Fingertip fingerprints are an individual characteristic well known for their use in forensic science for the identification of individuals. Its formation occurs during fetal developmentbeginning at about tenth week of gestation and completing in week 17, but it has not yet been possible to decipher exactly how these unique patterns are formed in each person.

Skin stress formation

According to one of the most widespread theories, fingerprints would be formed by tension in the epidermis generated by a different growth rate between its different layers. The tension would generate the deformation in the surface layer and with it the ridges and patterns of the fingerprints.

The epidermis It is the most superficial layer of the three layers that make up the skin. Within the epidermis, 4 layers or strata are distinguished, 5 in the epidermis of the soles of the feet and palms of the hands (including the fingers).

The basal layer of the epidermis is where the skin cells that form the outer layer of the skin multiply. As they multiply, they push the upper layers and generate the stratum corneum, which is the superficial layer in contact with the outside.

in the fetus, the stratum basale grows faster than the surrounding strata and layers (stratum corneum of the epidermis above, and the layers of the dermis below). The tension from this different rate of growth creates folds and twists in the basal layer of the skin boundary zonessuch as the fingertips and knuckles.

The folds formed in this way remain permanently registered in the basal layer and are the guide for the ridges that will give rise to fingerprints.

Being recorded in the basal stratum, fingerprints cannot be destroyed by superficial wounds. However, there are still doubts about how it is possible that the patterns generated in such early stages of fetal development are maintained in later stages.

In addition to fingerprints, the skin of the fingers and the palms of the hands have other characteristics that are different from the skin of the rest of the body. For example, they have a noticeably larger number of sweat glands and no hair follicles.

Basic Pattern Types

As has been seen, fingerprints are formed by ridges in the skin of the fingertips. These ridges draw three types of basic patterns: arches, spirals and loops. Of the three types, loops are the most common pattern type, appearing in 70% of people.

All three patterns can occur at the same time in the same person, although the most common is that this is not the case. They can also be combined or appear in a more or less complex way and with different inclinations, giving rise to a wide range of types of patterns from the three basic ones.