Which structure has a lumen that contains air rather than fluid?

Which structure has a lumen that contains air rather than fluid?

• A. Trachea
• B. Femur
• C. Muscle
• D. Nerve

Answer: (A)

Lumen means the hollow interior of a tube or vessel, and structures that handle air have lumens filled with air when functioning. The trachea is an airway, a hollow tube through which air travels to the lungs, so its lumen is air-filled during breathing. The femur is a bone with a marrow cavity rather than air in its hollow space. Muscle tissue isn’t organized as a hollow tube with an air-filled lumen, and nerves aren’t air conduits either; they’re bundles of cells and connective tissue with fluid surrounding them. So the structure with an air-filled lumen is the trachea.

Lumen means the hollow interior of a tube or vessel, and structures that handle air have lumens filled with air when functioning. The trachea is an airway, a hollow tube through which air travels to the lungs, so its lumen is air-filled during breathing. The femur is a bone with a marrow cavity rather than air in its hollow space. Muscle tissue isn’t organized as a hollow tube with an air-filled lumen, and nerves aren’t air conduits either; they’re bundles of cells and connective tissue with fluid surrounding them. So the structure with an air-filled lumen is the trachea.