Eyebrow Structure & Function: What You Need to Know

Eyebrows do far more than frame your eyes and complete your look. They play key roles in protection, expression and anatomy. In this post I’ll discuss the anatomy of the eyebrow region, the muscles that control its position, how it performs functional roles, what changes occur with age or environmental factors, and finally what this means for your brow health.

Anatomy of the eyebrow

The eyebrow sits above the superior orbital margin (the bony ridge above the eye socket) and follows that supra-orbital rim. The area between the eyebrows is called the glabella which is most commonly referred to as a key site for botox injection. The skin over the bony ridge has a higher amount of fat and connective tissue, the galeal fat pad, than the upwardly surrounding tissue which gives it more tissue in which the hairs and associated glands are found. The hair follicle is deeper than an eyelash, but not as deep as scalp hair, and its growth cycle is shorter than the scalp too.

Function of the eyebrows

While we often focus on the cosmetic or beauty aspects of eyebrows, they serve several important functional roles.

PROTECTION OF THE EYE

The primary function of the eyebrow arch and eyebrow hair is to divert sweat, rain and moisture away from the eye itself. The combination of the projection of the fat pad with the underlying bony ridge acts like a sloping canopy to divert liquid laterally towards the side of the face. The brow hair gives a raised, slightly absorbent edge, and the combination means that the path of least resistance for water running down the forehead is away from the eye. Additionally the hair of the brow can help trap small debris before it reaches the eye region, either airborne or carried in liquid, which is then naturally wiped away by our hand.

SENSORY FEEDBACK

Related to the protection of the eye is the sensitivity of the area. Hair follicles are associated with nerve endings, especially Merkel cells that are especially sensitive to the most minute touch. In the brows, this helps to detect objects or movement close to the eye region, giving us an early-warning system of sorts. It is partly automatic and the resulting action can be as simple as a blink of the eye. The glebellar reflex is an example described in the literature in which the glabella (between the brows) is tapped, which causes the eyes to reflexively blink.

Dr Tom Walker

Dr Tom Walker is one of the founders of Opti Laboratories, the successor to Mylash which he founded in 2007. He graduated from the University of Glasgow with a degree's in medicine and anatomy. His work has been featured in publications including The Times newspaper and Vogue magazine. He has a passion for bringing innovative and evidence based treatments to the market. The eyelash and eyebrow growth treatment he introduced is the only clinically proven growth treatment available.

ALL POSTS

EXPRESSION

A fact that should not “raise any eyebrows” is the importance of the brow in communication. Surprise, anger, sadness and curiosity amongst others are conveyed partly by brow movement. Such tiny movements can change the meaning of a sentence as “really” with an arched eyebrow is different compared to the same word with a furrowed brow.

AESTHETICS

Aesthetic analysis studies underline that the brow is often termed the “master line of the face” since it influences how the upper third of the face is perceived. Without going into detail, it is often the case that a more feminine look involves a higher arch to the brow which opens the eye area. In contrast, a masculine look tends towards a flatter brow that more tightly follows the orbital ridge and gives a more commanding look to the brows.

Typical structural and functional changes with age & environment

As you age the structure of the eyebrow region changes which can impact both appearance and how the brows perform their functions.

Muscle and skin changes

According to Langsdon & Petersen (2014), forehead and brow ageing involve not only skin deterioration and volume loss, but also changes in muscle tone (both elevation and depression muscles). The study by Yun et al. (2014) found that orbicularis oculi and corrugator supercilii muscle indices were higher in older individuals and that the overall muscle thickness declines. A 2020 study by Suchonwanit et al. showed that eyebrow hair density and diameter decreases as we age.

Skin, fat and bony support changes

Another affect of ageing is a decrease in the subcutaneous fat in the area, and a reduced structural support of the brow by degrading connective tissue. The reduction in the galeal fat pad as well as increased skin laxity allows the brow to drop, changing its arch and thereby altering the appearance and how it functions.

Environmental factors, especially UV exposure also contribute but the brow can also be influenced by the way we move our face. It is common sense that excessive movement of the forehead can increase wrinkle formation, but a 2025 study by Okazaki et al. in Nature provided a positive angle on facial expression. The abstract of the paper concludes with:

We found that the act of smiling activates zygomatic major and suppresses the corrugator reducing the appearance of glabellar lines. The results offer a novel perspective on smiling and suggests that smiling not only facilitates positive emotional exchanges but may also help maintain a youthful facial appearance

Functional implications

In combination, these changes from ageing reduce the strength of the protective reflexes around the eye and diminish the physical protection that the brow provides.

Brow droop or arch flattening may reduce the ability of the brow hair to divert moisture or provide shading.

Thinner hairs may reduce tactile sensory capacity.

Changes in muscle balance may alter expression, giving a “tired” or “angry” look even when neutral.

SUMMARY

The eyebrow is a complex anatomical and functional system: skin, hair, follicles, muscles and bony support all play parts. Beyond appearance, eyebrows protect the eye, provide sensory input, and contribute heavily to facial expression. The complex muscle balance around the brow is key to brow shape and position. but age and repetitive expression shift this balance and impact brow aesthetics and function.

Practical Tips

Consider your climate: even in the UK, UV damage will break down your hair.

Groom safely: avoid over-plucking the tail or arch high beyond your natural position. Beyond the shape, excessive plucking can sometimes result in the follicle slowing down or stopping its normal growth cycle.

Ready to strengthen your brows?

Discover the world’s first UV-protective brow serum developed by Opti Laboratories. Scientifically formulated to protect and enhance your natural brow structure.

The UK experts in lash and brow care with 18 years experience

Find out more about our clinically proven, innovative solutions

Dr Tom Walker

Dr Tom Walker is one of the founders of Opti Laboratories, the successor to Mylash which he founded in 2007. He graduated from the University of Glasgow with a degree's in medicine and anatomy. His work has been featured in publications including The Times newspaper and Vogue magazine. He has a passion for bringing innovative and evidence based treatments to the market. The eyelash and eyebrow growth treatment he introduced is the only clinically proven growth treatment available.

All Posts

Reference:

Okazaki S., Suzuki M., Duncan K.K. (2025) The influence of repeated frowning and smiling on corrugator muscle activity and wrinkles between eyebrows. Scientific Reports. 15: 1467. https://www.nature.com/articles/s41598-024-84121-9

Suchonwanit P., et al. (2020) Eyebrow growth pattern analysis in patients with eyebrow thinning: density and diameter changes in eyebrow hair. J Cosmet Dermatol. https://onlinelibrary.wiley.com/doi/10.1111/jocd.13167

Yun S. et al. (2014) Changes of eyebrow muscle activity with ageing. PubMed PMID: 24378349. https://pubmed.ncbi.nlm.nih.gov/24378349

Langsdon P., Petersen D. (2014) Management of the Aging Forehead and Brow. Facial Plastic Surgery. 30(4): 422-430. https://doi.org/10.1055/s-0034-1383555

Yalçınkaya, Esin & Cingi, Cemal & Söken, Hakan & Ulusoy, Seçkin & Bayar Muluk, Nuray. (2014). Aesthetic analysis of the ideal eyebrow shape and position. European Archives of Oto-Rhino-Laryngology. 273. 10.1007/s00405-014-3356-0. researchgate.net/publication/267742996_Aesthetic_analysis_of_the_ideal_eyebrow_shape_and_position