Developmental Stages of Fingerprints on Palm & Sole

DEVELOPMENT OF FINGERPRINTS

·       During late embryological development, the embryo goes through "morphogenesis," or shape formation. The arms, legs, knees, elbows, fingers, and toes can all be seen in the second month after about 4 weeks of EGA(Estimated Gestational Age).

·       During this time, mesenchyme swellings known as "volar pads" appear on the palms of the hands and soles of the feet. Volar pads are transient swellings of tissue called mesenchyme beneath the epidermis on the palmar surface of the human fetus's hands and soles of the feet.

·       This tissue bed, i.e., volar pads and their regression, along with other features such as primary ridges, genetic traits, fetal position, and amniotic fluid amount, all contribute to forming ridge patterns.

·       This process begins at 5-6 weeks and is completed by the 6th month, or the 21st - 24th week (EGA).

Primary Ridge Formation:

·       Basal cells of the epidermis begin to divide rapidly around 10-10.5 weeks EGA.

·       Shallow "ledges" can be seen on the bottom of the epidermis as volar epidermal cells divide.

·       The visualization of the primary ridge structure includes active cell proliferation centers, which will become sweat gland development centers.

·       The resulting linear ridges of rapidly dividing epidermal cells fold into the dermis, forming the epidermal-dermal junction's first visible ridge structure.

·       These ledges or linear ridges represent the overall patterns that will become permanent on the volar surfaces several weeks later.

Primary Ridge Propagation:

·       From the time they form at 10.5 weeks EGA until around 16 weeks EGA, primary ridges mature and extend deeper into the dermis for about 5.5 weeks. Cell growth occurs along the primary ridge in what is known as the "proliferative compartment" during this stage of development.

·       The proliferative compartment contains basal and some suprabasal cells that are ultimately governed by stem cells and are responsible for the production of new skin cells in the basal layer of skin.

Secondary Ridge Formation:

·       The primary ridges are growing in two directions by 15 weeks EGA: downward penetration of sweat glands and upward push of new cell growth.

·       Secondary ridges appear between the primary ridges on the underside of the epidermis between 15 and 17 weeks EGA.

·       Secondary ridges are also cell proliferation that results in basal epidermis downfolding.

·       There is intense cell proliferation in the epidermis's basal layer, resulting in cylindrical cells that eventually fold towards the dermis to avoid stress. Primary and secondary ridge formation.

·       Formation of Dermal Papillae: Dermal papillae are dermal remnants that project upward into the epidermis and connect primary and secondary ridges.

·       They begin to form around 23 weeks EGA and continue to grow in complexity throughout fetal development and even into adulthood.

Ridge Formation and Volar pads:

·       In friction skin, ridges form transversely to the lines of growth stress. The hand grows primarily longitudinally (lengthwise), and ridges typically cover the volar surface transversely (side to side).

·       Friction ridge patterns are influenced by the size, height, and shape of the volar pad.

·       A symmetrical pattern (a whorl or an arch) will result if the volar pad and other elements of finger growth are symmetrical at the start of primary ridge formation. Ridges will form concentrically around a volar pad's apex.

·       If the volar pad and other growth factors of the finger are asymmetrical during the critical stage, the ridge flow of the resulting pattern will be asymmetrical as well.

·       Volar pad regression: As the volar pads' growth slows, their contour becomes progressively less distinct on the faster-growing surface.

·       The term "regression" refers to this process. However, it is critical to understand that the pad is not shrinking; rather, the volar pads are being surpassed by the faster growth of the larger surrounding surface.