Epidermis

Question 1

WHat is the function of the epidermis and what is it derived from?

Answer 1

• derived from ectoderm
• outermost layer of skin
• barrier function

Question 2

What are the layers of the epidermis?

Answer 2

stratum corneum/cornified layer

stratum granulosum/granular layer

stratum spinosum/spinosous layer

stratum basale/basal layer

Question 3

WHich layer of the skin is the stratum basale (basale layer)

Answer 3

deepest layer

attached to the basment membrane

contains keratinocyte stem cells

Question 4

What is te stratum spinosum (spoinous layer)?

Answer 4

• composed of differentiating keratinocytes
• in most parts of the body, makes up the epidermis
• synthesize keratin

Question 5

What are the 5 junctions of the epidermis?

Answer 5

tight junctions

adherens junctions

desmosomes

focal adhesions

hemidesmosomes

Question 6

What are the spine like features in this image?

Answer 6

Desmosomes connecting the keratinocyte! In the spinous layer!

Question 7

Describe the production of intermediate filaments from Keratin

Answer 7

• 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

Question 8

What are the 2 types of granules in the stratum granulosum (granular layer) and what macromolecues are within these granules?

Answer 8

• Keratohyalin granules-contain protein
  
  • Filaggrin
  • Involucrin
  • Loricrin
• Lamellar granules (Odland bodies)- lipid
  
  • ceramides
  • cholesterol
  • fatty acids
  • hydrolytic enzymes

Question 9

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?

Answer 9

• 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

Question 10

What is keratinization?

Answer 10

process of keratinocyte migration and maturation

28 days

stratum basale to stratum corneum=14 days

stratum to shedding =14 days

Question 11

How does keratinization work? WHat is another name for Keratinization?

Answer 11

Also called cornification

1. differentiation of stem cells into keratinocyte
2. Separation of keratinocyte from basale membrane
3. Keratinocyte migrates to skin surface and flattens out/loses water
4. Lamellar granules and keratohyaline granules start to form
5. keratinocyte loses cellular organelles and nucleus and releases its intracellular granules
6. keratinocyte becomes an anucleate corneocyte within the cornified envelope and is eventually shed via desquamation

Question 12

WHat is the lipid envelope of a coreocyte primarily composed of?

WHat is the protein/Cornified envelope primarily composed of?

Answer 12

Cornified/Protein=Filaggrin (bricks)

Lipid =Ceramide (mortar)

Question 13

How do you get Pemphigus Vulgaris and what is the mechanism of pathogenesis? What does Pemphigus Vulgaris cause?Intraepidermal blistering

Answer 13

• acquired
• autoimmune bullous disease
• auto-antibodies to desmosomal proteins
  
  • Desmoglobin 1 and 3
• Intraepidermal blistering

Question 14

What are the clinical features of Pemphigus vulgari and what are the possible treatments?

Answer 14

flaccid, easily ruptures bullae

oral and mucosal lesions

Nikolsky’s sign positive (skin rubs off easily)

Treatement: Prednisone, Azathioprine, Mycophenolate Mofetil

Rituximab

Question 15

How do you get Ichthyosis Vulgaris? What is the pathogenesis of disease?

Answer 15

• Autosomal dominant genetic condition
• caused by mutations in proflaggrin gene= defective filaggrin protein (which helps form the cornified layer)
• Affects 1 in 250

Question 16

What are the clinical features of Icthyosis Vulgaris and what are some associated problems?

Answer 16

Features: “fish scales” especially on shins, dry skin, hyperlinear palms

Associations: Atopic dermatitis, allergic rhinitis, food allergies, asthma

Question 17

WHat are the 3 different type fo UV light and the significance of each?

Answer 17

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

Question 18

WHat is UV light? What is the source and what cna it penetrate?

Answer 18

sun

highlest levels are from 10am-4pm

it is not visible light

can penetrate clouds, water and glass

Question 19

What are the functions fo the physcial and chemical ingredients of sunscreen? WHat are some exampls?

Answer 19

• 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

Question 20

What is SPF and how is it calculated?

Answer 20

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!

Question 21

How much more effective is SPF 60 to SPF 30?

Answer 21

just a little!

Question 22

What is the ideal sunscreen?

Answer 22

broad-spectrum (broad band, UVA and UVB)

water-resistant

SPF30 or above.

Question 23

When should you apply sunscreen? How much should you apply? and how often should you reapply?

Answer 23

• 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

Question 24

What else besides sunscreen should be a part of the photoprotective regimen?

Answer 24

avoid midday sun

seek shade

wear sun-protective clothing/hat

Question 25

Where in the body is the thickest stratum corneum?

Answer 25

palms and soles of feet

Question 26

What is mutated in ichthyosis vulgaris?

Answer 26

Profillaggrin

Question 27

How long is the process of keratinization?

Answer 27

28 days

Question 28

What layer of the epidermis are the keratinocyte stem cells located?

Answer 28

stratum basale