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Zak, Embryology > Lecture 17: Development of Integument > Flashcards

Lecture 17: Development of Integument Flashcards

1
Q

What is cytodifferentiation?

A

Differentiation of a cell (becoming specialized)

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2
Q

What is histogenesis?

A

Development of tissues (involves different cell types)

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3
Q

What layer of skin is formed by the end of the first month and made of a single layer of ectodermal cells?

A

Periderm

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4
Q

When is the epidermis formed by and what layers does it consist of?

A

End of 3rd month.

Basal, intermediate, & superficial peridermal layers

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5
Q

What transcription factor initiates the formation of the 3 layered epidermis and where does it come from?

A

p63 from dermal mesenchyme

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6
Q

What inhibits p63 activation?

A

miR-203

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7
Q

What factors contribute to the formation of the basal layer of epidermis?

A

Keratins K5, K14, & K15

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8
Q

What factors contribute to the formation of the intermediate layer of epidermis?

A

Keratins K1 & K 10, loriccrin, & filaggrin

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9
Q

What allows the intermediate layer to form into the stratum spinosum and stratum granulosm?

A

Loss of integrins attached to basal lamina

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10
Q

What appears when the stratum granulosum is made?

A

Keratohyalin granules

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11
Q

The stratum corneum resembles flattened bags and the cells are interconnected via what protein?

A

Filaggrin

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12
Q

When do volar pads form on the palm and fingers?

A

Palm: 6.5 weeks
Fingers: 7.5 weeks

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13
Q

When do the volar pads begin to regress forming epidermal ridges?

A

10.5-11 weeks

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14
Q

Which epidermal cells undergo apoptosis?

A

Peridermal

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15
Q

What cells from the neural crest migrate into the dermis and then into the epidermis?

A

Melanobasts

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16
Q

What causes albinism?

A

Inability for melanocytes to convert tyrosine to melanin via the enzyme tyrosinase.

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17
Q

T/F: Albinos have normal number of melanocytes in their skin.

A

True

18
Q

What are Langerhans’ cells and where do they form

A

APC’s.

From bone marrow

19
Q

What are merkel cells and where are they from?

A

Slow adapting mechano-receptors.

From neural crest

20
Q

What forms the trunk dermis?

A

Somitic dermatomes

21
Q

What transcription factor causes the formation of somitic dermatomes from ectoderm?

A

Wnt

22
Q

What dermal marker is expressed by dermal cells?

A

Dermo 1

23
Q

By the 3rd month _____ develop from mesenchymal cells, _____ and _____ are secreted, and _____ are secreted from the somitic dermatomes.

A

Fibroblasts.
Collagens I and III
Elastic fibers

24
Q

What does limb dermis form from?

A

Lateral plate mesoderm

25
Q

What does the face and anterior neck form from?

A

Neural crest

26
Q

The mesenchyme contributes to what parts of the ectodermal-mesodermal interactions and inductions?

A

Hair papilla, outer hair follicle, arrector muscles, & support tissue of mammary glands

27
Q

What are the 4 stages of the hair cycle?

A

Anagen: growth
Catagen: folicular regression
Telogen: resting
Exogen: shedding

28
Q

What are the initial signaling molecules from the dermis?

A

Wnte-1–>Wnt-11.

FGF

29
Q

T/F: BMP’s are activated due to signaling from the dermis.

A

False, inactivated

30
Q

How is BMP inactivated?

A

Wnt-11 & FGF–>Noggin–>Inactivate BMP.

Eda–>Edar–>Inactivate BMP

31
Q

What signaling molecules inhibit hair follicle development in interfollicular zones?

A

BMP & dickkopf inhibit Wnt

32
Q

Edar stimulates _____ for what purpose?

A

Shh & Cyclin D1 for induction of dermal papilla from epidermal placodes

33
Q

T/F: BMP activates hair follicle development.

A

False, BMP suppresses development of hair follicle

34
Q

Induction of dermal papilla is done via _____ induction.

A

Epidermal

35
Q

Induction of hair germ is done via _____ induction.

A

Dermal

36
Q

What determines final differentiation of hair primordia?

A

Hox genes

37
Q

What is the first evidence of mammary gland development?

A

Appearance of two bands of ectodermal thickening called milk lines

38
Q

What role does neuregulin-3 play in mammary production?

A

It induce the formation of mammary placodes

39
Q

What role does Tbx-3 play in mammary production?

A

Marks the location for neuregulin-3 to be expressed, marking mammary locations

40
Q

What do PTH, BMP-4, and Msx-2 do in terms of mammary production?

A

PTH stimulates increased sensitivity of mesenchymal cells to BMP-4. BMP-4 stimulates further down growth and expression of Msx-2 which inhibits hair follicle growth around nipple

41
Q

What is testicular feminization syndrome?

A

Lack of testosterone receptors in males that makes them develop a female phenotype

Zak, Embryology (25 decks)

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