Hairs Lecture

hair is composed of __ and __

1. keratins
2. disulfide bonds

approximately how many hairs on the head

90k-150k

avg person loses how many hairs a day

100

average hair rate of growth

1 cm per month

growth cycle of a hair lasts approx

2-6 years

what is hair’s forensic feature

morphology

hairs are resistant to biological and chemical __

decomposition

hair has the same structure as a (analogy)

pencil

the outer covering of the hair

cuticle

the cuticle consists of

overlapping scales of keratin

the free ends of scales point __ root and __distal tip

away from, towards

what are enlongated keratinized filaments that are aligned parallel to the hair

the cortex

black, brown, and yellow hairs have

melanin pigment granules

blonde and red hairs have

phaeomelanin pigment granules

what are the tiny silver bubbles of air, typically found near the root of the hair?

cortical fusi

what is the collection of cells that appear as a central canal down the shaft of the hair?

medulla

the medulla increases the __ of the hairs by adding internal air spaces

stability

what is the thickness of medulla relative to the total thickness of the hair shaft?

medullary index

the 4 degrees of medullation

1. continuous
2. interrupted
3. fragmented
4. absent

when is the diameter of the hair narrower?

early growth stage and end of growth

which part of the hair is thickest?

the middle

Anagen is the

active growth phase

in the anagen phase, the root bulb has a

flame or pulled taffy appearance

catagen is when the

hair growth slows down

in the catagen phase, the follicle ceases __ and the root bulb __

pigment production, appears enlongated

approximately __% of hairs on your head are in the catagen phase

2

approximately __% of hairs on your head are in the anagen phase

80-90%

what happens in the telogen phase

hair growth ends

in the telogen phase, hairs will naturally

shed

in the telogen phase, the root takes on a

club-shaped appearance

approximately __% of hairs on your head are in the telogen phase

10-18%

what is a root sheath

translucent piece of tissue surrounding the hair shaft at the root

when do we usually see the root sheath/follicular tag?

with forcibly removed hairs

we can use the follicular tag and/or root sheath for

nDNA

Follicular tags and/or root sheaths exist during the

anagen phase

animal hair typically has color

banding

Human hair pigment is usually __ distributed

evenly

animal hair scales are often

patterned

human hair scales are

imbricated

animal hair medulla are

patterned

animal hair medulla are

amorphous

animal roots often have a __ shape

characterisitc

human hair roots are often

bulbous

diameter of animal hairs

5 um to 2mm

human hair diameters range from

30-110 um

scale casts use

clear nail polish

medulla for an animal

greater than 1/3 the shaft diameter in a repeating pattern

human medulla is typically

less than 1/3 the shaft diameter, amorphous

dog hair is a

fine to coarser diameter

dog hair is usually _ than cat hair

coarser

dog hair has a __medulla that is ____

continuous, amorphous, less than 1/2 the shaft diameter

dog hair has many __ and a __ root

ovoid bodies, spade-shaped

dog hair is not typically __and has __ scales

banded, non-prominent

dog hair medulla looks like

chunky marshmallows

cat hair has 5 features

fine diameter, continuous medulla greater than 1/2 diameter with a picket fence appearance, spinous scales, elongated root with fibrils, may be banded

three categories for animal hairs

deer family and antelope, commercial fur animals, domestic animals

general characteristics of the deer and antelope families

coarse constant diameter (300 um), medulla takes up entire diameter, wineglass shaped root, regular wave/crimp in the hair, scale cast examination to determine the species

unique to deer

round scales like fish scales, color banding

commercial animal fur

very fine to medium diameter (20 um to 150 um), characteristic medullas, wide diameter variation within hair, usually banded

rabbits have a

multi-serial ladder medulla with a ribbon-like appearance

seals usually have an

absent or globular medulla with easily seen scales

which other animals have imbricate scales

mink, muskrat, bear, horse, cow, and goat

chinchillas have

several hairs coming from a single follicle

which animal hair is most often confused with human hair

bear

characteristics of domestic animal fur

medium overall diameter (75 um to 150um), amorphous medulla, usually unbanded, characteristic roots

the root of a cat hair is __ and may have __

elongated, fibrils

horse hair has a

very coarse diameter

horse medulla is

absent to continuous, amorphous or cellular with a mosaic pattern

horse hairs __ to a __ root

taper, bulb shaped

goat has a __ medulla

continuous lattice

diameter of head hairs

moderate

medulla of head hairs

absent or discontinuous

pigment distribution of head hairs

uniform

head hairs are __ and __

soft and pliable

pubic hairs diameter

coarse

unique feature of pubic hair diameters

shouldering or buckling, wide diameter variations

medulla of pubic hairs

broad and continuous

root of pubic hairs has a

follicular tag

cross section of beard hairs

irregular or triangular

beard hairs also have a __ and __ medulla (__ medulla)

broad, continuous, double

european hair generally has __ shaft diameter with minimal variation

moderate

european hair has a(n) __ cross-section

oval

european pigment distribution

even

historically, europeans have been called __ in textbooks

caucasoid

“European” applies to

american and european white, mexicans, middle easterners

African shaft diameter is

fine to moderate with lots of variation

african hair has a __ cuticle

thin

african hair has a __ cross-section

flat

afrian hair is __ with __ pigments

kinky, dense/clumped unevenly distributed

african was called __ in textbooks

negroid

Asian refers to

asians and american indians

shaft diameter of asians

coarse with little to no variation

asians have a __ cuticle

thick, prominent

asian hair has a __ cross-section

round

pigment distribution of asian hair

densely distributed pigments in patches or streaks

asian hair may have an __ tint

auburn

asian was called __ in textbooks

mongoloid

2 types of hair diseases

genetic and infections (fungal)

monilethrix means

beaded hair

pili torti means

hair twisted along the axis, spiral twist