Flashcards in 44-Skin as a Protective Barrier Deck (57)
1
Functions of skin
Fluid and electrolyte homeostasis
Protect from toxic substances
Protect from trauma
Thermoregulation
Metabolic functions
Protect from infection
Protect from UV light
2
What is keratinization
Process of cell maturation to form flexible protective barrier
3
Characteristics of keratinization
Genetically programmed
In post mitosis keratinocytes
Morphologic changes
Regulated by extrinsic and intrinsic factors
Vulnerable to alteration
4
The steps of epidermal differentiation
alterations of plasma membrane antigens and receptors
Degradation of organelles
Cellular dehydration
5
What is the stratum corneum
semipermeable barrier to water and electrolytes
Protects internal environment
6
structure of stratum corneum
bicompartment of hydrophilic protein cells (corneocytes) surrounded by hydrophobic intercellular lipid matrix
7
What are corneocytes
metabolically inert
enucleated cells formed from keratinocytes
8
What is the cornified envelope
Component of corneocytes, cross linked proteins catalyzed by transglutaminase 1
loricrin, involucrin, keratolinin
9
What are the proteins in the cornified envelope
loricrin, involucrin,keratolinin
10
What catalyzes the cornified envelope cross linked proteins
transglutaminase 1
11
What surrounds the cornified envelope
lipid envelope
12
What makes the intercellular lipid matrix
lamellar granules from keratinocytes organelles
13
Where are lamellar granules found
Between the granular layer and the stratum corneum
14
What do the lamellar granules do
Fuse with membrane and discharge lipid contents
15
What are the major membrane lipids of stratum corneum
ceramides
Impermeable to water
16
What do epidermal lipids do
form cement to hold corneocytes together
17
what is in lamellar granules/Orland bodies
lipids
18
What is in keratohyalin granules
protiens
19
Where are lamellar/Odland found
Upper spinous, layer, granular cornified layer interface
20
Where are keratohyalin granules found
Upper spinous layer,
Granular and cornified layers
21
Do lamellar/Odland have membranes
Yes, membrane bound
22
Do keratohyalin have membranes
No, not membrane bound
23
What is the function of lamellar/ Odland
deliver precursors of corneum lipids
Lipids accumulate in lamellar granules and fuse with plasma membrane to exocytose lipid to intercellular space
24
What is the function of keratohyalin granules
deliver free amino acids to corneum (filaggrin monomers)
Conversion of profilaggrin to filaggrin
25
What cannot pass through corneum
Polar or large molecules (MW > 800-1000)
26
How does corneum protect from trauma
Strong stratum corneum
Highly resistant cornified envelope
corneocytes are interdigitated
desmosomes
corneum is elastic
Low conductivity-protection from electrical and thermal damage
Nerve sensations
27
What is core body temp
37
28
What temps can skin vary between without damage
20-40
29
How does body thermoregulate
Blood vessel and eccrin glands
30
What does the body do in cold environment
Use sympathetic to contract vessel, decrease peripheral flow and conserve central body heat
31
What does body do in hot environment
Decrease sympathetic and dilate blood cells for heat loss
32
What controls eccrine sweat gland
Hypothalamus for cooling
33
Production of active vita. d
7 dehydrocholesterol converted to cholecalciferol in skin using UV light
Converted to 1, 25 dihydroxycholecalciferol in liver and kidney
34
What is the function of vita. d
Increase Ca absorption from GI
Increase CA reabsorption from kidneys
35
What are the structural mechanisms to protect from infection
Intact stratum corneum
Dryness to stop growth
desquamation to remove microbes
36
What do Langerhans cells do
Recognize foreign antigen and present to t cell to start immune response
Delayed hypersensitivity reactions
Interact with keratinocytes to secrete cytokines
37
What inflammatory cells are found in the dermis
lympho, histo, neutron, eosino, mast
38
What do sebaceous glands do
Secrete protein and lipids for antimicrobial
39
What does UV light cause
Sunburn, chronic photodamage, carcinogens
40
UVC
Shortest, absorbed by ozon
41
UVB
Middle, causes burns
42
UVA
Longest, causes tans
43
What are chromophores
Molecules path absorb radiant energy, usually in low energy state and get activated.
To return to ground state, must release absorbed energy
44
Ways for chromophore to release absorbed energy
Photochemical reaction
Photosensitized reaction
Release as heat
45
What is a photochemical reaction
Undergo chemical change to form photoproduct (DNA pyramidine)
46
What is a photosensitized reaction
Transfer of energy to another molecule
47
What are mediators of erythema
Histamine, prostaglandins, cytokines, lysosomal enzymes
48
What is tanning
A response to UV induced skin damage
49
What does UV light do to melanocytes
Increase number, size and dendrite branching
Increase melanin and malanosome synthesis
50
What is dermatoheliosis
Chronic photodamage
51
Characteristics of chronic photodamage
(dermatoheliosis)- aged appearance, wrinkles, telangiectasias
52
What are telangiectasias
Dilated blood vessels
53
What acts as a photoprotection
Melanin
by block, scatter, and absorb UV light, trap free radicals
54
Who is more at risk for skin cancer
Fair skin
55
What percent of UVB and UVA penetrate to basal layer
5-10 of UVB
50 of UVA
56
Facts about sunscreen
Do not block all UV, use higher SPF
Apply generous amount every few hours
Many do not block UVA
57