The costal margin, sometimes referred to as the costal arch, is the medial margin formed by the false ribs, which in humans is from the eighth rib to the tenth rib. [ http://en.wikipedia.org/wiki/Costal_margin ]
- UMLS:C0230143 (ncithesaurus:Costal_Arch)
- EMAPA:37491 (MA:th)
we treat margin and arch in FMA as equivalent here, as a temporary measure. This may be split in future. We follow MA in making this a part of the rib.