Devo Lect 12 - Epidermis

Question 2

Epidermis and dermis from

Answer 2

From ectoderm and mesoderm respectively

Question 3

Malpighian cells

Answer 3

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

Question 4

Where does differentiation occurs in epidermis?

Answer 4

In the granular layer, keratin produced

Question 5

Keratin

Answer 5

Structural protein, released from keratin granules

Question 6

Transitional cells

Answer 6

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

Question 7

Cornified layer

Answer 7

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

Question 8

Melanocyte

Answer 8

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

Question 9

Growth factors involved in development of epidermis

Answer 9

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

Question 10

Psoriasis

Answer 10

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

Question 11

Psoriasis mouse

Answer 11

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

Question 12

Cutaneous appendages

Answer 12

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

Question 13

Hair production

Answer 13

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

Question 14

Trichology

Answer 14

Study of hair

Question 15

Lanugo hair

Answer 15

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

Question 16

Glabrous skin

Answer 16

skin that doesn’t have hair (ie palms)

Question 17

Vellus and terminal hairs

Answer 17

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

Question 18

Chemotherapy and hair

Answer 18

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

Question 19

Baldness

Answer 19

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.

Question 20

Finasteride

Answer 20

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

Question 21

Congenital universal hypertrichosis

Answer 21

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

Question 22

Hirsutism

Answer 22

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