Q6: HairQ6: Hair

By the NumberBy the Number

The average human has about 5 million The average human has about 5 million hairs on their entire bodyhairs on their entire body

Head Count!Head Count! Red Red 80,000 80,000 Brown/Black Brown/Black 100,000 100,000 Blondes Blondes 120,000 120,000 Shed about 100 hairs from your body every Shed about 100 hairs from your body every

24 hours24 hours

Pigment Distribution in Brown HairPigment Distribution in Brown Hair

Pigment Distribution in Red HairPigment Distribution in Red Hair

Hair Growth StagesHair Growth Stages

Hair grows about ½ inch per monthHair grows about ½ inch per month Grows in phasesGrows in phases

Stages are extremely sporadic and not all Stages are extremely sporadic and not all hairs are in the same stagehairs are in the same stage

1.1. Anagen PhaseAnagen Phase Growth StageGrowth Stage 90% of hair follicles are in this stage90% of hair follicles are in this stage Scalp Scalp 2-5 years 2-5 years Eyebrows Eyebrows 4-7 months 4-7 months

Hair Growth Stages cont…Hair Growth Stages cont…

2.2. Catagen PhaseCatagen Phase Regressing StageRegressing Stage

8-10 % of hair follicles are in this stage8-10 % of hair follicles are in this stage Scalp Scalp 1-2 months 1-2 months Eyebrows Eyebrows 3-4 weeks 3-4 weeks

3.3. Telogen PhaseTelogen Phase Resting StageResting Stage

About 1% of hairAbout 1% of hair Scalp Scalp 2-4 months 2-4 months Eyebrows Eyebrows 9-12 months 9-12 months

4.4. Exogen PhaseExogen Phase Exit PhaseExit Phase

Hair TypesHair Types

1.1. Lanugo HairLanugo Hair Hair that covers the entire body of the fetusHair that covers the entire body of the fetus

2.2. Vellus HairVellus Hair Covers the entire human body exceptCovers the entire human body except

1.1. LipsLips2.2. Palms of handPalms of hand3.3. Soles of feetSoles of feet4.4. Scar TissueScar Tissue5.5. NipplesNipples

Females have more Vellus hair than malesFemales have more Vellus hair than males

3.3. Terminal Hair (Permanent Hair)Terminal Hair (Permanent Hair) Fully developed hair Fully developed hair

Longer, thicker, more developedLonger, thicker, more developed

Growth is a response to rising levels of Growth is a response to rising levels of hormones androgen and testosteronehormones androgen and testosterone

Sexual Dimorphism: Difference in traits Sexual Dimorphism: Difference in traits between gendersbetween genders Two areas where there is no sexual dimorphism Two areas where there is no sexual dimorphism

with terminal hairwith terminal hair Pubic AreaPubic Area UnderarmsUnderarms

As EvidenceAs Evidence

Good piece of evidence for a number of Good piece of evidence for a number of reasonsreasons

1.1. Resistant to chemical decompositionResistant to chemical decomposition Made of proteinMade of protein

Helps it to outlast all but the skeleton and the teethHelps it to outlast all but the skeleton and the teeth Ability to retain structural featuresAbility to retain structural features

2.2. Provides clues to race and sexProvides clues to race and sex

3.3. Easily distinguishable from other animals Easily distinguishable from other animals (except that of apes)(except that of apes)

FollicleFollicle

Organ in which the hair growsOrgan in which the hair grows Does so by packing old cells togetherDoes so by packing old cells together

Sebaceous Gland: Provides fats and greases Sebaceous Gland: Provides fats and greases

Forensic Importance:Forensic Importance: Linked to the body’s Linked to the body’s blood supply (DNA)blood supply (DNA)

ShaftShaft

Actual hair itselfActual hair itself Consists of 3 partsConsists of 3 parts

1.1. CuticleCuticle Transparent, outside covering of the hairTransparent, outside covering of the hair

Overlapping scales that point toward the tip of the hair (roof Overlapping scales that point toward the tip of the hair (roof shingles)shingles)

Proximal end Proximal end closest to scalp closest to scalp Distal end Distal end farthest from scalp farthest from scalp Provides protectionProvides protection Forensic Importance:Forensic Importance:

Species IdentificationSpecies Identification Direction in which ends point indicate use of toxinsDirection in which ends point indicate use of toxins

Human CuticleHuman Cuticle

Shaft continued…Shaft continued…

2.2. CortexCortex Largest, main body of the hair shaftLargest, main body of the hair shaft Composed of spindle shaped cells that run Composed of spindle shaped cells that run

parallel to the hair lengthparallel to the hair length Contains the most hair granulesContains the most hair granules Forensic Importance:Forensic Importance:

Color Color ShapeShape

Cortical Fusi in Human HairCortical Fusi in Human Hair

Shaft continued…Shaft continued…

3.3. MedullaMedulla Cell column that runs through the center of Cell column that runs through the center of

the hairthe hair Lots of humans don’t have oneLots of humans don’t have one

Hair is a hollow tube!Hair is a hollow tube!

Forensic Importance:Forensic Importance: DiameterDiameter 5 different types of medulla 5 different types of medulla class evidence class evidence

5 Types of Medulla (human)5 Types of Medulla (human)

(a) Fragmented(a) Fragmented (b) Interrupted(b) Interrupted (c) Continuous(c) Continuous

Much thicker in Much thicker in animals than in animals than in humanshumans

StackedStacked 2 types2 types UniserialUniserial MultiserialMultiserial

Uniserial Stacked Medulla (rabbit)Uniserial Stacked Medulla (rabbit)

Multiserial Stacked Medulla (deer)Multiserial Stacked Medulla (deer)

Types of CuticlesTypes of Cuticles

There are 3 types of CuticlesThere are 3 types of Cuticles1.1. CoronalCoronal

Crown like shapedCrown like shaped In hairs with very fine diameterIn hairs with very fine diameter Commonly found in hairs of small rodents/batsCommonly found in hairs of small rodents/bats

Bat Hair (Coronal Cuticle)Bat Hair (Coronal Cuticle)

Types of CuticleTypes of Cuticle

2.2. SpinousSpinous Petal like scalesPetal like scales Triangular in shapeTriangular in shape ProtrudingProtruding Minks, Seals, Cats Minks, Seals, Cats

(never humans)(never humans)

Cat Hair (Spinous Cuticle)Cat Hair (Spinous Cuticle)

Types of CuticlesTypes of Cuticles

3.3. ImbricateImbricate FlattenedFlattened OverlappingOverlapping Common in humans and many other Common in humans and many other

animalsanimals

Human Hair (Imbricate)Human Hair (Imbricate)

Gray Human HairGray Human Hair

Medical TermsMedical Terms

Alopecia: Hair LossAlopecia: Hair Loss ClassificationsClassifications

1.1. Alopecia areata: baldness in patchesAlopecia areata: baldness in patches

2.2. Alopecia totalis: all hair on scalp is lostAlopecia totalis: all hair on scalp is lost

3.3. Alopecia universalis: total hair loss on all parts of Alopecia universalis: total hair loss on all parts of bodybody

Alopecia Alopecia UniversalisUniversalis

Trichotillomania (TTM)Trichotillomania (TTM)

Impulse control disorder characterized by Impulse control disorder characterized by the urge to pull out your own hairthe urge to pull out your own hair

HirsutismHirsutism

Abnormal hair growth in womenAbnormal hair growth in women Caused by excessive presence of androgensCaused by excessive presence of androgens

HypertrichosisHypertrichosis

Disease characterized by excessive body Disease characterized by excessive body hairhair

Also known as “Wolfman Syndrome”Also known as “Wolfman Syndrome”