Respiratory Tissues and Functions

Steps:

• Recall main tissues in respiratory tract: cartilage for support, ciliated epithelium for clearance, elastic fibers for recoil, smooth muscle for constriction.
• Evaluate A: Cartilage provides rigidity, not elastic recoil for exhalation.
• Evaluate B: Ciliated epithelium traps and moves particles upward for removal.
• Evaluate C: Elastic fibers enable stretch/recoil, but smooth muscle adjusts bronchiolar diameter.
• Evaluate D: Cartilage rings maintain openness of trachea/bronchi, not smooth muscle.

Why B is correct:

• Ciliated epithelium's cilia beat mucus containing suspended particles toward the throat, protecting lungs per mucociliary clearance mechanism.

Why the others are wrong:

• A: Cartilage maintains structural support; elastic recoil from lung tissue (elastin) forces air out during exhalation.
• C: Elastic fibers provide passive recoil; smooth muscle actively contracts/relaxes to control airflow resistance in bronchioles.
• D: Smooth muscle regulates diameter via contraction; cartilage's C-shaped rings prevent collapse and keep airways open.

Final answer: B