The V-shaped dip that forms between your upper lip and lower lip is called the philtrum. The philtrum is formed during embryonic development and plays an important role in the formation of the lips and mouth. Understanding the anatomy and function of the philtrum can provide insight into facial morphology and growth.
Anatomy of the Philtrum
The philtrum is the vertical groove that runs from the nose to the top of the upper lip. It is formed by the presence of two philtral columns, ridges of tissue that descend from the nose and merge at the top lip. These columns form the borders of the philtral groove.
Several structures contribute to the formation of the philtrum:
- Frontal nasal prominences – embryonic tissue that forms the forehead, nose bridge, and upper part of philtrum
- Medial nasal prominences – embryonic tissue that forms the middle and lower part of the philtrum
- Maxillary processes – embryonic tissue that forms the upper jaw and contributes to upper lip
The philtral columns contain a linear row of small pits called philtral pits or fossae. These pits are visible as small dimples along the upper portion of the philtrum. The skin overlying the philtral columns also contains sebaceous glands which open into hair follicles.
Musculature
The muscles of the upper lip overlap the philtral columns. The primary muscles are:
- Levator labii superioris – elevates the upper lip
- Levator labii superioris alaeque nasi – dilates the nostrils and elevates upper lip
- Zygomaticus minor – draws angle of mouth upward
- Zygomaticus major – draws angle of mouth back and upward
These muscles allow for the wide range of movements of the upper lip and modulation of the philtrum during facial expressions.
Vasculature
The philtrum receives its blood supply from branches of the facial artery, including the inferior labial arteries. These arteries run beneath the mucosa of the upper lip between the philtral columns before branching toward the lip margins.
The philtrum also overlies the incisive branch of the mental nerve, a terminal branch of the inferior alveolar nerve which supplies sensation to the upper lip.
Variation
The depth and shape of the philtral columns can vary substantially between individuals. Deeper, more prominent columns form a deeply grooved philtrum, while shallow columns create a more flattened philtrum.
The philtrum spans a section of the upper lip with significant muscular control, so its appearance can vary dramatically with different expressions.
Development of the Philtrum
Facial development begins around the 4th week of embryonic growth and involves the fusion of five primordial facial prominences:
- Frontonasal prominence – forms forehead, bridge of nose, and upper portion of philtrum
- A pair of maxillary prominences – form upper jaw and upper lip
- A pair of mandibular prominences – form lower jaw and lower lip
As the medial nasal prominences merge with the maxillary prominences, the ridges known as the philtral columns are formed, with the groove between them becoming the philtrum.
Disruptions in this complex process of fusion can lead to malformations of the philtrum and upper lip. These include:
- Cleft lip – failure of the maxillary prominences to fuse with medial nasal prominences
- Cleft palate – failure of the maxillary prominences to fuse with each other
- Facial clefts – failure of the frontonasal prominence to fuse properly with other prominences
Proper philtral development is indicative of successful fusion and differentiation of the facial prominences.
Functions of the Philtrum
The philtrum serves several important functions:
Creates Distinct Upper Lip
The philtral columns and groove separate the upper lip into two distinct parts known as philtral ridges or peaks. This allows for complex motions of the upper lip.
Facilitates Drainage
The philtral groove helps collect and drain mucus secreted by the nasal passages down to the lip margins. This helps prevent buildup of mucus along the upper lip.
Enables Facial Expressions
As a highly mobile section of the upper lip, the philtrum is critical in forming facial expressions. Upward turning of the lips to show happiness, the pressing together of the lips to demonstrate thoughtfulness, and the tightening of the philtrum in disgust or anger all rely on philtral motion.
Aids Speech
Specific speech sounds such as “m” rely on changing the shape of the philtral region by pressing the philtral columns together. The mobility of the philtrum allows for the accurate formation of these sounds.
Determines Facial Appearance
The shape and dimensions of the philtrum have a strong influence on overall facial appearance. A long philtrum is commonly associated with youth, while a short philtrum tends to create a more mature or older look. An exaggerated groove or overprominent columns can lead to an unusual or dysmorphic appearance.
Significance of the Philtrum in Medicine
Examination of the philtrum can provide doctors with important medical information about a patient:
Assesses Fetal Alcohol Syndrome
Smooth philtrum lacking normal grooving or dimpling can indicate fetal alcohol syndrome, caused by alcohol exposure in the womb. Other related signs involve thin upper lip and reduced nose and jaw size.
Screens for Cleft Lip and Palate
Clefting of the lip at the philtrum or a notched shape of the upper lip may signify a congenital cleft lip. Cleft palate may also be present.
Evaluates Facial Paralysis
Since the philtrum is largely controlled by the facial nerve, asymmetry or lack of motion can indicate facial nerve paralysis. This is often linked to Bell’s palsy or acoustic neuroma.
Analyzes Syndromic Disorders
Various genetic syndromes like Down syndrome and DiGeorge syndrome can present with abnormal philtral shape such as transverse grooving or additional columns.
Assesses Lip Injuries
Lacerations, cuts, or penetration injuries involving the philtral area require careful repair to prevent distortion of the upper lip. Severed philtral columns may require surgical realignment.
Cultural Significance of the Philtrum
The appearance and emphasis of the philtrum have carried cultural symbolism and been an important cosmetic focus in various societies:
Ancient Egypt
Both men and women in Ancient Egypt used cosmetics to highlight and exaggerate their philtrum as part of beautification rituals reserved for the elite. Green malachite pigment was applied to emphasise the groove.
Middle Ages
During the European Middle Ages, women would pluck hairs from their philtrum line to achieve the long, smooth upper lip that was considered desirable at the time.
Aztec Tribal Rituals
The Aztec tribe would pierce the philtrum and insert labrets – ornamental plugs – into the holes as part of coming of age rituals and to signify social status. Gold labrets were reserved for nobility.
Modern Beauty Standards
The philtrum remains an important focus in modern ideals of beauty and cosmetic procedures. Injectable fillers are often used to enhance shallow philtral grooves and create a more desirable upper lip shape.
Folk Beliefs
In some cultures, reading the philtrum’s shape is believed to offer insight into personality and forecast events like relationships and lifespans. Divination performed in this way is a traditional practice in many communities.
Conclusion
The philtrum is such a ubiquitous small facial feature that its anatomical importance and cultural symbolism are often overlooked. This delicate groove between nose and lip facilitates drainage and speech, enables intricate lip motions, influences overall facial appearance, and can indicate underlying disorders.
For these reasons, the philtrum has been the focus of beautification practices across many cultures throughout history, signifying its role as a defining aspect of an attractive and healthy visage. Understanding the form and function of this modest groove provides deeper insight into the human face.