Which of the following organs is NOT classified as an accessory organ of digestion?

The stomach is classified as a primary organ of digestion rather than an accessory organ. Primary organs, including the stomach, are directly involved in the mechanical and chemical breakdown of food. The stomach plays a crucial role in this process by mixing food with digestive juices and facilitating the initial stages of digestion through churning and enzymatic action.

In contrast, accessory organs such as the liver, gallbladder, and pancreas contribute to digestion but are not directly involved in the digestive tract. They produce and store substances that aid in the digestion of food: the liver produces bile, the gallbladder stores bile, and the pancreas secretes digestive enzymes and bicarbonate into the small intestine. These organs support the digestive process without being part of the food passage itself. Therefore, identifying the stomach as a primary organ clarifies why it is not considered an accessory organ of digestion.