The pathological changes of chronic obstructive pulmonary disease mainly include those of chronic bronchitis and emphysema. The main pathological changes of chronic bronchitis include degeneration and shedding of bronchial epithelial cells. The bronchial tubes themselves have many cilia, just like a room with many brooms, which can be used to clear out substances such as phlegm through the swinging of the cilia. However, in patients with chronic bronchitis, the cilia may fall off, degenerate, collapse, and appear to be in a state where there is no way to carry out the cleaning. Of course, the mucus cells and the cells of the secretory glands in it may also change, and there may be a large accumulation of inflammatory cells. The recurrence of chronic bronchitis leads to a downward shift of inflammation, which may be surrounded by inflammatory changes, and the smooth muscle bundles may undergo repeated breaks and repairs, which in turn leads to tracheal remodeling. Airway remodeling, i.e., changes in the structure of the airways, can lead to incomplete reversibility of the airways. The pathological changes in emphysema are mainly abnormal dilatation of the terminal fine bronchioles, leading to hyperinflation of the alveoli and a decrease in elastic fibers. So both chronic bronchitis and emphysema lead to pathological changes in chronic obstructive pulmonary disease.