The present invention relates to a medical functional device (900) with a valve seat (803) for a check valve (1), wherein the check valve (1) is embodied such that it takes, in addition to a first position which is suitable for gas sterilization, a second, functional position, by means of applying force onto a section of the check valve (1) and/or by means of moving or shifting the section, in which the check valve adopts a check or non-return function, wherein the check valve (1) is embodied such that it remains in the second position after release or shortfall of the force and/or the moving effect following an accomplished transfer into the second position.
