An external functional means comprises at least one housing body, at least one chamber integrated into the housing body for receiving medical fluids, at least one passage integrated into the housing body for receiving and/or conducting a medical fluid, and at least one valve means completely or partly integrated into the housing body for controlling or regulating a fluid flowing through the external functional means. The invention further specifies a blood treatment apparatus and methods which may be carried out by means of the external functional means of the invention and by means of the blood treatment apparatus, respectively.