the respiratory system is a part of the body
respiratory_system is system. respiratory_tract is not body_part. respiratory_tract is internal_body_part. respiratory_system is organ_system. respiratory_tract is body_part. respiratory_system is body_part. respiratory_system is not body_part. respiratory_tract is not internal_body_part. mammal_respiratory_tract is body_part. lower_respiratory_tract is body_part.