Which best contrasts lumen with wall?

• A. Lumen is the interior space; wall is the surrounding tissue layers.
• B. Lumen is the outer surface.
• C. Lumen is a muscle layer.
• D. Lumen is a nerve ending.

Answer: (A)

Distinguishing a hollow interior from the surrounding boundary of a tube is what this item is testing. The lumen is the interior space through which contents flow, while the wall is the surrounding tissue layers that form the boundary and give the tube its structure and function. In vessels or digestive organs, the wall includes layers like mucosa, muscle, and connective tissue, all encasing the lumen.

So the statement that lumen is the interior space and wall is the surrounding tissue layers best captures how these two parts relate. The other ideas—lumen as an outer surface, a muscle layer, or a nerve ending—confuse the hollow space with a part of the wall or with tissue that isn’t the lumen itself.