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TAS Dermatology > Embryology > Flashcards

Embryology Flashcards

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Dermatology Board Prep flashcards
1
Q

What distinct layers is the skin divided into? -

A
  • Epidermis

- Dermis

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2
Q

What cell lines are the layers of the skin derived from?

A

Ectoderm and mesoderm

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3
Q

What is the surface ectoderm?

A

The initial single layered epithelium that covers the developing embryo

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4
Q

What happens to the surface ectoderm?

A

It proliferates and forms a layer of surface epithelium, the periderm

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5
Q

What is the role of the periderm?

A

It covers the developing epidermis until the cornified cell layer is formed

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6
Q

When does the embyronic epidermis begin to stratify?

A

Around 8 weeks’ estimated gestational age

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7
Q

What is the stratification of the embryological epidermis followed by?

A

Cornification

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8
Q

What happens in cornification?

A

‘Dead’ keratinocytes are held together with proteins and lipids

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9
Q

Until when is the fetal skin highly permeable?

A

Week 19

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10
Q

What is amniotic fluid volume mostly determined by in early gestation?

A

Fetal surface area

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11
Q

What happens to the skin at 19 weeks?

A

Keratinisation occurs, and the skin becomes impermeable

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12
Q

What happens when differentiation of the skin is complete?

A

The periderm detaches from the underlying epidermis

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13
Q

What happens to the remnants of the periderm?

A

They form the vernix caseosa

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14
Q

What is the vernix caseosa?

A

The greasy coat that protects the skin in utero from amniotic fluid

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15
Q

When is the fetal epidermis morphologically similar to adult skin?

A

By the mid third trimester

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16
Q

When does the epidermis acquire full barrier function?

A

A few weeks after birth

17
Q

What cell line are melanocytes derived from?

A

Ectoderm

18
Q

Where do melanocytes migrate to and from?

A

From the neural tube to the epidermis

19
Q

When are melanocytes fully functional?

A

The second trimester

20
Q

What happens to active melanocytes present throughout the dermis during embryonic development?

A

Most migrate to the epidermis or undergo apoptosis by the time of birth

21
Q

What happens if melanocytes fail to reach their proper location in the epidermis and are entrapped in the dermis at the time of birth?

A

It leads to the presentation of congenital dermal malnocytosis (Mongolian blue spot)

22
Q

What happens to Mongolian blue spots?

A

They resolve spontaneously with time

23
Q

What is often a feature of skin conditions that are a result of genetic abnormalities in the epidermis and/or its appendages?

A

They follow a distribution pattern

24
Q

Why do skin conditions resulting from genetic abnormalities often follow a distribution pattern?

A

Represents migration patterns of epidermal cells during embyronic development

25
Q

What is it called when skin conditions caused by genetic abnormalities follow a distribution pattern?

A

Blaschko’s lines

26
Q

What do Blaschko’s lines represent?

A

A manifestation of cutaneous mosacism

27
Q

When does cutaneous mosaicism occur?

A

When 2 or more genetically different populations of cells exist side by side within the skin

28
Q

What are the typical patterns of cutaneous mosaicism?

A
  • V-shaped on upper spine
  • S-shaped on abdomen
  • Linear on arms and legs
  • Spiral on scalp
  • Vertical in mid-face
29
Q

Give 4 patterns of cutaneous mosaicism

A
  • Narrow bands of Blaschko
  • Large bands of Blaschko
  • Chequerboard pattern
  • Phylloid pattern (leaf-like)
30
Q

What conditions cause narrow bands of Blaschko?

A
  • Incontinentia pigmenti

- Epithelial naevi, e.g. inflammatory linear verrucous epidermal naevus, hypomelanosis of Ito

31
Q

What condition can cause large bands of Blaschko?

A

McCune-Albright syndrome

32
Q

What conditions can cause chequerboard pattern?

A
  • Becker naevus

- Vascular malformation (port wine stain)

33
Q

What condition can cause phylloid pattern?

A

Mosaic trisomy 13

TAS Dermatology (5 decks)

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