Functional groups are defined as specific groupings of atoms or bonds which are part of a larger hydrocarbon chain. It is necessary that you are able to recognize these groups by structure and by name. The ending of the name as a suffix tells the type of compound or functional group present.
a slight constriction of the aorta immediately distal to the left subclavian artery at the point of attachment of the ductus arteriosus. aortic isthmus. A constriction in the fetal aorta between the ductus arteriosus and the left subclavian artery. The condition sometimes persists into adulthood.
isthmus. 1  a narrow strip of land, bordered on both sides by water, connecting two larger bodies of land. 2  Anatomy, Zoology. a connecting, usually narrow, part, organ, or passage, especially when joining structures or cavities larger than itself. 3  Ichthyology. the narrow fleshy area between the sides of the lower jaw of a fish.