Epidermis Flashcards
WHat is the function of the epidermis and what is it derived from?
- derived from ectoderm
- outermost layer of skin
- barrier function
What are the layers of the epidermis?
stratum corneum/cornified layer
stratum granulosum/granular layer
stratum spinosum/spinosous layer
stratum basale/basal layer
WHich layer of the skin is the stratum basale (basale layer)
deepest layer
attached to the basment membrane
contains keratinocyte stem cells
What is te stratum spinosum (spoinous layer)?
- composed of differentiating keratinocytes
- in most parts of the body, makes up the epidermis
- synthesize keratin
What are the 5 junctions of the epidermis?
tight junctions
adherens junctions
desmosomes
focal adhesions
hemidesmosomes
What are the spine like features in this image?
Desmosomes connecting the keratinocyte! In the spinous layer!
Describe the production of intermediate filaments from Keratin
- Keratins are a-helical proteins that make up the intermediate filaments of skin
- heterodimerization of a type I and type II forms a heterodimer
- the 2 heterodimers form a tetramer that is then further organized into keratin intermediate filaments
- intermediate filaments connect to desmosomes and hemidesmosomes to form the cytoskeleton network of the epidermis
What are the 2 types of granules in the stratum granulosum (granular layer) and what macromolecues are within these granules?
- Keratohyalin granules-contain protein
- Filaggrin
- Involucrin
- Loricrin
- Lamellar granules (Odland bodies)- lipid
- ceramides
- cholesterol
- fatty acids
- hydrolytic enzymes
What is the stratum Corneum composed of and what is its function? WHere do we find it and how is it different at these location?
- composed of corneocytes (which are keratinocytes that become corneocytes) that lack a nucles and organelles (dead) and are held together by corneodesmosomes
- primary barrier of epidermis
- Variable thickness
- no stratum corneum: oral, genital, ocular mucos
- thinnest: face, genital
- thickest: palms, soles
What is keratinization?
process of keratinocyte migration and maturation
28 days
stratum basale to stratum corneum=14 days
stratum to shedding =14 days
How does keratinization work? WHat is another name for Keratinization?
Also called cornification
- differentiation of stem cells into keratinocyte
- Separation of keratinocyte from basale membrane
- Keratinocyte migrates to skin surface and flattens out/loses water
- Lamellar granules and keratohyaline granules start to form
- keratinocyte loses cellular organelles and nucleus and releases its intracellular granules
- keratinocyte becomes an anucleate corneocyte within the cornified envelope and is eventually shed via desquamation
WHat is the lipid envelope of a coreocyte primarily composed of?
WHat is the protein/Cornified envelope primarily composed of?
Cornified/Protein=Filaggrin (bricks)
Lipid =Ceramide (mortar)
How do you get Pemphigus Vulgaris and what is the mechanism of pathogenesis? What does Pemphigus Vulgaris cause?Intraepidermal blistering
- acquired
- autoimmune bullous disease
- auto-antibodies to desmosomal proteins
- Desmoglobin 1 and 3
- Intraepidermal blistering
What are the clinical features of Pemphigus vulgari and what are the possible treatments?
flaccid, easily ruptures bullae
oral and mucosal lesions
Nikolsky’s sign positive (skin rubs off easily)
Treatement: Prednisone, Azathioprine, Mycophenolate Mofetil
Rituximab
How do you get Ichthyosis Vulgaris? What is the pathogenesis of disease?
- Autosomal dominant genetic condition
- caused by mutations in proflaggrin gene= defective filaggrin protein (which helps form the cornified layer)
- Affects 1 in 250
What are the clinical features of Icthyosis Vulgaris and what are some associated problems?
Features: “fish scales” especially on shins, dry skin, hyperlinear palms
Associations: Atopic dermatitis, allergic rhinitis, food allergies, asthma
WHat are the 3 different type fo UV light and the significance of each?
UVC= filtered out by ozone, not likely to cause damage
UVB= penetrate epidermis, most likely to cause redness of sunburn
UVA= penetrate into the dermis, most likely to cause damage to skin, associated with age
WHat is UV light? What is the source and what cna it penetrate?
sun
highlest levels are from 10am-4pm
it is not visible light
can penetrate clouds, water and glass
What are the functions fo the physcial and chemical ingredients of sunscreen? WHat are some exampls?
- physical= reflect and scatter UV light
- ex: titanium dioxide, zinc oxide (most protective and better if you have sensitive skin, less reactive)
- chemical= absorb UV light
- ex: PABA, oxybenzone, avobenzone
What is SPF and how is it calculated?
SPF= Sun Protection Factor
MED=minimal erythema dose (MED) =minimum amout of UVB that causes skin redness at 24 hrs.
SPF= MEDprotected/MEDunprotected
***only UVB protection!
How much more effective is SPF 60 to SPF 30?
just a little!
What is the ideal sunscreen?
broad-spectrum (broad band, UVA and UVB)
water-resistant
SPF30 or above.
When should you apply sunscreen? How much should you apply? and how often should you reapply?
- apply 15 minutes before sun exposure
- apply generously: 1 ounce (shot glass) for adult
- Reapply every 2 hours
- 40-80 minutes if swimming, sweating, and after towel drying
What else besides sunscreen should be a part of the photoprotective regimen?
avoid midday sun
seek shade
wear sun-protective clothing/hat
Where in the body is the thickest stratum corneum?
palms and soles of feet
What is mutated in ichthyosis vulgaris?
Profillaggrin
How long is the process of keratinization?
28 days
What layer of the epidermis are the keratinocyte stem cells located?
stratum basale
