Hair is a simple structure that is made up of Protein
filaments called Keratin which is also the primary
component of finger and toe nails.
Hair acts as a barrier to foreign particles.
It's an important part of appearance and creates
Hair is the only body structure that can completely
renew itself without scarring.
Humans develop hair follicles during fetal
development, and no new follicles are produced after
Hair color is mostly the result of pigments, which are
chemical compounds that reflect certain wavelengths
of visible light.
4. Hair shape (round or oval) and texture (curly or
straight) is influenced heavily by genes. The
physical appearance of hair can be affected by
nutritional status and intentional alteration (heat
curling, perms, straightening, etc.)
In order to test hair evidence for nuclear DNA, the
root must be present. The hair may also be tested
using mitochondrial DNA whether or not the root is
5. Types of Hair
Develops on an unborn baby
3 months after baby’s conception
Fine and soft
grows all over the body at the same rate
Shed about 4 weeks before the baby is due to be born
Short, fine, downy, unpigmented hair covering most of the body except the
palms and soles of feet
Women normally retain 55% more vellus hair than men
Follicle doesn’t have oil glands
Long, thick pigmented hair found on the scalp, legs, arms & bodies of
males & females
Coarser than vellus hair & with the exception of gray hair, it is pigmented
Produced by follicles with sebaceous glands
6. Hair Structure:
Hair is made up of two separate structures
The hair follicle: which exists below the skin.
The hair shaft: which is the hair that we see.
7. HAIR FOLLICLE: the living part of the hair
Contains the germinal matrix, which is where
cells produce new hairs.
Contains the bulb, which is the stocking-like
structure that surrounds the papilla and germinal
matrix. It's fed by capillaries.
The follicle is surrounded by an inner and outer
sheath that protects and molds the growing hair
The inner sheath follows the hair shaft and ends
just before the opening of the sebaceous gland. •
The outer sheath continues all the way up to the
8. HAIR SHAFT: the dead hair we can actually see.
The innermost layer: This is called the medulla.
Depending on the type of hair, the medulla isn't
The middle layer: This is called the cortex, which
makes up the majority of the hair shaft. Both the
medulla and the cortex contain pigmenting cells
that are responsible for giving hair color.
The outermost layer: This is called the cuticle,
which is formed by tightly packed scales in an
overlapping structure that resemble roof shingles.
Many hair conditioning products are formulated to
even out the cuticle by smoothing out its structure.
9. The Growth Cycle
The anagen phase
It is the active or growth phase of the hair. Most
hair is constantly growing and spends three to
four years in this stage.
Hair grows around half an inch a month, and
faster in the summer than in winter. In the growth
phase, or anagen phase, a full-length hair
averages 18 to 30 inches.
The anagen phase is generally longer in Asians,
and can last as much as 7 years with hair being
able to grow to 1 meter.
10. The span at which the hair remains in this
stage of growth is determined by genetics. The
longer the hair stays in the anagen phase, the
longer it will grow.
During this phase, cells neighboring the papilla
in a germinative layer divide to produce new
hair fibers and the follicle buries itself into the
dermal layer of the skin to nourish the strand.
About 85%–90% of the hairs on one's head
are in the anagen phase at any given time.
12. The catagen phase
It is a transitional stage, and 3% of all hairs are in
this phase at any given time. It lasts for two to
It allows the follicle to renew itself. During this
time, the hair follicle shrinks due to disintegration
and the papilla detaches and "rests," cutting the
hair strand off from its nourishing blood supply.
Signals sent out by the body determine when the
anagen phase ends and the catagen phase
13. The telogen phase
It is the resting phase, which lasts for about three
months and accounts for 10% to 15% of all hair.
During the telogen, the follicle remains dormant
for one to four months.
In this phase, the epidermal cells lining the follicle
channel continue to grow as normal and may
accumulate around the base of the hair,
temporarily anchoring it in place and preserving
the hair for its natural purpose without taxing the
body's resources needed during the growth
14. Hair facts
Each human head carries roughly 100,000 hair
Each follicle can grow many hairs during a lifetime;
on average, each grows a new hair around twenty
Not all these follicles are actively growing hairs at any
one time. From the moment when it is first formed,
each follicle undergoes repeated cycles of active
growth and rest. The length of the cycle varies with
the individual, and also with the part of the body on
which the hair is growing.
The hairs on adult scalp do not grow in unison, as
they do in an unborn baby. They are out of cycle with
each other. If they were not so, everyone would go
Laura Alonso, Elaine Fuchs, (2006) “The hair