Skin lines are anatomical features that include:
Langer's lines - sometimes called cleavage lines, are topological lines drawn on a map of the human body. They correspond to the natural orientation of collagen fibres in the dermis, and are generally parallel to the orientation of the underlying muscle fibres. They were historically defined by the direction in which the skin of a human cadaver will split when struck with a spike. Langer's lines have relevance to forensic science and the development of surgical techniques.
Source: https://en.wikipedia.org/wiki/Langer%27s_lines (derived 15-7-2016)
Blaschko's lines - are lines of normal cell development in the skin. These lines are invisible under normal conditions. They become apparent when some diseases of the skin or mucosa manifest themselves according to these patterns. The lines are believed to trace the migration of embryonic cells. They do not correspond to nervous, muscular, or lymphatic systems. The lines can be observed in other animals such as cats and dogs.
Source: https://en.wikipedia.org/wiki/Blaschko%27s_lines (derived 15-7-2016)
Kraissl's lines - are the lines of maximum skin tension. Although Langer's lines were defined in cadavers, Kraissl's lines have been defined in living individuals.
Source: https://en.wikipedia.org/wiki/Kraissl%27s_lines (derived 15-7-2016)