Abstract: An occluder (7) for sealing body orifices (6, 6a) of the human or animal body is illustrated and described, in particular an occluder (7) for percutaneous transcatheter sealing of atrium septum defects of the human or animal heart (1). According to the invention it is provided that the occluder (7) or parts of the occluder (7) form an electric oscillating resonance circuit, whereby at least one conductive loop forming the inductivity of the oscillating resonance circuit is provided and the occluder (7) or parts of the occluder (7) are formed by the conductive loop.