All about hair ppt
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All About Hair
Presented by: R, E. O. GaasGrade 7-NeptuneAlabel National Sciece High SchoolRegional Science High School for Region XII
Anatomy of Hair
What is a Hair?
Hair Growth Myths and Facts
Types of Hairs
Biological, Physical and Chemical Facts About Hair
All About Hair
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.
Anatomy of Hair
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.
Anatomy of HairCuticle
Characteristics of the cuticle may be important in distinguishing between hairs of different species but are often not useful in distinguishing between different people.
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.
Anatomy of Hair
CortexThe 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.
Anatomy of Hair
MedullaThe 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.
BiologicalPhysical
and ChemicalFacts 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.
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.)
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.
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.
Facts About Hair
The Cuticle of Human Hair is rough --- which is why we use Conditioner
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)
Facts About Hair
Types Of Hair
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
LanugaHair
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
VellusHair
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
TerminalHair
Cat
Horse
Types of Animal Hairs
Pig
Human
Dog
Deer
Rabbit
Rat
Human
Hair GrowthMyths
andFacts
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
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.
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
Credits to Referenceshttp://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