A medicinal device with a tubular wall made of webs which delimit the cells, and a flexible membrane which forms at least one flap which has a first end connected to at least one first web of a cell, and a free second end which is disposed opposite the first end in the longitudinal direction of the flap. The flap, in the closed position, extends along the tubular wall and at least partially closes the cells, and can be moved to an open position in which the flap is radially deviated in relation to the wall in order to open the cells in a valve-like manner.