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FD9 > 7 - Biology of Hair Follicles > Flashcards

7 - Biology of Hair Follicles Flashcards

(61 cards)

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1
Q

Primary purpose of hair in humans

A

Influence social interactions

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2
Q

First hairs formed

A

Lanugo hairs

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3
Q

Lanugo hairs are shed

A

Between the 32nd and 36th weeks of gestation

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4
Q

Responsible for the nonrandom and symmetrical distribution of hair follicles over the body

A

Homeobox genes

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5
Q

Responsible for dorsal-ventral patterning

A

Engrailed (type of homeobox gene)

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6
Q

Thicker hair found in Asians is associated with

A

Increased activity of Edar

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7
Q

Stage 1 of hair follicle development

A

Epithelial placodes

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8
Q

Epithelial placodes first appear around

A

10 weeks of gestation

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9
Q

Drives the growth of the fully formed follicle

A

Dermal papilla

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10
Q

Necessary for establishing epithelial competence, a state in which the epithelial tissue had the potential to form a hair follicle

A

WNT/beta-catenin pathway

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11
Q

Y/N: Normally the beta-catenin pathway is active in the adult epidermis

A

No - inactive

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12
Q

Bone morphogenetic protein (promote/inhibit) follicle formation

A

Inhibit

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13
Q

BMP antagonist

A

Noggin

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14
Q

Gene deficient in basal cell nevus syndrome

A

Patched

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15
Q

Stage 2 of hair follicle development

A

Bulbous peg or hair bud

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16
Q

Proliferation of the worthless cells and lateral expansion of the follicular placode are regulated by

A

Shh

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17
Q

Deepest portion of the follicle peg forms a bulbous structure surrounding the dermal papilla and goes on to form the

A

Matrix of the hair follicle

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18
Q

The matrix of the hair follicle gives rise to (2)

A

Hair shaft

Inner root sheath

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19
Q

The outer root sheath forms two bulges

A

Superficial bulge - develops into the sebaceous gland

Deeper bulge - future sure of epithelial stem cells

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20
Q

A third bulge develops superficial to the sebaceous gland bud and gives rise to

A

Apocrine gland

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21
Q

First hairs formed

A

Lanugo hairs

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22
Q

Duration of _____ determines the length of hair

A

Anagen

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23
Q

Shape of the _____is thought to determine the shape of the hair

A

Inner root sheath

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24
Q

Outer root sheath in the infundibulum vs isthmus

A

Infundibulum: with granular layer
Isthmus: without granular layer (trichilemmal)

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25
Inner root sheath parts (outermost to innermost) (4)
Companion layer Henle layer Huxley layer Cuticle
26
Provides a slippage plane between the outer root sheath, which is stationary, and the inner root sheath
Companion layer
27
Some cells within the Huxley layer protrude through the Henle layer and attach directly to the companion layer
Fluegelzellen or wing cells
28
Cells are overlapping forming a “shingled roof” appearance
Inner root sheath cuticle
29
Critical for inner root sheath differentiation and lineage
GATA-3
30
Forms bulk of the hair shaft and contains melanin
Cortex
31
Receptor of keratinocyte growth factor, found in the matrix keratinocytes
FGF receptor 2
32
Differentiation of hair shaft cells is dependent on
Lef-1 | BMP receptor type 1a
33
Core of mesenchymally-derived tissue envelopes by the matrix epithelium
Dermal papilla
34
Produced by the anagen dermal papilla
Keratinocyte growth factor
35
Free nerve endings transmit
Pain
36
Lanceolate nerve endings detect
Acceleration
37
Merkel cells sense
Pressure
38
Pilo-Ruffini structures detect
Tension
39
The perifollicular sheath consists of
Inner basement membrane | Outer connective tissue sheath
40
Has the longest anagen of 2 years to more than 8 years
Scalp hair
41
_____ of scalp follicles are in anagen
90-93% Rest are in telogen
42
Average number of hairs on the scalp
100,000-150,000
43
Exogen comprises _____ of the telogen hair follicles
1%
44
An adult loses _____ hairs per day
50-100
45
Scalp hair growth rate
0.37-0.44 mm/day | 1 cm/month
46
Bulge cells comprise approximately _____ of the cells in the regenerated epidermis during wound reepithelialization
30
47
Y/N: Bulge cells do not normally move to the epidermis
Yes
48
Anagen can be divided into _____ stages
7
49
There is similarity between _____ and the early events of anagen
Wound healing
50
The onset of _____ is marked by cessation of the mitotic activity of the matrix cells and by the coordinated apoptosis in the cyclic portion of the hair follicle
Catagen
51
Y/N: Pigment production my melanocytes ceases after matrix cell proliferation stops.
No - before matrix cell proliferation stops
52
At the end of catagen, the dermal papilla becomes situated
Below the bulge at the lower portion of the isthmus
53
The migration of the dermal papilla from the subcutaneous fat to the dermis during catagen is necessary for continued follicle cycling. This is illustrated by the syndrome
Atrichia with papules
54
Increase in shedding of club hairs within weeks of the precipitating event
Immediate telogen release (too soon to be caused by follicles prematurely entering telogen from anagen
55
Several months could transpire between hair shedding and regrowth. This “lag period” is normally not present or is very short but often lasts months in patients with
Androgenetic alopecia
56
Melanocytes in the skin arise from (2)
Neural crest cells | Schwann cell progenitors
57
Commitment of neural crest cells to the melanocyte lineage is regulated by (2)
Pax3 | Microphthalmia transcription factors (Mitf)
58
Melanoblast migration into the dermis and epidermis are controlled by signaling mechanisms activated through
Endothelin receptor type B (Ednrb) C-kit receptor Mutated jn Hirschprung disease and piebaldism, respectively
59
Maintenance of melanocyte stem cells during hair follicle cycling is controlled by
TGF-beta | Notch
60
Melanocytes producing pigment are located in the
Hair bulb
61
Hair follicle melanocytes are maximally proliferative during
Early and midanagen

FD9 (108 decks)

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