Human Hair Flashcards
1
Q
is a flexible thin keratin thread present on almost all surfaces of the human skin
A
hair
2
Q
hair is present in all surfaces of the human skin except
A
palms, soles, and vermillion part of lips (red part)
3
Q
- produced by rapidly multiplying matrix
keratinocytes - Made up entirely of dead cells composed mainly
of keratin which are held together by intracellular cement-like substance
A
Hair Shaft
4
Q
- Part of the pilosebaceous unit
> Composed of a hair follicle, arrector pili muscle, and sebaceous gland
> Sebaceous gland - secrete sebum - Covered by inner and outer root sheaths
- Sebum produced by sebaceous glands coats
the hair and skin - Contraction of the arrector pili muscle attached to the hair follicle causes hair to stand up (goosebumps)
A
Hair follicles
5
Q
covered by hair follicle
A
hair root
6
Q
- Hair Papilla
- Hair Matrix
A
parts of hair bulb
7
Q
Contain blood vessels for nutrients and oxygen supply
A
hair papilla
8
Q
Active cell division happens:
- When cells are pushed up, these are dead cells
- Access to nutrients
A
hair matrix
9
Q
Shaving or cutting the hair can make it grow faster
A
Myth - (Hair shaft is dead cells so no impact)
10
Q
- Outermost structure
or is translucent - Composed primarily of keratin
- Translucent color
- Target for conditioning product because it defines the outer structure of the hair
A
cuticle
11
Q
- protects the cortex
- acts as a barrier from the entry of water
- regulates the water content of the hair fiber
- responsible for hair luster (shine) and texture
A
functions of cuticle
12
Q
- Major component of hair shaft (thickest part of hair)
- Contributes to mechanical properties of hair fiber like
strength, elasticity, and curliness - Cells rich in keratin filaments with amorphous matrix of sulfur proteins
- Contains melanin; hair color is due to melanin
- In older people: less melanin production and more spaces between the cortex, results in white hair
A
cortex
13
Q
every cortical cells in the cortex contains ______
A
macrofibrils
14
Q
macrofibrils consist of ______
A
microfibrils
15
Q
microfibrils is made of ______
A
protofibrille
16
Q
every 1 protofibrille has ______
A
4 keratin helix
17
Q
- known as the core
- composed of flattened cornified cells
- keratin framework supporting thin shells of amorphous material bonding air spaces
>hollow
A
medulla
18
Q
Thick hair is more resistant to stretching than thin hair
A
FACT: (thicker hair has thicker cortex, more resistant to
breakage or stretching)
19
Q
Hair growth cycle and hair loss
A
- anagen
- catagen
- telogen
20
Q
- Growth phase
- Nourishment of hair follicle via blood supply enables hair growth
- Different for each type of hairs
- Active growth, cells are pushed up
- (lasts on scalp) Scalp: 2-6 years
> continuous growth occurs so hair in this area can be long - Brows have a shorter anagen stage
A
anagen
21
Q
- Transition phase
- Hair follicle detaches from nourishing blood
supply - Scalp: 2-3 weeks
A
catagen
22
Q
- Resting phase
- Hair fall out is normal (100-150 telogen hairs falling out in scalp)
- Without nourishment, the hair dies and falls out
- Scalp: 2-3 months
- If anagen hair ang nagfall out of scalp: not normal
A
telogen
23
Q
scalp is 85-95% in what phase?
A
anagen
24
Q
How to know if anagen hair or telogen hair
A
Telogen hair:
- Has white ends
indicating melanin
production has
stopped
- Cannot feel the
fallout, no pain
25
hair composition and properties
- strong bonds
- weak bonds
- surface charge of human hair
- physical properties of human hair
- human hair types
26
- Disulfide bonds are formed between sulfur atoms of
cysteine
>Only type of strong bonds
>Cysteine is an amino acid containing sulfur
>Aligned by S-S linkages
- Contribute to shape, stability, and texture of hair
- Can only be broken up chemically
>Altered by permanent hair straightening,
waving, or coloring
>Not altered by temporary treatments like
blow-drying
- Allows hair to resume its original shape
strong bonds
27
- Hydrogen Bonds (H-bonds)
- Salt Bonds (Ionic bonds to Coulomb interaction)
- Van der Waals force
Weak bonds
28
- Weak bonds that are easily broken by water and
heat
>Shower / blow dry hair
- Can alter hair's overall shape
- Most abundant and common type of bond
Hydrogen Bonds (H-bonds)
29
- Sensitive to pH and readily broken by alkaline or
acidic conditions
- Alkalinizers (pH 9-10) are usually added to affect change for permanent formulations to straighten/add waves
Salt Bonds (Ionic bonds to Coulomb interaction)
30
- Weak attractive forces between neutral molecules
- May be broken by water and head
Van der Waals force
31
Wet hair is more vulnerable than dry hair
FACT
- Wet hair has altered weak bonds due to the
presence of water
32
- Untreated hair comprises proteins that exhibit an
isoelectric point near pH ________
pH 3.7
33
Hair usually carries a _______ charge
negative
34
__________ ingredients are attracted to the hair more
readily than _______ ingredients
Cationic; anionic
35
- durable and strong
- elasticity
- water content
- High electrical resistivity and low dielectric constant
physical properties of human hair
36
due to keratin in the cortex
- Similar strength to copper wires of the same
diameter
durable and strong
37
related to the diameter of hair shaft
elasticity
38
causes cortex to swell and edges of the cuticle scales to lift
water content
39
makes it easy to generate electrostatic charges by
brushing & combing
High electrical resistivity and low dielectric constant
40
- based on thickness
- based on color
- based on condition
- based on shape size and color
- based on curliness
- based on greasiness
human hair types
41
- Fine
- Medium
- Coarse
Based on Thickness
42
Function of melanin
Based on Color
43
- Damaged
- Healthy
based on condition
44
- lanugo
> very fine hair
> babies only
> shed moments after birth
- vellus
> fine hair
> Seen in areas where hair is not too
> Purpose: Thermal control through evaporation / perspiration visible
- terminal hair
> Scalp, brows
> Darker, more visible
> Distinct function is protection
Based on Shape, Size, and Color
45
type of hair may change
(t or f)
Terminal → Vellus: Balding
Vellus → Terminal: Mustache
46
- Excess sebum production
- Usually associated with dandruff
Greasy hair
