Hair analysis

what are the longitudinal components of a hair?

Root-shaft-tip

hair structure from outside in

cuticle, cortex, medulla

Cuticle (Hair)

outermost layer, consists of a single layer of thin, flat cells that are the most heavily keratinized

How are the scales on the cuticle oriented?

Towards the distal end (tip)

What is the main function of the cuticle?

Chemical and structural protection and resistance

What is one of the main conclusions you can draw from analyzing the cuticle of hairs?

Differentiating between human and animal hair

Exocuticle

The rigid, sclerotized outer layer of the procuticle separated into a-layer and exocuticle

a-layer

part of the cuticle, situated just beneath the outermost cuticle layer
- rich in cysteine

Which cuticle layer is Amorphous, Rich in keratin and keratin-associated proteins (KAP)?

Exocuticle

endocuticle

The inner-most layer of the cuticle. It is amorphous and derived from nucleus and cells organelles

Cortex

Main body of the hair shaft made of spindle shaped cortical cells (80 to 115 µm long)

Which layer of hair contains the natural pigments?

cortex

Unit length filament (ULF)

32-mer (8x tetramer)

Keratin --> intermediate filament --> hair shaft

a-helix --> dimer --> tetramer--> 32-mer (ULF)--> elongation of ULF --> KIF --> macro fibrils made by Keratin associated proteins --> disulfide bonds to make shaft

cross linking

a way to harden polymer; disulfide bonds between keratin filaments hold them together

Orthocortical cells

twisted cortical cells

Mesocortical cells

straight cortical cells

Paracortical cells

in between twisted and straight

Hair is a bundle of fibers connected by crosslinks

true

What defines the curvature of hair?

The difference in length of ortho cortical and paracortical cells

Pheomelanin

Melanin that provides yellow pigment yo natural hair colors

Eumelanin

melanin that provides black pigment to hair

medulla (hair)

core of loosely arranged keratin cells and air spaces

The main component of the medulla is

trichohyalin and citrulline

which layer is predominant in thick hair, not always present, and can differ for a single individual in different hairs

medulla

Medulla hair and shape depends on

the curl

The flatter the medulla, the __________ the hair

curlier

If a cross section was done of a hair follicle, the different components (from inside to outside) would be

hair shaft --> inner root sheath --> outer root sheath --> fibrous sheath

Anagen

First stage of hair growth during which new hair is produced/The period of active growth - 80-95% of total hair for humans - 400 µm/day

catagen

The period of break down and change of hair growth (1-2 weeks)

telogen

Also known as resting phase; the final phase in the hair cycle that lasts until the fully grown hair is shed. - 2-3 months - 5-15% of total human hair

Exogen

the stage of the hair cycle where old hairs are shed.

Kenogen

balding

most people shed _____ hair/day

50-150

Human hair during life

Luango (fetus hair)--> Vellus (child) --> terminal (puberty)

What characteristic of hair can be used to distinguish it from other fibers?

scales

What characteristic of hair can be used to distinguish it from animal hair?

scale pattern, medulla, root

coronal cuticle

crown like cuticle found in cats

spinous scales

imbricate scales

overlapping scales

Medullary index

ratio medulla diameter/hair diameter

Human MI

less than 1/3

Animal MI

greater than 1/2

Scalp hair

Long with moderate shaft diameter and diameter variation
- Medulla absent to continuous and relatively narrow
- Often with cut or split tips
- Can show artificial treatment, solar bleaching, or mechanical damage
- Soft texture, pliable

pubic hair

Shaft diameter coarse with wide variations and buckling
- Medulla relatively broad and usuallycontinuous when present
- Root frequently with follicular tissue
- Tip usually tapered, rounded, or abraded
- Stiff texture, wiry

Limb hair

- Diameter fine with little variation
- Gross appearance of hair is arc-like in shape
- Medulla is discontinuous to trace with a granular appearance
- Tips usually tapered, often blunt and abraded, rounded scale ends due to wear
- Soft texture

Facial Hair

- Diameter very coarse with irregular or triangular cross-sectional shape
- Medulla very broad and continuous, may be doubled
- Usually cut

ovoid bodies

Oval or round pigmented bodies usually found in the hair cortex

Human hair

- imbricate scale pattern
- medullary index < 1/3
- consistent pigmentation along shaft
- uniform pigmentation towards cuticle
- club shaped root

Animal hair

Spinous or coronal scale pattern
- medullary index > 1/2
- banded pigment along shaft
- pigment centrally distributed towards medulla
- various root shapes