How the upper lip comes together
Early in pregnancy, the face does not begin as a single, fully formed piece. Small areas of developing tissue grow around the openings that will become the nose and mouth. The central upper lip forms as these structures meet and join, including tissue from the developing middle of the face.
The philtrum is the shallow vertical groove between the base of the nose and the upper lip. Its shape reflects how the central upper lip developed as facial tissues came together. It is not a scar left by an injury; it is a normal feature of facial anatomy.
When the joining process differs
Facial tissues have to grow and connect in a coordinated way. If the tissues that form the upper lip do not fully join, a cleft lip can result—a gap in the lip that may extend toward the nose. A cleft can range from a small notch to a wider opening, and it may occur on one or both sides.
The philtrum makes this developmental story visible in an ordinary feature of the face: the groove sits where the central upper lip’s tissues formed and joined, while a cleft reflects an incomplete connection.
