Hairs, Fibers, and Paint

Chapter 8

Dermis• Contains

- smooth muscle- blood vessels- nerve tissue- hair follicles (accessory organ of skin)- sweat glands (accessory organ of skin)- sebaceous glands (accessory organ of skin)

• Contains nerve receptors – to sense light/heavy touch or pressure

• Contains connective tissue made of collagen and elastic fibers

Full-thickness Skin

Accessory Organs of the Skin

• Hair follicles• Nails• Skin glands

– Sebaceous glands– Sweat glands (a.k.a sudoriferous glands)

• Eccrine• Apocrine

Hair Follicles

• Follicles are present on all skin excepts palms, soles, lips, nipples

• In some areas that grow hair, the hair may be fine, while in others it may be thick

• A hair grows out of a deep tube that extends from the surface of the skin, all the way into the dermal layer – this is a follicle

• Each hair follicle is also connected to sebaceous glands that produce oils and other secretions

Hair Follicle, cont’d.

• The follicle contains the growing hair shaft• The base of the hair is composed of

actively dividing epidermal cells • These epidermal cells are nourished by

dermal blood vessels near the hair base – this area at the base of the hair follicle is called the hair papilla

Hair Growth• As the epidermal cells divide,

they push older cells upward through the follicle

• As the older cells move away from the nutrient supply, they become keratinized and die

• These dead keratinized epidermal cells are what make up a strand of hair

• Hair color is genetically determined and is pigmented by melanocytes - the more the melanin in the dead epidermal cells, the darker the hair

Phases of Hair Growth1. Anagen – can last up to 6 years. In this phase, the

hair root is still attached to the hair follicle and grows. The root appears plump and “flame-shaped”

2. Catagen – the hair continues to grow, but at a slower rate. This slowed-down growth rate can last for 2 to 3 weeks. The root bulb shrinks and appears elonated.

3. Telogen – Telo means “end”. This is the phase in which the root begins to look like a club. The hair will slowly get pushed out of the follicle. This slow loss can take 2 to 6 months.

A strand of hair has three layers: cuticle, cortex, and medulla. The outermost covering, cuticle consists of hard overlapping protein scales that point toward tips end. The cortex contains pigment granules that give hair its color. The medulla is a hollow tube within the hair, which may be present or absent. Depending on the hair, this hollow tube is continuous, or fragmented.

Layers of a hairA strand of hair has three layers:

1. Cuticle - the outermost covering, cuticle consists of hard overlapping, transparent cells filled with keratin protein. These cells appear like scales that point toward tips end.

2. Cortex - contains pigment granules that give

hair its color.

3. Medulla - a hollow tube within the hair, which may be present or absent. Depending on the hair, this hollow tube is continuous, or fragmented.

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The Function of Hair

• Regulates body temperature • Decreases friction• Protects against sunlight

Treated Hair

• Bleaching – disturbs the scales on the cuticle and – removes pigment – leaves hair brittle and yellowish

• Dyeing colors the cuticle and the cortex

Medullae

•Continuous•Discontinuous or Interrupted•Fragmented or Trace•Absent

Interrupted or discontinuous

Medulla absent

Continuous

Follicular Tags

• If you pull a hair that is in anagen phase, it has a follicular tag attached to the root – this tag is very important for forensic analysis – – tells you if a hair has fallen out or pulled out – hair

pulled out usually has the follicular cells– How quickly it has been pulled out – hair pulled

quickly has the follicular cells attached

• The follicular tag is also a useful source of DNA

Nuclear DNA from Hair

• Best source of nuclear DNA is the Follicular tag

• If absent, nuclear DNA can be retrieved from the root however, hair in anagen phase will yield more DNA than hair in other phases.

• So hairs found at a crime scene will not necessarily be good sources of nuclear DNA – unless they were pulled out.

Mitochondrial DNA

• If nuclear DNA is not found, an examiner can locate the mitochondria of the hair cells – they also contain DNA!

• Each cell has multiple copies of mitochondria, and each mitochondrion has multiple copies of DNA; so you may be able to find at least one copy.

• mtDNA is only passed from mother to child, whereas nuclear DNA is passed by both parents

Hair Color• White – lacks melanin (albinism)• Gray hair – a mix of pigmented and

unpigmented hair• Black and brown – tons of melanin• Blonds – Less melanin• Red hair – contains an extra pigment

called trichosiderin (iron based)

Goosebumps!• Smooth muscle attached to each hair follicle can

contract and cause short hairs to stand on end• These muscle bundles are called arrector pili

muscles• They appear when scared, excited, cold, etc.

Glands - Sebaceous

• Usually associated with hair follicles• Specialized epithelial cells in this gland produce

a fatty secretion that accumulates and bursts through cells

• The final product is a mix of cell debris and fatty fluid – this is called Sebum

• Sebum is secreted into hair follicles• Keeps skin and hair soft, flexible and waterproof• Too much sebum causes pores to clog and

results in acne

Part of the body• Yes, one can determine which part of the body

the hair came from, based on the structural analysis.– Most head hair are similar to each other in diameter

and the pigment is evenly distributed throughout the shaft, unlike other body hair. They may have absent, continuous or discontinuous medullae.

– Pubic hair is short, coarse and curly and they exhibit considerable diameter variation or “buckling”. The medullae are usually present and can be discontinuous or continuous. While tapered tips are common, these hairs may also be abraded or cut.

Part of the body, cont’d.

– Beard / Mustache hairs are coarse and triangular in cross section – they have wide medullae and blunt ends due to shaving.

– Limb HairsHairs from the legs and arms constitute limb hairs. These hairs are shorter in length, arc-like in shape, and often abraded or tapered at the tips. The pigment in limb hair is generally granular in appearance, and the medulla is trace to discontinuous.

Hair from different parts of the body

Buckled Blunt Double Medulla

• A cross section: circular, triangular, irregular, or flattened

• Shape: influences the curl of the hair• Texture: coarse or fine

Racial Differences• Broad, racial groups do exhibit some

shared physical characteristics • But NOT applicable to all individuals in

these groupsTherefore, • Individual hairs CANNOT be assigned to

any of these groups

• EuropeanHairs of Caucasoid or Caucasian origin can be of fine to medium coarseness, are generally straight or wavy in appearance, and exhibit colors ranging from blonde to brown to black. The hair shafts of Caucasian hairs vary from round to oval in cross section and have fine to medium-sized, evenly distributed pigment granules.

Racial origin of hair

Asian• Hairs of Asian origin are regularly

coarse, straight, and circular in cross section, with a wider diameter than the hairs of the other racial groups. The outer layer of the hair, the cuticle, is usually significantly thicker than the cuticle of African and Caucasian hairs, and the medulla, or central canal, is continuous and wide. The hair shaft, or cortex, of Asian hair contains pigment granules that are generally larger in size than the pigment granules of Caucasian hairs and which often appear to be grouped in patchy areas within the shaft. Asian hair can have a characteristic reddish appearance as a product of its pigment.

African• Hairs of African origin are regularly

curly or kinky, have a flattened cross section, and can appear curly, wavy, or coiled. African pigment granules are larger than those found in Asian and Caucasian hair and are grouped in clumps of different sizes and shapes. The density of the pigment in the hair shaft may be so great as to make the hair opaque. A African hair shaft exhibits variation or apparent variation in diameter because of its flattened nature and the manner in which it lies on the microscope slide. Twisting of the hair shaft, known as buckling, can be present, and the hair shaft frequently splits along the length.

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Animal Hair and Human Hair

• Pigmentation: – animal hair is denser toward the medulla– human hair tends to be denser toward the

cuticle• Banded Color Patterns:

– possible in animals– not in humans

• Medulla: much thicker in animals

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Medulla Index—Animals vs. Humans

Imbricate Scales

The imbricate or flattened scales type consists of overlapping scales with narrow margins. They are commonly found in human hairs and many animal hairs.

Coronal Scales

Crown-like Scales that completely encircle the hair shaft. They have a very fine diameter and resemble a stack of paper cups. Coronal scales are commonly found in the hairs of small rodents and bats but rarely in human hairs.

Spinous Scales

• Spinous or petal-like scales are triangular in shape and protrude from the hair shaft. They are found at the proximal region of mink hairs and on the fur hairs of seals, cats, and some other animals. They are never found in human hairs.

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Using Hair in an Investigation • Macroscopic investigations indicate

– length – color – curliness

• Phase contrast microscopy shows– presence of dye or other treatments

• Electron microscopes yield yet more detail

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Using Hair in an Investigation

Note the overlapping scales and the pigment granules in the cortex

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Testing for Substances in the Hair Shaft

• Chemical tests – presence of various substances

• Examining a hair shaft– timeline for exposure to toxins

• Neutron Activation Analysis (NAA)– concentrations of substances

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Testing the Hair Follicle

• Microscopic assessment– Cost effective and quick

• Blood test– Determine blood type

• DNA analysis – Identification with a high degree of

confidence

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Microscopic Assessment

• Preparation