The respiratory system is in charge of carrying out normal gas exchange for body cells to receive the oxygen required for life. Thus, its anatomy is especially prepared for this function.On the other hand, the air that comes in with each inspiration is capable of carrying –in addition to vital oxygen–, multiple potentially pathogenic substances dispersed in air, which represents permanent exposure to risk of disease.Respiratory infections are a very common reason for seeking medical attention. Because of their significant impact on morbidity and mortality, knowing the major mechanisms involved in the development of the most common respiratory infections is of paramount importance.
