1. Properties of the Hair & Scalp
Chapter 11
Properties of the Hair & Scalp

2. 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) 2

3. 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.
WHY STUDY PROPERTIES OF THE HAIR AND SCALP?
Cosmetologists should study and have a thorough understanding of the properties of the hair and scalp because:
You need to know how and why hair grows and how and why it falls out in order to be able to differentiate between normal and abnormal hair loss.
Knowing what creates natural color and texture is a vital part of being able to offer a variety of chemical services to clients.
Spotting an unhealthy scalp condition that could be harboring a communicable disease or even be causing permanent hair loss is a way to aid your client in caring for their scalp and their hair’s well-being. 3

4. 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.
INTRODUCTION
The term crowning glory aptly describes the importance placed on hair, how good we feel when our hair looks great, and just how distressing a bad hair day really can be.
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. 4

5. 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
DISCOVER THE STRUCTURE OF HAIR
Trichology
The scientific study of hair, its diseases, and its care.
The term is derived from the Greek words trichos, meaning “hair,” and ology, meaning “the study of.“
Hair parts
Hair root: The part of the hair located below the surface of the scalp.
Hair shaft: The part of the hair that projects above the skin. 5

6. 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. 6

7. LESSON ACTIVITY 1
Ask for volunteers to come up and write in the various parts of the hair structure on a previously prepared flip chart or the Milady Chart. 7

8. 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. 8

9. 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. 9

10. COHNS Elements Carbon – 51 percent Oxygen – 21 percent
Hydrogen – 6 percent
Nitrogen – 17 percent
Sulfur – 5 percent 10

11. 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. 11

12. Amino Acids Linked like pop beads Peptide or end bonds
Polypeptide chain
Helix
AMINO ACIDS
Proteins are made of long chains of amino acids, units that are joined together end-to-end like pop beads.
The strong, chemical bond that joins amino acids is a peptide or end bond.
A long chain of amino acids linked by peptide bonds is called a polypeptide chain.
Proteins are long, coiled complex polypeptides made of amino acids. The spiral shape of a coiled protein is called a helix which is created when the polypeptide chains intertwine with each other. 12

13. 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. 13

14. LESSON ACTIVITY 2
Create a matrix on the board or flip chart containing five rows and five columns (like Table 11-2).
List the column headings of Table 11-2 across the grid in the first row.
In advance of the class, prepare 20 post-it-notes containing the terms or phrases found in the remaining four rows of the grid.
Have students close their books and ask for volunteers to come to the front of the class and select one term or phrase and place it appropriately on the grid. Reward those who answer correctly.
NOTE: After completion of this activity, go to the next slide to show correct answers. 14

15. Bonds of the Hair 15 BONDS OF THE HAIR
NOTE: After completion of the activity on the previous slide, go to this slide to show correct answers. 15

16. Hair Pigment Melanin – tiny grains of pigment
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
HAIR PIGMENT
All natural hair color is the result of pigment located within the cortex.
Melanin: The tiny grains of pigment in the cortex that give natural color to hair.
Eumelanin: Provides dark brown and black color to hair.
Pheomelanin: Provides natural hair colors from red and ginger to yellow-blond tones.
Natural hair color: Natural hair color in a person’s hair is due to the presence of the mixture of these pigments. More eumelanin gives darker hair and the amount can vary from person to person and also across a person’s head. When we look at a hair under the microscope, the eumelanin pigment granules are oval (elliptical) in shape and the pheomelanin pigments are partly oval and partly rod-shaped.
Gray hair: Gray hair contains only a few scattered melanin granules and white hair does not contain any melanin. 16

17. Wave Patterns Straight hair Wavy hair Curly hair Extremely curly hair
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 and Native Americans 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. 17

18. The Truth About Hair Growth
Types of hair
Vellus hair: short, fine, downy, unpigmented hair on body
Terminal hair: long, thick, pigmented hair found on scalp, legs, arms, and body
Pfizer Inc.
THE TRUTH ABOUT HAIR GROWTH
The two main types of hair found on the body are vellus hair and terminal hair.
Vellus hair: Also known as lanugo; this is short, fine, downy, unpigmented hair covering most of the body except the palms and soles of the feet. Women normally retain 55 percent more vellus hair than men.
Terminal hair: Long, thick, pigmented hair found on the scalp, legs, arms, and bodies of males and females; it is coarser than vellus hair and, with the exception of gray hair, it is pigmented. It usually has a medulla. 18

19. Growth Cycles of Hair Anagen – growing phase
Catagen – transition phase
Telogen – resting phase
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 are anagen, catagen, and telogen.
Anagen phase is the growing phase. The average growth of healthy scalp hair is about ½ inch (.5) or 1.25 centimeters per month. Ninety percent of hair is growing in the anagen phase at one time. It grows for a period from two to six years. The duration of hair life is affected by gender, age, type of hair, heredity, nutrition, and health.
Catagen is the transition phase that ends the growth phase and lasts only one to two weeks. The follicle canal shrinks and detaches from the dermal papilla. The hair bulb disappears and the shrunken root end forms a rounded club. Less than one percent of the scalp hair is in the catagen phase at any one time.
Telogen is the resting phase. After catagen, the follicle begins a three to six month phase of resting. About 10 percent of hair is in telogen phase at one time. After telogen, the cycle begins again. The entire growth cycle repeats itself every four to five years. 19

20. Myths and Facts About Hair Growth
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.
MYTHS AND FACTS ABOUT HAIR GROWTH
Shaving, clipping, and cutting the hair on the head makes it grow back faster, darker, and coarser.
FACT: Shaving or cutting the hair on the head has no effect on hair growth
Scalp massages increase hair growth.
FACT: There is no evidence to indicate this is true. Minoxidil and Finasteride are the only treatments that have been proven to increase hair growth and are approved for that purpose by the FDA.
Gray hair is coarser and more resistant than pigmented hair.
FACT: Other than lack of pigment, gray hair is exactly the same as pigmented hair. It is not resistant because it is gray, and is not more resistant than the pigmented hair on the same person’s head.
The amount of natural curl is always determined by racial background.
FACT: Anyone of any race, or mixed race, can have hair from straight to extremely curly. It is also true that within races individuals have hair with varying degrees of curl in different areas of the head.
Hair with a round cross-section is straight; hair with an oval cross-section is wavy; hair with a flat cross-section is curly.
FACT: Cross-sections of straight hair tend to be round and curlier hair tends to be more oval, but cross-sections of hair can be almost any shape, including triangular; the shape of the cross-section does not always relate to the amount of curl or the shape of the follicle. 20

21. 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
UNDERSTAND HAIR LOSS CAUSES AND TREATMENT
Hair loss is the natural shedding of hair accounts for normal daily hair loss.
Recent measurements indicate that the average rate of hair loss is about 35 to 40 hairs per day. 21

22. Emotional Impact of Hair Loss
Perception of bald and balding men:
Less attractive
Less assertive
Less successful
Less personally likeable
Older by five years
EMOTIONAL IMPACT OF HAIR LOSS
Perceptions of bald and balding men recent studies show that, compared to men who have hair, bald men are perceived as being less attractive, assertive, successful, and likeable, as well as appearing older by five years.
(continues) 22

23. 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
EMOTIONAL IMPACT OF HAIR LOSS (continued)
Men with hair loss:
A study of how bald men perceive themselves showed that greater hair loss had a more significant impact than moderate hair loss. Men with more severe hair loss:
Experience significantly more negative social and emotional effects.
Are more preoccupied with their baldness.
Make some effort to conceal or compensate for their hair loss.
Women with hair loss:
Abnormal hair loss is not as common in women as it is in men, but it can be very traumatic and devastating for women who experience it.
Women have a greater emotional investment in their appearance.
Many women with abnormal hair loss feel anxious, helpless, and less attractive. 23

24. 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
TYPES OF ABNORMAL HAIR LOSS
Alcopecia: Abnormal hair loss
The three most common types of abnormal hair loss:
Androgenic alopecia
Alopecia areata
Postpartum alopecia

25. Androgenic Alopecia
Progressive shrinking or miniaturization of terminal hair
Affects millions of men and women in the United States
ANDROGENIC ALOPECIA
Also known as androgenetic alopecia.
Hair loss that is characterized by miniaturization of terminal hair that is converted into vellus hair.
It is usually the result of genetics, age, or hormonal changes that cause terminal hair to miniaturize.
Can begin as early as the teens and is frequently seen by the age of 40.
By age 35, almost 40 percent of both men and women show some degree of hair loss.
In men, androgenic alopecia is known as male pattern baldness and usually progresses to the familiar horseshoe-shaped fringe of hair.
In women it shows up as generalized thinning over the entire crown area.
Androgenic alopecia affects millions of men and women in the United States.
Pfizer Inc. 25

26. 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 of all ages and races
Courtesy of Robert A. Silverman, M.D., Clinical Associate Professor, Department of Pediatrics, Georgetown University.
ALOPECIA AREATA
An autoimmune disorder that causes the affected hair follicles to be mistakenly attacked by a person’s own immune system.
White blood cells stop the hair growth during the anagen phase.
It is a highly unpredictable skin disease that affects an estimated 5 million people in the United States alone.

This hair disorder usually begins with one or more small, round, smooth bald patches on the scalp and can progress to total scalp hair loss, or complete body hair loss (alopecia universalis).
Alopecia areata occurs in males and females of all ages, races, and ethnic backgrounds and most often begins in childhood. 26

27. Postpartum Alopecia Temporary hair loss at conclusion of pregnancy
Growth cycle returns to normal within one year after delivery of baby
POSTPARTUM ALOPECIA
Temporary hair loss at conclusion of pregnancy
The growth cycle generally returns to normal within one year after the baby is delivered. 27

28. Hair Loss Treatments Minoxidil – topical treatment
Finasteride – oral treatment
HAIR LOSS TREATMENTS
Minoxidil:
A topical (applied to the surface of the body) medication that is put on the scalp twice a day and has been proven to stimulate hair growth.
It is sold over the counter (OTC) as a nonprescription drug.
Available for both men and women.
Comes in two different strengths: 2 percent regular-strength solution and 5 percent extra-strength solution.
It is not known to have any serious negative side effects.
Finasteride:
An oral prescription for men only.
Side effects include weight gain and loss of sexual function. 28

29. Recognize Disorders of the Hair
Canities
Congenital canities
Acquired canities
Ringed hair
Hypertrichosis
Trichoptilosis
Courtesy of P&G Beauty from the World of Hair by John Gray.
RECOGNIZE DISORDERS OF THE HAIR
Canities: Technical term for gray hair. Caused by loss of natural pigment in hair.
Congenital canities: Exists at or before birth. Occurs mostly in albinos, occasionally in persons with normal hair.
Acquired canities: Usually due to old age; onset may occur prematurely in early adult life. May develop due to prolonged anxiety or illness.
Ringed hair: Alternating bands of gray and dark hair.
Hypertrichosis: Superfluous hair; also known as hirsuties; characterized by the growth of terminal hair in areas of body that normally only grow vellus hair. Can be tweezed or removed by depilatories, electrolysis, shaving, or epilation.
Trichoptilosis: Split hair ends; can be treated with conditioner to lubricate and soften ends, or by cutting.
(continues) 29

30. Recognize Disorders of the Hair (continued)
Trichorrhexis nodosa
Monilethrix
Fragilitas crinium
Courtesy of P&G Beauty from the World of Hair by John Gray.
RECOGNIZE DISORDERS OF THE HAIR (continued)
Trichorrhexis nodosa: Knotted hair; a dry, brittle condition including formation of nodular swellings along the hair shaft. The hair breaks easily, which creates a brushlike spreading of fibers along the hair shaft. Treated by softening the hair with conditioners and moisturizers.
Monilethrix: Beaded hair; hair breaks between the beads or nodes. Can be treated with scalp and hair conditioning.
Fragilitas crinium: Brittle hair, which causes splitting. Treated with hair and scalp conditioning. 30

31. LESSON ACTIVITY 3
Write technical terms on the board, flipchart, or write-on transparency and have students describe and pronounce them out loud as a group. 31

32. Recognize Disorders of the Scalp
Pityriasis
Malassezia
Pityriasis capitis simplex
Pityriasis steatoides
Photography: Courtesy of P&G Beauty
RECOGNIZE DISORDERS OF THE SCALP
The skin is in a constant state of renewal. The outer layer of skin that covers your body is constantly being shed and replaced by new cells from below. The average person sheds about nine pounds of dead skin each year. The skin cells of a normal, healthy scalp fall off naturally as small, dry flakes, without being noticed.
Dandruff:
Pityriasis is the technical term for dandruff, which is characterized by the excessive production and accumulation of skin cells. Instead of the normal, one-at-a-time shedding of tiny individual skin cells, dandruff is the shedding of an accumulation of large, visible clumps of skin cells.
Malassezia: A naturally occurring fungus that is present on all human skin but causes the symptoms of dandruff when it grows out of control.
Pityriasis capitis simplex: Classic Dandruff; it is characterized by an itchy scalp and large flakes attached to the scalp or scattered loosely in the hair. Regular use of antidandruff shampoos, conditioners, and topical lotions are the best treatment.
Pityriasis steatoides: More severe case of dandruff characterized by an accumulation of greasy or waxy scales, mixed with sebum, that stick to the scalp in crusts. As explained in Chapter 8, Skin Disorders & Diseases, when this condition is accompanied by redness and inflammation, it is called seborrheic dermatitis. Seborrheic dermatitis also can be found in the eyebrows or beard. 32

33. Fungal Infections Tinea Tinea capitis Tinea favosa 33
Clinical Associate Professor, Department
Courtesy of Robert A. Silverman, M.D.,
of Pediatrics, Georgetown University.
FUNGAL INFECTIONS
Tinea: The technical term for ringworm. Caused by vegetable parasites; highly contagious. Begins with small reddened patch of little blisters; refer to a physician.
Tinea capitis: Ringworm of the scalp; characterized by red papules or spots at opening of hair follicle; causes hair to break.
Tinea favosa: Honeycomb ringworm; characterized by dry, sulfur-yellow, cuplike crusts on scalp called scutula; give off odor; scars from favus are pink or white, shiny bald patches. Very contagious and should be referred to a physician. 33

34. Parasitic Infections Scabies – itch mite
Pediculosis capitis – head lice
Courtesy of The National Pediculosis Association,® Inc.
Courtesy of Hogil Pharmaceutical Corporation.
PARASITIC INFECTIONS
Scabies: A highly contagious skin disease caused by a parasite called a mite that burrows under the skin. Vesicles (blisters) and pustules (inflamed pimples with pus) usually form on the scalp from the irritation caused by this parasite. Excessive itching accompanies this condition and scratching the infected areas makes the affected area worse.
A client with this condition must be referred to a physician for medical treatment.
Pediculosis capitis is a contagious condition caused by head lice infesting the hair and scalp; itching occurs and resultant scratching can cause an infection. Refer to a physician. 34

35. Bacterial Infections Furuncle Carbuncle Folliculitis 35
© Inxti/Shutterstock.com
BACTERIAL INFECTIONS
Bacterial infections of the scalp are caused by two strains of bacteria known as staphylococci and streptococci. Most common types of staphylococci infections are furuncles, carbuncles, and folliculitis.
Furuncle
The technical term for a boil, an acute, localized bacterial infection of the hair follicle that produces constant pain.
It is limited to a specific area and produces a pustule perforated by a hair.
Refer to a physician.
Carbuncle
An inflammation of the subcutaneous tissue caused by staphylococci; it is similar to a furuncle but larger
Folliculitis
An infection of the hair follicles frequently caused by staphylococcus or other bacteria.
Infections are seen as small, white-headed pimples around one or more follicles.
Mild folliculitis may heal by itself in few days but deep or recurring ones need medical attention.
One common example seen in hair salons is folliculitis barbae, also known as pseudofolliculitis barbae, barbers itch or hot tub folliculitis. 35

36. Perform a Thorough Hair and Scalp Analysis
Hair Texture
Coarse
Medium
Fine
The Gillette Research Institute.
The Gillette Research Institute.
The Gillette Research Institute.
LEARN HOW TO PERFORM A THOROUGH HAIR AND SCALP ANALYSIS
Hair analysis is performed by observation, using the senses of sight, touch, hearing, and smell. The four most important factors to consider are texture, porosity, elasticity, and density. Other factors include the natural growth pattern and the degree of oiliness or dryness.
Hair Texture
The thickness or diameter of the individual hair strand. Hair texture can be classified as coarse, medium, or fine and can vary from strand to strand on the same person’s head.
Coarse has the largest diameter. Is stronger than fine hair. It is often more resistant to processing than medium or fine hair, so it usually requires more processing when you are applying products such as hair lighteners, hair colors, permanent waving solutions, and chemical hair relaxers.
Medium hair is the most common and is considered normal; it does not pose any special problems. It is thinner than coarse hair and thicker than fine hair.
Fine hair has the smallest diameter and is more fragile; fine hair is easier to process but more susceptible to damage. 36

37. LESSON ACTIVITY 4
Have students clip an individual hair strand from different areas of the head on several different student volunteers.
Have them hold the strand securely with one hand while feeling it with the thumb and forefinger of the other hand.
Have them describe the different feel between coarse hair and fine hair, and so forth. 37

38. Hair Density Low: thin Medium: medium High: thick dense
Average: 2,200 hairs per square inch
HAIR DENSITY
Measures the number of individual hair strands on 1 square inch (2.5 square cm) of the scalp.
The average hair density is about 2,200 hairs per one square inch.
Hair with high density (thick or dense hair) has more hairs per one square inch, and hair with low density (thin hair) has fewer hairs per one square inch.
The average head of hair contains about 100,000 individual hair strands.
The number of hairs on the head generally varies with the color of the hair.
Blonds usually have the highest density, and people with red hair tend to have the lowest.
Table 11-4 shows hair density by hair color. 38

39. Porosity Low porosity Average porosity High porosity 39 POROSITY
The Gillette Research Institute.
The Gillette Research Institute.
The Gillette Research Institute.
POROSITY
The ability of the hair to absorb moisture.
The degree of porosity is directly related to the condition of the cuticle layer.
Healthy hair with a compact cuticle layer is naturally resistant to being penetrated by moisture and is referred to as hydrophobic.
Porous hair has a raised cuticle layer that easily absorbs moisture and is called hydrophilic.
Hair with low porosity is considered resistant.
Chemical services performed on hair with low porosity require a more alkaline solution than those on hair with high porosity.
Alkaline solutions raise the cuticle and permit uniform saturation and processing on resistant hair.
Hair with average porosity is considered to be normal hair.
Chemical services performed on this type of hair will usually process as expected, according to the texture.
Hair with high porosity is considered overly porous hair and is often the result of previous overprocessing.
Overly porous hair is damaged, dry, fragile, and brittle.
Chemical services performed on overly porous hair require less alkaline solutions with a lower pH, which help prevent additional overprocessing and damage. 39

40. LESSON ACTIVITY 4
Have students pair up and check the porosity of each others’ hair by taking a strand of hair from four different areas of the head: the front hairline, the temple, the crown, and the nape.
Have them hold the strand securely with one hand while sliding the thumb and forefinger of the other hand from the end to the scalp.
If the hair feels smooth and the cuticle is compact, dense, and hard, it is considered resistant.
If the strand ruffles or they feel roughness, the hair is considered porous. If it feels very rough, dry, or breaks, it is considered overly porous.
Have students discuss results. 40

41. Elasticity Normal elasticity Low elasticity Testing for elasticity 41
Hair elasticity is the ability of the hair to stretch and return to its original length without breaking.
Hair elasticity is an indication of the strength of the side bonds that hold the hair’s individual fibers in place.
Normal Elasticity
Wet hair with normal elasticity will stretch up to 50 percent of its original length and return to that same length without breaking.
Dry hair stretches about 20 percent of its length.
If the hair stretches and returns to its original length without breaking, it has normal elasticity.
Low Elasticity
If the hair breaks easily or fails to return to its original length, it has low elasticity.
Hair with low elasticity is brittle and breaks easily.
It may not be able to hold the curl from wet setting, thermal styling, or permanent waving.
A result of weak side bonds that usually are a result of overprocessing.
Chemical services performed on hair with low elasticity require a milder solution with a lower pH to minimize further damage and prevent additional overprocessing. 41

42. LESSON ACTIVITY 5
Have students pair up and check the elasticity of each others’ hair by wetting a few hairs and taking an individual strand from four different areas of the head as in the porosity test.
Have them hold a single strand of wet hair securely and pull it (either a part or from the scalp).
If the hair stretches and returns to its original length without breaking, it has normal elasticity.
If it breaks or fails to return to original length, it has low elasticity.
Have students discuss results. 42

43. 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
HAIR GROWTH PATTERNS
Hair growth patterns are important to identify and consider, especially when preparing to shape and style the hair
Hair stream is hair flowing in the same direction, resulting from follicles sloping in the same direction. Two streams flowing in opposite directions from the head form a natural part in the hair.
A whorl occurs when hair leaves the follicles at an angle; the hair will lie in a particular direction forming patterns or streams on the head.
Often the streams spiral outward from a central point.
Usually run in clockwise direction and sometimes more than one whorl can be seen in certain individuals.
A cowlick is due to a particular pattern of hair stream on the forehead.
Cowlicks are usually more noticeable at the front hairline in people with short, thick hair but they may be located anywhere on the head. 43

44. Dry Hair and Scalp Hair appears dull, dry, lifeless.
Avoid frequent shampooing, strong soaps, detergents, or products with a high alcohol content.
DRY HAIR AND SCALP
Can be caused by inactive sebaceous glands; aggravated by excessive shampooing or by a dry climate.
Should be treated with products that contain moisturizers and emollients.
Avoid frequent shampooing along with the use of strong soaps, detergents, or products with a high alcohol content. 44

45. Oily Hair and Scalp Use normalizing shampoos.
Eat a well-balanced diet.
Exercise.
Shampoo regularly and frequently.
Practice good personal hygiene.
OILY HAIR AND SCALP
Characterized by a greasy buildup on the scalp and an oily coating on the hair.
Caused by improper shampooing or overactive sebaceous glands.
Treat by properly washing with a normalizing shampoo, a well-balanced diet, exercise, regular shampooing, and good personal hygiene are essential to controlling oily hair and scalp.
Healthy Hair, Happy Clients
The more you learn about the structure of hair and how to keep it healthy, the more you will understand how salon services affect different hair types. This is the key to consistent results with your services and happy clients who recommend you to their friends. 45

46. 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.
SUMMARY AND REVIEW
We have learned that trichology enables the professional cosmetologist to better understand both the physical and microscopic properties of the hair.
In order to give your clients the best possible consultative services, you must be able to recognize those conditions of the hair and scalp needing treatment.
We’ve also learned that practicing proper disinfection procedures that are approved by your oversight regulatory agency will prevent the spread of disease.

47. Chapter Review Questions
Name and describe the five main structures of the hair root.
Name and describe the three layers of the hair.
Describe the process of keratinization.
What are polypeptide chains?
CHAPTER REVIEW QUESTIONS
1. Name and describe the five main structures of the hair root.
Answer: The five main structures of the hair root are:
Hair follicle: the tube-like depression or pocket in the skin or scalp that contains the hair root; Hair bulb: the thickened, club-shaped structure that forms the lower part of the hair root; Dermal papilla: the small, cone-shaped elevation located at the base of the hair follicle that fits into the hair bulb; Arrector pili muscle: tiny, involuntary muscle fiber in the base of the hair follicle; Sebaceous glands: oil glands in the skin connected to hair follicles.
2. Name and describe the three layers of the hair shaft.
Answer: The three layers of the hair are:
Cuticle: outermost layer of hair consisting of overlapping layers of transparent, scale-like cells; Cortex: the middle layer of fibrous protein core formed by elongated cells containing melanin pigment; Medulla: the innermost layer composed of round cells.
3. Explain the process of keratinization.
Answer: As newly formed cells in the hair mature, they fill up with keratin, move upward, lose their nucleus, and die.
4. What are polypeptide chains?
Answer: Polypeptide chains are long chains of amino acids linked by peptide bonds. Polypeptide chains are cross-linked like the rungs on a ladder by three different types of side bonds. These side bonds hold the polypeptide chains in place and account for the incredible strength and elasticity of human hair.
(continues) 47

48. Chapter Review Questions (continued)
List and describe the three types of side bonds. Indicate whether they are strong or weak and why.
Name and describe the two types of melanin responsible for natural hair color.
CHAPTER REVIEW QUESTIONS (continued)
5. List and describe the three types of side bonds. Indicate whether they are strong or weak and why.
Answer: The three types of side bonds are:
Hydrogen bonds: a physical 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.
Salt bonds: another weak, physical cross-link side bond between adjacent polypeptide chains. They are easily broken by strong alkaline or acidic solutions and account for about one-third of the hair’s overall strength.
Disulfide bonds: a strong chemical side bond. The disulfide bond joins the sulfur atoms of two neighboring cysteine amino acids to create one cystine. The cystine joins together two polypeptide strands like rungs on a ladder. There are far fewer disulfide bonds than the physical bonds, but they are stronger and account for about one-third of the hair’s overall strength.
6. Name and describe the two types of melanin responsible for natural hair color.
Answer: The two types of melanin responsible for natural hair color are:
Eumelanin: provides dark brown and black color to hair.
Pheomelanin: provides natural hair colors from red and ginger to yellow/blond tones.
(continues) 48

49. Chapter Review Questions (continued)
Name and describe the two types of hair and their locations on the body.
What are the three phases of the hair growth cycle and what occurs during each?
What is the reason for normal daily hair loss?
What are the most common types of abnormal hair loss?
CHAPTER REVIEW QUESTIONS (continued)
7. Name and describe the two types of hair and their locations on the body.
Answer: The two types of hair and their locations are:
Vellus, or lanugo, hair is short, fine, and downy. On adults, is found in places that are normally considered hairless except the palms of the hands and soles of the feet; Terminal hair is the long, coarse hair found on the scalp, legs, arms, and body.
8. What are the three phases of the hair growth cycle? What occurs during each phase?
Answer: The phases of hair growth and what occurs during each phase are:
Anagen, or growth phase: when the new hair is produced
Catagen, or transition phase: the brief transition period between the growth and resting phases of a hair follicle
Telogen, or resting phase: the final phase in the hair cycle and lasts until the fully-grown hair is shed.
9. What is the reason for normal daily hair loss?
Answer: Normal daily hair loss is the natural result of the three phases of the hair’s growth cycle. The growth cycle provides for the continuous growth, fall, and replacement of individual hair strands.
10. What are the most common types of abnormal hair loss?
Answer: The most common types of abnormal hair loss are:
Androgenic alopecia: the result of genetics, age, and hormonal changes
Alopecia areata: when hair falls out in round patches or baldness in spots
Postpartum alopecia: experienced at the conclusion of a pregnancy.
(continues) 49

50. Chapter Review Questions (continued)
What are the only two approved hair loss treatments?
Name the two main types of dandruff and state whether either can be treated in the salon.
Which scalp and hair disorders cannot be treated in the salon?
What four factors should be considered in hair analysis?
CHAPTER REVIEW QUESTIONS (continued)
11. What are the only two approved hair loss treatments?
Answer: The only two approved hair loss treatments are Minoxidil and Finasteride. 
12. Name the two main types of dandruff. Can either one be treated in the salon?
Answer: The two main types of dandruff are:
Pityriasis capitis simplex: This type of dandruff can be treated in a salon with the use of mild or medicated shampoos, scalp treatments, regular scalp massage, daily use of antiseptic scalp lotions, and medicated scalp ointments.
Pityriasis steatoides: This type of dandruff must be referred to a physician.
13. Which hair and scalp disorders cannot be treated in the salon?
Answer: The types of hair and scalp disorders that cannot be treated in the salon are tinea, tinea capitis, tinea favosa, pediculosis capitis, scabies, carbuncles, furuncle and folliculitis.
14. What four factors about the hair should be considered in a hair analysis?
Answer: The four factors that should be considered in a hair analysis are:
Texture
Porosity
Elasticity
Eensity 50