Chapter 3: Hair Analysis

Outermost layer of skin

Layer of skin beneath the outer layer containing glands and follicles

Tubular sheath surrounding the root of the hair

Shaft that emerges above the skin surface

Small blood vessels within the skin

Protection from the sun and dirt

Regulation of body temperature

Detection of movement by nerves in the follicle

Camouflage for some animals

Increase in blood glucose levels

Outermost protective layer composed of scales

Thick middle layer containing pigment

Central core that may be hollow or filled

Medulla of the hair

Cortex of the hair

Cuticle of the hair

Irregular gaps

Missing central core

Fills most of the hair’s diameter

Repeating gaps in a pattern

No gaps or breaks

Flattened, overlapping scales; common in humans

Crown-like scales; bats and small rodents

Petal-like scales; common in cats

Very coarse; triangular cross-section; thick medulla

Uniform pigment; long and soft; often circular cross-section

Coarse and wiry; wider medulla

Asian hair tends to be straight and coarse with a round cross-section.

Caucasian hair is typically straight or wavy with an oval cross-section.

African hair is usually curly or coiled with a flat or elliptical cross-section.

Pigment distribution in the cortex is identical across all ethnic groups.

Color differences relate to variations in melanin concentration.

Width of the entire hair divided by the width of the medulla

Width of the medulla divided by the width of the entire hair

Diameter of the cortex divided by the total hair diameter

Number of medulla fragments divided by hair length

Humans typically have a small medullary index, while many animals have a large one.

Human cuticles are usually imbricate; animal cuticles can vary by species.

Animal medullae are often patterned or thick; human medullae are typically thin or fragmented.

Human medullae are usually solid along the entire diameter of the shaft.

All animals share the same cuticle type.