A sixth grade science teacher asks the students to explain the role of cilia in the lower respiratory tract. Which student response is the best?

Question

A) "These little hairs move germs trapped in mucous toward the throat so the body can cough them out."
B) "Cilia help to warm the airways so that moisture in the air can neutralize any germs that get in our lungs."
C) "Cilia can trap the microbes in one location so the body can grow scar tissue around them and wall them off so they can't cause disease."
D) "Cilia help facilitate a chemical defense against germs by secreting an enzyme that will cement the germ to the lining of the airways."

Answer 1

Ans: A
Feedback:
Also in the lower respiratory tract, hair-like structures called cilia protrude through the epithelial cells. The synchronous action of the cilia moves many microbes trapped in the mucous toward the throat. The physiologic responses of coughing and sneezing further aid in their removal from the body. Chemical defenses against trapped microbes include the following: lysozyme, which is a hydrolytic enzyme capable of cleaving the walls of bacterial cells; complement, which binds and aggregates bacteria to increase their susceptibility to phagocytosis or disrupt their lipid membrane; and members of the collectin family of surfactant proteins in the respiratory tract. The best-defined function of the surfactants is their ability to opsonize pathogens, including bacteria and viruses, and to facilitate phagocytosis by innate immune cells such as macrophages.