Mss 08: Epidermis

Front 1

What are the general functions of the skin?

Back 1

- Barrier protection
- Thermoregulation
- Sensation
- Immunologic defense

Front 2

What is the outermost layer of the skin? What is it derived from?

Back 2

Epidermis - derived from ectoderm

Front 3

What are the layers of the Epidermis from outer to inner?

Back 3

- Stratum Corneum / Cornified Layer
(Stratum Lucidum / Translucent Layer - only in palms and soles)
- Stratum Granulosum / Granular Layer
- Stratum Spinosum / Spinous Layer
- Stratum Basale / Basal Layer

Front 4

What is the deepest layer of the epidermis?

Back 4

Stratum Basale / Basal Layer

Front 5

What is the Stratum Basale attached to?

Back 5

Basement membrane

Front 6

What kind of cells are found in the Stratum Basale? Functions?

Back 6

- Keratinocyte stem cells (SC) responsible for maintenance of epidermis - divides into a daughter stem cell and a transient amplifying cell (TA)
- TA cell undergoes cell divisions before separating from BM and moves up to join Stratum Spinosum
- Also contains melanocytes - produce melanin (pigment)

Front 7

What kind of cells are found in the Stratum Spinosum? Functions?

Back 7

- Most of the keratinocytes of skin - differentiating and synthesizing keratin
- Langerhans cells - antigen-presenting cells localized to skin

Front 8

What kind of junctions occur between the keratinocytes in the Stratum Spinosum?

Back 8

Keratinocytes held together by desmosomes (also gap junctions, adherens junctions, and tight junctions help w/ communication and adhesion)

Front 9

What is the function of Desmosomes?

Back 9

Connect keratinocytes and their keratin intermediate filament network

Front 10

In most parts of the body, what makes up most of the epidermis?

Back 10

Stratum Spinosum

Front 11

What are Keratins? Types?

Back 11

- α-helical proteins that make up intermediate filaments of skin
- Type I (acidic) and Type II (basic)

Front 12

How do keratins form intermediate filaments?

Back 12

- Heterodimerization of type I (acidic) and type II (basic) keratins
- Two heterodimers form a tetramer
- Further organized into intermediate filaments

Front 13

What is the function of the keratin intermediate filaments?

Back 13

Connect to desmosomes and hemidesmosomes to form the cytoskeleton network of the epidermis

Front 14

What is the layer superficial to the Stratum Spinosum?

Back 14

Stratum Granulosum

Front 15

What is found in the Stratum Granulosum?

Back 15

- Flattened keratinocytes - losing nucleus and organelles
- Keratohyaline granules and Lamellar granules

Front 16

What is in the Keratohyalin granules? Function?

Back 16

- Filaggrin
- Involucrin
- Loricrin
- Important for formation of cornified envelope

Front 17

What is in the Lamellar granules? Function?

Back 17

- AKA Odland bodies
- Ceramides
- Cholesterol
- Fatty Acids
- Hydrolytic Enzymes
- Present in upper layer of Stratum Spinosum, but not secreted until granular layer
- Form lipid barrier of cornified layer; hydrolytic enzymes promote desquamation of the cornified layer

Front 18

What is the layer superficial to the Stratum Granulosum?

Back 18

- In palms and soles: Stratum Lucidum
- All others: Stratum Corneum

Front 19

What is found in the Stratum Corneum?

Back 19

Corneocytes: lack nucleus and organelles (dead)

Front 20

What holds the Corneocytes together in the Stratum Corneum?

Back 20

- Corneodesmosomes
- Filaggrin (from Keratohyalin granules)
- Lipids (from Lamellar granules)

Front 21

What is the thickness of the Stratum Corneum?

Back 21

Variable:
- None: oral, genital, and ocular mucosa
- Thinnest: face, genitalia
- Thickest: palms, soles

Front 22

What is the primary barrier of the epidermis?

Back 22

Stratum Corneum

Front 23

What is keratinization and how long does it last?

Back 23

- Process of keratinocyte migration and maturation
- Avg. 28 days:
- Stratum basale to stratum corneum - 14 days
- Stratum corneum to shedding - 14 days

Front 24

Where does cell renewal and proliferation of keratinocytes occur?

Back 24

Stratum Basale

Front 25

Where doe cells exit from cell cycle and act to reinforce the cytoskeleton?

Back 25

Stratum Spinosum

Front 26

Where do cells express late differentiation markers (eg fillagrin and loricrin) and extrude lipids?

Back 26

Stratum Granulosum

Front 27

Where do cells cornify (form cornified envelopes) and desquamate (shed dead corneocytes0?

Back 27

Stratum Corneum

Front 28

What forms the "bricks" and "mortar" of the corneocyte?

Back 28

- Mortar: lipid envelope
- Bricks: cornified envelope

Front 29

What are the steps of keratinization / cornification?

Back 29

1. Differentiation of stem cells into keratinocytes and separation from BM
2. Keratinocyte migrates to skin surface and flattens out, losing its water content
3. Lamellar granules and keratohyaline granules start to form
4. Keratinocyte becomes anucleate w/in cornified envelope
5. Shed during process of desquamation

Front 30

What are some disorders of the epidermis?

Back 30

- Pemphigus Vulgaris
- Ichthyosis Vulgaris

Front 31

How do you get Pemphigus Vulgaris? Who is most likely to get it?

Back 31

- Acquired
- Autoimmune disease
- Rare, but mainly affects elderly

Front 32

What causes Pemphigus Vulgaris?

Back 32

- Auto-antibodies to desmosomal proteins (Desmoglein 1 and 3)
- Weakened desmosomes leads to intraepidermal blistering

Front 33

What are the clinical features of Pemphigus Vulgaris?

Back 33

- Flaccid, easily ruptured bullae (quickly turn into erosions)
- Oral and mucosal lesions
- Nikolsky's sign positive (if you rub on fragile area of skin you can rub skin off - lateral shear pressure causes sloughing)

Front 34

How do you treat Pemphigus Vulgaris?

Back 34

- Immunosuppressive medications (prednisone, azathioprine and mycophenolate mofetil)
- Rituximab - monoclonal Ab against B cells - used recently too

Front 35

How do you get Ichthyosis Vulgaris? What is the cause?

Back 35

- Autosomal dominant
- Mutation in profillaggrin gene (defective filaggrin protein)
- 1 in 250 people

Front 36

What are the clinical features of Ichthyosis Vulgaris?

Back 36

- Ichthyosis means fish scale
- Large scales, especially on extremities, specifically shins
- Extremely dry skin
- Hyperlinear palms

Front 37

What other conditions is Ichthyosis Vulgaris associated with?

Back 37

- Atopic dermatitis
- Allergic rhinitis
- Food allergies
- Asthma

Front 38

What condition is associated with the following symptoms?
- Flaccid blisters that quickly turn into erosions
- Mucosal lesions (mouth, nose, genitals)
- Nikolsky's sign (rub on skin causes sloughing)

What is the cause and what should you do?

Back 38

- Pemphigus Vulgaris
- Caused by auto-antibodies agains Desmoglein 1 and 3
- Tx: immunosuppressive meds (prednisone, azathioprine, mycophenolate mofetil, or rituximab)

Front 39

What condition is associated with the following symptoms?
- Fish scales (especially on shins)
- Extremely dry skin
- Hyperlinear palms

What is the cause?

Back 39

- Ichthyosis Vulgaris
- Mutations in profilaggrin

Front 40

What is the wavelength of UV light?

Back 40

200-400 nm:
- UVC: 200-280 nm
- UVB: 280-320 nm
- UVA: 320-400 nm
(shorter than visible light)

Front 41

What are the characteristics of UVC light?

Back 41

- 200-280 nm
- Absorbed by ozone, very little reaches earth's surface

Front 42

What are the characteristics of UVB light?

Back 42

- 280-320 nm
- Penetrates the epidermis and superficial dermis
- Primarily responsible for erythema and sunburn

Front 43

What are the characteristics of UVA light?

Back 43

- 320-400 nm
- Penetrates through epidermis and into dermis
- Causes tanning and photoaging

Front 44

What types of cancer is UV radiation associated with?

Back 44

- Basal cell carcinoma
- Squamous cell carcinoma
- Melanoma

Front 45

What diseases are exacerbated by UV light?

Back 45

- Systemic lupus erythematosus
- Cutaneous porphyrias

Front 46

What are the types of sunscreen? How do they work?

Back 46

- Physical sunscreen: reflects and scatters UV light (ex: titanium dioxide and zinc oxide)
- Chemical sunscreen: absorbs UV light and emits heat (ex: PABA, oxybenzone, avobenzone)

Front 47

What does SPF mean? What does it measure?

Back 47

- Sun Protection Factor - measure of protection from UVB exposure
- SPF = MED_protected / MED_unprotected
- MED = minimum amount of UVB that causes skin redness at 24 hours

Front 48

What are the characteristics of a good sunscreen?

Back 48

- Broad spectrum
- Water resistant
- SPF 30 or greater
- 15 minutes prior to sun exposure
- 1 oz (shot glass) to cover entire body)

Front 49

How often should you reapply sunscreen?

Back 49

- Every 2 hrs
- More frequently when sweating or swimming