Which organ is NOT part of the digestive system?

The kidney is not part of the digestive system; it is part of the urinary system. The primary function of the kidneys is to filter blood and produce urine to excrete waste products from the body. In contrast, the digestive system includes organs such as the esophagus, liver, and stomach, which are involved in the processing and absorption of nutrients.

The esophagus transports food from the mouth to the stomach, where the food is mixed with gastric juices for digestion. The liver plays a crucial role in metabolism, including the production of bile, which helps in the breakdown and absorption of fats. These functions illustrate their vital roles within the digestive system, further reinforcing that the kidney does not have a role in digestion.