Properties of the Hair & Scalp Structure, Composition, and

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Properties of the Hair Scalp

• Structure, Composition, and Growth Cycles

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Questions to Consider

• Is hair alive or dead?
• What makes up hair?
• Hair consists of what chemicals?
• How can the family members have different hair
  color?
• Does hair grow in different cycles?
• Why does hair stop growing?

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Trichology

• Greek word meaning study of the hair
• Trichos means hair in Greek
• We study the structure of hair, composition, and
  grow cycles to understand how salon services
  effect different hair types, and to select better
  procedures and products for our clients.

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Structure of Hair

• Hair has two parts
• a) Hair root- Part of hair below the skins
  surface
• b) Hair shaft- Extends above the skin surface

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Structure of the Hair Root

• Follicle- Tube like depression in the skin that
  the hair grows out of onto the surface
• Hair Bulb Thick club shaped structure at the
  bottom of the hair root
• Arrector Pili Small involuntary muscle that
  makes hair stand straight up when scared or cold
• Sebaceous Gland Connected to the hair follicle,
  this gland secretes oil substance called sebum

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Structure of the Hair Shaft

• Cuticle - Outer layer of the hair, consist of
  overlapping scales. Provides the shine and feel
  of the hair, as well as protection
• Each scale is attached to the cortex
• Cuticles have the ability to open and close

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The Cortex

• Cortex is the middle layer of the hair
• 90 of the hair weight comes from the cortex
• Hair color pigment (melanin) is found in the
  cortex
• Physical and chemical changes in the hair take
  place in the cortex

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The Medulla

• Medulla- Innermost part of the hair strand
• Composed of circular cells
• Some hair may lack a medulla, (fine, natural
  blondes)
• Little is known about the function of the medulla
• The medulla does not effect salon services

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Chemical Composition of the Hair

• Hair is composed of protein, that grows from the
  cells in the hair follicle
• As the protein grows, it keratinizes (hardens)
• When hair pushes its way through the skin, it is
  no longer alive
• 90 protein, made up of amino acids, which make
  up elements

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COHNS Elements

• Hair is made of the COHNS elements
• C- Carbon 51
• O- Oxygen 21
• H- Hydrogen 6
• N- Nitrogen 17
• S- Sulfur 5

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Hair Structure

• Hair is like a ladder of chemical elements
• The COHNS elements join together by peptide
  bonds, (end bonds). Think of it as the two
  vertical parts of a ladder.
• The side bonds are the steps of the ladder

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Polypeptide Chain

• A Polypeptide Chain is made up of many amino
  acids (elements) connected by peptide bonds
• Polypeptide Chains are coiled in a spiral shape
  called a helix

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Side Bonds

• The side bonds of the cortex are made up of
  hydrogen, salt and disulfide bonds
• Side bonds holds the kertain (protein) fibers in
  place
• Account for the strength and elasticity of the
  hair

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Hydrogen and Salt Bonds

• Hydrogen and Salt bonds are weak and are easily
  broken by heat and/or water
• Example Styles that do not hold up in extreme
  heat or moisture outside
• Both account for 1/3 of the hairs strength

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Disulfide Bonds

• Disulfide bonds are chemical side bonds that are
  not easily broken, it requires chemicals to be
  broken, such as relaxers, permanent hair color,
  permanent waves, and bleach
• Joined by two cysteine amino acids to create a
  cystine
• Accounts for 1/3 of hairs strength

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Where does hair color come from?
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Hair Pigment ( Melanin )

• Melanin is located in the cortex
• Natural hair color pigment comes from tiny grains
  of pigment called melanin
• The type of melanin, amount and distribution
  determines someone's hair color

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Eumelanin

• Eumelanin pigment gives hair its black to brown
  hues
• All hair colors contain both eumelanin and
  pheomelanin. It is the ratio of pigment, and size
  of granules that determine the hair color

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Pheomelanin

• Phelomelanin provides hair colors from reds to
  blondes
• The color result will be determine by the size,
  distribution and type of color pigment

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Types of Hair

• Two main types of hair found on the body vellus
  and terminal
• Vellus- (lanugo) not pigmented and does not have
  medulla
• Found in areas normally considered hairless
• Aids in evaporation of perspiration

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Terminal Hair

• Terminal hair is found on the legs, arms, scalp
  and body areas of men and women
• Terminal hair is coarser than vellus, it is
  pigmented, except gray hair
• Depending on the age, genetics and hormones, all
  follicles can produce terminal or vellus hair

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Hair Growth Cycles

• Hair has three growth cycles that repeat itself
  over and over throughout life
• Anagen-Growth phase
• Catagen-transition phase
• Telogen- resting phase

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Anagen Growth Phase

• New hair is produced
• Cells grow faster than any other cell of the body
• Women's hair grows faster than men's
• 90 of hair in anagen phase
• Average growth 1 per month

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Catagen Transition Phase

• Catagen phase is between growing and resting
• It marks the end of the growing phase
• Follicle shrinks and detaches from the dermal
  papilla
• Less than 1 of hair is in the catagen phase
• Phase lasts from 1-2 weeks

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Telogen Resting Phase

• Telogen phase lasts until hair is shed or remains
  until new hair pushes it out
• 10 of hair is in the Telogen phase
• Phase lasts from 3 to 6 months
• The entire growth cycle repeats it self on the
  average of 4 to 5 years

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Works Sited

• Miladys Standard Cosmetology Textbook
• 2004 edition