sentences: the respiratory system transfers oxygen to the circulatory system
docs: circulatory_system is body_part. mammal_circulatory_system is circulatory_system. respiratory_system is body_part. respiratory_system is organ_system. circulatory_system is organ_system. respiratory_system is system. circulatory_system is vascular_system. vertebrate_circulatory_system is body_part. vertebrate_circulatory_system is circulatory_system. mammal_circulatory_system is vertebrate_circulatory_system.