Which feature disappears first along the respiratory tract during histologic remodeling?

• A. Elastic fibers
• B. Smooth muscle
• C. Cartilage
• D. Cilia

Answer: (C)

In this sequence, the airway’s supporting tissues change as you move from the trachea toward the bronchioles. Cartilage provides rigid support in the trachea and large bronchi, but as you progress to smaller airways, that cartilage disappears. This loss happens early in remodeling, before other features undergo major change.

Elastic fibers and smooth muscle remain present longer in the walls of smaller airways, contributing to recoil and airway tone, while the epithelium can become nonciliated as you reach the terminal bronchioles. Cilia persist into the larger airways and diminish later, but they don’t disappear first.

So, cartilage is the feature that disappears first.