Flashcards in Photobiology Deck (54)
What is the wavelength of UVR?
100-400nm; 5% of solar radiation
Wavelengths less than what wavelength do not penetrate the earth's atmosphere and what are these called?
290nm do not penetrate because of the ozone, called UVC and it can be lethal if it does
What light is between 290-320nm? What filters them out? What is this spectrum referred to as?
UVB; window glass filters out; sunburn spectrum; SPF testing based on this
What spectrum is UVA? Does it penetrate glass? How deep does it penetrate? What is it responsible for?
320-400nm; least potent and does penetrate glass but it does penetrate deeper than UVB so it is responsible for photo aging.
List some modifications in UVR on Earth.
Elevation, atmosphere, latitude, reflection, clouds, solar flare, season, time of day
How much does the ozone block?
Almost all <300nm
What is the percentage of light that is UVA that reaches the earth's surface?
95-98% which means the remaining percent is UVB and UVC blocked completely
How much % increase is seen in UVR with each 1000 feet increase in altitude?
How much do most surfaces reflect?
How much does water reflect?
How much does sand reflect?
How much does fresh snow reflect?
What does cloud cover do to UVR?
Scatters but doesnt absorb
What happens when sunlight hits the skin?
Some reflected, some absorbed in epidermis and dermis by DNA, some penetrates deeper
What is the reaction to a given wavelength called?
How is action spectrum determined?
Properties of molecule that initiates the response: chromophore
*****What is the major UVB chromophore in the skin?*****
DNA (urocanic acid, armoatic amino acid)
What is responsible for the majority of the effects of UVR on skin?
What do acute and chronic responses to UVR depend on?
What do skin types I-VI vary in?
Susceptibility to burning, ability to tan, and risk of skin cancer (pretty much goes from ginger/albino to black/brown skin)
What are some of the acute effects of UVR on skin?
Inflammation(sunburn), immunomodulation, tanning, epidermal hyperplasia, Vitamin D synthesis, DNA damage (apoptosis or repair)
What is sunburn mostly due to?
What is erythema from sunburn the result of?
What is heat of a sunburn the result of?
Increased blood flow
What is swelling of sunburn due to?
What is pain/pruritis of a sunburn due to?
Release of cytokines
When does hyperkeratosis and acanthosis happen in a cell that has been sunburned?
72 hours after sunburn
What are the two types of suntans?
Immediate and delayed
What is the immediate tan response caused by?
UVA and visible light, fades within an hour, due to oxidation and redistribution of existing melanin