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What does trichology mean?
the technical name for the study of hair.
According to your textbook, what are the main purposes of hair?
- protection from heat, cold and injury.
Where are the living cells of hair found?
What is the primitive hair germ?
a cluster of cells in the upper layer of skin, from fetal life, forms the hair bulb.
Explain how a hair follicle is formed.
the primitive hair germ grows downward toward the dermis to join with the papilla, a follicle is created.
What is the hair root?
the portion of hair that is inside the hair follicle under the skins surface.
What is the hair fiber?
(hair shaft/strand) : portion of hair that extends above the skin's surface.
List the hair follicle shapes and which texture of hair each follicle shape creates.
- Round: Straight
- Oval: Wavy/Curly
- Elliptical: Tight Curls
What is the papilla and why is it important?
- Papilla: Cells filled with capillaries that supply nourishment to the cells around it.
- Important: Origin of hair.
When will hair not grow again?
if the papilla is destroyed.
What is keratinization?
a process where cells changes their shape, dry out and form keratin protein. (Hardening) the keratinized cells that form the hair strand are no longer alive.
Name the three layers of the hair fiber and describe the characteristics of each one.
- Medulla: central core of the hair shaft.
- Cortex: second layer of hair consisting of unique protein structures.
- Cuticle: outer cover of hair shaft made up of overlapping layers of transparent scales.
What are sebaceous glands, what do they produce?
oil glands, attached to the hair follicle, produce sebum (oil).
How does sebum make it to the skin's surface?
it's sent up through the hair follicle to the surface of the skin. prevents the hair from becoming too dry.
What is the acid mantle composed of and why is it important?
sebum mixed with perspiration, it protects the cuticle layer and maintains the acid balance of the skin and hair.
What are the arrector pili muscles attached to and what do they do?
attached to the hair follicle, causes the hair to stand on end when scared or cold.
What protein makes up hair?
What shape does this protein take when linking together to form the cortex?
What gives hair the ability to stretch without breaking?
protein chains coiling or twisting as they are formed.
Name the three stages of hair grow and describe what happens in each stage.
- Anagen: active growing stage. hair bulb has attached root sheath. 90% of each persons hair is in this stage. last 2-6 years. hair color is darker.
- Catagen: brief transitional stage. all cell division stops, lasts only a few weeks.
- Telogen: resting stage. hair bulb is not attached to the root sheath. hair falls out. 10-15% of hair on the head is in this stage at any given time. lasts 3-4 months.
What is the average rate of hair growth?
1/2" a month.
What are the things that will affect hair and hair growth?
- Lack of necessary vitamins/minerals
- Any alteration to the physiological state of the body
Where does hair not grow on the body?
- soles of feet
- palms of hands
How often is eyebrow/eyelash hair replaced?
every 4-5 months.
What is the technical name for eyelashes?
What are the three factors that affect hair and how hair behaves?
Up to what percentage of fine hair is cuticle?
up to 40%
Up to what percentage of coarse hair is cuticle?
up to 10-12%
What does it mean to say that hair behaves like the cuticle or cortex?
- behaves like the cuticle: more resistant to taking new shape
- behaves like the cortex: more pliable- holds shape better.
What is melanin?
the pigment that gives skin and hair it's color.
What are melanocytes?
pigment producing cells, located near the papilla, cells collect together to form bundles of melanosomes.
What are melanosomes?
bundle of melanocytes.
What is eumelanin and what color does is produce?
type of melanin: brown/black.
What is pheomelanin and what color does is produce?
type of melanin: red.
What is albinism and what is the term for a person with this condition?
- total lack of pigmentation in the hair and skin.