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The Wonderful World of Hairs and Fibers

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The Wonderful World of Hairs and Fibers

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  1. The Wonderful World of Hairs and Fibers

  2. Different Scopes used to analyze hair and fiber • Compound light • Comparison • Dissecting • Polarized • Scanning Electron Microscope (SEM)

  3. Stages of Hair “Life” • Anagen • Growing stage • Up to 6 years possible • Root shaped like “flame” • Hair grows ~1cm/month (1” every 10 weeks)

  4. Stages of Hair “Life” • Catagen • ~3 weeks long • Dormant, resting stage • Root gets longer and thinner

  5. Stages of Hair “Life” • Telogen • ~6 months • Root  • Club shaped • Pushes out and is shed • Lose approximately 70 hairs/day

  6. Human Hair Parts • 1. Root • 2. Follicle • 3. Shaft • 4. Tip 4 2 3 1

  7. Human Hair Parts • 1. Distal (tip) • 2. Proximal (root end) • 3. Medulla • 4. Cuticle (contains scale pattern) • 5. Cortex 1 4 3 5 2

  8. Scale patterns • Imbricated • Mosaic • Petal • Pectinate • Chevron

  9. Medulla Types • Continuous • Fragmented • Intermittent/interrupted

  10. Medullary Index of Hair • To find the MI • Diameter of medulla/hair shaft diameter • Humans = <1/3 • Other animals = >1/2 • Classify Medulla as: • Continuous, Interrupted, Fragmented, or Absent

  11. Example Medulla Patterns that can be seen • Lattice • Vacuolated • Uniserial • Multiserial

  12. Deer, Dog & Muskrat hair Deer Muskrat

  13. Which is Caucasian, Negroid, Mongoloid Head Hair? Caucasian, Europeans, Mexicans, Middle Easterners: oval to round Negroid, Africans oval to flat Mongoloid, Orientals, American Indians: round

  14. Pulled Hair v. Shed Hair Anagen Stage Pulled Hair Telogen stage

  15. Razor, Cut hair & Split hair Split Razor Cut

  16. Human eyebrow

  17. Burned hair

  18. Buckling of hair seen in pubic hair

  19. Hair match • This is the view that a comparison scope can give when comparing two matching hairs

  20. Dust Mite The small things in life Eyelash mites Bedbug feeding on flesh

  21. Fibers

  22. Types of fibers • Natural fibers • Animal fibers are most common at crime scene • Man-made

  23. Natural fibers • Animal: • Wool from sheep most common • Goats, camel, alpaca, rabbit, mink, llamas, beaver • Plant: • Cotton most common • Flax (linen), ramie, sisal, jute, hemp • Excrement: • Silk from silkworm (cellulose from mulberry leaves) • Mineral: • Asbestos

  24. Cotton fibers cross-section

  25. Wool fibers v. Cotton fibers Cotton Wool

  26. Flax Fibers

  27. Hemp fibers

  28. Silk fibers • Raw thrown • Wild silk

  29. Asbestos fibers

  30. Man-Made fibers • Regenerated fibers • Machine made from natural materials like cotton or wood • 1910 rayon, then acetate, then triacetate • Synthetic fibers • Most fibers are made synthetically from chemicals • 1939 nylon, then polyester and acrylic • Shape or cross-section can determine value of the fiber; manufacturer specific

  31. Nylon fiber cross sections

  32. Acetate Fibers

  33. Nylon fibers

  34. Orlon Fibers

  35. Polypropylene fibers