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28 Cards in this Set
- Front
- Back
Mutation in WNT10A? |
WNT is essential for placode formation. Loss of function of this gene leads to hypotrichosis, nail dystrophy, PPK and hidrocystomas.
1. Tricho-odonto-onycho-dermal dysplasia: oligodontia, dystropic nails, sparse hair
2. Schopf-Schulz-Passarge syndrome: they WNT through a PASSAGE, eyelid hidrocystomas, PPK, hypodontia, hypotrichosis |
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Just review these steps: |
0. undifferentiated epithelium- B catenin is the first signal from mesenchyme (dermis) to start the process. B catenin degradation is prevented by WNT.
1. Placode- small collection of cells that appear at 10-12 weeks in response to dermal signaling
2. Germ phase- SHH helps form dermal condensate
3. Peg phase- dermal condensate signals follicular epithelium (peg) to proliferate and grown down into dermis, dermal condensate becomes enveloped by follicular epithelial cells and dermal papillae is formed, SHH drives this
4. Bulbous peg phase- mature hair follicle is formed, under control of NOTCH1, bulbous b/c 3 bulges form: 1. highest is apocrine, 2. middle is sebaceous, 3. lowest is hair bulge where mm. attaches |
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What is Ambras syndrome? Gene defect? |
Congenital hypertrichosis-- terminal hairs at vellus follicle sites
mutation in TRPS1 |
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MOA of finasteride? |
blocks 5a reductase from converting testosterone to DHT (which increases TGFB1 in scalp and inhibits growth) |
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Mutations in K81, 83, 86? |
monilethrix (AD) |
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Mutation in monilethrix? |
AD- K81, 83, 86 AR- DESMOGLEIN 4 |
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Mutation in K75? |
PFB, loose anagen syndrome
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Mutation in PFB and loose anagen syndrome? |
K75 |
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Mutation in desmoglein 4? |
Monilethrix (AR) |
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List the layers of hair from outermost to innermost... |
1. connective tissue 2. outer root sheath 3. companion layer (not pictured) 4. Henle's layer (IRS) 5. Huxley's layer (IRS) 6. Cuticle (IRS) 7. Cuticle (shaft) 8. Cortex (shaft) 9. Medulla (shaft) |
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The outer root sheath is contiguous with the epidermis. How does it changes as it gets closer to the epidermis? Function? |
The ORS at the isthmus (deeper) has NO hyaline (only trichilemmal keratinization), the ORS at the infundibulum DOES have keratohyaline keratinization
ORS is continuously repopulated via K5, 14
Fx: transit nutrients and O2, stem cell reservoid, glycogen storage |
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Main differences between an Infundibular cyst and a Pilar cyst? |
Infundibular cyst (aka EIC), +trichohyaline keratinization, +granular layer, duh this comes from the infundibulum
Pilar cyst (aka trichilemmal cyst)- trichilemmal keratinization, NO trichohyaline granules, NO granular layer |
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What is the companion layer? |
between IRS and ORS, single cell thick, enables directional hair grown, has desmogleins 1 and 3 to anchor hair shaft into hair follicle |
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IRS is composed of what? |
Henle's --> Huxley's --> IRS cuticle
dossolves at sebaceous duct entry, so not present in infundibulum |
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Hair bulb consists of the critical line of Auber and the dermal papilla. What is the critical line of Auber. Which of these determines how thick our hair is? |
Auber- is the widest diameter of the hair bulb, highest mitotic activity
The thicker the dermal papilla, the thicker our hair |
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The hair shaft consists of what? |
cuticle, cortex, medulla |
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The medulla is only found in large terminal hairs How is it similar to the IRS? |
it contains CITRULLINE! |
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Which layer of the inner root sheath keratinizes first? |
Henle's |
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What are the layers of the inner root sheath? |
Henle's, Huxley's, cuticle |
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Area of the hair shaft where the most BCCs arise from? |
OUTER ROOT SHEATH |
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Where are hair melanocytes found? |
located in the hair bulb where they synthesize and transport melanin to shaft keratinocytes |
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Anagen: |
growth phase, root of hair is embedded deep in dermis, large and has pigment
1000 days (3-6 years)
80-90% of scalp hair
cyclosporine, minoxidil, PTH and estrogen receptor antagonists induce anagen |
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Catagen: |
regression phase, hair does not grow
10 days (2-3 weeks)
1% of follicles |
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Hair stem cells are in the: |
bulge |
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Telogen: |
resting phase, hair considered dead, will get pushed out by new hair growing in or will re enter anagen
100 days (3 months) |
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Control of hair growth: how fast? |
scalp hair grows at 1cm/month or 0.34mm/day
plucking of telogen hairs seems to advance onset of anagen |
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Auber's line in the hair bulb also plays a role in hirsuitism and miniturization, how? |
Influx from connective tissue sheath to dermal papillae leads to hirsuitism
Efflux from dermal papillae to connective tissue sheath leads to miniturization |
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As we age, we get increased levels of what to decrease hair growth? |
OLD: increased levels of WNT inhibitors (DKK and BMP2) |