Sputum can be formed in the lungs in the lumen of the trachea, bronchi, and fine bronchi, as well as in the alveolar lumen.
The bronchial mucosal glands and alveolar cells normally secrete only a small amount of mucus to keep the respiratory mucosa moist, but when the respiratory tract is invaded by pathogens or stimulated by physical and chemical factors, the respiratory mucosa will become congested, edematous, and secrete a large amount of mucus, and at the same time the body will secrete a large number of inflammatory cells, which will form phlegm after mixing the respiratory secretion with the dust inhaled and necrotic material of the tissues. It is eventually expelled from the body by coughing and ciliary movement of the respiratory tract.
Coughing up sputum is seen in almost all kinds of lung diseases, such as all kinds of pneumonia, tuberculosis, bronchiectasis, lung cancer, chronic obstructive pulmonary disease, etc. If coughing up sputum symptoms, it is recommended to consult a doctor to clarify the cause and give targeted treatment.