Saturday, September 28 (2019); Respiratory system
Pleural pressure is usually negative, due to the recoil of the chest wall, the recoil of the lungs, and the negative pressure exerted by the lymphatic system, In the upright subject, it is more negative in the apices, and less negative in the bases. The vertical pleural pressure gradient is the difference between the apical and basal pleural cavity pressures. This gradient is due to the effects of gravity (i.e. weight of the lung), pressure from mediastinal contents and pressure from abdominal contents.