How can sunburns and sun exposure cause permanent skin damage if your skin is constantly replacing itself?

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Recently read something about how a few bad sunburns when you’re young can cause a large increase in cancer later in your life. How can you develop cancer several decades after you’re burnt if your skin cells are constantly dying, falling off, and regrowing?

In: Biology
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Basically the sun sends out UV rays which go through our bodies, hitting the skin the hardest. These rays can damage the DNA in a cell, causing it to grow improperly. If enough get damaged in this way then it can present itself as a growth, or tumor.

If a cell that tells skin how to make itself gets damaged, the same thing happens but more aggressively.

One of the best ways to think about it is not as “sun burn” but as a radiation burn. The skin is constantly replacing the top layer but more severe burns penetrate deeper into the skin and surrounding tissues. Sometimes this can damage the skin all the way to the lowest skin layers and when the tissues heal scarring forms as the skin cannot adequately regrow across the urn.

Your skin is like a layer cake. The frosting is constantly sloughing off and being replaced, and the first layer sometimes takes damage but it can grow back.

Getting a sunburn is like microwaving the cake.

Human skin consist of three layers. The outermost layer called epidermis and responsible for protecting body from environment including UV lights. Epidermis have 5 more layer within. The ability of renewal of skin comes from this 5 layer. The deepest layer contains melanocytes which provides melanin to skin and basal cells. Basal cells duplicate and grow outwards and while going out they get less and less supply from body and slowly dies. But the basal cells are always there are functioning. Sunburn cause damage basal cells and melanocytes because UV lights are something called ionizing radiation. UV lights produces ions which interfere with duplication on cell nuclei of said cells. Little amounts of sunlight damage often can be tolerated but in sunburn situation cells are dying from nuclear damage from UV not from the sun heat.
The basal cells are the type of cell that does the replacing process. But they aren’t replaced and thus the damage from sun exposure builds up entire life.

We had a saying during Navy Nuke school: Good Daughters, Bad Daughters, Dead Daughters, No Daughters.

When your cells are exposed to ionizing radiation, it can cause mutations. When that cell reproduces, it can not pass on the mutation (Good Daughter), it can reproduce, but the daughters die (Dead Daughters), the cell could die (No Daughters), or it can pass the mutation on (Bad Daughters).

Cancer would be Bad Daughters, cells that mutate and then pass those mutations on.

Not really eli5, but it damages the DNA and raises the chances of a mutation that would be detrimental to your health

The sun’s radiation is filtered through our atmosphere and a fraction of it reaches the ground level where we live. Of this, some is filtered through our skin too but a fraction reaches the ground level of our skin called the basal layer. When the sunlight hits the basal layer its either absorbed by pigments called melanin or its absorbed by other sensitive cells. When its absorbed by sensitive cells it can cause the burning sensation. This basal layer doesn’t replace itself as quickly as the outermost layer of ‘dead skin’.

Interestingly, we only get exposed to a small percentage of the sun’s energy. Imagine how burned you would get if you were on top of a mountain or high up in the atmosphere! Also, sunscreen works by adding an extra layer of filters at the top layer of your skin.

First of all the top layer of the skin is constantly replaced, but the lower layers aren’t.

This is why tattoos are permanent, and why superficial burns can heal completely but deeper burns won’t.

Also, the skin regenerates itself by dividing the cells.

When a call divides it makes a copy of itself. If a cell’s DNA is damaged then the new cells that come from that cell will have the same damaged DNA from then on, until that cell line dies.

The UV rays damage DNA. Most of the time the DNA can be fixed or the cell dies. Some of the damage can’t be fixed and the cell doesn’t die, so any further copies of this cell will contain the damaged DNA.

And sometimes this damaged DNA causes the cells to divide forever and become cancer.

The longer you are exposed to the sun, the more the plans for rebuilding get faded and harder to read.

Over a long period of time, skin cells begins to have errors as the dna structure is mutated/damaged by radiation.

Basically cell maintenance and replacement is like a photocopy of a photocopy. Eventually there’s loss of information.

Sun burns are kinda like at one point you touch a copy with dirty hands and that exacerbates the information loss of all copies after that one.

The lost information could be nothing or it could have vital information on what the next copy should have to be legible and do its work, in this case, proper cell formation which is affected can cause abnormalities such as cancer.