accessory structures HAIR

Question 1

what is hair

Answer 1

slender nonliving filament of keratinized cells growing from a tube in the skin called a HAIR FOLLICLE

Question 2

where is hair found

Answer 2

everywhere EXCEPT palms, soles, lips, nipple, parts of genitalia, and distal finger/toes

Question 3

divided in 3 zones along LENGTH

Answer 3

-shaft: above skin surface
-root: below skin surface
-hair bulb: swelling at the base in DERMIS (only living cells)

Question 4

divided in 3 layers in CROSS SECTION

Answer 4

-medulla: central axis
-cortex: bulk of hair
-cuticle: hair surface

Question 5

hair follicle

Answer 5

tube that extends into dermis

a) epithelial root sheath:
-extension of epidermis
-external part: stratum basale remains and supplies source of new epidermis
-internal part: pulled out when hair pulled out

b) dermal root sheath:
-part of dermis that surrounds epithelial root sheath

Question 6

hair bulb

Answer 6

bottom of root of hair

-DERMAL PAPILLA: dermis projects into bulb; blood is only source of nutrition for hair
-matrix: mitotically active cells above papilla
-hair growth center
-cells divide - daughter cells pushed
toward surface

Question 7

hair growth

Answer 7

1. growth stage:
   -matrix adds cells at base hair root and hair elongates
   -hair cells pushed upwards- become keratinized- die
2. rest stage:
   -matrix stops dividing- follicle atrophies- hair stops growing
   -hair falls out- new hair replaces old hair