Final answer:
The stomach is the first internal organ affected by orally taken medications. It is where the medication starts to break down before moving to the small intestine for absorption and then undergoes first-pass metabolism in the liver.
Step-by-step explanation:
The internal organ first affected by medications taken orally is the stomach (Option B). When you swallow a medication, it passes through your esophagus and enters your stomach, where it begins to break down. The contents of the stomach, including the medication, then move into the small intestine where most of the absorption of the medication into the bloodstream takes place. However, before reaching the bloodstream, the medication must pass through the liver via the portal circulation, an essential step known as first-pass metabolism. This is where the liver can modify the medication through metabolic processes. However, the stomach is the first internal organ to be directly affected by oral medications as it is where the medication is initially processed before absorption.