Pleural recesses

Any of the four spaces in the pleural cavity taken up by the lungs as they expand during inhalation. For example, the costodiaphragmatic recess is a potential space in the pleural cavity located at the junction of the costal and diaphragmatic parietal pleurae. 

The lungs expand into this recess during forced inspiration, however the recess never fills completely. During expiration, it contains no lung tissue, only pleural fluid.