Which of the following is NOT an organ of the digestive system?

The kidney is not an organ of the digestive system; rather, it is part of the urinary system. Its primary function is to filter blood, remove waste, and regulate fluid balance in the body. The digestive system, on the other hand, includes organs that are involved in the process of breaking down food, absorbing nutrients, and eliminating waste.

The stomach, pancreas, and esophagus are all integral components of the digestive system. The stomach plays a key role in breaking down food using acids and enzymes. The pancreas contributes by producing digestive enzymes and hormones that help regulate metabolism. The esophagus is the tube that transports food from the mouth to the stomach, facilitating the movement of food through the digestive tract. Each of these organs plays a crucial role in digestion, while the kidney's functions are not related to this system.