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Each Follicle contains a muscle and a sweat gland • Arrector Pili – the muscle that lifts your hair on end when you’re cold or scared
Apocrine Gland Produces scent hormones called pheromones
Epidermis Outer layer of skin Made up of 5 dead layers – of keratin packed cells
Dermis – follicle sits in the dermal layer Directly beneath the epidermis. Packed with nerve endings and blood vessels
Layers of Hair Follicle Internal and External Root Sheath – molds and forms growing hair Papilla – Actively dividing cells that produce hair Blood Vessels – feed the growing hair Bulb – Bottom of Hair Follicle – contains the papilla and blood vessels Hair Shaft – Made up of Cuticle, Cortex, Medulla
Human, Cat, Dog, Mouse • Animals have characteristic cuticle scales that scientists can use to determine the source of hair evidence
Forensic Scientists make a glass slide prep to view animal hair on a Comparison Microscope
In some cases Forensic Scientists make a cast of the cuticle pattern • Cellulose cast
Medulla Patterns • Broken • Intermittent • Continuous
Animal Hair vs. Human Hair • Animal Hair falls into 3 main categories, Guard Hairs, Wool Hairs, Whisker hairs • Human Hairs don’t have a structured medulla ( some human hairs have no Medulla) • - Animal Medulla’s are quite structured
Rabbit • Cuticle • Pattern >
Hair is made of Protein • Hair is made of tight, closely packed dead cells that are made up of myofibrils or bundles of helical keratin
Myofibril - • Bundles of protein filaments that make up muscles and hair
Protein • Long chain of amino acids • Make up muscles, skin, hair nails and all the enzymes in your body
What are amino acids again? • Amino acids make up Protein • Keratin is protein and is therefore made up of amino acids in the form of a helix
As hair grows, new helical Keratin is added quickly • Papilla cells whip out 10 turns of the protein every second!!!
Hair is extremely STRONG • Try to break a piece apart…
Hair gets strength from 3 kinds of Chemical bonds • 1) Individual Keratin Molecules are held together by Hydrogen Bonds
3) DiSulfide Bridges • Link a Specific Amino Acid together • Cysteine ---Cysteine • When Hair stretches, These bridges break apart • These are COVALENT bonds
2) Hydrogen Bonds between Helices • Hair is stiff because of H bonds between individual Helices of Keratin. When your hair gets wet, these H bonds break apart and your hair gets limp and looses some of its structure • Why does WATER cause The H bonds in hair to be Rearranged?
Proteins have 4 levels of organization • Primary level --- Sequence of amino acids… polypeptides are thousands of aa’s long… and correct order is crucial
Secondary level • Amino acids react with each other forming • Alpha helices • Beta Sheets
Third level • More folding
Quaternary Structure • Many Poly peptides together • I.e. Keratin
Hair stretches… • When you stretch hairs H- bonds between helices break, allowing the helix to extend.
Hair Can be Straight or Curly • Hair that is straight has a circular shape • Hair that is curly has an elliptical hair shaft
Curly haired people also have MORE disulfide bridges than straight haired people
When people get a Perm (anent)… Heat is used to Physically change hair • 2 lotions are applied • First Lotion breaks their disulfide bridges
When is hair evidence important in a case? • Animal or Human determination • Body area determination • Race association with hair