Mucociliary clearance respiratory defense mechanism

The structural configuration of the nasal and oral passageways markedly restrict the access of large particles to the lower respiratory tract. Under normal circumstances, the filtration system of the upper airway and the mucociliary clearance system of the larger airways protect the lower respiratory infection from bacteria that may be present in the patient s environment or that reside in the upper respiratory tract. Nosocomial pneumonia and tracheitis may occur when the mucociliary and cellular defense mechanisms of the lower respiratory tract are evaded. 

Disruption of these defense mechanisms can lead to bacterial colonization or viral infection. Mucus temperature is important in controlling respiratory infections because decreasing below central body core temperature not only impairs ciliary movement,hut also enhances viral replication,- greatly increasing the likelihood of respiratory infection. Drying of airway mucus also increases the possibility of respiratory infection by reducing mucus thickness and impairing mucociliary clearance, i- i--... 

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