During weeks 10 through 24 of gestation (when a fetus is developing inside of its mother’s womb, also called in utero), ridges form on the epidermis, which is the outermost layer of skin, on the fingertips of the fetus. The pattern that these ridges make is known as a fingerprint and looks like the drawing shown in Figure 1 below.
Fingerprints are static and do not change with age, so an individual will have the same fingerprint from infancy to adulthood. The pattern changes size, but not shape, as the person grows. (To get a better idea of how that works, you can model the change in size by inking your fingerprint onto a balloon and then blowing up the balloon.) Since each person has unique fingerprints that do not change over time, they can be used for identification. For example, police use fingerprints to determine whether a particular individual has been at a crime scene. Although the exact number, shape and spacing of the ridges changes from person to person, fingerprints can be sorted into three general categories based on their pattern type: loop, arch and whorl, as shown in Figure…
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