[Campbell Biology P.992] The “mucus escalator” is a crucial defense mechanism in the mammali... | Practice Question

The “mucus escalator” is a crucial defense mechanism in the mammalian respiratory system. Which of the following statements about it is correct?

  • A: It primarily functions in the alveoli to remove foreign particles.
  • B: It involves cilia beating to move trapped contaminants upward to the pharynx, where they can be swallowed.
  • C: The “mucus escalator” is primarily responsible for gas exchange between the air and blood.
  • D: It is composed of a thick layer of mucus that traps oxygen and facilitates its absorption.

Explanation

The text states that the epithelium lining the major branches of the respiratory tree is covered by cilia and a thin film of mucus. The mucus traps dust, pollen, and other particulate contaminants, and the beating cilia move the mucus upward to the pharynx, where it can be swallowed into the esophagus. This process is referred to as the “mucus escalator” and plays a crucial role in cleansing the respiratory system.