Langer's lines are lines which can be extrapolated by connecting linear openings made when a round pin is driven into the skin of a cadaver, resulting from the principal axis of orientation of the subcutaneous connective tissue (collagen) fibres of the dermis; they vary in direction with the region of the body surface. Skin tends to be much stiffer along these lines rather than across them.
These lines were developed by Karl Langer , an anatomy professor, from cadavers in rigor mortis. Kraissl , however, preferred lines oriented perpendicular to the action of the underlying muscles. Later, Borges described relaxed skin tension lines, which follow furrows formed when the skin is relaxed and are produced by pinching the skin.