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Flashcards in UVR and skin Deck (57):
1

UVR wavelengths and damage

100-400nm (short) allows DNA damage

2

What is significant about UVC rays?

only 290nm so no atmospheric penetration but most potent of all UVL

3

What happens when UVC rays are produced artificially then absorbed by DNA?

RNA and proteins are damaged and may be unviable leading to lethality of epidermal cells

4

What waveband is SPF testing done on?

UVB (290-320nm)

5

Can a person inside get UVB rays?

no; glass filters it out

6

What is the most active in producing photochemical reactions in skin?

UVB

7

What is the least potent of all UVR?

UVA

8

What is responsible for photoaging? why?

UVA => penetrates deeper than UVB

9

What are factors that modify UVR at earth?

atmosphere; latitude; altitude; surface reflection; cloud; solar flare activity; time of day; season

10

What blocks most wavelengths below 300nm?

ozone: UVC completely blocked; UVB up to 5% remains

11

Why is skin cancer expected to continue to rise?

depletion of ozone layer

12

Why are you more likely to burn on equivalent days in Texas as compared to vermont?

sunlight travels through more atmosphere to reach surface

13

Who is more likely to burn on a sunny day: person in denver or in San Fransisco?

Denver as UVR is increased by 4% every 1000ft increase in altitude

14

Give order of most likely to burn from UVR: sand, water, snow

Snow (most likely) > Sand > water

15

Why can a person burn on a cloudy day?

clouds scatter the UVR but do not absorb it

16

What are the 3 options that sunlight has when it hits the skin?

reflect; absorbed by epidermis and dermis DNA, proteins; penetrates into tissues and dissipates

17

How is action spectrum determined?

UV absorbing properties of molecule that initiates the response: chromophore

18

What are the major UVB chromophores in skin?

DNA; urocanic acid; aromatic amino acids

19

Acute and chronic responses to UVR depend on what?

skin phototype (types I-VI)

20

What are acute effects of UVR on skin?

sunburn; immunomodulation; tan; epidermal hyperplasia; Vit D photosynthesis; DNA damage (apoptosis, cell cycle arrest)

21

What is the erythema and heat of a sunburn a result of?

vasodilation and increased blood flow

22

Why is pain/pruritus associated with sunburn?

release of cytokines

23

In an acute sunburn, what can be seen histologically?

keratinocyte damage; inflammation; intercellular edema; perivascular edema

24

72 hours after a sunburn, what can be seen?

hyperkeratosis, acanthosis

25

What is the pathogenesis of a suntan (immediate response)?

begins during radiation; oxidation/redistribution of melanin; no protection against UVB

26

What causes a suntan (immediate response)?

UVA and visible light

27

What causes the delayed tanning response of a suntan?

UVB

28

What is the pathogenesis of a delayed tanning suntan?

visible 72hrs later and lasts weeks due to increased melanin synthesis and transfer of melanosomes to keratinocytes to provide photoprotection

29

What are 2 chronic effects of UVR on skin?

photaging and photocarcinogenesis

30

What are typical cancers associated with UVR and photocarcinogenesis

BCC; squamous cell carcinoma; melanoma

31

What is solar elastosis?

result of chronic UV radiation seen on histological slides

32

clinical features of chronologic aging

smooth, pale finely wrinkled skin w/ benign growths

33

clinical features of photoaging

dry, deeply wrinkled, inelastic leathery, atrophic; telangiectasias; irregular pigmentation; comedone and cyst formation; actinic keratoses; benign growths

34

What are examples of irregular pigmentation associated with photoaging?

ephelides (freckles); solar lentigo (age spots); hypopigmentation

35

What are deep wrinkles on the posterior neck?

cutis rhomboidalis nuchae

36

What is a poikiloderma

reticulate hyperpigmentation; telangiectasia; mild atrophy

37

What UVRs cause photoaging?

UVB and UVA

38

Direct damage from UVB occurs via what mechanism?

direct absorption of photons by bases of DNA

39

What are DNA photoproducts?

dimers formed by covalent binding of 2 adjacent pyrimidines in same polynucleotide chain

40

stratum corneum defense against UVR

reflection

41

Melanin defense against UVR

melanin

42

tumor suppressor genes against UVR

p53; patched; CDKN2A

43

What are intracellular ways of defense against UVR?

DNA repair pathways; apoptosis

44

What is xeroderma pigmentosum?

heritable disease characterized by marked sensitivity to UV radiation

45

What are patients with XP deficient in?

deficient repair of UV induced DNA damage affecting nucleotide excision repair

46

What is the result of most XP patients?

high rates of skin cancers at young age with increased risk for other malignancies

47

What are first signs of XP?

very early photodamage=> freckles; early wrinkling; skin atrophy

48

When does XP typically present?

early childhood w/ marked photosensitivity

49

When does first skin cancer typically present in XP patients?

median age of 8

50

Other than skin, what other body locations are affected by XP?

CNS (neurologic degen); Eyes (premature agin, dry, corneal scarring, tumors)

51

What and when do most patients with XP die of?

32 y/o from metastatic skin cancer and neurologic degeneration

52

How does UVR cause immunosuppression?

local and systemic effects => sun exposure causes Langerhans to disappear from skin in mild sunburn due to DNA damage

53

When is UV light considered for Tx?

skin diseases caused or enhanced by lymphs or Langerhans => psoriasis; cutaneous lymphoma; eczema

54

What is significant about UVA suntans?

provide 10x less protection against sunburn than UVB

55

What skin diseases are strongly associated with tanning beds?

melanoma; non melanoma skin cancers

56

T/F Risk of skin cancer increases by 75% in ppl who use tanning beds

true

57

What is Favre-Racouchot syndrome?

skin disease in sun damaged individuals characterized by yellowish thickening of skin w/ nodules, comedones and follicular cysts