Hair Structure Linch CA et al. 2001 JFS 46: 844

STRUCTURE OF HAIR

STRUCTURE OF HAIR: SHAFT Cuticle – the collective appearance of the scales of the hair Cortex- rod-like shaft that contains proteins (hair color), surrounds medulla Medulla – hollow tube or core in the center of cortex

Cuticle Overlapping scales Always point toward the tip of each hair Scales of animals appear almost like Shingles on a roof Structure of scales can be useful in species determination Animal only

Comparison of Animal Cuticle scales http://www. rit Cat Rabbit Rat Human Dog

CORTEX Forensic Significance It’s embedded with the pigment granules that impart hair with color The color, shape and distribution of these granules that provide examiners with many points of comparison between hairs of individuals

Medulla The medulla may vary in thickness, continuity (one continuous structure interrupted into pieces), and opacity (how much light is able to pass through it) continuous medulla interrupted medulla Fragmented medulla May also be absent. Like the cuticle, the medulla can be important for Distinguishing between hairs of different species, but often does not lend much to human hair

HUMAN VS ANIMAL ANIMAL -diameter of animal widens then narrows - medullas occupy more than ½ of diameter - display ladder-like patterns - cuticles are coarse HUMAN - diameter is uniform - medullas occupy no more than 1/3 of diameter - never display ladder- like patterns - cuticles are relatively smooth

ROOT Cells in root and around follicle provide growth Three stages of development Anagen- (approx. 6 yrs) initial growth phase, when pulled good chance of follicular tag-tissue/ important for DNA analysis Catagen- root bulb shrinks in this transition phase Telogen- Hair is pushed out of the follicle and rood takes on a club-shaped

Three Stages of Hair Growth

Hair Collection When questioned hairs are submitted must have plenty of Controls Head hairs: 50 hairs from different areas Pubic Area: 24 hairs Should be pulled or cut at scalp/skin line

Hair Root with Tissue Attached – contains DNA Each case takes a different amount of time….it’s difficult to predict the timeframe ROOT