Flashcards in Devo Lect 12 - Epidermis Deck (21)
Epidermis and dermis from
From ectoderm and mesoderm respectively
aka basal cells; stem cells in bottom of epidermis; 2 weeks to reach cornified layer then 2 weeks before shed
Where does differentiation occurs in epidermis?
In the granular layer, keratin produced
Structural protein, released from keratin granules
After granular layer, protein synthesis decreasing, cells flattening out and dying
Dead cells on the outer surface, Loaded with keratin. Key for protection.
Pigment cell, in the epidermal layer but not from the ectoderm, it’s from the neural crest cells, produces melanosomes
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
Over-expression of TGFa; get thickened cornified layer, produced faster (like 2 days instead of 2 weeks)
Transgenic test, gain of function, increased TGF-a expression
hair, scales, feathers; interaction of ecto- and mesoderm; all made similarly
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
Study of hair
Hairs developing in the fetus, shed just before birth, then normal hair development starts after birth
skin that doesn’t have hair (ie palms)
Vellus and terminal hairs
Fine hairs (like fingers) vs large hairs (head); affected by combination of growth factors
Chemotherapy and hair
Chemo stops fast growing cells, hairs are some of the fastest in the body.
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.
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side affects?); it’s a competitive inhibitor of the enzyme that converts testosterone to DHT, helps convert hairs back; originally made to help lower elevated testosterone from prostate cancer
Congenital universal hypertrichosis
Ambras syndrome; aka werewolf syndrome, terminal hairs all over, esp on face