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Dermatology Board Prep > DERM (01) Cutaneous Basic Science > Skin development > Flashcards

Skin development Flashcards

1
Q

what types of cells comprise the epidermis?

A

keratinoytes, melanocytes, merkel cells and langerhans cells.

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2
Q

what are melanocytes derived from?

A

Neural crest

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3
Q

the first primordial hair follicles form on the eyebrows, upper lip and chin at what gestational age?

A

9-12 weeks

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4
Q

when does epidermal stratification occur?

A

8 weeks

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5
Q

what is required for epidermal stratification to occur?

A

TP63 expression

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6
Q

when do melanocytes, langerhan cells, and merkel cells migrate into the epidermis?

A

9-12 weeks

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7
Q

when does terminal differentiation wiht full stratification occur?

A

late second trimester

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8
Q

when in the epidermis similar to adult skin morphologically?

A

third trimester

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9
Q

When does epidermal melanin production start?

A

12-16 weeks

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10
Q

what markers do langerhan cell precursors express?

A

CD45, HLA-DR, CD1c. @ 13 weeks CD1a, langerin, and birbeck granules present

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11
Q

what directs the migration of melanocytes?

A

KIT and KIT ligand

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12
Q

when are melanocytes in the epidermis?

A

12 weeks

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13
Q

when does melanin production begin?

A

12-16 weeks

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14
Q

when are melanocytes fully functional and can transfer melanosomes to keratinocytes?

A

16-20 weeks

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15
Q

where is dermal mesenchyme of face and anterior scalp derived from?

A

neuroal crest ectoderm

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16
Q

where does dermal mesenchyme of the back orignate from?

A

dermomyotome of embryonic somite

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17
Q

where does dermal mesenchyme of extremities and ventral trunk arise from?

A

lateral plate mesoderm

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18
Q

what types of collagen are made by embryonic dermal cells?

A

Tyeps I, III, IV

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19
Q

what type of collagen is most common in embryonic dermal cells

A

type III

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20
Q

When does the dermis shift from non-scarring to scarring?

A

end of second trimester

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21
Q

when do fibroblasts appear in the dermis?

A

6-8 weeks

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22
Q

when does a distinct border between the epidermis and dermis occur

A

9 weeks

23
Q

when does primordial vasculature form?

A

9-12 weeks

24
Q

when does fat form in the subcutis?

A

16-18 weeks

25
Q

when does mature thickness of dermis occur with dermal ridges present?

A

20 weeks

26
Q

when does mature thickness of dermis occur with dermal ridges present?

A

20 weeks

27
Q

what two overal structures make up the DEJ?

A

lamina lucida and lamina dense

28
Q

what types of collagen are present in the lamina lucida?

A

XVII and IV

29
Q

what types of collagen are present in the lamina dense?

A

IV

30
Q

when do epidermal placodes induce dermal papilla formation?

A

18-20 weeks

31
Q

when is hair canal fully formed?

A

18-20 weeks

32
Q

when do hairs start cycling between anagen, catagen, and telogen?

A

24-28 weeks

33
Q

what signalling molecule is important for telogen to anagen transition?

A

sonic hedghog

34
Q

what is the down stream mediator of WNT signalling?

A

beta catenin

35
Q

there are two parts ot the superior bulge pair in the hair follicle. What one si the more superifical one?

A

the sebaceous gland

36
Q

there are two parts ot the superior bulge pair in the hair follicle. Which one is the more inferior one?

A

insertion point for the arrector pili muscle

37
Q

when does nailbed demarcation occur?

A

8-10 weeks

38
Q

when does proximal hail fild form?

A

12-13 weeks

39
Q

when does nail plate form and cover the nail bed completely?

A

17-20 weeks

40
Q

when does toenail formation start?

A

4 weeks after fingernails (12-14 weeks)

41
Q

when does the eccrine gland begin formation

A

10 weeks

42
Q

where does eccrine gland formation begin?

A

on the palms and soles

43
Q

when does the eccrine primordia bud down and glands begin to develop?

A

14-16 weeks

44
Q

when does apocrine gland formation begin?

A

22 weeks

45
Q

when does sebaceous gland formation start?

A

13-16 weeks

46
Q

where are keratinocyte stem cells located?

A

bulge region of the hair follicle and base of rete ridges of interfollicular epidermis

47
Q

how long does complete renewal of epidermis take?

A

40-56 weeks

48
Q

what helps control blood flow to the fingers (involved in hot and cold and resulting blood shunting)?

A

glomus body

49
Q

what type of structures consists of endothelial cells attached to basement membrane w/o associated pericytes or smooth muscle?

A

lymphatic

50
Q

basement membrane of both the epidermis and cutnaeous blodo vessels are composed of what tyep of collagen

A

type IV

51
Q

what type of collagen is most abundant in the dermis?

A

type I (80%), collagen III makes up 10%

52
Q

in the axillary and anogenital regions the outer root shieath froms 3 not 2 bulges. What is the most likely thing to develop from the most superifical bulge?

A

apocrine

53
Q

What skin structures are derived from the ectoderm?

A

Epidermis, adnexal structures, merkel cells, melanocytes (neural crest), and nerves (neuroectoderm)

54
Q

What skin structures arise from the mesoderm?

A

fibroblasts, Langerhans cells, vessels, and inflammatory cells

DERM (01) Cutaneous Basic Science (4 decks)

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