All About Hair

Presented by: R, E. O. GaasGrade 7-NeptuneAlabel National Sciece High SchoolRegional Science High School for Region XII

Anatomy of Hair

What is a Hair?

Hair Growth Myths and Facts

Types of Hairs

Biological, Physical and Chemical Facts About Hair

All About Hair

What is a Hair?

• is a protein filament that grows from follicles found in the dermis, or skin.

• is one of the defining characteristics of mammals.

• an important biomaterial primarily composed of protein, notably keratin. 

Anatomy of Hair

Anatomy of Hair

Hair is composed of three principal parts:

Cuticle – outer coating composed of overlapping scales

Cortex – protein-rich structure around the medulla that contains pigment

Medulla- central core(may be absent)

The structure of hair has been compared to that of a pencil with the medulla being the lead, the cortex being the wood and the cuticle being the paint on the outside.

Anatomy of HairCuticle

Characteristics of the cuticle may be important in distinguishing between hairs of different species but are often not useful in distinguishing between different people.

The cuticle varies in:• Its scales,

How many there are per centimeter, How much they overlap, Their overall shape, and How much they protrude from the surface

• Its thickness, and• Whether or not it contains pigment.

Anatomy of Hair

CortexThe cortex varies in:

• Thickness• Texture• Color

• Distribution of the cortex is perhaps the most important component in determining from which individual a human hair may have come.

• Microscopic examination can also reveal the condition and shape of the root and tip.

Anatomy of Hair

MedullaThe medulla may vary in:

• Thickness• Continuity - one continuous

structure or broken into pieces

• Opacity - how much light is able to pass through it

• It may also be absent in some species.

Like the cuticle, the medulla can be important for distinguishing between hairs of different species, but often does not lend much important information to the differentiation between hairs from different people.

BiologicalPhysical

and ChemicalFacts About Hair

• Hair is composed of the protein keratin, which is also the primary component of finger and toe nails.

• Humans develop hair follicles during fetal development, and no new follicles are produced after birth.

• Hair color is mostly the result of pigments, which are chemical compounds that reflect certain wavelengths of visible light.

Facts About Hair

Hair shape (round or oval) and texture (curly or straight) is influenced heavily by genes. The physical appearance of hair can be affected by nutritional status and intentional alteration (heat curling, perms, straightening, etc.)

Facts About Hair

The body area (head, arm, leg, back, etc.) from which a hair originated can be determined by the sample’s length, shape, size, color, and other physical characteristics.

Facts About Hair

In order to test hair evidence for nuclear DNA, the root must be present. The hair may also be tested using mitochondrial DNA whether or not the root is present.

Facts About Hair

The Cuticle of Human Hair is rough --- which is why we use Conditioner

Facts About Hair

Animals have characteristic cuticle scales that scientists can use to determine the source of hair evidence. Human, Cat, Dog, and Mouse respectively (photo below)

Facts About Hair

Types Of Hair

Types of Hair• Develops on an unborn

baby

• 3 months after baby’s

conception

• Fine and soft

• grows all over the body at

the same rate

• Shed about 4 weeks before

the baby is due to be born

LanugaHair

Types of Hair• Short, fine, downy,

unpigmented hair covering most of the body except the palms and soles of feet

• women normally retain 55% more vellus hair than men

• Follicle doesn’t have oil glands

VellusHair

Types of Hair• Long, thick pigmented

hair found on the scalp, legs, arms & bodies of males & females

• Coarser than vellus hair &, with the exception of gray hair, it is pigmented

• Produced by follicles with sebaceous glands

TerminalHair

Cat

Horse

Types of Animal Hairs

Pig

Human

Dog

Deer

Rabbit

Rat

Human

Hair GrowthMyths

andFacts

Hair Growth Myths and Facts• Gray hair is coarser and more resistant than pigmented hair.

FACT: other than lack of pigment, gray hair is exactly the same as pigmented hair. It is not resistant because it is gray, & is not more resistant than the pigmented hair on the same person’s head

• Amount of natural curl is determined by racial background.

FACT: anyone of any race can have straight or extremely curly hair

Hair Growth Myths and Facts• Clipping, shaving, trimming & cutting makes hair grow faster

FACT: have no effect on hair growth

• Scalp massage increases hair growth

FACT: no evidence to indicate this is true. Minoxidil and Finasteride are the only treatments that have been proven to increase hair growth and are approved for that purpose by the FDAS.

Hair Growth Myths and Facts• Hair with round cross-section is straight; hair with oval cross-

section is wavy; hair with flat cross-section is curly

FACT: cross-sections of straight hair tend to be round and curlier hair tends to be more oval, but cross-sections of hair can be almost any shape, including triangular; the shape of the cross-section does not always relate to the amount of curl or the shape of the follicle

Credits to Referenceshttp://library.thinkquest.org/04oct/00206/lesson.htm#t_hair

http://www.fbi.gov/hq/lab/fsc/backissu/july2000/deedric1.htm#Index%20(Hairs)

http://library.thinkquest.org/04oct/00206/lesson.htm#t_hair

http://www.fbi.gov/hq/lab/fsc/backissu/july2000/deedric3.htm#Fiber%20Evidence

http://www.fireflydiapers.com/articles/diaperarticle_naturalfibersabsorb.htm

http://micro.magnet.fsu.edu/primer/techniques/polarized/gallery/images/humansmall