Which of the following defines lumen? a. The opening between the duodenum and jejunum b. The intestinal enzyme that hydrolyzes dietary nucleic acids c. The conduit from the mouth to the stomach d. The continuous inner space within the GI tract e. The flavor of monosodium glutamate

Answer: Option d: the continuous inner space within the GI tract.

Explanation: In the GI tract, lumen is a hollow space, through which food passes. Lumen should be clear and there should be no obstruction when food passes through it. GI tract consist of mouth, stomach, small intestine, large intestine and anus. Each part has different functions and different enzymes and chemicals are produced and mixed with food you ingest for the process of digestion. Lumen is covered with mucosa.