Epidermis Flashcards
keratinocytes
majority of cells in epidermis
confer structural properties
corneocytes
end product of keratinization
anucleate cells that are shed from skin surface
lines of Blaschko
the linear and whorled pattern of migration that keratinocytes follow during embyrogenesis
linear epidermal nerves
variant of mole that follows lines of Blaschko and may develop inflammation and itching
epidermis layers
stratum basale: cubical cells, prolif function, hemidesm.
stratum spinosum: as cells migrate towards surface they lose water and become flattened, some keratohyaline and lamellar granules present, Langerhans cells, desmo
stratum granulosum: 2-3 cells thick, keratohyaline and lamellar granules
stratum corneum: anucleate cells, varying thickness
desmoglein
transmembrane linking protein in desmosomes
desmoglein 1: entire epidermis, concentrates in upper layers
desmoglein 3: basal layer
keratohyaline granules
contain profilaggrin (composed of filaggrin) and keratin filaments
filaggrin: promotes aggregation and stabilization of intermediate filaments in cornified layer
lamellar granules
aka: Odland bodies
contain lipids, free sterols, hydrolases, ceramics
barrier function and role in apoptosis
hydrolases: contribute to normal desquamation by disrupting intercellular cohesion
ceramides: assist with proper cellular organization
keratin
intermediate filament that comprises the cytoskeleton
alpha helical structures (type I-acidic and II-basic)
Type I and II assemble into heteropolymers –> align to make keratin filaments which insert into desmo
keratization
enlargement and flattening of keratinocytes as they migrate towards skin
cornified envelope forms from keratin filament parallel assembly and cross linking of proteins
release lamellar granules –> hydrophobic layer
organelles degrade
apoptosis
natural moisturizing factors (NMF)
free AA, lactic acid, urea, salts
hygroscopic (attract water) –> epidermis pliability
xerosis
dry, rough, scaly skin, sometimes itching
decrease in intercellular lipids and NMF, failure of adherent bods of st. corn. to break down, dehydration of corneocytes
exogenous causes : dry climate, excess exposure to hot water, exposure to detergents/soaps
endogenous causes: atopy, ichthyosis vulgaris, renal insuff, lipid lowering meds, malnutrition
transit time from basal to granular layer
12-14 days
*cells in cornified layer take extra 12-14 to desquam
atrophy
results from decreased cell prolif
thinning of skin
hyperplasia
increase in skin thickness
acanthosis: inc. cell prolif in s. spin.
hyperkeratosis: thickening of s. corn from inc. production of corneocytes or reduced desquam
lichenification: thickening of s. spin. and corn. in response to repeated scratching and rubbing –> leathery and hyper pigmented skin
ichthyosis vulgaris (IV)
disorder of cornification
dry skin w/ white, adherent scales fish scales
favors trunk and extremities
retention hyperkeratosis from failure of signals to trigger corneocytes shedding
auto dom w/ variable expression
often improves w/ age
atopic triad association
may have keratosis pilaris
keratosis pilaris
follicular retention hyperkeratosis overlying hair follicles of extensors and butt
palmoplantar keratoderma (PPK)
hyperkeratosis of palms and soles
auto dom and rec
keratin mutations –> abnorm pairing of type I and II
diffuse: thick, yellow plaques of entire palm, sole, erythema border, excess sweating common
focal: hyperkeratosis on pressure pts
punctate: hyperkeratotic papules and nodules
treatment: topical moisturizers and humectants
atopic dermatitis
aka: eczema
part of atopic triad
genetic influence
filaggrin defects
psoriasis
inflam disease–> shortened cell turnover time/inc. prolif. (4 days basal to gran)
red plaques, thick and adherent scale, nail changes
staphylococcal scalded skin syndrome (SSSS)
malaise, irritability, fever, skin pain
cutaneous erythema starts at head then generalizes
flaccid bullae
caused by exotoxin (ETA and ETB target desmo 1)
inc. risk for:
emollients
moisturizer
lotions= least hydrating
creams
ointments=most hydrating
humectants
pull water into cells
e.g. ammonium lactate and urea creams
