2. WHAT IS A HAIR?
Hair is a simple structure that is made up of strong structural
protein named as keratin.
Hair is act as a barrier to foreign particles.
Its an important part of appearance.
Hair is the only body structure that can completely renew itself
without scarring.
STRUCTURE OF HAIR
Hair is made up of two separate structures :
Hair follicle : Which exist below the skin.
Hair Shaft : Located above the epidermis.
3. Structure of hair root
Hair bulb: lowest part of strand of hair; thickened, club shaped.
Hair follicle: tube like depression or
pocket in the skin or scalp that
contains a hair root.
The germinating layer of the
epidermis starts growing down into
the dermis, and forms the outside of
each hair follicle.
4. Sebaceous gland : oil glands in the skin that are connected to the
hair follicles; secretes sebum (fatty, oily substances)
Structure of the hair shaft
Hair cuticle : outermost layer of hair consist of a single,
overlapping layer of transparent, scale like cells, protects inner
structure of hair; creates shines and smoothness.
Dermal Papilla: small, cone shaped elevation located at the base
of the hair follicle that fits into the hair bulb.
Arrector pili muscle : small, involuntary muscles in the base of
the hair follicle; when it contracts. We get goose bumps.
5. Cortex : middle layer of the hair; 90% of total hair weight comes
from the cortex; elastically and colour are the result of protein in
the cortex.
Medulla : innermost layer of hair; generally only thick. Coarse
hair contains a medulla; has no known purpose.
6. Chemical composition of hair
Keratinization : process by which newly formed hair cell in the
hair bulb mature, fill with keratin, move upward, lose their nucleus
and die.
COHNS : major elements that make up the human hair: carbon,
oxygen, hydrogen, nitrogen, sulfur.
7. Side bonds of the cortex
Side bonds : link the polypeptide chains (long chain of amino
acids linked together by peptide bonds) together, responsible for
the strength and elasticity of human hair.
Hydrogen bond : weak, physical cross linked bond that is easily
broken by water or heat.
Salt bond : weak. Physical cross linked bond that is broken by
alkaline or acidic solutions.
Disulfide bond : strong, chemical side bond can be broken by
extreme heat, some high temperature styling tools, permanent
waves and chemical relaxers.
8. Hair pigment
Melanin : the tiny grains of pigment in the cortex that give hair its
natural colour.
Eumelanin : provides natural dark brown to black hair colour.
Pheomelanin : provide natural colors ranging from red to ginger
to yellow and blonde tones.
9. HAIR GROWTH
Two main types of hair found on the body are vellus hair and
terminal hairs.
Vellus hair (lanugo hair) : short, fine, unpigmented, downy;
appears on part of the body that are normally considered hairless
(forehead, eyelids, bald scalp) almost never has a medulla; helps
with evaporation of perspiration; women normally retain 55%
more vellus hair than men.
Terminal hair : long, coarse, pigmented hair found on the scalp,
legs, arms, and bodies of both males and females; it usually has a
medulla.
10. HAIR GROWTH CYCLE
Hair growth cycle comprises of 4 phases :
1. Anagen phase
2. Catagen phase
3. Talogen phase
4. Exogen phase
Each strand of hair on the human body is as its own stage of
development.
Once the cycle is complete, it restarts and a new strand of hair
begins to form.
The rate or speed of hair growth is about 1.25cm or 0.5 inches
per month, or about 15cm or 6 inches per year.
11.
12. 1) Anagen phase (growing phase) :
The growing phase last 2-7 years and determine the length of
hair.
Hair grows around half an inch a month and faster in summer
than winter. The Anagen phase last and average of 3-5 years, a
full length hair averages 18-30 inches.
The Anagen phase is generally longer in Asian and last as much
as 7 years with hair being able to grow to one meter.
13.
14. 2) Catagen phase (transition phase) :
The Catagen phase is also known as transitional phase, allows
the follicle to, in a sense, renew itself. During this time, which
lasts about two weeks, the hair follicle shrinks due to
disintegration and the papilla detaches and rests, cutting the
hair strand off from its nourishing blood supply.
Signal sent out by body (that only selectively affect 1% of all
hair of ones body at any given time) determine when the
anagen phase ends and the catagen phase begins.
15. The first sign of catagen is the cessation of melanin production
in the hair bulb and aptosis of follicular melanocytes.
Ultimately, the follicle is in its original length, causing the hair
shaft to be pushed upward.
While hair is not growing during this phase, the length of the
terminal fibers increases when the follicle pushes them
upward.
16. 3) Talogen phase (resting phase) :
This is the resting phase which are less around 3 month.
Around 10-15% of hair are in this phase.
The old hair is resting, a new hair begins the growth phase.
Lastly hair enters the anagen phase, hair is release and false out.
17. The follicle that remain inactive for 3 months the whole process
is repeated.
During the talogen phase the follicle remains for 1-4 months.
Each hair follicle is independent and grows through the growth
cycle at a different times, otherwise all hair will fall out at once.
1-50% of the hair are in this phase growth at any event time.
At some point the follicle begins to grow again, softening the
anchor point and hair base will break free from the root and the
hair will be shed.
Within 2 weeks new hair shaft will begin to emerge once the
talogen phase is complete.
18. 4) Exogen phase :
This is the part of resting phase where the old hair falls and
new hair continuous to grow.
The thickness, texture and shape of the hair is determine in
this stage.
19. The following factors create an interruption of the normal cycle
causing excessive hair loss :
• Stress
• Change in diet
• Drugs
• Illness
• Post pregnancy
21. Dandruff: Dandruff, scaly particles that cling to the root of hair,
can be caused by a poor diet, an infection, or even a sluggish
metabolism.
Hair loss: Although historically discussed as a problem among
men, hair loss or thinning hair is also common among women.
• For most men, it may be male pattern balding. Female hair loss is
often caused by stress, medication, changing hormone and even
menopause.
• Additionally many hair styling products (chemicals/excessive
heat) can contribute to hair loss.
22. Dry hair: Shampooing too often causes dry hair. Although squeaky
clean hair is a good thing, many overdo it by washing once,
sometimes twice per day.
That will strip away all of the hairs natural oils.
Split ends: Over brushing hairs, excessive perming, too much heat
and lack of good conditioner causes split ends.
Oily or greasy hair: Oily hair is caused when the scalp produces
too much of natural oil called sebum.
Sebum is produce by sebaceous glands which can sometimes
overtime, resulting in excessive amount of oil.
23. Frizzy hairs: Frizzy hairs occurs when the hairs moisture level falls
below normal levels and it can also be hereditary.
Dull hair: There are many causes of dull looking hair chemical or
heat styling damage and environmental soils.
Heat damaged hair: use your curling iron or flat iron too much and
hair become damaged.
Colour damaged hair: When you colour your hair, chemicals are
used to open your shaft, leaving hair extremely porous and prone to
brittleness and breakage.
