10.1 Hair Structure and the Follicle
Key Takeaways
- NIC Scientific Concepts I.G tests hair as a skin appendage: shaft (cuticle, cortex, medulla), root, follicle, bulb, papilla, arrector pili, and sebaceous gland — hair-removal PROCEDURES are Chapter 16.
- The dermal papilla’s blood supply nourishes the matrix; if the papilla is destroyed, that follicle cannot grow a new hair, which is why electrolysis is a separate Illinois electrologist license, not esthetics under 225 ILCS 410/3A-1.
- Lanugo is fetal hair, vellus is fine peach fuzz, and terminal hair is long, coarse, and pigmented; dermaplaning shaves vellus plus stratum corneum and remains surface scope after Public Act 104-0134.
- Follicles sit at an angle; waxing is previewed by mapping the direction of growth (typically apply with the grain and remove against it) so the pull follows that slant instead of snapping the shaft.
- 68 Ill. Adm. Code 1175.835 puts tweezer, depilatory, and waxing methods in the 500-hour practices block; 3A-1 names threading and authorizes removing superfluous hair, while coloring hair except the scalp is a separate 3A-1 cosmetic act.
This chapter is hair science, not hair-removal technique. NIC Scientific Concepts I.G tests structure, growth, and abnormal growth so you can explain why a follicle behaves the way it does. Hair-removal procedures — hard versus soft wax, pot temperature, Accutane wait times, blood-exposure cleanup — belong in Chapter 16. Illinois writes the same split into the 750-hour program. 68 Ill. Adm. Code 1175.835 parks histology and disorders in the 150-hour Scientific Concepts block and parks hair removal; including tweezer method, depilitators (depilatories), waxing and their use in the 500-hour Practices and Procedures block. 225 ILCS 410/3A-1 authorizes removing superfluous hair from the body for cosmetic purposes, names threading in the esthetician definition, and excludes electrologist services from esthetics. Section 3A-1 also allows lightening or coloring hair on the body except the scalp — lash and brow tint live there; scalp color does not. Learn the follicle so you can wax, tweeze, thread, and dermaplane on the surface. Do not confuse that knowledge with a license to destroy the papilla.
Hair is a skin appendage made of hard keratin (denser than the soft keratin of the stratum corneum). The part you see is the hair shaft. The part inside the skin is the hair root. The hair follicle is the tube-like pocket that holds the root and plunges from the epidermis into the dermis (and, for coarse terminal hair, toward the hypodermis).
Three Layers of the Hair Shaft
Teach the shaft outside-in. That is the order a chemical, a wax strip, or a dermaplane blade actually meets.
| Layer | Location | Structure | Exam hook |
|---|---|---|---|
| Cuticle | Outermost | Transparent, overlapping keratin scales, like shingles pointing toward the tip | Protects the cortex; raised scales increase porosity; wax and depilatories grip this layer |
| Cortex | Middle; most of the fiber | Elongated keratin cells; melanin pigment; tensile strength and elasticity | Color, strength, and “body” live here — about 90% of hair mass in standard textbook teaching |
| Medulla | Innermost core | Soft, airy cells; may be discontinuous | Often absent in vellus and very fine hair; not required for a hair to exist |
Cuticle
The cuticle is a thin armor of overlapping scales. Healthy scales lie flat; that is why hair looks shiny and resists chemical entry. A disrupted cuticle is porous. On a waxing stem, the cuticle is what the wax holds. On a depilatory stem, the alkaline cream begins breaking keratin disulfide bonds at that outer layer. You do not “treat the medulla” with a muslin strip.
Cortex
The cortex is the bulk of the hair. Melanin granules here decide eumelanin (brown/black) versus pheomelanin (red/yellow). Gray hair is lost melanin, not a new layer you wax off. Elasticity — the fiber’s ability to stretch and return — is cortical. If a stem asks where pigment and strength live, the answer is the cortex, not the cuticle and not the papilla.
Medulla
The medulla is the innermost canal. It may be present, fragmented, or missing. Vellus (“peach fuzz”) often has no medulla. Do not pick “every hair has a medulla” on a national item.
Root, Follicle, Bulb, and Papilla
The root is the portion of the fiber below the surface. It sits in the follicle, an epidermal invagination lined by inner and outer root sheaths. At the base, the follicle swells into the hair bulb. Inside the bulb, matrix cells divide (mitosis) and keratinize to build the shaft. New hair is manufactured at the bulb. The visible tip is dead keratin.
The hair papilla (dermal papilla) is a cone of connective tissue that indents the bulb from below. Blood vessels in the papilla deliver oxygen and nutrients to the matrix. That blood supply is why growth happens at the bulb, not at the free end, and why a follicle that loses its papilla cannot restart a fiber. If the papilla is destroyed, that follicle cannot grow a new hair. That sentence is the biology behind true permanent epilation.
Illinois estheticians do not destroy papillae. Electrolysis (a needle delivering current at the papilla) is an electrologist service under a separate IDFPR license (profession 220, a 600-hour program and the IBEC examination). 225 ILCS 410/3A-1 states that esthetics does not include the services provided by a cosmetologist or electrologist. Waxing, tweezing, and threading pull the shaft and root; they do not legally or biologically equal papilla destruction. The papilla usually survives, so the hair returns. That is expected. It is not a failed wax.
Arrector pili and sebaceous gland
The arrector pili is a small smooth muscle attached to the follicle. Cold or fear contracts it: goosebumps. That tug also helps express sebum from the attached sebaceous gland onto the hair and surface. Most sebaceous glands empty into follicles (holocrine sebum). For hair science, remember the unit: follicle + papilla + arrector pili + sebaceous gland = the pilosebaceous unit. Heat, massage, and steam can increase sebum flow around that unit; they do not “kill” a follicle.
Lanugo, Vellus, and Terminal Hair
Three textbook types, not three diseases:
- Lanugo — fine, unpigmented fetal hair. It sheds in utero or shortly after birth. A healthy adult face does not grow lanugo as a normal service category. Lanugo-like down appearing in an adult with sudden weight loss or illness is a referral, not a waxing diagnosis.
- Vellus — short, fine, soft, usually unpigmented or lightly pigmented “peach fuzz” covering most of the body. Vellus follicles are shallow. Dermaplaning shaves this hair at the stratum corneum.
- Terminal — longer, coarser, pigmented hair: scalp, eyebrows, eyelashes, axilla, pubic hair, and androgen-dependent sites such as a beard. Terminal follicles are deeper, with a larger papilla, and usually a medulla.
Puberty converts some vellus follicles to terminal under androgens. That conversion on a woman’s face, chest, or abdomen is the biology behind hirsutism (Section 10.3). Ethnicity and genetics also set baseline density and coarseness; that is not automatically disease.
Follicle Angle and Direction of Growth (Waxing Preview)
Hair does not grow straight out of the skin. Each follicle sits at an angle. In a given zone the shafts lean in a consistent direction of growth (the grain). That angle is why you map the grain before you wax:
- Soft wax is typically applied with the direction of growth and removed against it, so the pull follows the follicle’s slant and extracts the root instead of snapping the shaft.
- Tweezing is taught in the direction of growth to reduce breakage.
- Threading follows the hair’s lie.
Chapter 16 will drill method and temperature. The science here is simple: follicle angle decides pull direction. Ignore the grain and you break hairs at the surface, leave fragments, and inflame the follicle. That is a technique failure rooted in anatomy, not in “stronger wax.”
Illinois Dermaplaning: Vellus Hair Plus Stratum Corneum
Public Act 104-0134 (effective August 1, 2025) named dermaplaning in 225 ILCS 410/3A-1 as a stratum-corneum skin-care method when used for cosmetic purposes. A dermaplane blade, held at a shallow angle (classically taught near 45 degrees), shaves dead corneocytes and vellus hair on that dead plane. It is still surface scope. It is not permission to scrape living epidermis or dermis, not a substitute for electrolysis, and not a scalp service. Illinois esthetics coloring already excludes the scalp; the blade’s legal target remains the stratum corneum. Terminal beard hair is the wrong target for a cosmetic blade. Vellus comes off because it sits on the surface, not because you entered the papilla.
Exam filter: name every structure — cuticle, cortex, medulla, root, follicle, bulb, papilla, arrector pili, sebaceous gland, lanugo, vellus, terminal. Work only with methods that pull or shave superfluous hair without claiming you destroyed the blood supply that keeps the matrix alive.
Why does the dermal papilla’s blood supply matter for hair growth?
Where do melanin pigment and most of the hair’s tensile strength live?
Under 225 ILCS 410/3A-1 as amended by Public Act 104-0134, what does Illinois dermaplaning remove when used as a cosmetic surface service?
Which statement correctly matches a hair type to its textbook description?