The smooth muscle is the generic term for the unstriated muscle, which is composed of mononuclear cells with long spindles. It does not constitute an independent organ, but only a factor (muscle layer) that constitutes the body wall and the visceral wall. Smooth muscle cells are connected to each other to form a tubular structure or a hollow organ; The organ can be moved and deformed by shortening and generating tension, and can also produce continuous contraction or tension contraction, so that the organ maintains its original shape against the applied load. The contraction, relaxation, proliferation and apoptosis of bronchial smooth muscle cells are related to the pathophysiological processes of many clinical diseases. Such as bronchial asthma, chronic obstructive pulmonary disease and so on. For example, in the onset of asthma, hyperplasia and hypertrophy of the tracheal smooth muscle can be detected, the phenotype also changed, from contractile to synthetic and secretory, and secreted multiple and cytokines; and signs of migration to the tracheal cavity, and there are signs of migration to the trachea.
