Bafl Exam 2: Biology Of Hair And Nails

Front 1

Mutation in WNT10A?

Back 1

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

Front 2

Just review these steps:

Back 2

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

Front 3

What is Ambras syndrome? Gene defect?

Back 3

Congenital hypertrichosis-- terminal hairs at vellus follicle sites

mutation in TRPS1

Front 4

MOA of finasteride?

Back 4

blocks 5a reductase from converting testosterone to DHT (which increases TGFB1 in scalp and inhibits growth)

Front 5

Mutations in K81, 83, 86?

Back 5

monilethrix (AD)

Front 6

Mutation in monilethrix?

Back 6

AD- K81, 83, 86

AR- DESMOGLEIN 4

Front 7

Mutation in K75?

Back 7

PFB, loose anagen syndrome

Front 8

Mutation in PFB and loose anagen syndrome?

Back 8

K75

Front 9

Mutation in desmoglein 4?

Back 9

Monilethrix (AR)

Front 10

List the layers of hair from outermost to innermost...

Back 10

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)

Front 11

The outer root sheath is contiguous with the epidermis. How does it changes as it gets closer to the epidermis? Function?

Back 11

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

Front 12

Main differences between an Infundibular cyst and a Pilar cyst?

Back 12

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

Front 13

What is the companion layer?

Back 13

between IRS and ORS, single cell thick, enables directional hair grown, has desmogleins 1 and 3 to anchor hair shaft into hair follicle

Front 14

IRS is composed of what?

Back 14

Henle's --> Huxley's --> IRS cuticle

dossolves at sebaceous duct entry, so not present in infundibulum

Front 15

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?

Back 15

Auber- is the widest diameter of the hair bulb, highest mitotic activity

The thicker the dermal papilla, the thicker our hair

Front 16

The hair shaft consists of what?

Back 16

cuticle, cortex, medulla

Front 17

The medulla is only found in large terminal hairs How is it similar to the IRS?

Back 17

it contains CITRULLINE!

Front 18

Which layer of the inner root sheath keratinizes first?

Back 18

Henle's

Front 19

What are the layers of the inner root sheath?

Back 19

Henle's, Huxley's, cuticle

Front 20

Area of the hair shaft where the most BCCs arise from?

Back 20

OUTER ROOT SHEATH

Front 21

Where are hair melanocytes found?

Back 21

located in the hair bulb where they synthesize and transport melanin to shaft keratinocytes

Front 22

Anagen:

Back 22

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

Front 23

Catagen:

Back 23

regression phase, hair does not grow

10 days (2-3 weeks)

1% of follicles

Front 24

Hair stem cells are in the:

Back 24

bulge

Front 25

Telogen:

Back 25

resting phase, hair considered dead, will get pushed out by new hair growing in or will re enter anagen

100 days (3 months)

Front 26

Control of hair growth: how fast?

Back 26

scalp hair grows at 1cm/month or 0.34mm/day

plucking of telogen hairs seems to advance onset of anagen

Front 27

Auber's line in the hair bulb also plays a role in hirsuitism and miniturization, how?

Back 27

Influx from connective tissue sheath to dermal papillae leads to hirsuitism

Efflux from dermal papillae to connective tissue sheath leads to miniturization

Front 28

As we age, we get increased levels of what to decrease hair growth?

Back 28

OLD: increased levels of WNT inhibitors (DKK and BMP2)