Epidermis

Question 1

Epidermis:
Derived from__
Layers:

Answer 1

Epidermis:
Derived from ectoderm
Outermost layer of skin
Barrier function

Layers:
Stratum corneum/Cornified layer
Stratum granulosum/granular layer
Stratum spinosum/spinous layer
Stratum basale/basal layer

Question 2

Stratum basale

Answer 2

deepest layer, attached to basement membrane, contains keratinocyte stem cells

Basal stem cells (differentiates to a TA, then travels up to a SP)

Question 3

Stratum spinosum

Answer 3

composed of differentiating keratinocytes, in most of the epidermis, synthesize keratin

Question 4

Junctions of the epidermis

Answer 4

Tight junction (actins)
Adherens (actin)
Desmosome (IFs)

To basement membrane:
Focal adhesions and Hemidesmosomes

Question 5

Assembly of IFs

Answer 5

intermediate filaments

Keratin–> heterodimer –> Tetramer–> protofilament –> intermediate filament

Question 6

Stratum granulosum (granular layer)

Answer 6

Keratohyalin granules (filaggrin, involurcin, loricrin)

Lamellar granules (Odland bodies): Ceramides, cholesterol, Fatty acids, hydrolytic enzymes

Question 7

Stratum Corneum

Answer 7

Composed of corneocytes:
lack a nucleus/organelles are dead, held together by corneodesmosomes

Primary barrier of epidermis

Variable thickness: no stratum corneum (oral, genital and ocular mucosa). Thinnest: face, genitalia. Thickest palms soles

Question 8

Keratinization

Answer 8

process of keratinocyte migration and maturation

Average 28 days (14 basal to corneum, 14 corneum to shedding)

Proliferating layer (basal-layer, constant cell renewal by proliferation)

Differating layers (stratum spinosum, granulosum, corneum)

Spinosum- exits from cell cycle, reinforcement of the cytoskeleton

Stratum granulosum-lipid extrusion, expression of late differentiation markers (flaggarin and loricrin)

Corneum-Cornification (formation of cornified layers) and Desquamation (shedding of dead corneocytes)

Question 9

Bricks and mortar of stratum corneum

Answer 9

Keratinocyte has Keratinocyte granules (filaggrin, involucrin, loricrin, other protein). Lamellar granule (Ceramides, cholesterol, fatty acids, other lipid)

Keratinocyte–>corneocyte:
Mortar: lipid envelope
Bricks: Cornified envelope

Question 10

Pemphigus Vulgaris

Answer 10

Acquired, autoimmune bullous disease

Auto-antibodies to desmosomal proteins (desmoglein 1 and 3)

Intraepidermal blistering

Clinical features: flaccid, easily ruptured bullae, oral and mucosal lesion, positive Nikolsky’s sign

Treatment: prednisone, azathioprine, mycophenolate mofetil, rituximab

Question 11

Icthyosis vulgaris

Answer 11

Autosomal dominant genetic condition

Mutations in the profilaggrin gene (defective filaggrin protein)

Affects 1/250

Clinical features: fish scales (esp on shins), dry skin, hyperlinear palms

Associations: atopic dermatitis, allergic rhinitis, food allergises, asthma

Question 12

UVA vs UVB

Answer 12

UVA penetrates the dermis

UVB only the epidermis

Sun is the main source of UV
Highest levels of UV (10-4 and hig altitudes)

Can penentrate clouds and water and glass

Question 13

Sunscreen ingredients

Answer 13

Physical ingredients: Reflect and sctter UV light (titanium dioxide, zinc oxide)

Chemical sunscreen ingredients: absorb UV light (PABA, and -benzones)

Question 14

SPF

Answer 14

Sun protection Factor

MED: minimal erythema dose: amount of UVB time that causes skin redness after 24 hours

SPF= MEDprotected/MED unprotected

SPF only measures UVB protection!
Ideal: broadspectrum, water resistant, SPF 30

Question 15

Sunscreen application

Answer 15

Apply 15 minutes before sun exposure, apply generously (oz, every 2 hrs)

avoid the sun