Development and Structure of the Epidermis Flashcards
histological description of the epidermis
stratified squamous epithelium that contains keratinocytes
what type of tissue is the dermis
connective tissue
describe generally how the epidermis is formed embryologically
ectodermal cells form a single layer called the periderm, there is a gradual increase in cell layers and the periderm falls off
what layer is the dermis derived from
mesoderm
where do melanocytes originate
neural crest
what are the layers of foetal skin at 4 weeks (superficial to deep)
periderm -> basal layer -> dermis
what are the layers of foetal skin at 16 weeks (superficial to deep)
keratin layer -> granular layer -> prickle cell layer -> basal layer -> dermis
melanocytes migrate from the neural crest
when is skin development complete
26 weeks
what are the appendages of the skin
nails, hair, glands, mucosae
where are there 5 layers of the epidermis and what is this 5th layer called and where is it
palms and soles
stratum lucidum - between the keratin and granular layers
what other cell types are present in the epidermis
melanocytes, Langerhans cells and Merkel cells
what are the 4 epidermal layers from superficial to deep
keratin layer
granular layer
prickle cell layer
basal layer
what controls epidermal turnover
growth factors, hormones, cell death
describe the differentiation of keratinocytes
migrate from the basement membrane and continually regenerate the epidermis
takes roughly 28 days
describe the basal layer
1 cell thick, small cuboidal keratinocyte stem precursors many intermediate filaments very metabolically active - constantly undergoing mitosis anchored to dermis by basement membrane
describe the prickle cell layer
large polyhedral cells, 8-10 layers
some dendritic cells
desmosomes anchor the tightly packed keratinocytes
intermediate filaments connect to desmosomes
describe the granular layer
2-3 layers of flatter cells large keratinohyalin granules that contain filaggrin and involucrin proteins contains lamellar bodies high lipid content origin of cornified envelope
what layer are keratinocyte nuclei lost in
granular
what are lamellar bodies
processing and repository areas for lipids
describe the keratin layer
corneocytes (non-nucleated cell remnants) of keratin lineage overlap
contains insoluble cornified envelope
lamellar granules release lipids
tight waterproof barrier
describe the different mucosa in the oral mucosae
masticatory - keratinised for friction/pressure
lining mucosa - non-keratinised
specialised mucosa - tongue papillae for taste
what is the function of cytokeratin
cytokeratin is a fibrous intra-cellular protein that gives hair, skin and nails their tough, water-resistant properties
what are keratinocytes called when they become anucleauted
corneocytes
