IS: Hair Flashcards
Sparse body hair function:
sense when insects are on the skin before the bite/sting
Hair on the scalp guards that head against what?
physical trauma, heat loss, and sunlight
Nose hairs filter […] like lint and insects from the air we inhale.
large particles
Hair/[…] are flexible strands produced by hair […] and consist of largely of […] keratinized cells.
pili; follicles; dead
What are the two characteristics of hard keratin? Are they more dominant than soft keratin?
- tougher, more durable
- its individual cells do not flake off
hard is more dominant than soft
What are the chief regions of the hair?
- root
2. shaft
Shaft = flat/ribbon like
kinky hair
Shaft = oval
silky and wavy
Shaft = perfectly round
straight and coarse
What are the three concentric layers of kerantinized cells?
- medulla
- cortex
- cuticle
Medulla’s core consists of […] cells and […] spaces. The only part of the hair that contains […] (absent in fine hairs).
large; air; soft kertain
Where is the cortex? What does it consist of?
bulky layer that surrounds the medulla
consists of layer of flattened cells
What is the cuticles arrangement? What is it’s purpose?
a single layer of cells overlapping one another like shingles on a roof
separates neighboring hairs so the hairs does not mat
The outermost […] is the most heavily […] part of the hair.
cuticle; kerantinized
How are split ends created?
when cuticles wear away at the tip of the hair shaft– allowing keratin fibrils (cortex) and medulla to frizz
Hair pigment is made by […] at the […] of the hair follicle.
melanocytes; base
What is red hair pigmentation made by?
phenomelanin
When melanin production […] and air bubbles replace melanin in the hair […], hair turns […] or white.
decrease; shaft; gray
Hair follicles […] from the epidermis into the […] sometimes into the subcutaneous tissue.
fold down; dermis
The deep end of a follicle expands to form a …
hair bulb
What wraps around each hair bulb? What do they act as?
knot of sensory nerve endings called a hair follicle receptor/root hair plexus
act as sensitive touch receptors
Hair papilla:
dermal papillae that protrude into the hair bulb
What does papilla contain?
a knot of capillaries that supply nutrients to the growing hair and signals it to grow
If the hair papilla is destroyed…
follicle permanently stops producing hair
The wall of a hair follicle has two components:
- dermal component
2. epidermal component
What is the dermal component? What does it form?
peripheral connective tissue sheath (fibrous sheath)
forms the external layer of the follicle wall
Glassy membrane:
junction of the fibrous sheath and the epithelial root sheath
basement membrane of the follicle epithelium
What is the epidermal component?
epithelial root sheath
What are the two components of the epithelial root sheath? Define them.
- external root sheath: direct continuation of the epidermis
- internal root sheath: derived from the matrix cells
Hair […] because cells in the […] of the follicle divide rapidly. This makes up the […].
grows; bulb; hair matrix
Division of the hair matrix cells are replenished by […] that migrate down to the […] from a region closer to the skin surface called the […].
stem cells; bulb; hair bulge
What muscle cells are associated with each hair follicle?
arrector pili
Arrector pili:
“raiser of hair”
tiny, smooth muscles attached to hair follicles– contraction causes the hair to stand upright
T/F: The “hair raising” response is very useful to humans. Explain.
false– only animals to retain heat and protect themselves
What is the more important role of the arrector pili?
contractions forces sebum out of hair follicles to the skin surface– acts as a lubricant
Hairs can be classified as […] or […].
vellus; terminal
Where can you find pale/fine vellus hair?
body hair of children and adult females
Where can you find coarser, longer terminal hair?
eyebrows, eyelashes, scalp– after puberty also in the axillary and pubic regions
Terminal hairs grow in response to the […] effects of […].
stimulating effects; androgens
Growth cycles:
active growth phase and resting phase
What happens in the resting phase?
the matrix is inactive and the follicle shrinks somewhat
By age […] coarse terminal hair is replaced by […] and the hair becomes increasingly […].
60-65; vellus hairs; wispy
Male pattern baldness changes the response of…
hair follicles to androgens
