Which of the following is an organ of the hepatopancreas system?

The liver is an essential organ of the hepatopancreatic system, which plays a crucial role in the digestion and metabolism processes in the body. The term "hepatopancreas" refers to the combined functions of the liver and pancreas, which work closely together in producing digestive enzymes, hormones, and bile that aid in the digestion and absorption of nutrients.

This system is integral to processing substances absorbed from the gastrointestinal tract and provides vital metabolic functions, such as regulating blood sugar levels, synthesizing proteins vital for blood clotting, and detoxifying various metabolites.

The other options listed, such as the stomach, lungs, and kidneys, serve distinct functions unrelated to the specific interactions facilitated by the liver and pancreas. The stomach primarily assists in food digestion, the lungs are responsible for gas exchange, and the kidneys play a critical role in filtering blood and regulating fluid balance. Each of these organs is vital to other body systems but does not belong to the hepatopancreas system.