UV Exposure Flashcards
WHat are the divisions of the UV spectrum
UVA (320 - 400 nm)
UVB (290 - 320 nm)
UVC (200 - 290 nm)
What is the most potent of all UVR?
UVC (200 - 290 nm)
- is abs by DNA, RNA, and proteins and is lethal to epidermal cells
- ** OZONE FILTERS OUT UVC COMPLETELY (well is supposed to…)
The ozone is important for our protection from
UVC and VVB
i.e. UVC should not be able to penetrate atmosphere and very little UVB should
What type of light causes sunburn?
UVB
** hinted to know this
Window glass filters out wavelengths less than _____. What is the significance of this?
320
ie. UVB filtered
SPF is based of off UV__
B
What type of light is responsible for “photo aging”
UVA
*UVB is more efficient at it but there is a higher conc of UVA + it penetrates deeper
Factors that modify composition and intensity of UVR at earths surface
Coud Cover Time of day Atmosphere Reflection (surface) Season Altitude Latitude Solar flare
95% of UVR reaching earth’s surface is ____ and the remaining is ____
95% = UVA 2-5% = UVB
UVA or UVB penetrates skin more deeply
UVA (even though it has the least amt of energy/bigger wavelength)
What surfaces reflects more than avg?
water, sand, FRESH SNOW
T or F: cloud cover protects you from UVR
F: it scatters it but does not abs it but you can still get UVB/burns
What type of UVR would hit vessels in the dermis
UVA
What is an “action spectrum”
certain reaction caused by a specific wavelength
What are chromophores
molecules that abs UVR to determine action spectrum responses
What is the major UVB chromophore in skin?
DNA
** hinted to know this
What is the action spectrum that causes burns? Used for the treatment of psoriasis?
300 nm
310 nm
** not imp to know number but should know that diff wavelengths have different effects/action spectrums
What are the skin phototypes?
types I-VI
I = always burn and never tans
VI = always tans and rarely burns
What are acute effect of UVR on skin?
“IT DIED” from a sunburn
Inflammation Tanning DNA damage Immunomodulation Epidermal Hyperplasia vit D synthesis
Why are sunburns... Red? Hot? Swollen? Painful? Itchy?
red = vasodilation Heat = increased blood flow swelling = secondary to vasopermeability Pain = cytokines Itchy = cytokines
What are the “sunburn cells” (aka the ones damaged by acute UVR)
keratinocytes
What are the differences between immediate tanning response and delayed tanning response?
Causes?
Time frame?
protection?
immediate is caused by UVA and delayed is UVB
immediate is due to oxidation and redistribution of existing melanin and delayed is due to increased melanin synthesis and transfer
immediate fades w/in 1 hr and delayed is visible after 72 hrs and last for weeks
immediate is not protective and delayed is photoprotective
What are the chronic effects of UVR on skin
photoaging and photo-carcinogenesis
Histological changes with chronic UVR on skin?
dermis is more blue bc collagen and elastin is damaged
How is chronological aging of skin different than photoaging of skin?
chronologic = smooth, pale, finely wrinkled
photo= dry, deep wrinked, inelastic, leathery, irregular pigmentation, telangiectasias
solar lentigines
“age spot” due to chronic UVR exposure
Poikiloderma
reticulate hyperpigmentation, telangiectasia and mild atrophy
cyst and comedone formation
assc with chronic UVR
when seen with yellow thickening of skin with nodules = Favre-Racouchot syndrome
DNA is damaged mostly by UVA or UVB
UVB
*bases abs photons
What are DNA photoproducts
dimers formed by covalent binding of 2 adjacent pyrimidines (C and T)
- cyclobutane dimers
- 6, 4 photoproducts
What are the innate defense mechanisms against UVR?
stratum corneu, reflects UVR melanin abs UVR Nucleotide excision repain apoptosis Tumor supressor genes (p53, PTCH)
Heritable disease characterized by marked sensitivity to UV radiation, see evidence of photo damage much earlier in life (freckles, wrinkles, skin atrophy)
xeroderma pigmentosum
What causes XP?
defect in DNA repair mech (usually a step in NT excision repair)
WHat are consequences/effects of XP?
- get skin cancers very early in live (<10 yo)
- Eyes: cataract, corneal scaring, dryness, aging and degeneration
- CNS: neurologic degeneration
Describe the effect of UVR on the immune system
ImmunoSUPPRESSIVE effects:
- langerhan cells disappear from kin following mild sunburn
- lymphocytes are also sensitive
What skin conditions can be treated with light? Why?
psoriasis
cutaneous lymphoma
eczema
due to immunosuppresive effects of UVR
What type of UVR do tanning beds primarily emit?
UVA
**5X the amt/unit time than solar UVA
T or F: tans from a tanning bed is just as protective as one from UVB sunlight
F: 10x less protective
