Mechanism of a suntan

Question 1

Step 1

Answer 1

Exposure of skin to UV light

Question 2

step 2

Answer 2

Keratinocytes experience DNA damage and increase p53 activity (tumor suppressor gene, regulates cell cycle and prevents gene mutations)

Question 3

step 3

Answer 3

p53 stimulates cascade the releases CRH which stimulates POMC (pre-opiomelanocortin)

Question 4

Step 4

Answer 4

POMC is broken down to form alpha MSH (melanin stimulating hormone) in the pituitary.

Question 5

Step 5

Answer 5

Alpha MSH in the blood stream binds to receptors on melanocytes (MC1R) stimulating second messenger cAMP

Question 6

Step 6

Answer 6

cAMP stimulates melanocytes to increase production of melanin

Question 7

Step 7

Answer 7

Melanin is packaged into vesicles and exocytosed into interstitial fluid.

Question 8

step 8

Answer 8

Melanin enters keratinocytes

Question 9

step 9

Answer 9

Melanin migrates to the nucleus of keratinocyte protection DNA from further damage

Question 10

Step 10

Answer 10

As keratinocytes move toward the skin surface, they die and leave a later of melanin in the dead cells

Question 11

step 11

Answer 11

Melanin in the stratum corneum cells provides both the color of a suntan and further UV protection to underlying layers.

Question 12

Why do those with addison’s disease appear tan?

Answer 12

Addison’s disease is a primary adrenal insufficiency. So the adrenal glands are not producing steroid hormones due to a defect in the adrenal glands. Your body is confused why steroids are not being produced, so it makes a bunch of ACTH, which is a hormone that stimulates the adrenal glands. ACTH is made from POMC. So to increase ACTH, there is an increase in POMC. POMC is broken down into alpha MSH, which increases melanin production.