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The anatomy and physiology of the friction ridge skin form the basis for several critical elements that underlie the examination process. The anatomy and physiology explain how the features of the skin persist, how the features of the skin age, how the skin responds to injury, and why scars that form are unique. Another element explained by the structure of the skin is the mechanics of touch. Understanding how the friction ridge skin reacts when it contacts a surface can provide valuable assistance during the examination of friction ridge impressions.