Source:http://linkedlifedata.com/resource/umls/id/C1744602
UWDA: Anatomical structure, which consists of a specific set of the members of (predominantly) one organ or organ part subclass interconnected by zones of continuity or body substances; is demarcated from other subdivisions of the same organ system by one or more zones of continuity or anatomical lines; together with other subdivisions of the same organ system, it constitutes an organ system. Examples: rib cage, facial skeleton, portal system, central nervous system, upper respiratory tract, muscle group of back.