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Flashcards in Hair analysis Deck (24)
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1
Q

Foetal Hair

A

primordial hairs = appears 3rd month of gestation

lanugo = shed after the 6th month of gestation

2
Q

Adult hair

A

vellus hairs = body surface

terminal hair = scalp, eyebrows, eyelashes

3
Q

Uses of hair analysis

A

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

4
Q

Anatomy of hair

A

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

5
Q

Cuticle

A

outer layer

keratin scales that overlap

6
Q

What are 3 types of cuticle?

A
coronal = crown like
spinous = petal like
imbricated = flattened
7
Q

Cortex

A

main body

location of pigment granules which give hair colour

8
Q

Medulla

A

centre
made from collapsed cells+air spaces
may not be present
function not known

9
Q

What are 4 ways the medulla can come in?

A

fragmented
absent
continuous
interrupted

10
Q

Medullary index

A

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

11
Q

Human hair vs animal hair
The root
which has a round bulb shape and which has an arrow shape?

A
human = round bulb shape
animal = arrow-shaped
12
Q

What are the three types of animal hair?

A
Brush = outer guard hair
Wool = inner fur or down
Vibrissa = tactile hairs (whiskers)
13
Q

Human hair vs animal hair
The tip
Which has a fine tapered pointed end and which is cut/broken?

A
human = cut or broken
animal = fine tapered pointed hair
14
Q

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?

A
human = fine scales, slightly raised and overlapping strongly
animal= thick scales, raised, less strongly overlapped
15
Q

Human hair vs animal hair
The medulla
which has continuous, interrupted, fragmentary or absent and which has well defined, patterned shapes, higher MI?

A
human = continuous, interrupted, fragmentary or absent
animal = well defined, patterned shapes, higher MI.
16
Q

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?

A
human =  consistent in colour+pigmentation, evenly distributed pigment
animal = colour banding, pigmentation more dense towards medulla
17
Q

What are the three stages of hair growth?

A

Anagen, catagen, telogen

18
Q

What is the anagen phase in hair growth?

A

fully active hair follicle
hair grows 0-3-0.5mm/day
phase lasts 3-5 years

19
Q

What is the catagen phase in hair growth?

A

3 week period of self-destruction

follicle shrinks and breaks away from blood supply

20
Q

What is the telogen phase in hair growth?

A

5-6weeks
the follicle is dormant, no hair growth
hair shed naturally

21
Q

Features of Caucasian hair (European)

A
straight to wavy
70-100um diameter
evenly distributed pigment granules
fragmented medullae/absent
cross section oval/round
fine to coarse pigment
22
Q

Features of Monogoloid hair (Asian)

A
90-120um diameter
dense pigment distributed evenly
cross section round
hair shaft coarse and straight
presence of continuous medullae
23
Q

Features of Negroid hair (afro-Carribean)

A
twist+curl
60-90um diameter approx
heavy pigment distributed unevenly
variations in diameter
fragmented medullae or absent
cross section flat to oval
24
Q

Laboratory analysis

A

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