The area informally known as the “mustache area” is a highly structured region of the upper face with specific anatomical names. Situated beneath the nose and above the upper lip, this region is a central feature of facial architecture. Understanding the terminology provides insight into its structure, development, and potential conditions.
The Philtrum and Surrounding Structures
The anatomical term for the vertical indentation between the base of the nose and the upper lip is the philtrum. This structure is a shallow, midline groove bordered by two raised ridges of tissue known as the philtral columns.
These philtral columns descend symmetrically from the nose, terminating at the upper lip’s border. The lower margin of the philtrum contributes directly to the double curve of the upper lip known as the Cupid’s Bow. The peak of this bow, where the philtral column meets the lip, forms the tubercle.
The colored surface of the lip is called the vermilion, distinct from the surrounding facial skin. The sharp border separating the vermilion from the normal skin is the vermilion border. These structures collectively define the aesthetic and structural characteristics of the central upper lip region.
The Embryological Origin of the Midface
The structure of the philtrum and upper lip originates from a process of fusion during embryonic development. Around the fourth week of gestation, the face forms from five primary swellings called prominences. These prominences must merge to establish the final facial structure.
The philtrum is formed by the fusion of the medial nasal prominences, which descend from the developing forehead and nose. These two prominences fuse in the midline to create the intermaxillary segment. This segment is the precursor that gives rise to the central portion of the upper lip, including the philtrum and parts of the upper jaw.
The maxillary prominences, which form the cheeks and lateral parts of the upper lip, grow toward the center. They merge with the intermaxillary segment, completing the formation of the upper lip structure and the philtral columns. This fusion occurs within the first two months of development, setting the pattern for the entire midface.
Dermatological and Developmental Anomalies
The philtral area is susceptible to developmental and dermatological conditions as a site of embryonic fusion and terminal hair growth. Failure in the complete fusion of the medial nasal and maxillary prominences (sixth to seventh week of gestation) can result in a cleft lip. This is an incomplete joining of the facial segments that form the upper lip and jaw.
In some developmental syndromes, the philtrum may appear flattened or smooth, lacking the normal concave groove and pronounced columns. This variation can indicate conditions such as Fetal Alcohol Syndrome. The definition of the philtrum is a diagnostic feature in clinical genetics.
The skin of the upper lip is a common site for hair- and gland-related issues. Hirsutism, the excessive growth of coarse, dark hair in a male-like pattern, frequently affects the upper lip in women. This condition is linked to elevated levels of androgens, often associated with hormonal disorders like Polycystic Ovary Syndrome (PCOS).
The perioral skin, including the philtrum, is also a frequent site for recurrent Herpes Simplex Virus type 1 (HSV-1). These lesions, known as cold sores, appear as a cluster of small, fluid-filled vesicles that crust over and heal. The proximity of this facial skin to the lip’s nerve pathways makes it a predictable location for the virus to reactivate.