Final answer:
Cilia are microscopic projections that, along with mucus, form the mucociliary escalator, trapping and removing harmful particles from the respiratory system. They move the mucus and entrapped particles toward the throat where they can be expelled or swallowed, eventually reaching the stomach acid which neutralizes pathogens.
Step-by-step explanation:
The cilia and mucus in the respiratory system play a crucial role in protecting the body from potential harm. Cilia are microscopic, hair-like projections found on cells that line the airways, while mucus is a sticky substance secreted by these cells. Together, they form the mucociliary escalator, which is vital for trapping and removing dust, germs, and other foreign particles. The cilia constantly move in a coordinated, wave-like motion, pushing the mucus and entrapped particles up toward the throat. This action enables the removal of these substances from the body when you cough or swallow.
In the respiratory system, the cilia are supported by microtubules and beat in unison to move both mucus and trapped particles. While most of the mucus movement is directed upward towards the throat, nasal cilia move the mucus blanket downward towards the throat to be expelled or swallowed. After swallowing, the particles are subjected to the acidic environment of the stomach, which neutralizes many pathogens. The efficiency of the mucociliary escalator is dependent on the viscosity of the mucus. A balanced transport of ions, including chloride (Cl-) and sodium (Na+), ensures that mucus remains at an optimal consistency for clearance.