organ simple organ AAO:0010051 AEO:0000190 TAO:0001492 CARO:0000021 BILA:0000021 XAO:0003038 HAO:0000021 TGMA:0001836 this class was introduced for consistency with CARO, however, it has yet to be used in this or other ontologies. It may be retired in the future EHDAA2:0003190 ZFA:0001492 UBERON:0000472 simple organs Multi-tissue structure that is not part of a compound organ.