If they say that all human cells replace themselves every 7 years or so, why can scars remain on your body for the entire life?
In:
First of all, human cells don’t replace themselves after 7 years. This idea is false.
We have about 50-75 trillion cells in our bodies, and there’s tons of types, each with their own life-span:
* Red blood cells – 4 months
* White cells – 1 year
* Colon cells – 4 days
* Sperm cells – 2-3 days
* Neurons – Our entire lifetime
Cells aren’t all the same age. They die and are replaced all the time, in a continual process.
There’s also the matter that scars are the consequence of open wounds. An open wound triggers a quick reaction during which the body tries to seal off the entry to prevent infection as soon as possible. That’s the most important matter, and not aesthetics.
With a larger wound, once the “crust” is formed (which is basically layers upon layers of dead cells), skin cells start filling in the gap. Some of them start on the edges of the cut, and as such will connect quite well to the unharmed cells. But part of them come up from the middle and underneath the scar, forming basically a new “batch” of skin.
The gaps need to be bridged and the imperfect connections between the edge and middle replacement skin are how scars show up.
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