Forensics

medulla

Innermost layer of hair
Can be interrupted, continuous, fragmented, solid, or absent

cortex

the middle layer of hair that also is the layer that holds color (contains pigment)

cuticle

tough, clear outside covering of the hair shaft

interrupted medulla

a medulla that consists of a pigmented line broken at regular intervals

fragmented medulla

breaks that are unevenly placed in the medulla

continuous medulla

medullary appearance showing no disruptions along the shaft of the hair (straight line)

absent medulla

hair showing no medulla

solid medulla

pigmented area filling both the medulla and the cortex

hair shaft

visible part of the hair, includes the medulla, cortex, and cuticle

follicular tag

A translucent piece of tissue surrounding the hair's shaft near the root that contains the richest source of DNA associated with hair.

bleached hair

pigment granules are removed, hair will have yellowish tint, hair will be brittle, cuticle scales may be disturbed

dyed hair

cuticle and cortex take on color of the dye

medullary index

the ratio of the diameter of the medulla to the diameter of the entire hair

animal medullary index

.5 or greater

human medullary index

0.33 or less

imbricate cuticle scale pattern

most common in humans

spinous cuticle scale pattern

never found in humans, can be found in cats, minks, seals, and some other animals

coronal cuticle scale pattern

rarely found in humans, often found in small rodents and bats

keratin

hard but flexible protein that makes up hair

functions of hair

regulate body temp, decrease friction, protect against sunlight, camouflage