What are flexure lines?

The deeper part of the dermis is responsible for markings on our skin surface called Flexure lines. These lines are easily observed as the deep skin creases on the palms. Flexure lines result from a continual folding of the skin, often over joints, where the dermis attaches tightly to underlying structures. Flexure lines are also visible on the wrists, soles of the feet, fingers, and toes.