What are the tiny hair-like structures that help keep air passages clean called?

• A. Cilia
• B. Flagella
• C. Microvilli
• D. Filaments

Answer: (A)

The tiny hair-like structures that help keep air passages clean are called cilia. These structures line the respiratory tract and play a crucial role in maintaining respiratory health. Cilia work by continuously beating in a coordinated fashion to move mucus, which traps dust, pathogens, and other debris, upward toward the throat. This mechanism, known as the mucociliary escalator, helps to clear the airways, preventing infections and keeping the lungs clear of contaminants.

In contrast, flagella are longer whip-like structures primarily involved in movement in certain cells, typically sperm cells, and are not involved in respiratory function. Microvilli are small projections that increase the surface area for absorption in certain types of cells, such as those in the intestines, but they do not have the same protective function as cilia. Filaments generally refer to thread-like structures but do not specifically describe the cleaning function in the context of respiratory air passages.