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 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