A fingerprint is the impression left as a
result of the friction ridges (or raised
portion of the skin consisting of multiple
connected ridges) on a human finger (or other
primates). Human fingerprints are detailed,
nearly unique, difficult to alter, and persist
over a whole human lifespan.
These ridges are caused by the underlying
dermal papillae (small, nipple-like extensions of
the uppermost layer of the dermis) into the
epidermis. The ridge patterns are partly
determined by genetics that develop before
birth; even identical twins who share DNA will
not have identical fingerprints. And they are
partly developed from the pressure on a fetus's
developing fingers in the womb.
The main purpose of the dermis is to support
the epidermis. The ridges cause an increase in
surface area between these two layers, thus
strengthening their connection and helping prevent
the layers from separating. These ridges also
assist in helping the finger sense fine textures,
and may assist in gripping wet surfaces.
The patterns of these ridges are commonly
described as arches, single loop, double loop, and
whorls. The flexibility of friction ridge skin
means that no two finger prints are ever
exactly alike in every detail. Even two prints
from the same finger may be slightly different.
When fingerprints are used for identification,
the prints are scored using a set of thresholds to
determine the probability that the prints come
from the same person. Modern day live scanning
devices image your fingers and measure the
physical differences between ridges and valleys.
The uniqueness of fingerprints is determined by
the arrangement, shape, size, and number of lines
within the pattern. Scientists analyze very
tiny characteristics, called minutiae,
which cannot be seen with the naked eye.
Therefore, you may have looked at your
fingers, but the prints will still have distinct