Chapter 11

Properties of the Hair & Scalp

• 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.

Learning Objectives

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• 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.

Learning Objectives (continued)

• 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.

Introduction

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

• 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

– Vellus hair: short, fine, downy, unpigmented hair on body(not palms or soles) We have 55% more than men

– Terminal hair: long, thick, pigmented hair found on scalp, legs, arms, and body. Coarser than vellus P

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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

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• Men– Negative social and emotional effects– Preoccupation with baldness– Effort made to conceal

• Women– Devastation– Anxiety– Feelings of helplessness and unattractiveness

Emotional Impact of Hair Loss (continued)

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

• Affects millions of men and women in the United States

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Alopecia Areata

• 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

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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

• Canities– Congenital canities– Acquired canities

• Ringed hair

• Hypertrichosis

• Trichoptilosis

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• Trichorrhexis nodosa

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• Fragilitas crinium

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Recognize Disorders of the Scalp

• Pityriasis

• Malassezia

• Pityriasis capitis simplex

• Pityriasis steatoides

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Fungal Infections

• Tinea

• Tinea capitis

• Tinea favosa

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Parasitic Infections

• Scabies – itch mite• Pediculosis capitis – head lice

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Bacterial Infections

• Furuncle

• Carbuncle

• Folliculitis

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Perform a Thorough Hair and Scalp Analysis

• Hair Texture– Coarse– Medium– Fine

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Hair Density

• Low: thin

• Medium: medium

• High: thick dense

• Average: 2,200 hairs per square inch

Porosity

• Low porosity

• Average porosity

• High porosity

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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)

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.

Chapter Review Questions (continued)

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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?

Chapter Review Questions (continued)

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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?

Chapter Review Questions (continued)