Hair analysis Flashcards
Foetal Hair
primordial hairs = appears 3rd month of gestation
lanugo = shed after the 6th month of gestation
Adult hair
vellus hairs = body surface
terminal hair = scalp, eyebrows, eyelashes
Uses of hair analysis
match hairs to evidence
can give an idea of colour, length and race
DNA analysis = hair shaft for MtDNA, root for DNA
long term drug history of donor
illegal fur trade
Anatomy of hair
elongated keratinised structures
keratin is a strong protein, resistant to damage
each hair protrudes through an indentation in the epidermis
hair shaft is part we see on outside
hair follicle part buried in skin
hair bulb is terminal part of follicle
cuticle, cortex, medulla
Cuticle
outer layer
keratin scales that overlap
What are 3 types of cuticle?
coronal = crown like spinous = petal like imbricated = flattened
Cortex
main body
location of pigment granules which give hair colour
Medulla
centre
made from collapsed cells+air spaces
may not be present
function not known
What are 4 ways the medulla can come in?
fragmented
absent
continuous
interrupted
Medullary index
hair classification
describes the relationship between diameter of medulla and diameter of the whole hair shaft
-humans = medulla is <1/3
-animals = medulla is >1/2
Human hair vs animal hair
The root
which has a round bulb shape and which has an arrow shape?
human = round bulb shape animal = arrow-shaped
What are the three types of animal hair?
Brush = outer guard hair Wool = inner fur or down Vibrissa = tactile hairs (whiskers)
Human hair vs animal hair
The tip
Which has a fine tapered pointed end and which is cut/broken?
human = cut or broken animal = fine tapered pointed hair
Human hair vs animal hair
The cuticle
which has thick scales, raised, less strongly overlapped and which has fine scales, slightly raised and overlapping strongly?
human = fine scales, slightly raised and overlapping strongly animal= thick scales, raised, less strongly overlapped
Human hair vs animal hair
The medulla
which has continuous, interrupted, fragmentary or absent and which has well defined, patterned shapes, higher MI?
human = continuous, interrupted, fragmentary or absent animal = well defined, patterned shapes, higher MI.
Human hair vs animal hair
The cortex
which has cortex consistent in colour and pigmentation, evenly distributed pigment and which has colour banding, pigmentation more dense towards medulla?
human = consistent in colour+pigmentation, evenly distributed pigment animal = colour banding, pigmentation more dense towards medulla
What are the three stages of hair growth?
Anagen, catagen, telogen
What is the anagen phase in hair growth?
fully active hair follicle
hair grows 0-3-0.5mm/day
phase lasts 3-5 years
What is the catagen phase in hair growth?
3 week period of self-destruction
follicle shrinks and breaks away from blood supply
What is the telogen phase in hair growth?
5-6weeks
the follicle is dormant, no hair growth
hair shed naturally
Features of Caucasian hair (European)
straight to wavy 70-100um diameter evenly distributed pigment granules fragmented medullae/absent cross section oval/round fine to coarse pigment
Features of Monogoloid hair (Asian)
90-120um diameter dense pigment distributed evenly cross section round hair shaft coarse and straight presence of continuous medullae
Features of Negroid hair (afro-Carribean)
twist+curl 60-90um diameter approx heavy pigment distributed unevenly variations in diameter fragmented medullae or absent cross section flat to oval
Laboratory analysis
Macroscopical and stereomicroscopical examination
-useful for observing colour length, shape and texture
-presence of other trace materials
Transmitted light microscopy
-to observe interval microscopic characteristics
Comparison microscopy
-matching colour, length and diameter
