Lecture 17: Development of Integument

Question 1

What is cytodifferentiation?

Answer 1

Differentiation of a cell (becoming specialized)

Question 2

What is histogenesis?

Answer 2

Development of tissues (involves different cell types)

Question 3

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

Answer 3

Periderm

Question 4

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

Answer 4

End of 3rd month.

Basal, intermediate, & superficial peridermal layers

Question 5

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

Answer 5

p63 from dermal mesenchyme

Question 6

What inhibits p63 activation?

Answer 6

miR-203

Question 7

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

Answer 7

Keratins K5, K14, & K15

Question 8

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

Answer 8

Keratins K1 & K 10, loriccrin, & filaggrin

Question 9

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

Answer 9

Loss of integrins attached to basal lamina

Question 10

What appears when the stratum granulosum is made?

Answer 10

Keratohyalin granules

Question 11

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

Answer 11

Filaggrin

Question 12

When do volar pads form on the palm and fingers?

Answer 12

Palm: 6.5 weeks
Fingers: 7.5 weeks

Question 13

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

Answer 13

10.5-11 weeks

Question 14

Which epidermal cells undergo apoptosis?

Answer 14

Peridermal

Question 15

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

Answer 15

Melanobasts

Question 16

What causes albinism?

Answer 16

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

Question 17

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

Answer 17

True

Question 18

What are Langerhans’ cells and where do they form

Answer 18

APC’s.

From bone marrow

Question 19

What are merkel cells and where are they from?

Answer 19

Slow adapting mechano-receptors.

From neural crest

Question 20

What forms the trunk dermis?

Answer 20

Somitic dermatomes

Question 21

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

Answer 21

Wnt

Question 22

What dermal marker is expressed by dermal cells?

Answer 22

Dermo 1

Question 23

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

Answer 23

Fibroblasts.
Collagens I and III
Elastic fibers

Question 24

What does limb dermis form from?

Answer 24

Lateral plate mesoderm

Question 25

What does the face and anterior neck form from?

Answer 25

Neural crest

Question 26

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

Answer 26

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

Question 27

What are the 4 stages of the hair cycle?

Answer 27

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

Question 28

What are the initial signaling molecules from the dermis?

Answer 28

Wnte-1-->Wnt-11. | FGF

Question 29

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

Answer 29

False, inactivated

Question 30

How is BMP inactivated?

Answer 30

Wnt-11 & FGF-->Noggin-->Inactivate BMP. | Eda-->Edar-->Inactivate BMP

Question 31

What signaling molecules inhibit hair follicle development in interfollicular zones?

Answer 31

BMP & dickkopf inhibit Wnt

Question 32

Edar stimulates _____ for what purpose?

Answer 32

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

Question 33

T/F: BMP activates hair follicle development.

Answer 33

False, BMP suppresses development of hair follicle

Question 34

Induction of dermal papilla is done via _____ induction.

Answer 34

Epidermal

Question 35

Induction of hair germ is done via _____ induction.

Answer 35

Dermal

Question 36

What determines final differentiation of hair primordia?

Answer 36

Hox genes

Question 37

What is the first evidence of mammary gland development?

Answer 37

Appearance of two bands of ectodermal thickening called milk lines

Question 38

What role does neuregulin-3 play in mammary production?

Answer 38

It induce the formation of mammary placodes

Question 39

What role does Tbx-3 play in mammary production?

Answer 39

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

Question 40

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

Answer 40

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

Question 41

What is testicular feminization syndrome?

Answer 41

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