HISTOLOGY OF THE HAIR OF THE
BODY
We
have approximately 5 million
hairs on our body
Of these, about 150,000 (more if
you're blond, less if you're a
redhead) are found on our scalp.
The
only parts of our body where
there are no hair follicles are the
palms, soles, lips, and genitalia
HAIR GROWTH CYCLE
Each
hair grows from a pocket in
the skin called the hair follicle.
During its growing (anagen)
phase, the follicle has a bulbshaped bottom, the center of
which is called the dermal
papilla.
HAIR GROWTH CYCLE
 The
papilla protrudes into the hair
bulb and is responsible for
instigating and directing hair
growth.
 The lower part of the dermal
papilla is connected to the fibrous
root sheet.
 The hair matrix surrounds the top
and sides of the dermal papilla.
NORMAL HAIR FOLLICLE
HAIR GROWTH CYCLE: ANAGEN
 The
papilla is fed by very small
blood vessels, which bring food and
oxygen and take wastes away. The
papilla is highly sensitive to
hormones. It is here that hormones
and chemicals secreted by your
body (or ingested as a medicine)
work on the hair, making it grow
faster, slower, or not at all.
HAIR GROWTH CYCLE: ANAGEN
Hair
grows by forming new cells
at the base of the root. These
cells multiply to form a rod of
tissue in the skin. The rods of
cells move upward through the
skin as new cells form beneath
them.
HAIR GROWTH CYCLE: CATAGEN
As
they move up, they're cut off
from their supply of
nourishment and start to form a
hard protein called keratin in a
process called keratinization.
As this process occurs, the hair
cells die. (catagen) The dead
cells and keratin form the shaft
of the hair.
HAIR GROWTH CYCLE: TELOGEN
The
length of a person's hair
depends on the length of the
growing phase of the follicle.
Follicles are active for 2 to 6
years; they rest for about 3
months after that (telogen)
 A person becomes bald if the
scalp follicles become inactive
and no longer produce new hair.
HAIR GROWTH CYCLE: ANAGEN, CATAGEN,
TELEOGEN
Each
hair grows about ¼ inch
(about 6 millimeters) every
month and keeps on growing for
up to 6 years. The hair then falls
out and another grows in its
place.
HAIR GROWTH CYCLE
 Within
every head of hair, each hair
grows, falls and grows again, quite
independently from its neighbor.
 Despite differences in speed of growth all
the hair in the world follows this timeless
cycle which seems capable of reproducing
itself many times over.
 However, very often this fine system of
constantly regenerated life becomes seized
up - so that little by little hair loss
increases, the hair becomes rarer and
finishes by disappearing altogether
HAIR PIGMENT
The
color of our hair is
determined by pigmented cells
growing at the dermal papilla.
These cells (melanocytes),
contain a chemical pigment
(melanin). The amount and
density of melanin in these cells
determines the exact color of
your hair.
HAIR PIGMENT
There
are two types of melanin,
one coloring hair brown to black
(eumelanin) and one coloring
hair blond to red (pheomelanin).
The color, shape and thickness of
hair is in a large part
determined by genetics...just
look at your folks!
HAIR PIGMENT/GROWTH CYCLE
 In
darkly pigmented individuals,
melanin can be found in abundance
within the melanophages of the dermal
papilla.
 The hair matrix is the actively growing
portion of the follicle consisting of a
collection of epidermal cells that
rapidly divide, move upward, and give
rise to the hair shaft and the internal
root sheath.
HAIR PIGMENT/GROWTH CYCLE
 Melanocytes
can be found between
the basal cells of the hair matrix.
 Melanin is transferred from these
melanocytes into the cells that make
up the hair shaft and is responsible
for the color of the hair according to
its quantity.
 The hair matrix cells give rise to 6
different types of cells that make up
the different layers of the hair shaft
and the inner root sheath.
FOLLICLE SIZE AND SHAPE
Thick
hair grows out of large
follicles; narrow follicles produce
thin hair.
Hair shape is also determined by
the shape of the follicle
FOLLICLE SIZE AND SHAPE
Size
and shape matter
Studies seem to increasingly
indicate that these two elements
are closely implicated with the
shape of the hair follicle and its
position in the scalp.
FOLLICLE SIZE AND SHAPE
We
can now say with certainty
that this "biological factory"
functions as a mold, giving the
hair its shape from the moment
it is reproduced.
Hair is a biologically dead
material, subsequently hair fiber
keeps this original shape.
FOLLICLE SIZE AND SHAPE
 The
shape of a hair is never completely
circular. The cross-section of a hair is
an ellipse which can tend towards a
circle or be distinctly flattened.
 An analogy with other materials shows
how this cross-section influences the
appearance of the hair: a virtually flat
ribbon rolls up much more easily than
a cylindrical length of string.
FOLLICLE SIZE AND SHAPE
Asian
hair has a round ,
cylindrical cross-section and is a
thicker hair. Most Asian hair is
straight
FOLLICLE SIZE AND SHAPE
African
hair has a flattened
cross-section and is finer, the
ringlets of which can form tight
circles with diameters of only a
few millimeters.
FOLLICLE SIZE AND SHAPE
Caucasian
hair is much more
variable and as its cross section
forms a more or less accentuated
ellipse, Caucasian heads of hair
range from straight, through
wavy to very curly.
FOLLICLE SIZE AND SHAPE
These
general points should not
make us forget that a hair, of
whatever sort, is never totally
consistent in size throughout its
entire length. In this respect,
Asiatic hair can be observed as
being the most regular while
African hair is the most
irregular.
THE HAIR FOLLICLE IS A SAC-LIKE
STRUCTURE THAT SURROUNDS THE HAIR
ROOT. IT IS FOUND BELOW THE SKIN, AND
HAS VERY SMALL BLOOD VESSELS GIVING
IT NOURISHMENT.
EXOCRINE GLANDS
 Sebaceous
glands
surrounding the
hair root secrete oil
(sebum) while saltwater (perspiration)
is secreted from
nearby sweat
glands.
 Sebum protects the
hair and keeps it
shiny and
waterproof,sweat is
a way for the body to
cool down if it's too
hot.
SEBACEOUS AND SUDERIFEROUS GLANDS
PURPOSE OF BODY HAIR
Keep
body heat in.
 Warm-blooded
mammals require
a warm body temperature to
survive (cold-blooded animals,
like snakes and other reptiles,
metabolize and survive at "roomtemperature" and thus neither
need, nor have, hair).
PURPOSE OF BODY HAIR:
MUSCLE
The arrectorpili, contracts when
in a cold environment, or when
fearful.
The hair is pulled downwards so
it stands up straight (goosebumps or gooseflesh)
Warm air trapped between each
hair.
This functions like a layer of
clothing, keeping warmth in.

PURPOSE OF BODY HAIR
Thus
reducing cooling by air
convection of the skin, as well as
in response to central nervous
stimulus, similar to the feeling
of 'hairs standing up on the back
of your neck’
This phenomena also occurs
when static charge is built up
and stored in the hair.
HAIR COMPOSITION
Hair
is composed of a protein
called keratin.
Same protein found in our nails
and in our skin.
Amino acids form polypeptide
chains that combine to form the
hair filament
AMINO ACID CHEMICAL COMPOSITION
STRANDS OF KERATIN MADE UP OF AMINO
ACIDS
HAIR COMPOSITION: CUTICLE
 The
hair shaft consists of 3 layers The
outermost layer is called the cuticle. It is
transparent and acts to protect the inner
layers.
 . The outermost layer of the hair shaft
(cuticle) consists of overlapping cells that
are arranged like shingles. They point
outward and upward and interlock
 As a result, they move upward in the
follicular canal as a single unit.
HAIR COMPOSITION: MEDULLA
The
innermost layer (medulla) is
composed of large baggy cells
that may have a hollow-like
appearance.
Difficult to visualize. this layer
is discontinuous in many cases
and is often completely absent.
Medullary cells contain
glycogen-rich vacuoles and
medullary granules.
HAIR COMPOSITION: CORTEX
 The
middle layer of the hair shaft is
the hair cortex
 Constitutes the bulk of the hair and
consists of cells that keratinize
gradually as they move upward
from the hair matrix.
 The bulk and strength of hair is
from this compact area of cells
 The hair cortex cells keratinize
without forming granules
 The keratin produced is termed
hard keratin.
HAIR AND HUMANS: WHY?
 The
thermodynamic properties of
hair are based on the properties of
the keratin strands and amino acids
that combine into a 'coiled' structure.
 This structure lends to many of the
properties of hair, such as its ability
to stretch and return to its original
length.
HAIR AND HUMANS
 Hair
is a very good thermal
conductor and aids both heat
transfer into and out of the body.
 This is often seen as a problem with
straighteners and blow drying as the
hair quickly transfers the heat into
the inner hair shaft and heats the
water in the hair to boiling point
resulting in dry brittle hair if
silicone insulating oils are not used.
HAIR AND HUMANS
 Keratin
can easily be damaged by
excessive heat and dryness,
suggesting that extreme sun
exposure, perhaps due to a lack of
clothing, would result in perpetual
hair destruction, eventually
resulting in the genes being bred out
in favor of high skin pigmentation.
HAIR AND HUMANS
Parasites live on and in hair
 Peoples who preserved their
body hair would have required
greater general hygiene in order
to prevent diseases
 A need for grooming, two
predominant factors in the
civilization of homo sapiens.[2]

HAIR AND HUMANS
It
had been believed that body
hair was lost and replaced by
increased fat storage.
However, this is often found to
be quite untrue, where people
with excessive weight tend to
also have increased body hair
production.]
HAIR AND HUMANS
•It is more correct to understand fat
storage as a means of storing energy
evolved due to infrequent sources of
food being available commonly seen
in people of nomadic descent
•Hair production as a result of
increased weight may be due to
sensitive skin attempting to prevent
abrasion where skin to skin contact
may occur,
HAIR AND HUMANS SUMMARY
Hair is an appendage of the skin
 Hair is made of Keratin
 Hair has a 3 stage growth cycle
 Hair holds body heat
 Follicles are where hair is produced
 Follicle size and shape determine hair siaze and
shape
 Hair color is from melanocytes
 The hair follicle holds the sebaceous gland
 Hair growth can be hormonally stimulated

http://en.wikipedia.org/wiki/Androgenic_hair
 Milady Comprehensive Training for Estheticians
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Delmar Learning, Thompson Publishing 2007
Salon Fundamentals, Pivot Point Intl. 2000