Skin development Flashcards
what types of cells comprise the epidermis?
keratinoytes, melanocytes, merkel cells and langerhans cells.
what are melanocytes derived from?
Neural crest
the first primordial hair follicles form on the eyebrows, upper lip and chin at what gestational age?
9-12 weeks
when does epidermal stratification occur?
8 weeks
what is required for epidermal stratification to occur?
TP63 expression
when do melanocytes, langerhan cells, and merkel cells migrate into the epidermis?
9-12 weeks
when does terminal differentiation wiht full stratification occur?
late second trimester
when in the epidermis similar to adult skin morphologically?
third trimester
When does epidermal melanin production start?
12-16 weeks
what markers do langerhan cell precursors express?
CD45, HLA-DR, CD1c. @ 13 weeks CD1a, langerin, and birbeck granules present
what directs the migration of melanocytes?
KIT and KIT ligand
when are melanocytes in the epidermis?
12 weeks
when does melanin production begin?
12-16 weeks
when are melanocytes fully functional and can transfer melanosomes to keratinocytes?
16-20 weeks
where is dermal mesenchyme of face and anterior scalp derived from?
neuroal crest ectoderm
where does dermal mesenchyme of the back orignate from?
dermomyotome of embryonic somite
where does dermal mesenchyme of extremities and ventral trunk arise from?
lateral plate mesoderm
what types of collagen are made by embryonic dermal cells?
Tyeps I, III, IV
what type of collagen is most common in embryonic dermal cells
type III
When does the dermis shift from non-scarring to scarring?
end of second trimester
when do fibroblasts appear in the dermis?
6-8 weeks
when does a distinct border between the epidermis and dermis occur
9 weeks
when does primordial vasculature form?
9-12 weeks
when does fat form in the subcutis?
16-18 weeks
