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Embryo Exam II > Lecture 13 - Dev of the Integument > Flashcards

Lecture 13 - Dev of the Integument Flashcards

1
Q

Periderm

A
  • Single layer of ectodermal cells

* Formed by end of first mont

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2
Q

Three-layered epidermis

A
  • Formed by end of third month
  • Basal (germinative) layer
  • Intermediate layer
  • Superficial peridermallayer
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3
Q

Intermediate layer

A

Stratum spinosum
Stratum granulosum
Loss of integrins attached to basal lamina
Inactivation of p63

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4
Q

Role of apoptosis

A
  • Postnatal layers of epidermis during sixth month

* Peridermal cells undergo apoptosis

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5
Q

Stratum granulosum

A

Interconnected by fillagrin

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6
Q

Stratum spinosum

A

Appearance of keratohyalin granules

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7
Q

Epidermal Ridges/Creases

A

fingerprints

by the end of the third month of gestation, fetuses have fingerprints

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8
Q

Immigrant Cells

A

Melanoblasts
Langerhans’ cells
Merkel cells

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9
Q

Melanoblasts:

A
  • From neural crest
  • Migrate into dermis and then into epidermis
  • Stain with HMB-45
  • Produce pigment by mid-pregnancy
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10
Q

Langerhans’ cells:

A
  • Derived from bone marrow

* Antigen-presenting cells

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11
Q

Merkel cells

A
  • From neural crest

* Slow-adapting mechanoreceptors

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12
Q

Origin of Dermal Cells

Dorsal surface of body

A

Mesenchyme from dermatome

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13
Q

Origin of Dermal Cells

Ventral and lateral surfaces of body

A

Mesenchyme from lateral plate mesoderm

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14
Q

Mesenchymal cells can develop into ___ cells under influence of ___.

A

Dermal Cells

Wnt

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15
Q

Dermal Cells

A

Loosely aggregated; Interconnected by tight junctions; Secrete thin watery matrix rich in glycogen and hyaluronic acid;
express Dermo1
can produce mesenchymal cells again, which give rise to fibroblasts

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16
Q

Origin of Dermal Cells

Cranial and anterior neck

A

Mesenchyme mostly from cranial neural crest

17
Q

Origin of Dermis

Trunk Dermis

A

From somatic dermatomes

•Aggregated mesenchymal cells develop tight junctions

18
Q

Limb Dermis

A

from lateral plate mesoderm

19
Q

face and anterior neck

A

neural crest

20
Q

Dermal-Epidermal Interactions

A
  • The underlying dermis influences the development of the epidermis and especially of the epidermal derivatives.
  • There is a reciprocal influence by the epidermis on the dermis.
21
Q

By the third month: (three things happen)

A

fibroblasts develop from mesenchymal cells.
•Collagens I and III are secreted.
•Elastic fibers are secreted

22
Q

Instructive Induction

A

one germ layer instructs another on how to differentiate

A: Ectoderm and mesenchyme are separated. Neither differentiates any farther.
B: Abdominal ectoderm is combined with sole mesoderm. Abdominal ectoderm differentiate as thickened skin typical of the sole.
C: Sole ectoderm and scalp mesoderm are combined. Ectoderm differentiates as scalp epidermis with hair.

23
Q

Epidermal Derivatives:

A
  • Hair
  • Nails
  • Mammary glands
24
Q

Commonalities: Epidermal Derivative

A
  • Development of these derivatives involves ectodermal-mesodermal interactions and inductions.
  • Hairs, nails, and mammary glands begin as epidermal down growths (ingrowths) into mesenchyme.
  • Ectoderm contributes to the hair follicle, hair shaft, sebaceous glands, nails, eponychium, hyponychium, and secretory and duct components of the mammary glands.
  • Mesenchyme contributes to the hair papilla, outer hair follicle and arrector muscles.
25
Q 
What roles do the following play in hair development and distribution? 
•Wnt-1 
•Wnt 11 
•BMP 
•Eda/Edar 
•Noggin 
•Dickkopf 
•Shh
A

Refer to Figure 9.8B-D and text.

26
Q

Induction of ectodermal placode (thickening):

A
  • Dermal induction
  • Wnt-11and FGF from mesoderm cause ectoderm to express Noggin
  • Eda from mesoderm causes ectoderm to express Edar
  • Edar and Noggin in ectoderm block BMP
  • Other Wnts act through β catenins
  • In interfollicular zones:
  • Dickkopf blocks Wnt
  • BMP inhibits follicle development
27
Q

Induction of dermal papilla:

A
  • Epidermal induction
  • Expression of Shhvia the signaling pathway involving Edar receptor stimulates formation of dermal papilla below epidermal placode.
28
Q

Induction of hair germ

A
  • Dermal induction
  • Various inducers from dermal papilla along with Shh and Cyclin D1 in epidermal placode stimulate further downgrowth of proliferation of epidermal placode.
  • Final differentiation of hair primordia involves Hox genes.
29
Q

Nails:

A

Refer to text and Figure 9.10.

30
Q

Mammary glands:

A

•Refer to text and Figures 9.12-9.14

Embryo Exam II (8 decks)

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