chapter 3 the study of hair n.
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Chapter 3 THE STUDY OF HAIR - PowerPoint PPT Presentation

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Chapter 3 THE STUDY OF HAIR. Sept. 3, 2013. Trichology. The scientific study of the structure, function, and diseases of human hair. Very valuable in Forensic Science More resistant to decay Remains intact much longer . Class Evidence.

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  • The scientific study of the structure, function, and diseases of human hair.
  • Very valuable in Forensic Science
    • More resistant to decay
    • Remains intact much longer
class evidence
Class Evidence
  • Material that connects an individual or thing to a certain group.
  • Cannot be used to identify a specific individual
    • Can identify a group or class that share similar hair type.
  • Secondary Transfer
    • Pet hair
analyzing hair
Analyzing Hair
  • Physical Characteristics: Broad racial background
  • Chemical Characteristics: Drug use and other toxins, heavy metals, nutritional deficiencies.
  • Follicle present, potential to recover DNA
individual evidence
Individual Evidence
  • A kind of evidence that identifies a particular person or thing
    • DNA
    • Fingerprint
  • Trace Evidence: small but measureable amounts of physical or biological material found at a crime scene.
comparison microscope
Comparison Microscope
  • A compound microscope that allows the side-by-side comparison of samples, such as hair or fibers
  • Today!
    • Neutron activation analysis and DNA fingerprinting and is considered a standard tool in trace evidence analysis.
function of hair
Function of Hair
  • All mammals have hair.
  • Regulate body temperature
  • Decrease friction
  • Protect against sunlight
  • Sense Organ
  • Very dense Hair=Fur
  • Temperature Regulation
    • Hair and muscles work together to regulate body temp.
    • Muscles pull hair upright, creating pockets that trap air
    • Muscles relax and hair flattens against the body, releasing trapped air
  • Humans are born with about 5 million hair follicles, only 2% of which are on the head.
  • As humans age, hair density decreases
structure of hair
Structure of Hair
  • Follicle
    • The actively growing root or base of a hair containing DNA and living cells
  • Papilla
    • Network of blood vessels that supply nutrients to feed the hair and help it grow.
  • Sebaceous gland (bulb)
    • Secretes oil to help the hair conditioned
    • Erector muscle causes the hair to stand up
structure of the hair
Structure of the Hair
  • Shaft
    • Composed of the protein Keratin;
      • a type of fibrous protein that makes up the majority of the cortex of a hair.
      • Makes hair both strong and flexible
  • Inner Medulla, Cortex, and Outer Cuticle
    • Pencil
  • The Cuticle
    • Transparent tough outer layer of the hair composed of overlapping scales.
  • The Cortex
    • The region of a hair located outside of the medulla containing granules of pigment (melanin) which gives the hair its color.
  • The Medulla
    • The center of the hair, can be hollow or filled with cells.
    • Classify hair into 5 different groups depending on the appearance of the medulla.
hair classification
Hair Classification
  • See Figure 3-6 on page 53
  • Continuous: one unbroken line of color
  • Interrupted: Pigmented line broken at regular intervals
  • Fragmented: Pigmented line unevenly spaced
  • Solid: Pigmented area filling both the medulla and the cortex
  • None: No separate pigmentation in the medulla
types of hair
Types of Hair
  • Hair can vary in so many ways!
  • Cross section view
  • Textures
  • Color
  • Not all hairs on a person’s head are exactly the same
    • Sample of 50 from head
    • Sample of 25 from pubic region
hair in different regions of the body
Hair in Different Regions of the Body
  • 6 Types on Human Body
    • Head Hair
    • Eyebrow and Eyelashes
    • Beard and Mustache
    • Underarm Hair
    • Auxiliary or Body Hair
    • Pubic Hair
body hair
Body Hair
  • Distinguished by their Cross-sectional Shape
    • Head- circular or elliptical
    • Eyebrow/eyelashes- also circular, but have tapered ends
    • Beard- thick and triangular
    • Body hair- oval or triangular (depending on shaved often or not)
    • Pubic- oval or triangular
life cycle of hair
Life Cycle of Hair

3 Stages of Development

  • Anagen Stage: lasts approximately 1,000 days. Period of active growth when the cells around the follicle are rapidly dividing and depositing materials with in the hair.
  • Catagen Stage: next stage as hair grows ad changes.
  • Telogen Stage: final stage, the follicle is dormant or resting and hairs are easily lost.
  • Racial Differences (page 55)
  • Animal Hair and Human Hair (page 55)
  • Hair in an investigation
  • Microscopy
substances in hair
Substances in Hair
  • Drug Tests
  • Timeline
  • 1.3 cm per month (.44 mm per day)
    • 9 cm = approximately 7 months
  • NAA (Neutron Activation Analysis)
    • 14 different elements in a single 2cm long strand
  • DNA
    • Follicular tag