An external functional device is disclosed, comprising at least one housing element, at least one chamber (9, 15, 21, 57) that is integrated into the housing element and holds medical fluids, at least one duct (17, 19, 49) that is integrated into the housing element and holds and/or conducts a medical fluid, and at least one valve mechanism (35, 36, 39, 40, 47, 51, 53, 61) that is entirely or partly integrated into the housing element and controls or regulates a fluid flowing through the external functional device. The invention further relates to a blood treatment apparatus and methods that can be carried out using the external functional device or blood treatment device of the invention.
