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.

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