Why can’t the lungs breathe on their own?

Lung tissue consists of a thin layer of cells, between which there are small capillaries. In these capillaries, the blood becomes rich in oxygen during respiration. But there is no muscle tissue in the lungs. Therefore, they themselves cannot perform any movements. To do this, the lungs are surrounded by the rib cage, which contains the muscles responsible for breathing. During inhalation, they tense, expand the chest, reduce the pressure inside the pleural cavities. Due to this, the lungs are stretched, an inhalation is made. Exhalation does not require the expenditure of energy from a person – it is completely passive – the pressure in the pleural cavity rises, the muscles relax and the lungs collapse.