Which organ is NOT part of the digestive system?

The heart is not part of the digestive system; it is primarily a muscular organ responsible for pumping blood throughout the body, thereby playing a crucial role in the circulatory system. The digestive system comprises organs involved in the processing and breakdown of food, nutrient absorption, and waste elimination. In contrast, the pancreas, liver, and stomach are all integral components of the digestive system. The pancreas produces digestive enzymes and hormones, the liver processes nutrients, detoxifies substances, and produces bile, while the stomach is involved in the storage and initial breakdown of food. This delineation helps in understanding the functions of various organs in the body and their respective systems.