Hair Flashcards
Name the three types of hair and describe them.
- Lanugo- fine hairs shed late in gestation and in first months of life
- Vellus- fine hairs over face, trunk, and extremities
- Terminal- coarse, darker hairs of scalp, eyebrows, and eyelashes; postpubertal androgens switch to terminal hairs at other sites
How many hairs on scalp?
100,000 (more in blonde and fewer in red-hair)
Name follicular layers from outer to inner.
- glassy membrane –> outer root sheath –> inner root sheath (Henle hugs Huxley, cutely=cuticle) –> hair shaft (cuticle. cortex)–> medulla
Function of cuticle of hair?
- helps to keep hair intact
damage of cuticle of hair leads to____
- split ends (trichoptilosis)
Describe the hair cycle.
- Anagen is growth phase (Anogen Adds hair)
- Catagen is regression phase (cat eating the hair)
- Telogen (club hairs) is the resting phase
How long does each phase of hair cycle last?
- Anagen lasts 2-6 years
- Catagen lasts 2-3 weeks
- Telogen lasts 3 months
What percentage of hairs are in each phase of growth cycle at any given moment?
- Anagen= 85-90% (anagen-eighty five)
- Catagen= 1-2%
- Telogen= 10-15% (telogen-ten)
phase of active shedding of club hair between telogen and anagen is called _____
- Exogen
how many hairs do we lose in one day?
100
How fast does hair grow/day/month?
0.4mm/day, 1cm/month
What happens to melanocytes in hair matrix during Catagen phase?
- they apoptose
What phase of hair cycle do melanocytes produce pigment?
- only in Anagen (anagen–>adding pigment)
Hair follicle melanin unit is ____# of melanocytes and ____ keratinocytes
1 melanocyte: 5 keratinocytes
hair follicle stem resides in the ____ and contributes to tissue regeneration and hair cycling
- bulge
