non-material anatomical boundary

A non-material anatomical boundary is a two-dimensional, immaterial anatomical entity that marks the border or limit of a physical structure. It is not itself a physical object but rather a conceptual demarcation, such as the boundary between one organ region and another.

Non-material anatomical boundaries enable precise spatial descriptions of where one anatomical structure ends and another begins. For example, the boundary between the endocervix and ectocervix, or between the cortex and medulla of the kidney, are non-material boundaries used to define anatomical regions.

An anatomical surface is the outer face of a three-dimensional structure and can be considered a special case of boundary. A non-material anatomical boundary more broadly refers to any 2D demarcation — whether an external surface, an internal interface between tissue types, or a conceptual dividing plane — that is contiguous and defines a spatial limit.