1. Why would a patient with gallstones be advised to eat a low-fat diet?

2. A search on the internet will likely indicate that the stomach is considered part of the upper gastrointestinal (GI) tract. But this is a classical view. In more modern terms, the stomach has properties it shares with the upper GI and with the lower GI. What are the properties? What could make the stomach be considered part of the upper GI, and what could make the stomach be considered part of the lower GI?

3. Bilirubin is a component of bile and urobilinogen is a component of urine. What molecule from the blood are both derived from?