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Dermatology > photobiology: sun and the skin > Flashcards

photobiology: sun and the skin Flashcards

(79 cards)

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1
Q

what is the range of UVC?

A

200-290nm

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2
Q

Wavelengths less than ______ do not penetrate atmosphere to reach earth’s surface

A

290nm

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3
Q

what is the most potent UVR

A

UVC

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4
Q

when produced artificially, what type of damage does UVC cause

A

UVC is absorbed by DNA, RNA and proteins and can be lethal to viable epidermal cells

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5
Q

UVB =

A

290-320nm

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6
Q

320nm is upper limit of most_________ wavelengths reaching earth’s surface

A

erythemogenic (sunburn spectrum)

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7
Q

Window glass filters out wavelengths < ______nm

A

320

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8
Q

which UVR is referred to as sunburn spectrum and is most active in producing photochemical reactions in skin

A

UVB

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9
Q

SPF is based on testing against this waveband

A

UVB

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10
Q

UVA =

A

UVA = 320 to 400nm

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11
Q

what is the least potent of all the UVRs but also penetrates glass?

A

UVA

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12
Q

which UVR is thought to be responsible for photoaging?

A

UVA

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13
Q

t/f. UVA Penetrates deeper than UVB and thought to be largely responsible for “photoaging”

A

true

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14
Q

Factors that modify composition and intensity of UVR at Earth’s surface :

A 
Atmosphere
Latitude
Altitude
Surface reflection
Cloud cover –modulates, does not protect from sun
Solar flare activity
Time of day 
Season
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15
Q

Ozone blocks almost all wavelengths < _____nm from reaching earths surface

A

300

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16
Q

95% to 98% of UVR reaching earth’s surface is _____1__

Remaining 2 to 5% is __2____

A
  1. UVA

2. UVB

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17
Q

t/f UVC is completely blocked by ozone

A

true

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18
Q

what are three modifiers of UVR

A

altitude, surface reflection, cloud cover

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19
Q

With each 1000 foot increase in altitude

_______increase in UVR

A

4%

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20
Q

Most surfaces reflect ________UVR

Water 7%, sand 25%, fresh snow up to 80%

A

< 5% UVR

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21
Q

____________

Scatters UVR but does not absorb it

A

cloud cover

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22
Q

what happens to sunlight when it hits the skin?

A

some is reflected
some is absorbed in the epidermis and dermis by DNA, proteins and other substances in the skin
some penetrates the tisues and it is dissipated(felt as heat)

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23
Q

KNOW: what are the three major UVB chromophores in skin?

A

DNA
urocanic acid
aromatic amino acids

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24
Q

t/f. UVA chromophores are less well understood.

A

true

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25
which wavelength is responsible for the majority of the effects of UVR on the skin?
UVB
26
how to the four skin phototypes Type I(pale) - IV(dark) vary?
vary in: 1. susceptibility to burning 2. ability to tan 3. risk of skin cancer
27
name 6 acute effects of UVR on the skin
``` inflammation (sunburn) immunomodulation tanning epidermal hyperplasia vitamin D photosynthesis DNA damage(apoptosis and cell cycle arrest to repair) ```
28
what is sunburn mostly due to?
UVB
29
what is the mechanism of redness(erythema)?
vasodilation
30
heat felt in sunburn is from ____
increased blood flow
31
in sunburn, Pain and pruritus due to release of ____________`
cytokines
32
t/f IFN is released when you have a sunburn
true
33
what are some of the histological changes that occur after sunburn?
1. damaged keratinocytes = sunburn cells = keratinocytes that have undergone apoptosis 2. inflammation 3. intercellular edema 4. perivascular edema 5. hyperkeratosis, acanthosis after 72 hours
34
define hyperkeratosis
hyperplasia of the stratum corneum
35
defien acanthosis
diffuse epidermal hyperplasia
36
what causes the immediate tanning response?when does it begin?
caused by UVA and visible light | begins during radiation, is maximal immediately afterward
37
how long does the immediate tanning response last?
fades within an hour
38
mech of immediate tanning response?
oxidation and redistribution of existing melanin
39
does the immediate tanning response protect against UVB?
NO!
40
Delayed tanning response caused by _______
UVB
41
when is delayed tanning response visible?
Gradual, becomes visible after about 72 hours, lasts for weeks
42
mechanism of delayed tanning response
Increased melanin synthesis and increased transfer of melanosomes to keratinocytes
43
does delayed tanning response provide photoprotection
Increased melanin synthesis and increased transfer of melanosomes to keratinocytes
44
name two chronic effects of UVR on skin?
1. photoaging | 2. photocarcinogenesis (basal cell and squamous cell carcinomas, melanoma)
45
smooth, pale, finely wrinkled skin with benign growth describes ____
chronologic aging
46
dry, deeply wrinkeld, inelastic, leathery atrophic skin with telangiectasias(dilated BVs), irregular pigmenation (ephelides, solar lentigo, hypopigmentation), comedone and cyst formation, actinic keratoses and malignancies, benign growths all describe_______
chronologic aging
47
t/f. UVB is 20-50 times more efficient at photo aging
true
48
t/f in photoaging: UVA is present in greater concentrations, is capable of deeper penetration and more dermal damage
true
49
Both UVB and UVA irradiation result in changes of photoaging
true
50
how does DNA damage by UVA occur?
Damage occurs from direct absorption of photons by bases of DNA
51
how are DNA photoproducts produced?
DNA photoproducts are dimers formed by covalent binding of two adjacent pyrimidines in same polynucleotide chain
52
what are two DNA photoproducts
cyclobutane dimers | 6.4 photoproducts
53
What happens if UV-induced DNA damage is not efficiently repaired?
UV- signature mutations
54
what are defense mechanisms against UVR at the stratum corneum?
reflection
55
function of melanin in protection against UVR?
absorption
56
tumor suppressor genes that help protect from DNA induced damage?
p53, patched, CDKN2A(p16)
57
DNA repair pathways, apoptosis
know just as more defense mechanisms against UVR
58
what is xeroderma pigmentosa?
heritable disease marked by sensivity to UV radiation
59
what is deficient in xeroderma pigmentosa?
deficient repair of UV-induced DNA damage (usually defects in nucleotide excision repair)
60
what are kids with xeroderma pigmentosa at risk for?
high rates of skin cancers at very young ages; increased risk of other malignancies
61
how does xeroderma pigmentosa manifest?
manifests in early childhood with marked photosensivity evidence of photodamage seen much earlier than normal: freckles, early wrinkling, skin atrophy, at 3 or 4 years have skin cancer
62
median age of onset for first cancer?
Median age of onset for first skin cancer: 8 yo
63
For XP pts under age of 20(have all had _______)
skin cancer
64
Incidence of nonmelanoma cancer 10,000-fold greater than US general population for whom?
pts of xeroderma pigmentosa
65
Incidence of melanoma 2000-fold higher for whom?
pts of xeroderma pigmentosa
66
effects of xeroderma pigmentosa not limited to th eyes. what other body parts are affected?
eyes and CNS Eyes - premature aging and degeneration, dry eyes corneal scarring, Cataracts, tumors CNS=Neurologic degeneration
67
what is the median age of death for xeroderma pigmentosa pts?
32 years
68
most common causes of death for xeroderma pigmentosa pts?
metastatic skin cancer and neurologic degeneration
69
which immune cells are particularly sensitive to UV induced DNA damage?
Lymphocytes and Langerhans cells are particularly sensitive to UV-induced DNA damage
70
__________largely disappear from the skin following sun exposure strong enough to cause a mild sunburn
Langerhans cells
71
t/f. UVR has both local and systemic immunosuppressive effects
true
72
which skin diseases caused or enhanced by lymphocytes and/or langerhans cells can be treated successfully with UV light
psoriasis cutaneous lymphoma eczema
73
In all cases of UV light tx, risk-benefit ratio of treatment is judged to be less than with other/no treatments Patients treated with phototherapy are followed for subsequent _______
skin cancers
74
tanning beds primarily emit _______
Primarily emit UVA -
75
_____________per unit time than solar UVA | reaching earth’s surface at equator
> 5 X amount of UVA
76
UVA induced tans provide _____ times less protection against sunburn than UVB
10
77
tanning beds strongly associated with which cancers?
Strongly associated with melanoma and non melanoma skin cancer
78
Risk of skin cancer increases _______percent in individuals who start using tanning beds before 30
75
79
World Health Organization’s cancer research agency has deemed ____________ to be unequivocally carcinogenic…. Along with tobacco, asbestos, hepatitis B virus, and plutonium
tanning beds

Dermatology (18 decks)

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