9.1 Hair Anatomy, Growth Cycles & Types of Hair
Key Takeaways
- The hair follicle is a mass of epidermal cells forming a small tube, and the papilla provides nourishment to the hair bulb.
- Hair grows in three distinct phases: Anagen (growth), Catagen (transition), and Telogen (resting/shedding).
- Vellus hair is fine and unpigmented, while terminal hair is thicker, longer, and pigmented.
- Hirsutism is excessive male-pattern hair growth in women caused by androgen dominance, whereas hypertrichosis is excessive hair growth in any area of the body.
- Hormonal imbalances, specifically involving androgens, significantly impact the Anagen phase and the conversion of vellus to terminal hair.
Hair Anatomy, Growth Cycles & Types of Hair
Understanding the anatomy and biological cycles of hair is fundamental for an esthetician. Effective hair removal requires deep knowledge of how hair grows, the structures that support it, and the biological or hormonal factors that influence its patterns. This comprehensive foundation ensures safety, efficiency, and optimal results for clients.
Anatomy of the Hair Follicle
The hair follicle is a mass of epidermal cells forming a small tube, or canal. Follicles extend deep into the dermis. The main structures of the hair follicle include:
- Hair Root: The part of the hair that lies within the follicle at its base, where the hair grows.
- Hair Bulb: A thick, club-shaped structure made from epithelial cells that surround the papilla. This forms the lower part of the hair root. It is where hair grows from cell division.
- Hair Papilla: A cone-shaped elevation at the base of the follicle that fits into the hair bulb. The papillae are filled with tissue that contains the blood vessels and cells necessary for hair growth and follicle nourishment.
- Hair Shaft: The portion of the hair that extends or projects beyond the skin, consisting of the outer cuticle, inner cortex, and medulla.
- Sebaceous Gland: Attached to the follicle, this gland secretes sebum (oil), which lubricates the skin and hair, helping keep them healthy and pliable.
- Arrector Pili Muscle: A small, involuntary muscle in the base of the hair follicle that causes goosebumps when it contracts due to cold or emotional stimuli.
The Three Phases of Hair Growth
Hair growth occurs in a continuous cycle comprised of three distinct phases. Hair removal is most effective during the Anagen phase.
| Phase | Scientific Name | Characteristics and Esthetic Implications |
|---|---|---|
| Anagen | The Growth Phase | New hair is produced. New keratinized cells are manufactured in the hair follicle. This is the ideal stage for hair removal because the hair is deeply rooted in the follicle, and removing it damages the follicle structure, leading to longer-lasting results and eventual hair reduction. |
| Catagen | The Transition Phase | This is the regression stage where the hair shaft grows upward and detaches itself from the bulb. The follicle shrinks, and the hair loses its inner root sheath. It is the shortest phase of the cycle. |
| Telogen | The Resting Phase | The final phase where the hair is at its full size and is erect in the follicle. It is ready to shed. The hair may fall out naturally or be pushed out by a new anagen hair. Epilation during this stage is less effective for long-term reduction. |
Types of Body Hair
Human hair is categorized into three main types based on its structure and location:
- Lanugo Hair: The extremely soft and downy hair found on a fetus. It is typically shed before or shortly after birth.
- Vellus Hair: Very fine, soft, and unpigmented downy hair that covers most of the body (e.g., women's cheeks). Removing vellus hair against its natural direction can sometimes stimulate it to become terminal hair, so care must be taken during services like dermaplaning or waxing.
- Terminal Hair: Thicker, longer, and heavily pigmented hair found on the scalp, eyebrows, eyelashes, underarms, and pubic areas. Hormonal changes during puberty cause many vellus hairs to transition into terminal hairs.
Hirsutism vs. Hypertrichosis
Estheticians frequently treat clients seeking relief from excessive hair growth. It is crucial to distinguish between two specific conditions:
- Hirsutism: Excessive hair growth on the face, chest, underarms, and groin, especially in women. It is characterized by terminal hair growing in a male-like pattern. This condition is primarily caused by an imbalance of androgens (male hormones). Polycystic Ovarian Syndrome (PCOS) is a common cause of hirsutism. Estheticians can manage the symptoms through hair removal, but medical intervention is required to treat the root hormonal cause.
- Hypertrichosis: An excessive growth of terminal hair in areas of the body that normally only grow vellus hair. Unlike hirsutism, it is not necessarily androgen-dependent. It can be genetic or induced by certain medications.
Hormonal Influences on Hair Growth
Hormones act as the chemical messengers that regulate the hair growth cycle. Androgens are the most significant hormones influencing hair. They can stimulate the growth of facial and body hair while concurrently causing scalp hair loss (androgenetic alopecia) in individuals with a genetic predisposition.
During pregnancy, elevated estrogen levels can prolong the anagen phase, resulting in thicker hair. Postpartum, estrogen drops, causing many hairs to enter the telogen phase simultaneously, leading to noticeable shedding. Menopause also brings a drop in estrogen, which can allow androgens to become dominant, often resulting in new facial hair growth in women. Understanding these hormonal shifts allows the esthetician to set realistic expectations for clients undergoing hair removal series.
Which phase of the hair growth cycle is the most effective for long-term hair reduction when performing epilation services?
What is the term for excessive, male-pattern hair growth in women, typically caused by an overproduction of androgens?
Which structure of the hair follicle contains the blood vessels necessary for hair growth and nourishment?