Question

The function of tracheal cilia is to
A. Pass mucus out
B. Pass mucus in
C. Pass air out
D. Pass air in

Answer 1

Hint: Ciliated epithelium is a thin tissue that has hair-like structures embedded. These hairs, called cilia, generate a wave-like motion back and forth to assist the movement of particles in the areas where they are present.
The cilia located within the lining of the trachea and bronchi act as a defense system for the body by keeping the airways clean.

Complete answer: The trachea is lined with a moist mucous membrane layer composed of cells containing small hairlike projections called cilia.
The cilia extend further into the channel (lumen) of the trachea to trap particles. Additionally, there are certain cells and ducts within the mucosa that secrete mucus droplets and water molecules.
Cilia within the trachea trap foreign particles such as bacteria and viruses.
The cilia displace the harmful foreign particles inhaled along with the air up to the pharynx where it's either coughed out or swallowed into the alimentary canal.

So, the correct answer is option A. Pass mucus out.

Note: If there's any kind of injury with either the mucus or the cilia, the airways may become blocked, and therefore the harmful germs and particles are often trapped within the lungs, causing damage.