External functional means, blood treatment apparatus for receiving an external functional means in accordance with the invention, and method

A medical device, comprising:

• 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 at least one of receiving and conducting a medical fluid;
• at least one valve completely or partly integrated into the housing body for controlling or regulating a fluid flowing through the medical device;
• and
• at least one venous blood chamber;
• wherein the medical device is a cassette configured for a blood treatment by dialysis having at least one single-needle chamber for a single-needle access to a patient;
• wherein the single-needle chamber is disposed on a venous blood side of the medical device and above the venous blood chamber relative to an orientation of the medical device during its use, the single-needle chamber being in fluid communication with the at least one passage integrated into the housing body for at least one of receiving and conducting a medical fluid only via the venous blood chamber.