mouth and begins breaking down carbohydrates. Pepsin in the stomach helps digest proteins. Lipase, trypsin, and other digestive enzymes are introduced in the small intestine, where the majority of chemical digestion takes place.

The duodenum is the first section of the small intestine. It is the site of the most digestion in the small intestine (and the digestive tract in general) because pancreatic enzymes and bile are released into its lumen. These enzymes break down proteins and carbohydrates, while the bile helps to digest lipids and fats. The jejunum and ileum are primarily involved in absorbing nutrients. The cecum is part of the large intestine.

While the pancreas is responsible for the secretion of the majority of digestive enzymes, the liver is responsible for the creation of bile. The gall bladder is responsible for the storage of bile. When the gall bladder is stimulated, bile is released into the small intestine, where it helps with the emulsification and digestion of fats.

The liver has a variety of functions, including blood detoxification, glycogen formation, and blood filtration. The liver is not responsible for chemical digestion, but is needed to synthesize and store key nutrients and macromolecules. Protein digestion primarily takes place in the small intestine, though the process begins in the stomach.

The digestive system consists of the organs that food passes through, from the mouth to the anus, as well as the accessory organs that influence digestion. This includes organs that produce materials aiding in digestion, for example the liver, which produces bile the digest fats. The mouth is the first step in the digestive tract, the duodenum is a region of the small intestine, and the colon is a region of the large intestine.

The lymph nodes are part of the lymphatic system and do not play a role in the digestive system.

The large intestine is located near the end of the gastrointestinal tract. Its primary function is to reabsorb water and nutrients prior to elimination of waste. Mechanical digestion of food occurs in the mouth and stomach. Chemical digestion of food occurs in the mouth (saliva has amylase), stomach, and early in the small intestine. Blood glucose levels are maintained by the pancreas.

Bile is a dark greenish brown substance continuously produced by the liver. It is stored and concentrated in the gallbladder, and is released into the small intestine after eating. In the small intestine, bile aids in the digestion of lipids (this is a very important part of the absorption of fat soluble substances such as certain vitamins).  

The digestive system begins at the mouth where food is chewed into pieces small enough to be digested. In the mouth, food is already starting to be digested by enzymes, and is lubricated by saliva (saliva starts to be secreted even before you take your first bite). Next the pharynx, also called the throat, receives the food from the mouth. The food is then moved to the esophagus, which carries food to the stomach.  From the stomach food is moved to the small intestine, then to the colon, rectum, and anus. During this process there are a number of motility types, hormones, secretions, and accessory digestive organs involved in the digestive process. 

The trachea, also known as the windpipe, moves air from the pharynx (shared with the digestive system) to the bronchi and then into the lungs. It plays no role in digestion.  

The pancreas is an important organ in digesting fats. The fat soluble vitamins (A, D, E, K) rely on the pancreatic function for their absorption into the body. Without the pancreas, an individual with cystic fibrosis will have fat soluble vitamin deficiencies and steatorrhea (fatty stools). 

Initial protein digestion takes place in the stomach. Chief cells are responsible for releasing pepsinogen into the stomach, an inactive enzyme (zymogen) that must be cleaved in order to form pepsin. The activation of this enzyme is accomplished by the release of hydrochloric acid into the stomach by parietal cells.

Goblet cells release mucus into the stomach to protect the epithelium from the acidic environment. G cells release gastrin, which stimulates parietal cells to release acid.