Hairs%20Fibers%20and%20Paint1

Hairs%20Fibers%20and%20Paint1 - Hair, Fibers, and Paint...

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Hair, Fibers, and Paint
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Hair Preview • Morphology of Hair • Identification and Comparison of Hair • Collection and Preservation of Hair Evidence
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Morphology of Hair • Cuticle • Cortex • Medulla
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Morphology of Hair • Cuticle – “shingle-like” scale structure covering the exterior of the hair – scales point towards tip end of each hair – scale patterns are NOT useful for individualizing human hair, but can help in distinguishing species
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Morphology of Hair • Cortex – main body of the hair shaft – embedded with pigment granules which impart color to hair – made up of spindle-shaped cortical cells aligned parallel to length of hair
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Morphology of Hair Medulla – cellular column running through center of hair – “medullary index” = diameter medulla – continuous, interrupted, fragmented – shape variations: • humans medulla are cylindrical • others animals have patterned shapes diameter hair shaft
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Interspecies comparison of medullas
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Aardwolf Not related to the Aardvark, Proteles cristatus, or the Aardwolf, is actually a relative of the hyena family and found mainly in the open, sandy plains or bush country of eastern and southern Africa. Standing a mere 15-20” in height, the aardwolf possesses long loose under fur which is mixed with larger coarser guard hairs. They have a defense mechanism which enables them to erect the hair of the mane to appear twice their normal size to defend against predators. Their body hair is usually yellow-gray with black stripes. Their legs are banded black with entirely-black paws. They have a bushy, black-tipped tail. The Aardwolf is not on the endangered species list, but is classified as rare in South Africa due to human hunting and habitat destruction. At X300 in Meltmount™ 1.662 you will notice a very broad continuous medulla and moderately high birefringence using crossed polarized light. The cross-section shows the hairs to be oval-to-kidney shape. The medulla appears to be wide; the medullary index was calculated to be 0.62
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Root – hair growth begins from the root and follicle – shape of root depends on stage of development: • Anagen: initial growth phase (up to 6 years) • Catagen: transition between anagen and telogen • Telogen: final growth phase; hair falls out of skin
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Roots follicular tag: rich in DNA
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Identification and Comparison of Hair Must compare same type of hair (i.e., head, pubic, facial, etc.). Even within the same type of hair, there can be significant variation. Comparison microscope is used Features to compare: – Color, length, diameter, shape – Medulla features – Cortex features: pigment granules
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Comparison of Hair • Comparing suspect hair with crime scene hair is NOT adequate to definitively link suspect to crime.
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This note was uploaded on 03/06/2011 for the course CHS 3501 taught by Professor Perr during the Spring '09 term at FIU.

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Hairs%20Fibers%20and%20Paint1 - Hair, Fibers, and Paint...

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