Which of the following is NOT a part of the digestive system?

The kidneys are not part of the digestive system; rather, they are part of the urinary system. Their primary function is to filter blood, remove waste, and regulate fluid and electrolyte balance in the body. In contrast, the liver, gall bladder, and pancreas are all integral components of the digestive system, contributing to the process of digestion. The liver produces bile, which helps in the digestion and absorption of fats. The gall bladder stores and concentrates bile until it's needed in the digestive process. The pancreas produces digestive enzymes and hormones that are crucial for digestion and regulating blood sugar levels. Understanding the roles of these organs helps clarify their functions within the respective systems of the body.