Q. How does the body defend itself from microorganisms and other harmful substances that enter the airway during the breathing process?

The epithelium of the airway is a ciliated epithelium and has mucus-secreting specialized cells, the secreted mucus covers the internal wall of the airway retaining organisms and foreign particles that then are swept by the cilia of the epithelium.

In the mucous ciliated epithelium of the airway there is also intense activity of the immune system with leukocytes and antibodies destroying and inactivating foreign agents.

Other defense mechanisms of the airway are the cough and the sneeze. They help the elimination of semifluid and solid particles like pathologic residuals (sputum) and accidentally aspired objects.