Skin Function

Question 1

State the visibility and wavelength of UVA and UVB radiation.

Answer 1

UVA = visible + longer wavelength
UVB = invisible + shorter wavelength

Question 2

Where does vitamin D metabolism take place in the skin?

Answer 2

Keratinocytes

Question 3

Vitamin D is primarily taken in from the diet. True or False?

Answer 3

False - most is synthesised via skin processes

Question 4

Explain how vitamin D is formed in the skin.

Answer 4

UVB radiation causes 7-dehydrocholesterol to be converted to cholecalciferol

Question 5

How does the liver and kidneys store vitamin D which is the main hormone form?

Answer 5

Liver = hydroxycholecalciferol
Kidneys = 1,25-dihydroxycholecalciferol = main form used in the body

Question 6

The skin accounts for what % of tyrosine to T3 break down?

Answer 6

80%

Question 7

Keratinocytes secrete what 2 molecules during inflammation?

Answer 7

AMPs

Cytokines/chemokines

Question 8

Which chromosome codes for the MHC complex?

Answer 8

Chromosome 6

Question 9

MHC class I cells + antigen + presents to?

Answer 9

All cells
Endogenous
CD8+

Question 10

MHC class II cells + antigen + presents to?

Answer 10

APCs
Exogenous
CD4+

Question 11

What T cells are found in the epidermis vs dermis?

Answer 11

CD8+

CD4+ and CD8+

Question 12

Plasmacytoid DC secrete what molecule commonly found in diseased skin?

Answer 12

IFN alpha

Question 13

What does a tumour suppressor gene do?

Answer 13

Negatively controls cell division

Question 14

What is a proto-oncogene?

Answer 14

Normal gene which positively controls cell division

Question 15

What is an oncogene?

Answer 15

Overactive mutated proto-oncogene

Question 16

Does UVA and UVB cause direct or indirect damage to DNA + product + repair mechanism?

Answer 16

UVA = indirect + oxidation + BER
UVB = direct + pyrimidine dimers + NER

Question 17

Signature UVA vs UVB mutation?

Answer 17

C changes to A

C changes to T

Question 18

Name the 4 stages of skin healing.

Answer 18

Haemostasis
Inflammation
Proliferation
Remodelling

Question 19

Name the 3 ways in which itch is controlled?

Answer 19

Chemical mediators
CNS mediators
Nerve transmission via unmyelinated C fibres

Question 20

Name the 4 types of itch + meaning.

Answer 20

Pruritoceptive = trigger in skin
Neuropathic = nerve damage
Neurogenic = no nerve damage but CNS stimuated (e.g. chemical mediators)
Psychogenic = mental cause

Question 21

Th_ cells are associated with psoriasis
Th_ cells are associated with atopic dermatitis
Th_ cells are associated with psoriasis + atopic dermatitis

Answer 21

Th1
Th2
Th17

Question 22

Name the 2 essential types of vitamin D + their chemical name + where they come from.

Answer 22

Vitamin D2 (egrocalciferol) = plants
Vitamin D3 (cholecalciferol) = animal foods or skin