hair, hair types, structure of hair, facts about hair

1. All About
Hair
Presented by: R, E. O. Gaas
Grade 7-Neptune
Alabel National Sciece High School
Regional Science High School for
Region XII

2. All About Hair
What is a Hair?
Anatomy of Hair
Biological, Physical and Chemical
Facts About Hair
Types of Hairs
Hair Growth Myths and Facts

3. What is a Hair?
• is a protein filament that grows
from follicles found in the dermis, or skin.
• is one of the defining characteristics
of mammals.
• an important biomaterial primarily composed
of protein, notably keratin.

4. Anatomy of Hair

5. Anatomy of Hair
Hair is composed of three principal parts:
Cuticle – outer coating composed of overlapping scales
Cortex – protein-rich structure
around the medulla that contains
pigment
Medulla- central core
(may be absent)
The structure of hair has been compared to that of a pencil
with the medulla being the lead, the cortex being the wood
and the cuticle being the paint on the outside.

6. Anatomy of Hair
Cuticle
The cuticle varies in:
• Its scales,
How many there are per centimeter,
How much they overlap,
Their overall shape, and
How much they protrude from the
surface
• Its thickness, and
• Whether or not it contains pigment.
Characteristics of the cuticle may be important in
distinguishing between hairs of different species but are often
not useful in distinguishing between different people.

7. Anatomy of Hair
Cortex
The cortex varies in:
• Thickness
• Texture
• Color
• Distribution of the cortex is perhaps
the most important component in
determining from which individual a
human hair may have come.
• Microscopic examination can also
reveal the condition and shape of
the root and tip.

8. Anatomy of Hair
Medulla
The medulla may vary in:
• Thickness
• Continuity - one continuous
structure
or broken into pieces
• Opacity - how much light is
able to
pass through it
• It may also be absent in some
species.
Like the cuticle, the medulla can
be important for distinguishing
between hairs of different
species, but often does not lend
much important information to
the differentiation between hairs
from different people.

10. Facts About Hair
• Hair is composed of the protein keratin, which is also the
primary component of finger and toe nails.
• Humans develop hair follicles during fetal development,
and no new follicles are produced after birth.
• Hair color is mostly the result of pigments, which are
chemical compounds that reflect certain wavelengths
of visible light.

11. Facts About Hair
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.)

12. Facts About Hair
The body area (head, arm, leg,
back, etc.) from which a hair
originated can be determined by
the sample’s length, shape, size,
color, and other physical
characteristics.

13. Facts About Hair
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 present.

14. Facts About Hair
The Cuticle of
Human Hair is
rough --- which is
why we use
Conditioner

15. Facts About Hair
Animals have characteristic cuticle scales that
scientists can use to determine the source of hair
evidence. Human, Cat, Dog, and Mouse
respectively (photo below)

17. 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

18. Types of Hair
• 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

19. Types of Hair
• 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

20. Cat
Types of Animal Hairs
Horse
Pig
Human
Dog
Deer
Rabbit
Rat
Human

21. Hair Growth
Myths
and
Facts

22. Hair Growth Myths and Facts
• 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, & is not more resistant than the pigmented hair
on the same person’s head
• Amount of natural curl is determined by racial background.
FACT: anyone of any race can have straight or
extremely curly hair

23. Hair Growth Myths and Facts
• Clipping, shaving, trimming & cutting makes hair grow faster
FACT: have no effect on hair growth
• Scalp massage increases hair growth
FACT: 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 FDAS.

24. Hair Growth Myths and Facts
• Hair with round cross-section is straight; hair with oval cross-section
is wavy; hair with 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

25. Credits to References
http://library.thinkquest.org/04oct/00206/lesson.htm#t_hair
http://www.fbi.gov/hq/lab/fsc/backissu/july2000/deedric1.htm#Index%20(Hairs)
http://library.thinkquest.org/04oct/00206/lesson.htm#t_hair
http://www.fbi.gov/hq/lab/fsc/backissu/july2000/deedric3.htm#Fiber%20Evidence
http://www.fireflydiapers.com/articles/diaperarticle_naturalfibersabsorb.htm
http://micro.magnet.fsu.edu/primer/techniques/polarized/gallery/images/humansmall