Q. What are the two ADD: chief purposes of hair? • Protection • Adornment Add to the side bar: Hair is an appendage of the skin
TRICOLOGY • scientific study of hair, its diseases, and care • comes from Greek words: Trichos=hair ology=the study of
CHAPTER 9 PROPERTIES OF THE HAIR AND SCALP
INTEGUMENT ~the outer covering that encloses the entire body • includes the hair, skin, and nails • is the largest and fastest growing organ body
Hair: A slender, threadlike filament of protein keratin which is an appendage or outgrowth of the scalp and body.
hair is divided into two parts: Hair root ~located below the surface of the scalp Hair shaft ~projectsabovethe skin
HEALTHY HAIR • Proper nutrients required. • Amino acids: • Twenty amino acids make up hair. • The body produces only 11 of the 20. • The remainder must come from diet. • Proteins: • Proteins like meat, fish, eggs, and dairy products are • good sources of these amino acids as are food • combinations like peanut butter and bread, rice • and beans, and beans and corn
Structures of the Hair Root The main structures are: • Follicle • Bulb • Dermal papilla • Arrector pili muscle • Sebaceous glands
Follicle ~ tube-like pocket in the scalp ~ contains the hair root ~ distributed all over the body ~ except *palms of the hands *soles of the feet ~ multiple hairs/one follicle
The follicle • “Tunnel” epidermis(outer layer of the skin) • dermis • (inner layer • of the skin) • dermal • papilla Internet source: acne-site.com
Hair bulb-the lowest area or part of the hair strand. • thickened, club-shaped part of the hair root • fits over and covers thedermal papilla Internet source: Missinglink.ucsf.edu
Dermal papilla ~ cone-shaped ~ base of the hair follicle ~ fits into hair bulb. • contains theblood and nervesupply • providesnutrients
Arrector pili: • tiny, involuntary muscle ~ base of the hair follicle. • Fear or cold ~ contract “goose bumps” www.unexpectedpages.com/.../goosebumps.jpg
Sebaceous glands ~ oil glands ~connected to the hair follicles. ~ secretes oily substance ~sebum ~lubricates
Structures of the Hair Shaft Three main layers • 1. Cuticle ~ outermost layer of hair ~ overlapping layer of transparent, scale-like cells ~ shingles on a roof
~provides a barrier/protects inner structure ~ creates shine, smooth silky feel • hair’s primary defense against damage Internet source: the gentle touch.com
Individual cuticle scales are attached to the cortex • The hair has only one cuticle layer Q. Why are we cautioned that there is only one cuticle layer?
Swelling the hair: ~ raises the cuticle layer ~ opens the space between the scales ~allows liquids to penetrate
Internet source: Hairdressersus.com Damaged cuticle • Haircolor, permanent waving solutions, and chemical hair relaxers must have an alkaline (base) pH to penetrate the cuticle layer • Swells cuticle/lifts/exposes cortex
Cortex-is the middle layer of the hair ~ fibrous protein ~melanin pigment Q. What does the word melanin mean?
~ elasticity of the hair ~ natural color ~ located in thecortex • all changes (physical or chemical) take place within the cortex
Internet source: Hairdressersus.com Womensnet.com
Medulla-the inner most layer ~ composed of round cells *missing medulla ~ very fine hair ~ naturally blonde hair ~coarse hair contains a medulla
Internet source: Ecobyte.com.au Bfro.net
All beard hair contains a medulla • not involved in salon services Add to side bar: Until a child has became the age of puberty. Their hair has not fully matured and has no Medulla
THE CHEMICAL COMPOSITION OF HAIR • composed of protein in the hair follicle. • This is where the hair shaft begins • living cells form • journey upward through the hair follicle
process called keratinization. • As the cells mature ~ fill up with a fibrous protein ~keratin ~move upward Killerstrands.blogspot.com
~ lose their nucleus ~ die ~ emerges from the scalp, ~ cells are keratinized ~ no longer living ~ keratinized protein
~ 90% protein ~long chains of amino acids Main elements: (chemical composition) Carbon Oxygen Hydrogen NitrogenSulfur
Referred to as the COHNS elements Carbon 51% Oxygen 21% Hydrogen 6% Nitrogen 17%Sulfur 5%
Amino acids-long chains of protein • linked together like pop beads(candy necklace) The chemical bond that joins the amino acids to each other is called a peptide bond or end bond.
A long chain of amino acids linked by peptide bonds is called a polypeptide. • spiral shape of coiled protein is called a helix.
THE SIDE BONDS OF THE CORTEX • made up of millions of polypeptide chains • Polypeptide chains are cross- linked by three different types of side bonds:
Hydrogen bonds • Salt bonds • Disulfide bonds Backreaction.blogspot.com • incredible strength • elasticity
Essential to: • Wet sets • Thermal styling • Permanent waving • Chemical hair relaxing
Hydrogen bond • weak physical side bond • Easily broken by waterorheat • Accounts for 1/3 of hair’s strength
Salt bond • weak physical side bond • Broken by changes in the pH -strong alkaline or acidic solutions • Accounts for 1/3 of hair’s strength
Disulfide bond ~chemical side bond • accounts for 1/3 overall strength • Not broken by heat or water ~ permanent waves ~ chemical relaxers ~ chemically change disulfide bonds
Thio permanent waves (base) ~ break the disulfide bonds ~ reformed by thio neutralizer (acid) • Hydroxide chemical hair relaxers ~ break disulfide bonds ~ bonds are broken permanently (becomes lanthionine bond) ~ can never be reformed
Read: Table 9-2 Bond Read: Did you know
Hair Pigment: ~ pigment in the cortex Melanin ~ tiny grains of pigment ~ cortex
The two main types: • Eumelanin • brownand black 2.Pheomelanin redginger yellow/blonde ~ratio
Wave Pattern • amount of movement Described as: • straight • wavy • curly • extremelycurly
result of genetics General rule: Asians ~extremely straight hair Caucasians ~straight to wavy hair African Americans ~extremely curly hair
all wave patterns ~ in all races • vary from strand to strand ~ same person’s head
The shape of the cross-section (round, oval, flat), determines the amount of curl.