Bronchitis is damage to the tissues (mucous membranes and walls) of the bronchial apparatus, which is followed by increased mucus secretion and coughing, and is provoked by various factors. When infected, the mucous membranes of the nasal passages are initially affected and sinusitis develops. After the infection "descends” to the lower parts of the respiratory system and, as a result, reaches the bronchial apparatus. The inflammatory process develops from several hours to several days, after which a characteristic cough appears with expectoration of a sufficiently large amount of sputum. With long-term bronchitis, the inner surface of the bronchi hypertrophies or atrophies. Subsequently, both of these conditions can lead to the development of serious consequences of bronchitis.