The subtle vertical groove located in the middle area of the upper lip, extending from the base of the nose to the upper lip, is called the philtrum. This indentation is bordered by two ridges, known as philtral columns, which contribute to the distinct “cupid’s bow” shape of the upper lip. While it appears as a depression in humans, the philtrum is a feature common to many therian mammals. In these animals, it can serve a functional role, such as carrying dissolved odorants from the nose to an internal organ for enhanced smell. For humans and most primates, however, the philtrum is considered a vestigial structure, meaning it has no apparent function.
Its Developmental Journey
The philtrum forms during a precise and complex process of facial development while an individual is in the womb. Specifically, it originates from the fusion of different facial prominences around the sixth to eighth week of gestation. The medial nasal prominences, which are ridge-like formations, play a crucial role in forming the philtrum, the primary palate, and the Cupid’s bow of the upper lip. The maxillary processes, which are structures that contribute to the upper jaw and cheekbones, also participate in this fusion. When these medial nasal and maxillary processes meet and merge, they create the distinct vertical groove of the philtrum.
What Variations Can Tell Us
The appearance of the philtrum can vary among individuals in terms of its length, width, and depth. These natural variations are influenced by genetic factors and can differ across populations.
However, significant deviations from the typical philtrum shape can sometimes serve as important indicators of underlying developmental conditions or genetic syndromes. For instance, a philtrum that appears flattened, unusually long, or smooth, lacking its characteristic groove and ridges, is a recognized facial feature associated with Fetal Alcohol Syndrome (FAS). This specific appearance of the philtrum is one of the diagnostic criteria used for FAS and other Fetal Alcohol Spectrum Disorders (FASD). Abnormalities in philtrum formation can also relate to other genetic conditions, such as Williams syndrome or certain developmental disorders like cleft lip and palate. Observing the philtrum’s characteristics can therefore provide clues about proper facial development and potential health considerations.