Chapter 11
Properties of the
Hair & Scalp
Learning Objectives
• Identify and distinguish the different structures of the
hair root.
• Point out and differentiate the differences among the
three main layers of the hair shaft.
• Identify and explain the three types of side bonds in
the cortex.
• Name and compare the differences among the three
cycles of hair growth.
(continues)
Learning Objectives (continued)
• Give examples of the common types of hair loss and
explain what can cause hair loss.
• Identify and explain at least three options for hair loss
treatment.
• Learn to identify the most common hair and scalp
disorders seen in the salon and school, and then
name which ones a physician should treat.
• Compare and describe the different factors that
should be considered during a hair and scalp
analysis.
Introduction
• Hairstylists play an important role in many people’s
lives.
• All hair services must be based on a thorough
understanding of the growth, structure, and
composition of hair.
Discover the Structure of Hair
• Trichology – the scientific study of hair, its
diseases, and its care
• Hair root – the part of the hair located below the
surface of the epidermis (outer layer of the skin)
• Hair shaft – portion of the hair that projects
above the epidermis
Structures of the Hair Root
• Hair follicle
– Distribution
– Growth
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Hair bulb
Dermal papilla
Arrector pili muscle
Sebaceous glands
STRUCTURES OF THE HAIR ROOT
• Hair follicle: The hair follicle is the tube-like
depression or pocket in the skin or scalp that
contains the hair root. Hair follicles are
distributed all over the body, with the
exceptions of the palms of the hands and the
soles of the feet. The follicle extends
downward from the epidermis into the dermis
(the inner layer of skin), where it surrounds
the dermal papilla. Sometimes more than one
hair will grow from a single follicle.
• Hair bulb: The lowest area or part of a hair
strand, it is the thickened, club-shaped structure
that forms the lower part of the hair root. The
lower part of the bulb fits over and covers the
dermal papilla.
• Dermal papilla: A small, cone-shaped elevation
located at the base of the hair follicle that fits into
the hair bulb; it contains the blood and nerve
supply that provides the nutrients needed for
growth.
• Arrector pili muscle: These are minute,
involuntary muscle fibers in the skin inserted in
the base of the hair follicle. Fear or cold causes
them to contract, which makes the hair stand up
straight, resulting in goose bumps.
• Sebaceous glands: These are the oil glands of
the skin and are connected to the hair follicles.
The sebaceous glands secrete an oily
substance called sebum, which lubricates the
hair and skin.
Structures of the Hair Shaft
• Hair cuticle
• Cortex
• Medulla
STRUCTURES OF THE HAIR SHAFT
• The hair cuticle is the outermost layer of the hair;
it consists of a single, overlapping layer of
transparent, scale-like cells that overlap like
shingles on a roof. The cuticle layer provides a
barrier that protects the inner structure of the hair
as it lies tightly against the cortex. It is responsible
for creating the shine and the smooth, silky feel of
healthy hair.
• The cortex is the middle layer of hair; it is a
fibrous protein core formed by elongated
cells containing melanin pigment. About 90
percent of hair weight comes from the
cortex. Protein structures located in the
cortex provide hair elasticity. Changes
resulting from chemical services occur in the
cortex.
• The medulla is the innermost layer. It is
composed of round cells. Very fine and
naturally blond hair may not even have a
medulla. Thick coarse hair and beard hair
always contain a medulla. The medulla is
not involved in salon services.
Learn About the Chemical Composition of Hair
• Hair is approximately 90 percent protein.
• The protein is made up of long chains of amino
acids, which, in turn, are made up of elements.
• The major elements that make up human hair are
carbon, oxygen, hydrogen, nitrogen, and sulfur
and are often referred to as the COHNS elements.
• These five elements are also found in skin and nails.
LEARN ABOUT THE CHEMICAL COMPOSITION
OF HAIR
• Hair is approximately 90 percent protein.
• The protein is made up of long chains of amino
acids, which, in turn, are made up of elements.
• The major elements that make up human hair are
carbon, oxygen, hydrogen, nitrogen, and sulfur
and are often referred to as the COHNS
elements.
• These five elements are also found in skin and
nails.
COHNS Elements
• Carbon – 51 percent
• Oxygen – 21 percent
• Hydrogen – 6 percent
• Nitrogen – 17 percent
• Sulfur – 5 percent
Keratinization
• Keratinization – maturing process of living cells
that originate within the hair follicle.
• As these newly formed cells mature, they fill up
with a fibrous protein called keratin.
KERATINIZATION
• Hair is composed of protein that grows from cells
originating within the hair follicle. This is where the
hair begins. As soon as these living cells form, they
begin their journey upward through the hair follicle.
They mature in a process called keratinization.
•As these newly formed cells mature,
they fill up with a fibrous protein called
keratin. After they have filled with
keratin, the cells move upward, lose
their nucleus, and die. By the time the
hair shaft emerges from the scalp, the
cells of the hair are completely
keratinized and are no longer living. The
hair shaft that emerges is a nonliving
fiber composed of keratinized protein.
Amino Acids
• Linked like pop beads
• Peptide or end bonds
• Polypeptide chain
• Helix
Side Bonds of the Cortex
• Hydrogen bonds
• Salt bonds
• Disulfide bonds
• Lanthionine bonds
SIDE BONDS OF THE CORTEX
• The cortex is made up of millions of
polypeptide chains.
• Polypeptide chains are cross-linked like the
rungs on a ladder by three different types of
side bonds that link the polypeptide chains
together and are responsible for the extreme
strength and elasticity of human hair.
• They are essential to services such as wet
setting, thermal styling, permanent waving,
and chemical hair relaxing.
• The three types of side bonds are hydrogen, salt,
and disulfide bonds.
• A hydrogen bond is a weak, physical, cross-link
side bond that is easily broken by water or heat.
They are weak individually, but because there are so
many, they account for about one-third of the hair’s
strength.
• A salt bond is another weak, cross-link side bond
that can be broken by changes in pH. They are
easily broken by strong alkaline or acidic solutions
and account for about one-third of the hair’s overall
strength.
• Disulfide bond: A strong, chemical side bond that
joins the sulfur atoms of two neighboring cysteine
amino acids to create cystine. The cystine joins
together two polypeptide strands. Although there are
far fewer disulfide bonds than hydrogen or salt bonds,
disulfide bonds are so much stronger that they also
account for about one-third of the hair’s overall
strength. Disulfide bonds are not broken by water.
They are broken by permanent waves and chemical
hair relaxers that alter the shape of hair.
• Lanthionine bonds: The bond that occurs from
hydroxide chemicals relaxing the hair and breaking
the disulfide bonds.
Bonds of the Hair
Hair Pigment
• Melanin – tiny grains of pigment found in cortex
– Eumelanin – provides dark brown/black color
– Pheomelanin – provides yellow to red/ginger color
• Natural hair color – result of ratio of eumelanin to
pheomelanin
• Gray hair – absence of melanin
Wave Patterns
• Straight hair
• Wavy hair
• Curly hair
• Extremely curly hair
WAVE PATTERN
• Refers to the shape of the hair strand. It is described
as straight, wavy, curly, or extremely curly.
• Natural wave patterns are the result of genetics.
Although there are many exceptions, as a general rule,
Asians tend to have extremely straight hair,
Caucasians tend to have straight, wavy, or curly hair,
and African Americans tend to have extremely curly
hair.
• But straight, wavy, curly, and extremely curly hair occur
in all races—anyone of any race, or mixed race, can
have hair with varying degrees of curl from straight to
extremely curly.
• The wave pattern may also vary from strand to
strand on the same person’s head. It is not
uncommon for an individual to have different
amounts of curl in different areas of the head.
• Curly hair is oval in shape.
• Extremely curly hair grows in long twisted spirals.
Cross-sections appear flattened and vary in
shape and thickness along their length and has
a fairly irregular diameter, showing varying
diameters along a single strand.
Two types of hair on human
• Types of hair
– Terminal hair: long, thick, pigmented
hair found on scalp, legs, arms, and
body. Coarser than vellus
Pfizer Inc.
– Vellus hair: short, fine, downy,
unpigmented hair on body(not palms or
soles) We have 55% more than men
Growth Cycles of Hair
• Hair growth occurs in cycles. Each complete
cycle has three phases that are repeated over
and over again throughout life. The three phases:
Anagen – growing phase
• Catagen – transition phase
• Telogen – resting phase
Anagen
• growing phase
• average growth scalp hair is about ½ inch
per month.
• 90% of hair is in anagen at one time
• Lasts from two to six years depending on
gender, age, type of hair, heredity,
nutrition, and health.
Catagen
• transition phase that ends the growth
phase
• lasts 1-2weeks.
• follicle shrinks and detaches from the
dermal papilla. hair bulb disappears. the
shrunken root end forms a rounded club.
• Less than 1% of hair is in the catagen
phase at any one time.
Telogen
• resting phase.
• follicle begins a 3-6 month phase of
resting. After telogen, entire cycle starts
again
• 10 % of hair is in telogen phase at one
time.
• The entire growth cycle repeats itself
every 4-5 years.
Myths and Facts About Hair Growth
• Myths
– Shaving, clipping, cutting makes hair grow faster.
– Scalp massage increases growth.
– Gray hair is coarser and more resistant.
– Natural curl determined by race.
– Round cross section is straight; oval cross section is
wavy; flat cross section is curly.
Understand Hair Loss Causes and Treatment
• The growth cycle provides for the continuous
growth, fall, and replacement of individual hair
strands.
• Natural shedding: 35 to 40 hairs per day
Emotional Impact of Hair Loss
Perception of bald and balding men:
• Less attractive
• Less assertive
• Less successful
• Less personally likeable
• Older by five years
(continues)
Emotional Impact of Hair Loss (continued)
• Men
– Negative social and emotional effects
– Preoccupation with baldness
– Effort made to conceal
• Women
– Devastation
– Anxiety
– Feelings of helplessness and unattractiveness
Types of Abnormal Hair Loss
• Abnormal hair loss is called alopecia.
• The three most common types of abnormal hair
loss:
– Androgenic alopecia
– Alopecia areata
– Postpartum alopecia
Androgenic Alopecia
• Progressive shrinking or miniaturization of
terminal hair
Pfizer Inc.
• Affects millions of men and women in the
United States
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•
•
•
•
Sudden loss in round or irregular patches
Affects 5 million people in the United States
Immune system attacks hair follicles
Begins with small bald patches
Occurs in males and females
of all ages and races
Courtesy of Robert A. Silverman, M.D., Clinical
Associate Professor, Department of Pediatrics,
Georgetown University.
Alopecia Areata
Postpartum Alopecia
• Temporary hair loss at conclusion of pregnancy
• Growth cycle returns to normal within one year
after delivery of baby
Hair Loss Treatments
• Minoxidil – topical treatment
• Finasteride – oral treatment
Recognize Disorders of the Hair
– Congenital canities
– Acquired canities
• Ringed hair
• Hypertrichosis
• Trichoptilosis
Courtesy of P&G Beauty from the World of Hair by John Gray.
• Canities
(continues)
Recognize Disorders of the Hair (continued)
• Monilethrix
• Fragilitas crinium
Courtesy of P&G Beauty from the World of Hair by John Gray.
• Trichorrhexis nodosa
Recognize Disorders of the Scalp
• Malassezia
• Pityriasis capitis simplex
• Pityriasis steatoides
Photography: Courtesy of P&G Beauty
• Pityriasis
• Tinea favosa
Courtesy of Robert A. Silverman, M.D.,
Clinical Associate Professor, Department
of Pediatrics, Georgetown University.
Fungal Infections
• Tinea
• Tinea capitis
Courtesy of Hogil Pharmaceutical Corporation.
Courtesy of The National Pediculosis
Association,® Inc.
Parasitic Infections
• Scabies – itch mite
• Pediculosis capitis – head lice
Bacterial Infections
• Furuncle
• Folliculitis
© Inxti/Shutterstock.com
• Carbuncle
The Gillette Research Institute.
The Gillette Research Institute.
The Gillette Research Institute.
Perform a Thorough Hair and Scalp Analysis
• Hair Texture
– Coarse
– Medium
– Fine
Hair Density
• Low: thin
• Medium: medium
• High: thick dense
• Average: 2,200 hairs per square inch
The Gillette Research Institute.
The Gillette Research Institute.
The Gillette Research Institute.
Porosity
• Low porosity
• Average porosity
• High porosity
Elasticity
• Normal elasticity
• Low elasticity
• Testing for elasticity
Hair Growth Patterns
• Hair stream – hair flowing in same direction
• Whorl – hair forms in a circular pattern
• Cowlick – tuft of hair that stands straight up
Dry Hair and Scalp
• Hair appears dull, dry, lifeless.
• Avoid frequent shampooing, strong soaps,
detergents, or products with a high alcohol content.
Oily Hair and Scalp
• Use normalizing shampoos.
• Eat a well-balanced diet.
• Exercise.
• Shampoo regularly and frequently.
• Practice good personal hygiene.
Summary and Review
• Trichology enables the professional cosmetologist to
better understand both the physical and microscopic
properties of the hair.
• You must be able to recognize those conditions of the
hair and scalp needing treatment.
• Practicing proper disinfection procedures that are
approved by your oversight regulatory agency will
prevent the spread of disease.
Chapter Review Questions
1. Name and describe the five main structures of
the hair root.
2. Name and describe the three layers of the hair.
3. Describe the process of keratinization.
4. What are polypeptide chains?
(continues)
Chapter Review Questions (continued)
5. List and describe the three types of side bonds.
Indicate whether they are strong or weak and
why.
6. Name and describe the two types of melanin
responsible for natural hair color.
(continues)
Chapter Review Questions (continued)
7. Name and describe the two types of hair and
their locations on the body.
8. What are the three phases of the hair growth
cycle and what occurs during each?
9. What is the reason for normal daily hair loss?
10. What are the most common types of abnormal
hair loss?
(continues)
Chapter Review Questions (continued)
11. What are the only two approved hair loss
treatments?
12. Name the two main types of dandruff and state
whether either can be treated in the salon.
13. Which scalp and hair disorders cannot be treated
in the salon?
14. What four factors should be considered in hair
analysis?