← Trichology & Anatomy – Illinois Cosmetology State Board Exam

Illinois Cosmetology State Board Exam Study Guide

Key concepts, definitions, and exam tips organized by topic.

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Trichology & Anatomy – Illinois Cosmetology State Board Exam Study Guide


Overview

Trichology is the scientific study of hair and scalp, forming a critical foundation for cosmetology practice. This guide covers hair structure, the hair growth cycle, skin and scalp anatomy, and common disorders. Mastery of these concepts is essential for both the Illinois State Board Exam and safe, effective client care.


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Hair Structure


The Three Layers of the Hair Shaft

The hair shaft is composed of three concentric layers, each with a distinct function:


| Layer | Position | Key Function |

|---|---|---|

| Cuticle | Outermost | Protection; overlapping scale-like cells |

| Cortex | Middle | Bulk, strength, and pigment (melanin) |

| Medulla | Innermost | Loosely structured core; may be absent in fine hair |


Key Concepts

  • • Cuticle: Overlapping, scale-like cells that lie flat when hair is healthy. An open/raised cuticle indicates damage or high pH exposure.
  • • Cortex: Makes up the majority of the hair's mass. Contains melanin granules responsible for hair color. This is also where chemical services (perms, color, relaxers) take effect.
  • • Medulla: The hollow or spongy innermost core. Often absent in very fine or light-colored hair — this is normal.

    • Melanin & Hair Color

  • • Eumelanin → produces brown and black tones
  • • Pheomelanin → produces red, yellow, and blonde tones
  • • The ratio and distribution of these two pigments determines natural hair color.

    • Protein Composition

  • • Hair is approximately 97% keratin, a fibrous structural protein
  • • Keratin is built from amino acids linked into polypeptide chains

    • Chemical Bonds in Hair

    Understanding bonds is critical for chemical service questions:


    | Bond Type | Strength | Broken By | Reformed By | Service |

    |---|---|---|---|---|

    | Hydrogen bonds | Weak | Water or heat | Drying/cooling | Wet sets, thermal styling |

    | Disulfide bonds | Strong (covalent) | Waving/relaxing solution (reducing agent) | Neutralizer (oxidizing agent) | Permanent waves, relaxers |

    | Salt bonds | Moderate | Extreme pH changes | Normalizing pH | — |


    Key Terms – Hair Structure

  • • Cuticle – outermost protective layer of overlapping scales
  • • Cortex – middle layer containing pigment and bonds
  • • Medulla – innermost, sometimes absent core layer
  • • Keratin – the primary protein of the hair shaft
  • • Eumelanin – dark brown/black pigment
  • • Pheomelanin – red/yellow/blonde pigment
  • • Hydrogen bonds – weak bonds broken by water or heat
  • • Disulfide bonds – strong covalent bonds altered by chemical services
  • • Arrector pili muscle – small muscle attached to the follicle; causes goosebumps when contracted

    • ⚠️ Watch Out For

    > Hydrogen vs. Disulfide Bonds: A very common exam trap. Hydrogen bonds = temporary changes (blow-dry, wet set). Disulfide bonds = permanent changes (perm, relaxer). Know which bond each service targets.


    > Medulla confusion: The medulla being absent does NOT mean the hair is unhealthy — it is simply a characteristic of fine hair.


    > Pheomelanin vs. Eumelanin: Don't mix these up. "Pheo" = fair/red tones; "Eu" = dark tones.


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    Hair Follicle & Growth


    The Hair Follicle

  • • Hair root – the portion of hair below the skin's surface, enclosed within the follicle
  • • Dermal papilla – located at the base of the follicle; contains blood vessels and nerves that supply nutrients essential for hair growth
  • • The follicle originates in the dermis and extends into the subcutaneous layer

    • The Hair Growth Cycle

    Hair grows in a continuous three-phase cycle:


    | Phase | Name | Duration | % of Scalp Hair | Key Event |

    |---|---|---|---|---|

    | Active Growth | Anagen | 2–7 years | 85–90% | Hair actively grows; attached to papilla |

    | Transitional | Catagen | 1–2 weeks | ~1% | Follicle shrinks; growth stops |

    | Resting | Telogen | 3–4 months | 10–15% | Hair rests then sheds |


    Normal Hair Growth Facts

  • • Average shedding: 50–100 hairs per day (normal telogen shedding)
  • • Average growth rate: ½ inch (1.25 cm) per month
  • • Growth rate is influenced by genetics, age, health, hormones, and nutrition

    • Key Terms – Hair Growth

  • • Anagen – active growth phase
  • • Catagen – transitional/regression phase
  • • Telogen – resting/shedding phase
  • • Dermal papilla – nourishing structure at the follicle base
  • • Hair root – the hair below the skin surface

    • ⚠️ Watch Out For

    > Cycle phase percentages: Memorize these — 85–90% anagen, ~1% catagen, 10–15% telogen. Exam questions may ask which phase the majority of hairs are in (always anagen).


    > Normal shedding: 50–100 hairs/day is normal. Anything significantly above this may indicate a disorder.


    > Catagen is the shortest phase — only 1–2 weeks. Don't confuse it with telogen (months).


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    Scalp & Skin Anatomy


    The Three Layers of the Skin

    From outermost to innermost:

    1. Epidermis – outer protective layer; includes the stratum corneum

    2. Dermis – middle layer; contains hair follicles, sebaceous glands, arrector pili muscles, blood vessels, and nerves

    3. Subcutaneous layer (hypodermis) – deepest layer; composed of fat and connective tissue; anchors skin to underlying structures


    Where Hair-Related Structures Are Located

    | Structure | Location |

    |---|---|

    | Hair follicle | Originates in dermis, extends into subcutaneous layer |

    | Sebaceous gland | Dermis (attached to hair follicle) |

    | Arrector pili muscle | Dermis |

    | Dermal papilla | Base of follicle (deepest part) |


    The Sebaceous Gland

  • • Secretes sebum – the skin's natural oil
  • • Lubricates and protects both the hair and scalp
  • • Attached directly to the hair follicle

    • Skin pH

  • • Healthy hair and scalp: pH 4.5–5.5 (slightly acidic)
  • • This acidic environment:

    • - Keeps the cuticle closed and smooth

    - Protects against bacterial growth

    - Maintains hair's structural integrity

  • • High pH (alkaline) = opens/raises the cuticle = used in chemical services

    • The Stratum Corneum

  • • Outermost sublayer of the epidermis
  • • Composed of dead, flattened (keratinized) cells
  • • Acts as the skin's primary barrier against environmental damage and moisture loss

    • Key Terms – Scalp & Skin

  • • Epidermis – outermost skin layer
  • • Dermis – middle layer housing hair structures
  • • Subcutaneous layer/hypodermis – deepest fat layer
  • • Sebaceous gland – oil-secreting gland attached to follicle
  • • Sebum – natural oil that lubricates hair and scalp
  • • Stratum corneum – outermost sublayer of epidermis
  • • pH 4.5–5.5 – normal healthy scalp pH range

    • ⚠️ Watch Out For

    > Dermis vs. Epidermis: Hair follicles and sebaceous glands are in the dermis, not the epidermis. The epidermis is the surface layer with no follicles.


    > pH direction matters: Alkaline (high pH) products open the cuticle; acidic (low pH) products close it. Know which direction chemical services push the pH.


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    Hair & Scalp Disorders


    Dandruff

  • • Pityriasis capitis simplex – common dandruff

    • - Excessive shedding of dead scalp skin cells

    - Presents as dry, white flakes

    - Generally not contagious

    - Can be treated with medicated or anti-dandruff shampoos


    Fungal Infections

  • • Tinea capitis – ringworm of the scalp

    • - Contagious fungal infection

    - Presents as scaly, circular patches with possible hair loss

    - Must refer client to a physician — cosmetologists cannot treat this

    - Do NOT perform services on clients with tinea capitis


    Alopecia (Hair Loss Conditions)


    | Condition | Cause | Characteristics |

    |---|---|---|

    | Alopecia areata | Autoimmune (immune attacks follicles) | Smooth, coin-shaped bald patches |

    | Alopecia totalis | Progression of areata | Loss of all scalp hair |

    | Alopecia universalis | Progression of areata | Loss of all body hair |

    | Traction alopecia | Chronic tension (tight styles) | Hair loss at hairline from braids, ponytails |

    | Androgenic alopecia | Hereditary/hormonal | Patterned hair loss (male/female pattern) |


    Other Disorders

  • • Hirsutism – excessive hair growth in women in areas where it typically grows in men (face, chest, back); caused by hormonal imbalances; refer to physician

    • ⚠️ Watch Out For

    > Contagious vs. Non-Contagious: Tinea capitis IS contagious — refuse service and refer to a physician. Pityriasis (dandruff) is generally not contagious — services can proceed.


    > Alopecia types: Know the progression — areata → totalis (all scalp) → universalis (all body). Exam questions may ask you to distinguish between them.


    > Traction alopecia is preventable — it is caused by styling practices, not disease. This is a cosmetologist's responsibility to recognize and advise against.


    > Hirsutism is a medical condition requiring physician referral — cosmetologists do not diagnose or treat it.


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    Quick Review Checklist


    Hair Structure

  • • [ ] Name and function of the three layers of the hair shaft (cuticle, cortex, medulla)
  • • [ ] Eumelanin = dark tones; Pheomelanin = red/blonde tones
  • • [ ] Hydrogen bonds = temporary (water/heat); Disulfide bonds = permanent (chemicals)
  • • [ ] Hair is ~97% keratin protein
  • • [ ] Arrector pili muscle causes goosebumps

    • Hair Growth Cycle

  • • [ ] Anagen = active growth (2–7 years, 85–90% of hair)
  • • [ ] Catagen = transitional (1–2 weeks, ~1% of hair)
  • • [ ] Telogen = resting/shedding (3–4 months, 10–15% of hair)
  • • [ ] Normal shedding = 50–100 hairs/day
  • • [ ] Growth rate = ~½ inch/month
  • • [ ] Dermal papilla supplies blood/nutrients to follicle

    • Skin & Scalp Anatomy

  • • [ ] Three skin layers: epidermis → dermis → subcutaneous
  • • [ ] Hair follicles, sebaceous glands, and arrector pili are in the dermis
  • • [ ] Sebaceous glands produce sebum
  • • [ ] Healthy scalp pH = 4.5–5.5 (slightly acidic)
  • • [ ] Stratum corneum = outermost sublayer of epidermis

    • Disorders

  • • [ ] Pityriasis capitis simplex = common dandruff (not contagious)
  • • [ ] Tinea capitis = ringworm (contagious fungal; refer to physician; no service)
  • • [ ] Alopecia areata = autoimmune; smooth, coin-shaped patches
  • • [ ] Traction alopecia = caused by tight hairstyles; preventable
  • • [ ] Hirsutism = excessive female hair growth; hormonal cause; refer to physician

    • ---


    Pro Tip: On the Illinois State Board Exam, pay close attention to which conditions require physician referral (tinea capitis, hirsutism, alopecia areata) versus which can be addressed in the salon. When in doubt, refer out!

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