Source:http://linkedlifedata.com/resource/umls/id/C0449629
UWDA: Non-material physical anatomical entity of one dimension, which forms a boundary of an anatomical surface or is a modulation of an anatomical surface. Examples: margin of tongue, posterior border of right lung, inferior margin of liver, arcuate line of hip bone, sulcus terminalis of heart, pancreatic incisure.,FMA: Anatomical boundary entity which has one spatial dimension. Examples: margin of tongue, posterior border of right lung, inferior margin of liver, arcuate line of hip bone, sulcus terminalis of heart, pancreatic incisure.