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Dermatology > photobiology: sun and the skin > Flashcards

photobiology: sun and the skin Flashcards

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Dermatology Board Prep flashcards
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
Q

which wavelength is responsible for the majority of the effects of UVR on the skin?

A

UVB

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26
Q

how to the four skin phototypes Type I(pale) - IV(dark) vary?

A

vary in:

  1. susceptibility to burning
  2. ability to tan
  3. risk of skin cancer
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27
Q

name 6 acute effects of UVR on the skin

A 
inflammation (sunburn)
immunomodulation 
tanning 
epidermal hyperplasia 
vitamin D photosynthesis 
DNA damage(apoptosis and cell cycle arrest to repair)
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28
Q

what is sunburn mostly due to?

A

UVB

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29
Q

what is the mechanism of redness(erythema)?

A

vasodilation

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30
Q

heat felt in sunburn is from ____

A

increased blood flow

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31
Q

in sunburn, Pain and pruritus due to release of ____________`

A

cytokines

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32
Q

t/f IFN is released when you have a sunburn

A

true

33
Q

what are some of the histological changes that occur after sunburn?

A
  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
Q

define hyperkeratosis

A

hyperplasia of the stratum corneum

35
Q

defien acanthosis

A

diffuse epidermal hyperplasia

36
Q

what causes the immediate tanning response?when does it begin?

A

caused by UVA and visible light

begins during radiation, is maximal immediately afterward

37
Q

how long does the immediate tanning response last?

A

fades within an hour

38
Q

mech of immediate tanning response?

A

oxidation and redistribution of existing melanin

39
Q

does the immediate tanning response protect against UVB?

A

NO!

40
Q

Delayed tanning response caused by _______

A

UVB

41
Q

when is delayed tanning response visible?

A

Gradual, becomes visible after about 72 hours, lasts for weeks

42
Q

mechanism of delayed tanning response

A

Increased melanin synthesis and increased transfer of melanosomes to keratinocytes

43
Q

does delayed tanning response provide photoprotection

A

Increased melanin synthesis and increased transfer of melanosomes to keratinocytes

44
Q

name two chronic effects of UVR on skin?

A
  1. photoaging

2. photocarcinogenesis (basal cell and squamous cell carcinomas, melanoma)

45
Q

smooth, pale, finely wrinkled skin with benign growth describes ____

A

chronologic aging

46
Q

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_______

A

chronologic aging

47
Q

t/f. UVB is 20-50 times more efficient at photo aging

A

true

48
Q

t/f in photoaging: UVA is present in greater concentrations, is capable of deeper penetration and more dermal damage

A

true

49
Q

Both UVB and UVA irradiation result in changes of photoaging

A

true

50
Q

how does DNA damage by UVA occur?

A

Damage occurs from direct absorption of photons by bases of DNA

51
Q

how are DNA photoproducts produced?

A

DNA photoproducts are dimers formed by covalent binding of two adjacent pyrimidines in same polynucleotide chain

52
Q

what are two DNA photoproducts

A

cyclobutane dimers

6.4 photoproducts

53
Q

What happens if UV-induced DNA damage is not efficiently repaired?

A

UV- signature mutations

54
Q

what are defense mechanisms against UVR at the stratum corneum?

A

reflection

55
Q

function of melanin in protection against UVR?

A

absorption

56
Q

tumor suppressor genes that help protect from DNA induced damage?

A

p53, patched, CDKN2A(p16)

57
Q

DNA repair pathways, apoptosis

A

know just as more defense mechanisms against UVR

58
Q

what is xeroderma pigmentosa?

A

heritable disease marked by sensivity to UV radiation

59
Q

what is deficient in xeroderma pigmentosa?

A

deficient repair of UV-induced DNA damage (usually defects in nucleotide excision repair)

60
Q

what are kids with xeroderma pigmentosa at risk for?

A

high rates of skin cancers at very young ages; increased risk of other malignancies

61
Q

how does xeroderma pigmentosa manifest?

A

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
Q

median age of onset for first cancer?

A

Median age of onset for first skin cancer: 8 yo

63
Q

For XP pts under age of 20(have all had _______)

A

skin cancer

64
Q

Incidence of nonmelanoma cancer 10,000-fold greater than US general population for whom?

A

pts of xeroderma pigmentosa

65
Q

Incidence of melanoma 2000-fold higher for whom?

A

pts of xeroderma pigmentosa

66
Q

effects of xeroderma pigmentosa not limited to th eyes. what other body parts are affected?

A

eyes and CNS
Eyes - premature aging and degeneration, dry eyes
corneal scarring, Cataracts, tumors

CNS=Neurologic degeneration

67
Q

what is the median age of death for xeroderma pigmentosa pts?

A

32 years

68
Q

most common causes of death for xeroderma pigmentosa pts?

A

metastatic skin cancer and neurologic degeneration

69
Q

which immune cells are particularly sensitive to UV induced DNA damage?

A

Lymphocytes and Langerhans cells are particularly sensitive to UV-induced DNA damage

70
Q

__________largely disappear from the skin following sun exposure strong enough to cause a mild sunburn

A

Langerhans cells

71
Q

t/f. UVR has both local and systemic immunosuppressive effects

A

true

72
Q

which skin diseases caused or enhanced by lymphocytes and/or langerhans cells can be treated successfully with UV light

A

psoriasis
cutaneous lymphoma
eczema

73
Q

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 _______

A

skin cancers

74
Q

tanning beds primarily emit _______

A

Primarily emit UVA -

75
Q

_____________per unit time than solar UVA

reaching earth’s surface at equator

A

> 5 X amount of UVA

76
Q

UVA induced tans provide _____ times less protection against sunburn than UVB

A

10

77
Q

tanning beds strongly associated with which cancers?

A

Strongly associated with melanoma and non melanoma skin cancer

78
Q

Risk of skin cancer increases _______percent in individuals who start using tanning beds before 30

A

75

79
Q

World Health Organization’s cancer research agency has deemed ____________ to be unequivocally carcinogenic…. Along with tobacco, asbestos, hepatitis B virus, and plutonium

A

tanning beds

Dermatology (18 decks)

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