Answer
Epidermal ridges are produced by downward growth of cells of the basal layer of the embryonic epidermis into the less well-differentiated dermis. These downward folds of epidermal tissue --primary pegs--result in the formation of creases/grooves at the skin surface. The dermis responds by forming upward proliferations of tissue called dermal papillae which raise the epidermis between adjacent epidermal grooves to form epidermal ridges.
Epidermal grooves and ridges begin to form in about the 12th week of embryonic life, and the pattern is complete by the end of the 4th month of embryogenesis. Sweat ducts open on the tops of epidermal ridges as pores. And the combination of sweat with the pattern of epidermal ridges and grooves is responsible for the fact the we leave prints--fingerprints- on whatever we touch. Fingerprints are also called dermatoglyphs and the forensic/anthropological study of finger print patterns is called dermatoglyphics.
Epidermal ridges strengthen the connection between dermis and epidermis; they also increase the surface area of the epidermis which improves tactile sensitivity, and enhances the firmness/sureness of the hand grip.
Work Step by Step
Fingerprints exist on soles, palms and the solar and palmar surfaces of toes and fingers, respectively. They present as lines, whorls, loops and arches. It is true that not even twins have exactly the same finger print pattern, but similarities in overall patterns exist, based on genetic inheritance-- normal and pathological-- sex, age, and ethnicity.
