forensics: unit 4. 5 million hairs on your body!!! blondes have about 120,000 on their head ...
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Hair Analysis
Forensics: Unit 4
5 million hairs on your body!!! Blondes have about 120,000 on their head Brunettes have about 100,000 Red heads have about 80,000 Lose 100 hairs a day from your scalp
Hair Morphology
Hair is made of complex cross-linked protein
polymers… primarily keratin. Grows from underneath the skin… attached to
blood supply. 3-5 year lifespan. Grows 1cm/month.
Hair Morphology
What’s inside???
Cuticle
Cortex
• The Cortex holds the pigments of the hair as well as tiny air pockets within the hair, called cortical fusi.
• Four color pigments found in human hair: red, yellow, brown, and black.
Not found in all hairs. Can be continuous or interrupted. Never more
than 1/3 space of hair in a human. More commonly found in people w/ Asian or
Native American decent.
Medula
The tip naturally rounds over a 3 week period.
Hair Tip
Looks differ ripped out versus falling out
Hair Root
Hair in cross-section
Round hair has no twisting and is typically
very straight. Found in people of Asian and Native American
descent
Round Hair
Oval hair can show some twisting or
undulation, which creates a wavy appearance. Typically found in Caucasians, Mexicans, and
Middle Eastern people.
Oval Hair
Hair that is crescent shaped and/or almost
flat. This hair typically twists on itself or has large
amounts of undulation. Typically found in people
of African descent.
Crescent Hair
Often triangular in cross-section.
Beards sometimes feel “sharp” for this reason.
Facial and Body Hair
Stage 1: Anagen Phase
Last 3-5 years… hair has a defined root, connected to blood supply, and grows out of the skin.
Stage 2: Catagen Phase Intermediate phase… hair stops growing. Lasts 3-6
weeks
Stage 3: Telogen Phase Last 3-5 months of a hair. Loses connection to blood
supply and follicle slowly pushes it out.
Stages of Hair Growth
Stages Hair Growth
Human hair ranges from 25-125 micrometers
in diameter. Thicker hair grows slower than fine hair, but
falls out less easily.
Hair Thickness
Hair quality can be affected by dryness, lack
of conditioner, bleaches, straighteners, overuse of blow dryer (too hot), etc.
Lack of care