Source:http://linkedlifedata.com/resource/umls/id/C0817032
FMA: Anatomical boundary entity which has two spatial dimensions. Examples: body surface, epigastrium, precordium, right iliac fossa.,UWDA: Non-material physical anatomical entity of two dimensions, that is demarcated by anatomical lines or points on the external or internal surfaces of anatomical structures. Examples: body surface, epigastrium, precordium, right iliac fossa.