Devo Lect 12 - Epidermis Flashcards Preview

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Flashcards in Devo Lect 12 - Epidermis Deck (21):
2

Epidermis and dermis from

From ectoderm and mesoderm respectively

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Malpighian cells

aka basal cells; stem cells in bottom of epidermis; 2 weeks to reach cornified layer then 2 weeks before shed

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Where does differentiation occurs in epidermis?

In the granular layer, keratin produced

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Keratin

Structural protein, released from keratin granules

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Transitional cells

After granular layer, protein synthesis decreasing, cells flattening out and dying

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Cornified layer

Dead cells on the outer surface, Loaded with keratin. Key for protection.

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Melanocyte

Pigment cell, in the epidermal layer but not from the ectoderm, it’s from the neural crest cells, produces melanosomes

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Growth factors involved in development of epidermis

TGFa: autocrine from basal cells, regulates their division; KGF: keratinocyte growth factor, paracrine, from dermal fibroblasts, regulates basal cell proliferation

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Psoriasis

Over-expression of TGFa; get thickened cornified layer, produced faster (like 2 days instead of 2 weeks)

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Psoriasis mouse

Transgenic test, gain of function, increased TGF-a expression

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Cutaneous appendages

hair, scales, feathers; interaction of ecto- and mesoderm; all made similarly

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Hair production

Interaction between ectoderm and mesoderm, change initiated. Ectoderm starts to protrude down, produces condensed mesoderm which becomes dermal papilla (base of shaft); ectoderm cells pack together, lots of keratin, die off, then get pushed outward; hair stem cells (bulb), sebaceous gland

14

Trichology

Study of hair

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Lanugo hair

Hairs developing in the fetus, shed just before birth, then normal hair development starts after birth

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Glabrous skin

skin that doesn’t have hair (ie palms)

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Vellus and terminal hairs

Fine hairs (like fingers) vs large hairs (head); affected by combination of growth factors

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Chemotherapy and hair

Chemo stops fast growing cells, hairs are some of the fastest in the body.

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Baldness

it’s a conversion from terminal hair to vellus hair, a reverse of youth (vellus to terminal ie beard); caused by dihydroxy testosterone (DHT), the hormone is changed as you age.

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Finasteride

drug that reverses baldness, it’s a steroid (potential side affects?); it’s a competitive inhibitor of the enzyme that converts testosterone to DHT, helps convert hairs back; originally made to help lower elevated testosterone from prostate cancer

21

Congenital universal hypertrichosis

Ambras syndrome; aka werewolf syndrome, terminal hairs all over, esp on face

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Hirsutism

hypertrichosis in women, like bearded lady; caused by abnormal androgen secretions