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Quick Answer
The hair follicle is the living structure beneath the scalp that produces, nourishes, and anchors each hair strand. Its key components—including the hair bulb, dermal papilla, hair matrix, root sheaths, sebaceous gland, and arrector pili muscle—work together to support healthy hair growth. Each follicle also follows its own growth cycle through anagen, catagen, telogen, and exogen phases. Understanding this anatomy helps explain how nutrition, hormones, scalp health, and other factors can affect hair growth and shedding.
A hair follicle consists of concentric epithelial and connective-tissue layers. From the core of the hair shaft outward to the anchoring dermis, the layers work together to generate, nourish, and guide each strand of hair.
Understanding hair biology begins with understanding the hair follicle. It is the living part of the hair responsible for producing new strands, supporting pigmentation, and regulating the natural hair growth cycle.
What Is a Hair Follicle?
Your hair follicle is a tunnel-like structure within the skin and an essential part of scalp anatomy. It extends from the surface of your scalp into the deeper layers of the skin and contains everything needed to produce and support a hair strand.
While the hair shaft is the visible part of your hair, the follicle is the living structure beneath the skin. It contains specialised cells, blood vessels, nerves, oil glands, and stem cells that work together to support healthy hair growth.
According to the American Academy of Dermatology, the average scalp contains around 80,000 to 120,000 hair follicles, each functioning independently and following its own growth cycle.
Knowing the hair follicle structure helps you understand why different hair concerns occur. A healthy follicle is responsible for:
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Producing new hair strands
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Supplying nutrients through the blood
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Supporting hair pigmentation
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Anchoring hair securely within the scalp
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Producing natural oils that keep the scalp moisturised
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Helping regulate the hair growth cycle
When any part of your follicle is affected, it may influence the quality, thickness, or growth of the hair.
Hair Follicle Anatomy: Layer by Layer
Although a hair follicle is tiny, it consists of several specialised structures arranged in distinct hair follicle layers that work together to produce, protect, and support healthy hair.
Hair Shaft
The hair shaft is the part of the hair you can see above the scalp. It is made of keratin, a strong structural protein. It has three layers:
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Cuticle: the protective outer layer
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Cortex: provides strength, texture, and colour
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Medulla: the innermost layer, present in thicker hair types
The shaft itself is made up of dead cells, which is why cutting your hair is painless.
Hair Root
The hair root anatomy refers to the section of hair that lies beneath the skin. This part anchors the hair inside the follicle and connects it to the structures that support growth.
Hair Bulb
Located at the base of your follicle, the hair bulb is where new hair is formed. It contains rapidly dividing cells that continuously produce new hair fibres. As these cells multiply, older cells are pushed upwards, forming the hair shaft.
Dermal Papilla
The dermal papilla is a small tuft of tissue that pushes up into the base of the bulb, so the bulb
effectively wraps around it. It contains a rich network of tiny blood vessels, and its main role is to:
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Deliver oxygen and nutrients
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Supply growth signals
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Support active hair production
Without an adequate blood supply, healthy hair growth becomes difficult.
Hair Matrix
The hair matrix surrounds the dermal papilla and contains some of the fastest-dividing cells in the body. This area contains two kinds of cells working side by side: ones that build keratin and new hair cells, and pigment cells that add melanin, the natural colour of hair.
Inner Root Sheath
The inner root sheath surrounds the growing hair and helps guide it upwards as it emerges through the skin. It provides support while the hair strand is still developing.
Outer Root Sheath
The outer root sheath forms the outer wall of the follicle. It contains important stem cells that help maintain the follicle and play a role in repair and regeneration after minor injury.
Sebaceous Gland
Attached to each follicle is a sebaceous gland. This gland produces sebum, a natural oil that:
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Lubricates the hair
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Keeps the scalp moisturised
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Supports the skin barrier
Arrector Pili Muscle
This tiny muscle attaches to the follicle and contracts when you're cold or emotional. That's what causes goosebumps and makes the hair stand upright.
Hair Follicle Structure at a Glance
While each part of the hair follicle has a distinct role, they all work together to support healthy hair growth. The table below provides a quick overview of the key components of the hair follicle structure and what each one does.
|
Hair Follicle Part |
Primary Function |
|
Hair Shaft |
Visible part of the hair |
|
Hair Root |
Anchors the hair beneath the scalp |
|
Hair Bulb |
Produces new hair cells |
|
Dermal Papilla |
Supplies nutrients and growth signals |
|
Hair Matrix |
Generates keratin and pigment |
|
Inner Root Sheath |
Supports the developing hair |
|
Outer Root Sheath |
Protects the follicle and houses stem cells |
|
Sebaceous Gland |
Produces natural oils |
|
Arrector Pili Muscle |
Causes goosebumps |
The Hair Growth Cycle and the Follicle
Hair doesn't grow continuously. Instead, every follicle moves through a repeating cycle.
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Anagen (Growth Phase): This is the active growth stage, lasting anywhere from two to seven years. Around 85-90% of scalp hair is usually in this phase.
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Catagen (Transition Phase): Hair growth slows down, and the follicle begins to shrink. This phase lasts only a few weeks.
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Telogen (Resting Phase): The follicle rests while the existing hair remains in place.
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Exogen (Shedding Phase): The old hair naturally sheds, allowing a new strand to begin growing from the same follicle.
Because each follicle follows its own timeline, you don't lose all your hair at once. Shedding around 50 to 100 hairs a day is considered normal.
How Do Hair Follicles Support Hair Growth?
Hair follicles are active biological structures that constantly respond to signals from the body. Healthy follicles rely on:
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A good blood supply
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Adequate nutrition
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Hormonal balance
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Healthy scalp skin
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Proper functioning of follicle stem cells
If these factors remain balanced, your follicle can continue producing new hair through repeated growth cycles.
Traya's Perspective on Hair Follicle Anatomy
Healthy hair begins with healthy follicles. While external care helps maintain your hair shaft, the follicle itself is influenced by factors such as nutrition, hormones, scalp health, and overall well-being.
At Traya, we believe that understanding how the follicle works is the first step towards making informed decisions about your hair. If you're noticing persistent changes in hair density or shedding, the Traya Hair Test can identify the underlying cause, provide a personalised kit, and make a meaningful difference to long-term hair health.
Frequently Asked Questions
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What is hair follicle anatomy?
Hair follicle anatomy refers to the different structures that make up a hair follicle, including the hair bulb, dermal papilla, root sheaths, sebaceous gland, and hair matrix, all of which work together to support hair growth.
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What is the difference between the hair shaft and the hair follicle?
The hair shaft is the visible part of the hair above the scalp. The hair follicle is the living structure beneath the skin where the hair is formed and supported.
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What part of the hair follicle produces new hair?
The hair matrix, located within the hair bulb, contains rapidly dividing cells that produce new hair.
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Can damaged hair follicles grow hair again?
It depends on the cause. If your follicles are affected by temporary conditions, they may recover, whereas permanently scarred follicles may not produce new hair.
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How many hair follicles are on the scalp?
Most people have between 80,000 and 120,000 hair follicles on the scalp, though this varies from person to person.
References
National Centre for Biotechnology Information (NCBI). (2023). Anatomy, Hair. StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK513312/
National Centre for Biotechnology Information (NCBI). (2024). Hair Follicle. StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/
American Academy of Dermatology Association. (2024). Hair Loss: Diagnosis and Treatment. American Academy of Dermatology. https://www.aad.org/public/diseases/hair-loss/treatment/diagnosis-treat
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). (2023). Hair Loss. National Institutes of Health. https://www.niams.nih.gov/health-topics/hair-loss
Paus, R., & Cotsarelis, G. (1999). The Biology of Hair Follicles. New England Journal of Medicine, 341(7), 491–497. DOI: 10.1056/NEJM199908123410706
Schneider, M. R., Schmidt-Ullrich, R., & Paus, R. (2009). The Hair Follicle as a Dynamic Miniorgan. Current Biology, 19(3), R132–R142. DOI: 10.1016/j.cub.2008.12.005
Stenn, K. S., & Paus, R. (2001). Controls of Hair Follicle Cycling. Physiological Reviews, 81(1), 449–494. DOI: 10.1152/physrev.2001.81.1.449
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