The space located directly beneath the nose and above the upper lip is often casually referred to as the “mustache area.” While this common term describes where facial hair typically grows, anatomists use specific names to identify this small but complex region. Understanding this area requires distinguishing between the broader skin surface and a singular, vertical feature at the center.
The Central Groove: The Philtrum
The most recognizable feature of this upper lip area is the philtrum, which is the vertical indentation or groove running from the base of the nose down to the upper lip. This midline depression is bordered by two raised ridges of tissue known as the philtral columns. These columns descend to form the distinct curve in the center of the upper lip, known as the Cupid’s bow.
The philtrum is a remnant of embryological development, forming where facial processes fuse during gestation. In adult humans, the philtrum is considered a vestigial structure, meaning it has no apparent function. Despite lacking a functional purpose, the distinct shape and size of the philtrum are unique to each person and contribute significantly to facial aesthetics.
Defining the Broader Upper Lip Region
The entire area of skin between the nose and the red portion of the upper lip is anatomically known as the cutaneous upper lip. This region encompasses the philtrum at its center and extends laterally to the corners of the mouth. Its superior boundary is the base of the nose, or the nasal septum, while the inferior border is the vermilion border.
The vermilion border is the line that separates the pale skin of the cutaneous lip from the reddish, mucosal tissue of the lip itself. This expanse of skin serves as a flexible covering for the underlying orbicularis oris muscle, which encircles the mouth and is responsible for lip movement and facial expression. The skin of the cutaneous upper lip contains numerous microscopic hair follicles across its surface.
The Biological Basis of Mustache Hair
This anatomical region is associated with the “mustache” due to the concentration of hair follicles highly sensitive to androgens, or male sex hormones. During puberty, a surge in androgen levels stimulates these dormant follicles, causing a transformation in the type of hair produced. Before this hormonal shift, the area is covered in vellus hair, which is fine, light, and often called “peach fuzz.”
Increased androgen exposure converts these vellus follicles into terminal follicles, which produce the coarser, thicker, and darker strands characteristic of a mustache. This process represents secondary sexual characteristic development. The entire cutaneous upper lip contains these androgen-responsive follicles, making it the primary site for facial hair growth in men.