The respiratory system provides protection against irritants or foreign particles entering the lungs. The respiratory system has several protection mechanisms.
Firstly, the nose filters the air when breathing in, preventing irritants such as dust and foreign matter from entering the lungs.
Secondly, if an irritant enters the airways or breathing tubes, sputum that lines the airways traps unwanted particles. Tiny hair-like structures called cilia line the breathing tubes or airways. They move in a sweeping motion to help move the sputum and unwanted particles up into the mouth where they can be cleared. The function of the tiny hairs can be affected by smoke, alcohol and dehydration.
The third protective mechanism for the breathing system is the cough. A cough is the result of irritation to the breathing tubes (bronchi and bronchioles). A cough can clear sputum from the lungs.
Lastly, the lungs also have a built-in immune system that acts against germs.