Photobiology

Question 1

What percentage of solar radiation is ultraviolet?

Answer 1

About 5%

Question 2

UV light falls into what category of wavelengths?

Answer 2

100-400nm (really more like 200 to 400)

Question 3

Three types of UV light and their ranges?

Answer 3

UVC (200-290)
UVB (290-320)
UVA (320-400)

Question 4

What is significant about UVC light?

Answer 4

At the present time, it does not penetrate the earth’s atmosphere. When it is created artificually though, it is absorbed by DNA and RNA and is lethal to viable epidermal cells

Question 5

What uv light is responsible for sunburn

Answer 5

UVB (290-320)

Question 6

Is UVB blocked out by window glass?

Answer 6

Yeah

Question 7

What waveband is SPF testing based on?

Answer 7

UVB protection

Question 8

What is the least potent type of Ultraviolet radiation

Answer 8

UVA

However, UVA penetrates glass and penetrates deeply into the skin

Question 9

What is thought to be the prime cause of photoaging?

Answer 9

UVA light because it penetrates the skin so well.

Question 10

Ozone blocks what light

Answer 10

Pretty much everything under 300nm

Question 11

Most of the earth (95%) of what reaches earths surface is

Answer 11

UVA

Question 12

With each increase in altitude by 1,000 feet, UV radiation goes up

Answer 12

by 4%

Question 13

What is an action spectrum

Answer 13

Its a wavelength or range that elicits a certain reaction in the skin

Question 14

How is action spectrum determined?

Answer 14

Determined by UV absorbing properties of the molecule that initiates the reaction

Question 15

The molecule that initiates the reaction called

Answer 15

The chromophore

Question 16

WHAT ARE THE MAJOR UVB Chromophores in teh skin

Answer 16

DNA, urocanic acid, aromatic amino acids

Question 17

How many skin phototypes are there?

Answer 17

6…type 1= redhead, type 6= adam

Question 18

Erythema in sunburn due to

Answer 18

Vasodilation. This also results in the skin feeling hot.

Question 19

Pain and pruritis due to?

Answer 19

Cytokine release

Question 20

What is the “immediate tanning response”

Answer 20

Caused by UVA light. It fades within an hour and does not protect agianst UVB. It is a result of oxidation and redistribution of melanin

Question 21

What is the delayed tanning response

Answer 21

Caused by UVB. Becomes visible after 72 hours. Lasts weeks.
Increased Melanin synthesis and transfer of melanosomes to keratinocytes
Some photoprotection but not much

Question 22

What are the major histologic changes due to chronic UV radiation

Answer 22

Less Collagen, damaged elastin

Question 23

Chronologic aging looks like

Answer 23

skin will be smooth, pale, fine wrinkles and benign growths

Question 24

Photoaged skin

Answer 24

dry, deep wrinkles, inelastic, lethery and atrophic

Question 25

What is a DNA photoproduct

Answer 25

dimers formed by the covalent bonding of two adjacent pyrimidines in the same polynucleotide chain
Ex: cyclobutane dimers an d6,4 photoproducts.

Question 26

xeroderma pigmentosum

Answer 26

Extreme sensitivity to UV radiation due to an inability to repair DNA damamge caused by UV light.
Usually a problem with Nucleotide excision repair
High rates of skin cancer at an early age and risk of other malignancies

Question 27

Median age of first skin cancer for xp patients

Answer 27

Age 8

Question 28

XP and the eyes

Answer 28

premature aging and degeneration, dry eyes, corneal scarring, cataracts, tumors

Question 29

CNS and XP

Answer 29

Neurologic degeneration

Question 30

Median age of death in xp pts

Answer 30

32

Question 31

Because Langerhans cells disappear from the skin following sun exposure, UVB treatment can be helpful in diseases caused by lymphocytes and langerhans cells

Answer 31

Eczema, Psoriasis, cutaneous lymphoma