the digestive system breaks down food into nutrients for the body
mammal_digestive_tract is body_part. liver has produces_bile_to_help_digest_food digestive_system is system. digestive_tract is not body_part. digestive_system has not do_with_food digestive_tract is organ_system. digestive_tract is body_part. every_living_human_being has digestive_system digestive_system has do_with_food digestive_tract is not organ_system.