44-Skin as a Protective Barrier

Question 1

Functions of skin

Answer 1

Fluid and electrolyte homeostasis
Protect from toxic substances
Protect from trauma
Thermoregulation
Metabolic functions 
Protect from infection
Protect from UV light

Question 2

What is keratinization

Answer 2

Process of cell maturation to form flexible protective barrier

Question 3

Characteristics of keratinization

Answer 3

Genetically programmed
In post mitosis keratinocytes
Morphologic changes
Regulated by extrinsic and intrinsic factors
Vulnerable to alteration

Question 4

The steps of epidermal differentiation

Answer 4

alterations of plasma membrane antigens and receptors
Degradation of organelles
Cellular dehydration

Question 5

What is the stratum corneum

Answer 5

semipermeable barrier to water and electrolytes

Protects internal environment

Question 6

structure of stratum corneum

Answer 6

bicompartment of hydrophilic protein cells (corneocytes) surrounded by hydrophobic intercellular lipid matrix

Question 7

What are corneocytes

Answer 7

metabolically inert

enucleated cells formed from keratinocytes

Question 8

What is the cornified envelope

Answer 8

Component of corneocytes, cross linked proteins catalyzed by transglutaminase 1
loricrin, involucrin, keratolinin

Question 9

What are the proteins in the cornified envelope

Answer 9

loricrin, involucrin,keratolinin

Question 10

What catalyzes the cornified envelope cross linked proteins

Answer 10

transglutaminase 1

Question 11

What surrounds the cornified envelope

Answer 11

lipid envelope

Question 12

What makes the intercellular lipid matrix

Answer 12

lamellar granules from keratinocytes organelles

Question 13

Where are lamellar granules found

Answer 13

Between the granular layer and the stratum corneum

Question 14

What do the lamellar granules do

Answer 14

Fuse with membrane and discharge lipid contents

Question 15

What are the major membrane lipids of stratum corneum

Answer 15

ceramides

Impermeable to water

Question 16

What do epidermal lipids do

Answer 16

form cement to hold corneocytes together

Question 17

what is in lamellar granules/Orland bodies

Answer 17

lipids

Question 18

What is in keratohyalin granules

Answer 18

protiens

Question 19

Where are lamellar/Odland found

Answer 19

Upper spinous, layer, granular cornified layer interface

Question 20

Where are keratohyalin granules found

Answer 20

Upper spinous layer,

Granular and cornified layers

Question 21

Do lamellar/Odland have membranes

Answer 21

Yes, membrane bound

Question 22

Do keratohyalin have membranes

Answer 22

No, not membrane bound

Question 23

What is the function of lamellar/ Odland

Answer 23

deliver precursors of corneum lipids

Lipids accumulate in lamellar granules and fuse with plasma membrane to exocytose lipid to intercellular space

Question 24

What is the function of keratohyalin granules

Answer 24

deliver free amino acids to corneum (filaggrin monomers)

Conversion of profilaggrin to filaggrin

Question 25

What cannot pass through corneum

Answer 25

Polar or large molecules (MW > 800-1000)

Question 26

How does corneum protect from trauma

Answer 26

``` Strong stratum corneum Highly resistant cornified envelope corneocytes are interdigitated desmosomes corneum is elastic Low conductivity-protection from electrical and thermal damage Nerve sensations ```

Question 27

What is core body temp

Answer 27

37

Question 28

What temps can skin vary between without damage

Answer 28

20-40

Question 29

How does body thermoregulate

Answer 29

Blood vessel and eccrin glands

Question 30

What does the body do in cold environment

Answer 30

Use sympathetic to contract vessel, decrease peripheral flow and conserve central body heat

Question 31

What does body do in hot environment

Answer 31

Decrease sympathetic and dilate blood cells for heat loss

Question 32

What controls eccrine sweat gland

Answer 32

Hypothalamus for cooling

Question 33

Production of active vita. d

Answer 33

7 dehydrocholesterol converted to cholecalciferol in skin using UV light Converted to 1, 25 dihydroxycholecalciferol in liver and kidney

Question 34

What is the function of vita. d

Answer 34

Increase Ca absorption from GI | Increase CA reabsorption from kidneys

Question 35

What are the structural mechanisms to protect from infection

Answer 35

Intact stratum corneum Dryness to stop growth desquamation to remove microbes

Question 36

What do Langerhans cells do

Answer 36

Recognize foreign antigen and present to t cell to start immune response Delayed hypersensitivity reactions Interact with keratinocytes to secrete cytokines

Question 37

What inflammatory cells are found in the dermis

Answer 37

lympho, histo, neutron, eosino, mast

Question 38

What do sebaceous glands do

Answer 38

Secrete protein and lipids for antimicrobial

Question 39

What does UV light cause

Answer 39

Sunburn, chronic photodamage, carcinogens

Question 40

UVC

Answer 40

Shortest, absorbed by ozon

Question 41

UVB

Answer 41

Middle, causes burns

Question 42

UVA

Answer 42

Longest, causes tans

Question 43

What are chromophores

Answer 43

Molecules path absorb radiant energy, usually in low energy state and get activated. To return to ground state, must release absorbed energy

Question 44

Ways for chromophore to release absorbed energy

Answer 44

Photochemical reaction Photosensitized reaction Release as heat

Question 45

What is a photochemical reaction

Answer 45

Undergo chemical change to form photoproduct (DNA pyramidine)

Question 46

What is a photosensitized reaction

Answer 46

Transfer of energy to another molecule

Question 47

What are mediators of erythema

Answer 47

Histamine, prostaglandins, cytokines, lysosomal enzymes

Question 48

What is tanning

Answer 48

A response to UV induced skin damage

Question 49

What does UV light do to melanocytes

Answer 49

Increase number, size and dendrite branching | Increase melanin and malanosome synthesis

Question 50

What is dermatoheliosis

Answer 50

Chronic photodamage

Question 51

Characteristics of chronic photodamage

Answer 51

(dermatoheliosis)- aged appearance, wrinkles, telangiectasias

Question 52

What are telangiectasias

Answer 52

Dilated blood vessels

Question 53

What acts as a photoprotection

Answer 53

Melanin | by block, scatter, and absorb UV light, trap free radicals

Question 54

Who is more at risk for skin cancer

Answer 54

Fair skin

Question 55

What percent of UVB and UVA penetrate to basal layer

Answer 55

5-10 of UVB | 50 of UVA

Question 56

Facts about sunscreen

Answer 56

Do not block all UV, use higher SPF Apply generous amount every few hours Many do not block UVA

Question 57

What ingredients block UVA

Answer 57

Parasol 1789, titanium dioxide, zinc oxide