The philtrum (Greek φιλτρον philtron, from φιλειν philein 'to love; to kiss'), also known as the infranasal depression,'s the vertical groove in the upper lip, formed where the nasomedial and maxillary processes meet during embryonic development. The philtrum allows humans to express a much larger range of lip motions than would otherwise be possible, which enhances vocal and nonverbal communication. Pathology When these processe… (More on Philtrum)