Trichology Flashcards
Trichology
The study of hair
Hair is chiefly composed of the protein..
Keratin
Where is hair?
Everywhere except: Soles of the feet Palm of hands Nipples Some areas of the genitals Mucous membrane of lips Navel
Where is hairs heaviest concentration?
Scalp Axillary organ Arms Legs On and around genitals
Hair growth occurs in cycles consisting of 3 phases..
Anagen (growth phase)
Catagen (transitional phases)
Telogen (resting phase)
Anagen
Most hair is growing at any given time, each hair spends several years in this phase
Catagen
Over a few weeks, hair growth slows and the hair follicle shrinks
Telogen (resting phase)
Over months, hair growth stops and the old hair detaches from the hair follicle. New hair begins the growth phase, pushing the old hair out.
What is the average rate of hir growth?
Around 1/2 inch per month and 5 inches per year
3 hair conditions
Alopecia areata
Dandruff
Dead lice
Alopecia Areata
Round patches of total hair loss, usually from the scalp, the cause of alopecia is unknown; the hair usually grows back.
Dandruff
Ongoing mild inflammation of the scalp, resulting in scaly skin that may be itchy and flake off. May also effect the ear and face.
Head lice
Tiny insects that live on the scalp and feed on the blood. Young children are more susceptible. Only spread through close contact
Hair DNA testing
Hair follicles contain DNA; hair can be tested to establish paternity, of as evidence in a crime investigation
Functions of the hair:
Protection- comparatively little protective value, however eyelashes, eyebrows, and hair inside nostrils and ears, and those around above oral orifices have useful functions
Sensory reception- all hair follicles are surrounded by sensory nerves, which respond to pressure on the shaft
Factors influencing hair growth:
- Race
- Heredity
- Age
- Body region
- Sex
- Stress level
- Hormones
- Medication
- Nutrition
- Season of the year
- Illness
Hair shaft
Cuticle, cortex, medulla
The part of the hair above the scalp or skin - emerging from the follicle out of the follicular pore
Cuticle
-Outer layer of hair
-Single layer of over lapping scales
-Translucent
FUNCTION:
Holds cortex together
Gives the hair its elasticity
Cortex
- melanin granules are found in this layer (melanin gives hair its colour)
- in absence of melanin the hair becomes dull, white, translucent
- composed of more than one layer of keratinized cells
Medulla
- Centre of hair shaft
- Composed of large, loosely connected horny cells
- May be absent, as in very fine hairs
Hair follicle
Outer root sheath: lies furthest from the hair shaft. A bulge in the outer root sheath at the intersection of attractor pili muscles, houses several types of stem cells, which supply the hair follicle with new cells.
Inner root sheath: lies closest to the hair shaft. Consists of 3 layers of cells. The cells interlink to help secure the hair within the hair follicle.
Hair root
- The part of the hair below the skin.
- the cells within the matrix reproduce new cells by mitosis
Hair bulb
- Inferior and swollen part of the root
- Base of the hair follicle where new hair develops
Nerve endings
A collar of sensory nerve endings from a single nerve encircles the follicle about 1/2 way between base of follicle and skin surface.
Different changes in hair growth
Puberty
Pregnancy
Menopause
Where is most hair pigment
In the cortex
Melanocytes
Cells which produce melanin.
If pigment has disappeared, hair looks grey or white. The amount of melanin is genetically determined.
Red hair
Red hair is the product of a separate gene.
True red heads possess only special red pigment.