Which organ is part of both the digestive system and the endocrine system?

The pancreas is unique because it serves as both an essential organ of the digestive system and plays a critical role in the endocrine system. In the digestive system, the pancreas produces digestive enzymes that are released into the small intestine to help break down food. This enzymatic function is crucial for the proper digestion of carbohydrates, proteins, and fats.

Simultaneously, the pancreas also has endocrine functions. It contains clusters of cells known as the islets of Langerhans, which produce hormones such as insulin and glucagon. These hormones are vital for regulating blood sugar levels, making the pancreas integral to glucose metabolism. This dual functionality is what makes the pancreas a unique organ straddling both systems.

The other organs listed do not fulfill this dual role; they either serve one system or the other, making the pancreas the correct answer.