Advanced Laser Education Content - Part 1 Hair Anatomy

This page contains treatments advanced education content about laser and treatments. 


Hair Anatomy

  • Hair is made up of dead cells filled with hard keratin
  • Keratin is a very durable protein that grows upward from the hair follicle
  • As new cells are added at the bottom of the follicle, older cells are pushed up and eventually out of the follicle making the hair visible
  • The purpose of hair includes protection against sun damage filtering dust from the hair, maintaining warmth, cosmetic value

The 3 layers of the hair shaft

  • Cuticle
    • The outermost layer
    • Composed of primarily keratin scales that overlap slightly
    • Thin and colorless
    • Serves to protect the cortex
  • Cortex
    • Middle layer
    • Provides hair its strength
    • Color and texture
  • Medulla
    • Innermost layer
    • Flexibility
    • Only present in large, thick hairs

Cuticle

The cuticle provides:

  • Hard protective wall
  • Shields the inner fibrous cortex from water and dirt
  • The thicker the hair, the more cuticle layers

Cortex

  • Makes up the majority of the hair shaft
  • Gives hair its special qualities: elasticity, curl, coarseness
  • Packed with strands of keratin, lying along the length of the hair
  • Contains granules of the hair pigment melanin

Medulla

  • A central hollow core found in some terminal hair
  • Especially in unpigmented ones
  • Biological evolutionary purpose:
  • Extra heat and insulation

Components of Hair Follicle

 
 

Hair originates in the follicle, a cavity in the skin that holds and protects the active or living cells that become nonliving strand of hair

  • Shaft - Protruding from the epidermis
  • Root - Embedded in the dermis layer
  • Bulb - Located at the base of the root, contains that papilla at the subcutaneous layer

Vellus Hair

  • Short, fine, soft, usually non-pigmented and unmedullated
  • Found in children adult females
  • Can transform into terminal hairs when stimulated by androgens or with age
  • Replaces lanugo hair, that which normally grows only on fetuses
  • Provides thermal insulation and cooling for the body
  • Referred to as “peach fuzz”

Intermediate Hairs

  • Occurs on the scalp and demonstrate a morphology between those of the terminal and vellus hairs
  • Medullated and contain a moderate amount of pigment

Terminal Hairs

  • Long, coarse, thick, darkly pigmented and medullated
  • Makes up 90% of hairs on chest, trunk, shoulders, legs and arms
  • Normally found on the scalp, eyebrows, underarms, genital areas, arms, chest, face, legs and back

Hirsutism (HUR-soot-iz-um) is a condition of unwanted, male-pattern hair growth in women. Hirsutism results in excessive amounts of stiff and pigmented hair on face, chest and back


The hair growth cycles

  • Each individual hair is forms within the bulb
  • Hair growth cycles throughout and individual’s lifetime
  • Normal growth rate for scalp is 0.4 mm per day, ~0.5 inches per month
  • Hair growth is randomized for individual hairs
  • Growth rates are affected by age, gender, hair color, body region and ethnicity

Anagen Growth Phase

  • The active, growing phase
  • Hair contains an abundance of melanin during this phase
  • This phase contains 7 stages
  • Each body site has a different percent of hairs in anagen phase
  • Length of the anagen cycle is ~1,000 days

Catagen Growth Phase

  • Resting, intermediate or transition phase
  • New cells are not created
  • Hair follicle shrinks
  • Part of the hair root is destroyed
  • Phase lasts 1-2 weeks

Telogen Growth Phase

  • New hair begins to grow from the hair follicle
  • As the new hair grows the old hair will shed naturally
  • These are the hairs that come out when shampooing or brushing hair
  • Phase can last 3-4 months

Fitzpatrick Skin Type Scale

Type I – Pale white skin, blonde or red hair, blue eyes, freckles

  • Always burns, never tans

Type II – Fair white skin, blond or red hair; blue, green or hazel eyes

  • Usually burns, tans minimally

Type III – Creamy white to light brown skin, any hair or eye color

  • Sometimes mild burn, tans uniformly

Type IV – Moderate brown and olive, any hair or eye colors

  • Rarely burns, tans well

Type V – Dark brown skin, usually dark hair and eyes

  • Very rarely burns, tans very easily

Type VI – Deeply pigmented dark brown to black skin, dark hair and eyes

  • Never burns, tans very easily

What is my skin type?

The information will help evaluate the skin type so the laser treatments can be more effective. Skin type is often categorized according to the Fitzpatrick skin type scale which ranges from very fair to very dark

The 2 main factors that influence skin type are:

  • Genetics - Determines the overall appearance and eye and hair color
  • Sun exposure response - The way skin reacts is another way to correctly assess skin type