Which of the following is commonly considered an accessory organ of the digestive system?

• A. Esophagus
• B. Stomach
• C. Small intestine
• D. Teeth

Answer: (D)

Mechanical digestion begins in the mouth, where teeth grind and break down food into smaller pieces. This physical breakdown is essential because it increases surface area for enzymes to work on later, and it helps form a swallowable bolus. Teeth function as an accessory organ because they assist digestion without producing digestive enzymes or absorbing nutrients themselves. By contrast, the esophagus, stomach, and small intestine are the primary parts of the digestive tract: the esophagus mainly transports food to the stomach, the stomach begins chemical digestion with acid and enzymes, and the small intestine is where most digestion and nutrient absorption occur with help from bile and pancreatic juice. So teeth fit the label of an accessory organ since they support digestion without being the site of chemical digestion or absorption.